1. CNT-104S

1.1. GENERAL INFORMATION User Manual CNT-104S

Revision 1.1

12NC 4031.601.10401

About this Manual

This manual contains directions for use that apply to the the 4-channel CNT-104S Multi-channel Frequency Analyzer.

Warranty

The Warranty Statement is part of the folder Important Information that is included with the shipment.

Declaration of Conformity

The complete text with formal statements concerning product identification, manufacturer and standards used for certification type testing is available on request.

1.2. Preparation for Use

1.2.1. Preface

1.2.1.1. Introduction

Congratulations on your choice of instrument. It will serve you well and give you today’s ultimate performance for many years to come, whether you work with advanced ultra-high resolution frequency analysis in R&D, high-precision calibration in Metrology, or high speed testing of time & frequency in test systems.

Your instrument is the industry’s first bench-top multichannel frequency counter/analyzer designed to bring a new dimension to bench-top and system frequency counting and analysis. It gives significantly increased performance compared to traditional Timer/Counters. The CNT-104S offers for example the following benefits:

  • 4-parallel time-stamping input channels, means you have 4 independent frequency counters in one box. An enormous save of money and space in test systems
  • Phase-compare 4 stable frequencies continuously in real time in a time metrology lab, without the need for external signal switching
  • The parallel-channel time-stamping design, where all channels run on the same time scale, allows to measure Time Interval with multiple stop channels, which is very valuable for exact timing of one-shot events
  • Graphical intuitive User Interface, with large 5” color touch-screen control
  • Easy control of instrument via mouse or web interface.
  • Up to 13 digits of frequency resolution per second and up to 7 ps resolution/timestamp
  • A high measurement rate of up to 20M readings/s to internal memory
  • Optional oven-controlled timebase oscillators,Choice of RF prescaler options with upper frequency limits ranging from 3 GHz to 24 GHz
  • Integrated 1Gbit Ethernet and USB interfaces with SCPI commands support

1.2.1.2. Design Innovations

1.2.1.3. Remote Control

This instrument is programmable via Ethernet (ETH) or USB interfaces.

The ETH is the primary interface intended for use in test systems, on lab benches, and fully remote control and monitoring from “anywhere in the world”.

The web interface and VNC server are included, which gives you an exact copy, pixel by pixel, of the instrument’s screen. All instrument settings can be controlled from the web interface or VNC, and result data can be read.

In test systems, the CNT-104S uses the standardized SCPI language for programming the instrument’s functions and reading the results.
The USB interface is mainly intended for the lab environment with the “remote” controller in a nearby place.

1.2.2. Safety

1.2.2.1. Introduction

Please take a few minutes to read through this part of the introductory chapter carefully before plugging the line connector into the wall outlet.

This instrument has been designed and tested for Measurement Category I, Pollution Degree 2, in accordance with EN 61010-1:2011, and CSA C22.2 No 61010-1-12 (including approval). It has been supplied in a safe condition. Study this manual thoroughly to acquire adequate knowledge of the instrument, especially the section on Safety Precautions hereafter and the section on Installation.

1.2.2.2. Safety Precautions

All equipment that can be connected to line power is a potential danger to life. Handling restrictions imposed on such equipment should be observed.

To ensure the correct and safe operation of the instrument, it is essential that you follow generally accepted safety procedures in addition to the safety precautions specified in this manual.

The instrument is designed to be used by trained personnel only. Removing the cover for repair, maintenance, and adjustment of the instrument must be done by qualified personnel who are aware of the hazards involved.

The warranty commitments are rendered void if unauthorized access to the interior of the instrument has taken place during the given warranty period.

1.2.2.3. Caution and Warning Statements

CAUTION: Shows where incorrect procedures can cause damage to, or destruction of equipment or other property.

WARNING: Shows a potential danger that requires correct procedures or practices to prevent personal injury.

1.2.2.4. Symbols

Shows where the protective ground terminal is connected inside the instrument. Never remove or loosen this screw.

This symbol is used for identifying the functional ground of an I/O signal. It is always connected to the instrument chassis.

Indicates that the operator should consult the manual.

Personal safety is ensured when the input signal level is below 30 Vrms (when accidently touching the input signal lead)

Damage level for the input decreases from 350 Vp to 12Vrms when you switch the input impedance from 1 MΩ to 50 Ω.

Measurement BNC cables length shall be kept below 3m.

Circuits of external devices connected to BNC sockets, USB sockets and Ethernet sockets should be separated from the power supply network (and from other sources of dangerous voltage) at the level of reinforced insulation.This separation should not be confused with the permissible voltage of the external signal, including the voltage of 350 Vp referred to in the manual. If the equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may be impaired.

1.2.2.5. If in Doubt about Safety

Whenever you suspect that it is unsafe to use the instrument, you must make it inoperative by doing the following:

  • Disconnect the line cord
  • Clearly mark the instrument to prevent its further operation
Fig. 1‑1 Do not overlook the safety instructions!
  • Inform your Pendulum Instruments representative.

For example, the instrument is likely to be un­safe if it is visibly damaged.

1.2.2.6. Disposal of Hazardous Materials

There are no batteries or other potentially hazardous materials included.

You should dispose of your worn-out Frequency Analyzer, after a long and happily life, at an authorized recy­cling station or return it to Pendulum Instruments.

1.2.3. Unpacking

Check that the shipment is complete and that no damage has occurred during transportation. If the contents are incomplete or damaged, file a claim with the carrier immediately. Also notify your local Pendulum Instruments sales or service organization in case repair or replacement may be required.

1.2.3.1. Check List

The shipment should contain the following:

  • Multi-channel Frequency Analyzer CNT-104S Line cord
  • Printed version of the Getting Started Manual Brochure with Important Information Certificate of Calibration
  • Options you ordered should be installed. See Identification below.

Note: To ensure always up-to-date user documentation, the user manual (this document) is not included on any media in the shipment. Instead, the user documentation can be read on-line or downloaded as PDF from manuals.pendulum-instruments.com

  • Getting Started User’s Manual
  • User’s Manual
  • Programmer’s Handbook

1.2.3.2. Identification

The type plate on the rear panel shows type number and serial number. Installed options are listed under the menu About, where you can also find information on firmware version and calibration date.

1.2.3.3. Installation

1.3. Getting Familiar with the Instrument

1.3.1. Front & Rear Panels

1.3.2. Home Screen

Measurement State:

  • RUN – next measurement will start automatically as soon as current one is over. Pressing RESTART in this state starts new measurement, measurement state remains RUN. Pressing RUN/HOLD in this state changes the state to SINGLE, but current measurement continues. Exception is Totalize measurement functions, when state is changed to HOLD.
  • SINGLE – measurement is in progress. After measurement is over – measurement state will change to HOLD, no new measurement will start. Pressing RESTART in this mode starts new measurement, measurement state remains SINGLE. Pressing RUN/HOLD in this state stops the measurement and changes state to HOLD.
  • HOLD – measurement is not active. Results of previous measurement are displayed. Pressing RESTART starts new measurement and changes state to SINGLE. Pressing RUN/HOLD in this state starts new measurement and changes state to RUN.

Indicators:

  • Trigger indicators – if signal crosses set trigger level(s) for particular input, then corresponding trigger indicator is lit, otherwise it is grayed out.
  • GATE – red when measurement is active, grayed out otherwise.
  • MATH – Math function is active. User selectable formula is applied to one or all (depending on user choice) measurement series.
  • LIM – Limits function is active. Values of one or all (depending on user choice) measurement series are checked against the limit(s) specified by the user. User can configure the desired behavior when measurement data exceeds the limit(s).
  • ER – External Reference clock is used as a timebase for measurements.
  • REM – instrument is now in Remote state (controlled by remote application). In this state the instrument can not be controlled from the front panel. Press BACK to switch to Local state and enable front panel control.  If REM! indicator is displayed, Remote Lockout mode is active and BACK button cannot be used to return to Local Mode. Only remote party can undo this state. In web interface or VNC client use F7 key in place of BACK.
  • ARM – measurement configured to start and/or stop on arming signal.

1.3.3. Settings

Inputs description:

  • A, B, D, E – main inputs
  • A2, B2, D2, E2 – supplementary comparators of main inputs (e.g. for measuring time intervals inside multi-level signals)
  • С – optional High Frequency input
  • EA – External Arming input
  • ER – External Reference Input

1.3.4. Measurement Data Display

View large numeric data from 4 measurement channels at the same time along with auxiliary data (e.g. voltage)

View detailed statistics for all measurement channels (click numbers for particular channel to zoom)

1.4. Measurement principles and concepts

1.4.1. Time and Frequency measurement principles

Block diagram on Figure 1 demonstrates input signal transformation to series of time and frequency measurement data points.

First, input signal gets into input amplifier. The generic role of input amplifier circuits is matching the input to signal source, and optionally: attenuate or amplify it, remove DC offset and/or filter out high-frequency noise.

Please note: There are several kinds of input amplifier circuits (configurable input amplifiers, prescalers, fixed input amplifiers), please refer to 4.5 Input signal conditioning/Input Amplifiers chapter for more details about them.

After the input amplifiers the signal is digitized using one (inputs C, EA, ER) or 2 comparators (inputs A, B, D, E). It works the following way: when the signal crosses the set trigger level, comparator generates a positive (in case of transition from below to above the trigger level) or negative (in case of transition from above to below the trigger level) slope. Please refer to Figure 2 for an example.

Please note: For most measurement modes on inputs with 2 comparators, output of only one comparator is used for measuring the signal from this input. However, there are measurement modes using both comparators implicitly:

  • Rise/Fall Time and Slew Rate measurements use 2 comparators for getting Time Interval between lowest (10%) and highest (90%) levels of the signal (see details in 5.4.3 Rise Time, Fall Time, Rise-Fall Time);
  • Pulse width and Duty Cycle measurements use 2 comparators to produce pulses on positive and negative slope of a signal and measure Time Interval between these;
  • Frequency and Period Average use 2 comparators to implement implicit wide hysteresis targeted on improving noisy signals measurements (see details in 5.1.1 Frequency/Period Average measurements chapter).

Second comparator can also be explicitly selected for measurement. E.g., Time Interval A, A2 will measure time interval between signal level set by trigger level A and signal level set by trigger level A2 (can be useful for measuring characteristics of multi-level signals, e.g. TDR measurements – see 5.2.4 Measuring Time Interval between different trigger points of the same signal). It can also be explicitly used as a source of start or stop arming.

Digitized signals from physical inputs are just pulse trains which can be multiplexed to 4 internal measurement channels. Each measurement channel starts with Wide Hysteresis block. Wide Hysteresis block just passes through the signal for most measurement functions except Frequency, Period Average, their Smart versions, TIE, and Frequency Ratio for which implicit wide hysteresis is used for better noise tolerance (see 5.1.1 Frequency/Period Average measurements).

The resulting pulse train is then counted independently in each measurement channel. Measurement logic specific for each measurement mode makes snapshots of channel’s pulse counter, timestamps it and adds channel number, forming series of so-called raw results.

Raw results are further post-processed in calculation block to form series of final value-timestamps pairs.

See Figure 2 for a visualized example of signal processing happening inside CNT-104S.

Figure 1. Input signal to Time & Frequency measurement results transformation
Figure 2. Example of input signal to result transformation for Frequency measurement mode with Wide Hysteresis

1.4.2. Voltage measurement principles

Measuring voltage of the input signal is available only on inputs A, B, D, E. On each input there are 2 dedicated comparators used to search for signal’s lower and upper levels. 4 inputs can be measured in parallel.

Adaptive search algorithm is used which depends on Voltage Mode setting. Each voltage mode implies minimum input signal frequency which the voltage measurement can handle. E.g. in Normal Voltage mode (default) CNT-104S is able to measure voltage of signals with frequencies starting with 100 Hz and above. Allowing lower frequencies makes the voltage measurement slower so it is not recommended to set Voltage mode below Normal unless really needed (one might want to consider using Autoset instead).

Table below summarizes Voltage Modes available in CNT-104S:

Voltage ModeMinimum FrequencyAverage Time to measure 1 voltage sample
Very Slow1 Hz15 s
Slow10 Hz1.5 s
Normal100 Hz450 ms
Fast1 kHz65 ms
Very Fast10 kHz30 ms
Table 1. Voltage Modes
Figure 3. Input signal to Voltage measurement results transformation.

1.4.3. Sample Interval

On each measurement channel CNT-104S can produce gap-free samples back-to-back as fast as 1 sample per 50 ns which corresponds to setting Sample Interval to 0 s. However, for most cases one doesn’t need samples to be generated with such a high frequency, then using non-zero Sample Interval can be considered. In this case samples in each measurement channel will be generated not faster than once per set Sample Interval.

Figure 4. Example of how sample interval works with multi-channel Frequency measurement.

Sample Interval hints:

  • Sample Interval clock is not synchronized to signal, meaning actual Sample Interval between 2 consecutive samples can be less or more than Sample Interval set by the user.
  • When doing parallel measurement, sample interval is applied to each measured series independently. E.g., when measuring Frequency A, B, D, E and using 1 ms Sample Interval, one will get 1000 Frequency Samples per second from each input.
  • Sample Interval for averaging measurement functions (Frequency, Period Average and their Smart alternatives) acts as an averaging gate. The larger the gate (Sample Interval) – the greater the resolution.
  • The CNT-104S contains two cascaded memories for result saving. The first is the cache buffer that can holdup to 20000 raw samples with a maximum writing speed of 20 million Samples/s. The second is the main memory, that can hold up to 32 million results, with a maximum writing speed of 12.5 million samples per second, or 80 ns between samples. The data is written to the cache buffer in parallel from up to 4 inputs, meaning the capture speed is independent of the number of inputs used. The data transfer from the fast cache buffer to the slower main memory is done in serial, so the maximum capture speed varies with the number of channels  Setting max number of samples of samples to 20k for a single channel measurement, or 5k for a 4 channel measurement, will guarantee a sampling rate of 20 million values/s, at a sample interval of 50 ns. When setting a larger number of samples , the Sample Interval (given that signal period is less than or equal to the set Sample Interval) must be increased to minimum 80 ns for 1-channel and minimum 320 ns for 4-channel measurements, to avoid cache buffer overflow. If not, the measurement is aborted to avoid data loss.

Example. Measurement function is Frequency A,B,D,E, Sample Interval is 50 ns, Sample Count is set to 10000 and period of all input signals is 50 MHz. 4 measurement channels are used in parallel, each supposed to deliver samples at a rate of 20 million samples per second, which is greater than the speed cache buffer can be fetched with (12.5 million samples). Total number of samples to be generated is 4 x (10000 + 1) = 40004 (N + 1 raw samples are needed to calculate N frequencies), which is twice greater than measurement logic buffer capacity. So, the buffer will overflow and measurement will be aborted. Solution would be to either increase Sample Interval to 320 ns (4 channels x 80 ns, giving 12.5 million samples per second total) or to decrease Sample Count to 4999 (giving 4 x (4999 + 1) = 20000 samples total).

To avoid this situation please watch out for warning text when setting Sample Count and/or Sample Interval or warning icon when choosing measurement function and inputs.

Figure 5. Warning icon on Function/Inputs selection dialog (see clickable red button with exclamation sign to the left of Cancel).
Figure 6. Warning text when editing Sample Count
  • When using Sample Interval close to 50 ns, actual sample interval might vary between 50 ns and 100 ns. In case of Time Interval measurement – it can result in generating less samples than was ordered by Sample Count setting. To avoid this please consider setting Sample Interval to 0 if you need minimal sample interval between samples. Setting Time Interval to 0 disables Sample Interval clock, meaning taking samples as fast as possible (close to 50 ns if signal period is 50 ns or greater).
  • Sample Interval setting doesn’t affect Voltage measurement where interval between samples directly depends on Voltage Mode (please see Voltage measurement principles for details).
  • Sample Interval setting doesn’t affect manual Totalize measurement where interval between samples is always 100 ms.

1.4.4. Input signal conditioning/Input Amplifiers

1.4.4.1. Overview

The input amplifiers are used for adapting the widely varying signals in the ambient world to the measuring logic of the timer/Analyzer.

These amplifiers have many controls, and it is essential to understand how these controls work together and affect the signal.

1.4.4.2. Configurable amplifiers

Input amplifiers for inputs A, B, D & E are configurable (Inputs section of the Settings dialog) and allow to select a bunch of parameters described in the following sections.

Figure 7. Input amplifiers configuration menu

1.4.4.3. Input Amplifiers with fixed configuration

The following inputs have fixed amplifier parameters:

  • EA (External Arming) is fixed to 1 kΩ impedance and approx. 1.5 V trigger level;
  • ER (External Reference) is fixed to 50 Ω impedance and accepts signals with 0.1 to 5 Vrms amplitude;
  • C (Prescaler input) is fixed to 50 Ω impedance.

1.4.5. Arming

Arming, in general, gives the opportunity to start and stop a measurement when an external qualifier event occurs.

Arming can initialize either a single sample acquisition (Arm on Sample) or a single measurement session defined by sample count (Arm on Block). Measurement can be started and stopped by rising or falling edge of signals on instrument’s inputs and delayed from 0 ns (delay off) to 2 s with 10 ns resolution step. In case of Totalize measurement mode, timer (set by a combination of Sample Interval and Stop Source set to Timer) can be used as a source of stop arming.

Table 1 shows possible arming modes and their specifics. Modes absent in this table are not supported.

Start Arming SourceStop Arming SourceArm onMeasurement FunctionComment
OffOffN/AAnyArming is not used, measurement is started and stopped normally
InputOffBlockAny, except TotalizeStart arming input initialize measurement session (block). Measurement session ends when all samples (number is set by Sample Count) have been collected.


Figure 12. Frequency measurement with measurement session repeated after start arming pulses

Arming start pulses that occur during measurement session are neglected (see ).

Figure 13. Frequency measurement with arming start pulses occurring during the measurement session
InputInputBlockAny, except TotalizeStart arming starts measurement session (block). Measurement session ends when either all samples (number is set by Sample Count) have been collected or by signal front on stop arming input (whatever comes first).

Figure 14. Frequency measurement with measurement session controlled by start and stop arming signals
OffTimerSampleTotalizeTotalize measurement is started by pressing Restart button, Sample Interval defines Totalize Gate length. The Analyzer counts number of events during the gate and produces single sample (1 sample per series).
InputTimerSampleTotalizeStart arming pulses start Totalize Gates (gate length is defined by Sample Interval). Each gate produces 1 sample (per series). Measurement session ends once required number of samples (set by Sample Count) was collected.

Figure 15. Totalize measurement in timed mode (stop arming signal set to timer)
InputOffSampleAny, except TotalizeStart arming is used as a pacing clock – single sample measurement is executed just after the arming event.

Figure 16. Pulse width measurement with arming signal used as a pacing clock In case of Frequency/Period Average measurement, samples are measured with dead-time, no back-to-back. Maximum total number of samples is reduced to up to 16 million.

Figure 17. Frequency measurement initialized by arming pulses
InputInputSampleTotalize, Frequency, Period Average, Smart Frequency, Smart Period AverageStart arming events start Gate (gate length is defined by Sample Interval). Stop arming events end Gate. Each gate produces 1 sample (per series). Measurement session ends once required number of samples (set by Sample Count) was collected.
In case start and stop arming settings are not the same, neasurements are performed with dead-time, no back-to-back. Maximum total number of samples is reduced to up to 16 million.

Figure 18. Frequency measurement in a gate created by arming signals

When arming start and stop conditions are the same, measurements are performed continuously (back-to-back) with no dead-time.

Figure 19. Frequency measurement when arming stop is set the same as arming start (back-to-back measurements) In case Smart versions of Frequency/Period Average are used, each sub-gate (Sample Interval divided by 1000) is being armed, i.e. one sample is calculated using data from 1000 arming gates.
InputInputSampleAny, except Totalize, Frequency, Period Average, Smart Frequency, Smart Period AverageStart arming is used as a pacing clock – a single sample measurement is executed just after active edge of arming pulse. Stop arming delays registration of timestamps other than the first one.   Depending on particular measurement mode, two, three or four timestamps are registered that give a single result.

Figure 20. Pulse width measurement with arming on sample and start and stop arming active, case 1

Figure 21. Pulse width measurement with arming on sample, start and stop arming active, case 2
Table 2. Arming modes

Start arming is useful for measurement of frequency in signals, such as the following:

  • Pulse modulated RF signals (bursts) Single-shot events or non-cyclic signals.
  • Pulsed signals where pulse width or pulse positions can vary. Signals with frequency variations versus time (“profiling”).
  • A selected part of a complex waveform signal.

Signal sources that generate complex wave forms like pulsed RF, or sweep signals, usually also produce a sync signal that coincides with the start of a sweep, or start of a radar burst. These sync signals can be used to arm the Analyzer. See Figure 21.

Figure 22. Sync signal used as start arming starts the measurement.

You normally use stop arming together with start arming. That means that the external gating signal controls both the start and the stop of the measurement. Such a gating signal can be used to measure the frequency of an RF burst signal. Here the position of the external gate must be inside a burst. See Figure 22.

Figure 23. Start and stop arming together is used for burst signal gating.

Note that burst measurements with access to an external sync signal are performed in the normal Frequency mode. In time interval measurements, you can use the stop arming signal as a sort of “external trigger Hold Off signal”, blocking stop trigger during the external period. See Figure 24.

Figure 24. Using start/stop arming as an external Hold-Off

Please note: start arming setup time is up to 5 ns. Which means that the measurement is actually started within 5 ns since start arming event.

1.5. Measurement Functions

1.5.1. Frequency/Period

There are several functions suited for measuring Frequency or Period. Next sections provide details about each particular function and when one should be preferred over another.

1.5.1.1. Frequency/Period Average measurements

These are the most universal measurement functions for Frequency and Period. In this mode each sample is a Frequency/Period value averaged over sample interval (which acts as gate).

This is back-to-back measurement with no dead-time between the samples (see chapter 4.6 Arming for exceptions). 4 input signals can be measured in parallel. Minimal sample interval is 50 ns. Up to 32 million samples total can be measured in a single measurement session. Resolution is 12 digits per 1 s of gate time (Sample Interval).

If the signal period is greater or equal to the set Sample Interval – each signal period can be captured. When measuring Frequency/Period Average on inputs A, B, D, E and Trigger Mode is set to Auto or Relative, wide hysteresis (see details below) is used to improve noise tolerance. In this mode 2 comparators with different trigger levels are used for each input. First trigger level (e.g. Trigger Level A) defines the upper limit of wide hysteresis band and the second one (e.g. Trigger Level A2) defines the lower limit. Trigger Mode Auto sets trigger levels to 60% and 40% of signal’s voltage range and Relative allows modifying them to fine tune the hysteresis band.

Figure 25. Frequency/Period Average measurement with Wide Hysteresis

Without wide hysteresis, the signal needs to cross the approx. 20 mV in case of 1x Attenuation (200 mV in case of 10x) input hysteresis band before triggering occurs. This hysteresis prevents the input from self-oscillating and reduces its sensitivity to noise. If signal noise is comparable or higher than hysteresis band – it can result in false extra triggering producing erroneous counts. These could ruin the measurement.

Figure 11 shows how spurious signals can cause the input signal to cross the trigger or hysteresis window more than once per input cycle and give erroneous counts. Figure 12 shows that a wide enough hysteresis prevents false counts.

Figure 26. Too narrow hysteresis gives erroneous triggering on noisy signals.
Figure 27. Wide trigger hysteresis gives correct triggering.

1.5.1.2. Smart Frequency/Period

Smart Frequency/Period is based on the same principle as normal Frequency/Period Average. Measurement gate is divided into 1000 sub-gates, giving additional samples and statistics resolution enhancement algorithm is applied on top of it. Thanks to that it allows to get up to 1 extra digit of resolution per 1 s of gate time (depending on input signal and measurement settings).

This comes with expense of additional constraints though. Minimal possible Sample Interval for Smart Frequency/Period is 50 us with possibility to measure up to 32000 samples per measurement session. Setting Sample Interval to 40 ms or more allows to get up to 4290000 samples per measurement session.

This is back-to-back measurement with no dead-time between the samples (see chapter 4.6 Arming for exceptions). 4 signals can be measured in parallel. Wide Hysteresis is used in Trigger Modes Auto and Relative.

Smart Frequency/Period is the best choice when one needs maximal possible resolution and can bear with lower sampling rate and sample count per session.

Please, note: resolution enhancement algorithm is based on the assumption that signal frequency is static. If it is not the case – the algorithm won’t be effective and it might make sense to fall back to normal Frequency/Period Average. Please note: section Frequency C measurement. Applies to Smart Frequency C as well.

1.5.1.3. Period Single

This measurement function is handy if one needs to capture individual periods of continuous signals or single cycles which are less than 50 ns. Individual periods starting from 2.5 ns can be captured.

This is not a back-to-back measurement, meaning that there is a dead-time of 50 ns between the samples if High-Speed license is installed, 1 us otherwise. 2 signals can be measured in parallel. Up to 16 million samples total can be measured in a single measurement session.

Unlike Frequency/Period Average and their Smart versions, Period Single doesn’t use wide hysteresis. So only one comparator is used on A, B, D, E and Trigger Mode Auto sets trigger level to the middle of signal voltage range (Relative Trigger Level 50%).

Please, note: when measuring non-continuous signal or single cycles, Trigger Mode Auto/Relative might fail to find proper trigger level. One need to fall back to Manual Trigger Mode in this case.

1.5.1.4. Frequency Ratio

In Frequency Ratio mode, the instrument measures Frequency Average of up to 4 signals in parallel and then divides the resulting frequencies of any two signals. Since the instruments measures on four input channels in parallel, two frequency ratio values can be displayed in parallel.

This is back-to-back measurement with no dead-time between the samples. 4 input signals can be measured in parallel. Minimal sample interval is 50 ns if High-Speed license is installed, 1 us otherwise. Up to 16 million samples total can be measured in a single measurement session.

1.5.2. Time Interval and Phase

1.5.2.1. Time Interval

This function allows to measure phase delay between clock signals with the same nominal frequency. At least N + 1 signal cycles are needed on each measurement input to get N Time Interval samples.

Figure 29. Time Interval Continuous measurement mode

Time intervals in the range [-1000 s .. 1000 s] can be measured. Resulting values are normalized to always be in the range [-0.5 * Period .. Period].

4 input signals can be measured in parallel. Minimal sample interval is 50 ns. Up to 16 million samples total can be measured in a single measurement session.

Please note: Time Interval Continuous is not suitable for measuring time interval between single shot events, use Time Interval Single instead.

When using Sample Interval close to 50 ns, actual sample interval might vary between 50 ns and 100 ns. In case of Time Interval measurement – it can result in generating less samples than was ordered by Sample Count setting. To avoid this please consider setting Sample Interval to 0 if you need minimal sample interval between samples. Setting Time Interval to 0 disables Sample Interval clock, meaning taking samples as fast as possible (close to 50 ns if signal period is 50 ns or greater).

1.5.2.2. Accumulated Time Interval

Accumulated Time Interval is useful for comparing phase delay between signals with the same nominal frequencies, but when frequencies of individual signals have small constant offset to each other. Time Interval will gradually increase over time and then drop after reaching value equal to signal Period, thus forming a sawtooth like graph. Accumulated Time Interval corrects this by adding or subtracting signal Period to Time Interval values when necessary. Other than that, it is exactly the same measurement as Time Interval Continuous.

Figure 30. Time Interval Continuous of 2 clock signals with constant frequency offset
Figure 31. Accumulated Time Interval of the same clock signals

As can be seen on Figure 26 and Figure 27, Accumulated Time Interval gives much better view on relative clock drift over time.

1.5.2.3. Time Interval Single

This function should be used to measure Time Interval between single events. Sample Interval setting is discarded, samples are captured as fast as it is possible.

Time intervals in the range [-1000 s .. 1000 s] can be measured. Resulting values are not normalized.

4 input signals can be measured in parallel. Minimal sample interval is 50 ns. Up to 16 million samples total can be measured in a single measurement session.

1.5.2.4. Measuring Time Interval between different trigger points of the same signal

Thanks to the presence of 2 comparators on each of A, B, D, E inputs it is possible to measure Time Interval, Accumulated Time Interval, Time Interval Single, Phase and Accumulated Phase between 2 trigger points inside the same signal.

This can be useful for measuring intervals inside multi-level a signal, e.g. TDR measurement.

Figure 32. Measuring Time Interval between 2 levels of reflected signal in TDR measurement allows to calculate the distance to cable break
Figure 33. Analyzer configuration for TDR measurement on Figure 28

Another example is measuring time interval from start on input A positive slope to input A negative slope to input B positive slope to input B negative slope. This can be achieved by selecting Time Interval A, A2, B, B2 and specifying trigger levels and slopes accordingly (see Figure 30).

Figure 34. Example configuration for Time Interval A to A to B to B measurement

However, Time Interval A to A to A to A is not possible since that would require 4 different trigger conditions on input channel A, while only 2 comparators are present.

1.5.2.5. Phase

Phase is similar to Time Interval but with phase delay expressed as angle. This measurement assumes same nominal frequency on all measured inputs. At least N + 1 signal cycles are needed on each measurement input to get N Phase samples.

Figure 35. Phase measurement mode

During this measurement, the Analyzer estimates continuous Time Interval and clock Period and calculates Phase as following:

Phase= 360°×((Time Interval)/Period)

where

Time Interval=TSCH3-TSCH1Period= TSCH2-TSCH1

Resulting Phase values are normalized to always be in the range [-180° .. 360°].

2 input signals can be measured in parallel. Minimal sample interval is 50 ns. Up to 16 million samples total can be measured in a single measurement session.

The typical measurement case is to measure the phase shift in various electronic components or systems, for example, filters or amplifiers. In this case, the input A signal is the input signal to the filter/amplifier, and the input B signal is the output signal from the filter/amplifier. That means that the input A and B signals are typically sine waves, with exactly the same frequency per test point, and the phase should be constant with zero drift (per test point).

Another typical use case is to compare two ultra-stable signals from different sources, but with the same nominal frequency, and express their phase difference in degrees. Then the signal shape could be both sine or pulse, and there is a possibility for a small phase drift between the signals.

1.5.2.6. Accumulated Phase

The same as for Time Interval, there is an Accumulated version of Phase measurement function to ease drift visualization over time when clock signals in comparison have same nominal frequency with a slow phase drift. But it has no meaning for phase measurements on sources with a more erratic behavior, or when the two frequencies are not the same.

1.5.3. Time Interval Error (TIE)

Please note: license is needed to unlock TIE option.

TIE measurement uses continuous back-to-back time-stamping to observe slow phase shifts (wander) in nominally stable signals during extended periods of time. The measurement itself is performed the same way as Frequency/Period Average but different processing is applied.

TIE is only applicable to clock signals, not data signals. Monitoring distributed PLL clocks in synchronous data transmission systems is a typical application.

The nominal frequency of the signal under test can be either manually or automatically set. Auto detects the frequency from the first samples, and rounds to number of digits set by the user (5 by default). TIE is measured as the period deviation of the input signal from the “ideal” reference period, and the accumulated deviation, up or down, is calculated for each Sample Interval, and displayed.

4 input signals can be measured in parallel. Minimal sample interval is 50 ns. Up to 32 million samples total can be measured in a single measurement session. Resolution is 12 digits per 1 s of gate time (Sample Interval).

TIEA(B/D/E)(i) = TSCHx (i)-TSCHx (1)-(((EVENT_CNTCHx (i)-EVENT_CNTCHx (1))/F_ref)

Figure 36. TIE measurement

1.5.4. Pulse characterization

1.5.4.1. Positive and Negative Pulse Width

Positive pulse width measures the time between a rising edge and the next falling edge of the signal. Negative pulse width measures the time between a falling edge and the next rising edge of the signal.

The selected trigger slope is the start trigger slope. The Analyzer automatically selects the inverse polarity as stop slope.

Figure 37. Pulse width measurement

This is not a back-to-back measurement, meaning that there is a dead-time of 50 ns between the samples. 2 signals can be measured in parallel. Up to 16 million samples total can be measured in a single measurement session.

1.5.4.2. Positive and Negative Duty Cycle

Duty cycle (or duty factor) is the ratio between pulse width and period time. The Analyzer determines this ratio by simultaneously making a pulse width measurement and a period measurement, and calculates the duty factor as:

Figure 38. Duty cycle measurement

This is not a back-to-back measurement, meaning that there is a dead-time of 50 ns between the samples. 2 signals can be measured in parallel. Up to 16 million samples total can be measured in a single measurement session.

1.5.4.3. Rise Time, Fall Time, Rise-Fall Time

By convention, rise/fall time measurements are made with the trigger levels set to 10% (start) and 90% (stop) of the maximum pulse amplitude. For ECL circuits, the reference levels are instead nominally 20 % (start) and 80 % (stop). In this case one can use Relative Trigger Levels mode and set trigger levels to 20% and 80% respectively.

Figure 39. Rise Time and Fall Time measurement

These are not a back-to-back measurement, meaning that there is a dead-time of 50 ns between the samples.

Rise Time and Fall Time functions can measure up to 2 signals in parallel with up to 16 million samples per session total.

Rise-Fall Time function can measure only 1 signal but provides both rise and fall time at once. Up to 8 million samples total can be measured in one measurement session.

Figure 40. Rise Time vs Rise-Fall Time

1.5.4.4. Positive and Negative Slew Rate

Slew rate is the speed of voltage change on pulse positive or negative edge. Hence, Positive and Negative Slew Rate are based on Rise Time and Fall Time measurements, the following formulae are applied:1.1.1.     Positive and Negative Slew Rate

1.5.5. Totalize

Totalize functions count the number of trigger events on Analyzer inputs. There are few modes Totalize can operate in. See next sections for details. In each of these modes the user can choose between Totalize, Totalize X+Y, Totalize X-Y or Totalize X/Y.

1.5.5.1. Manual Totalize

If neither Start nor Stop Arming is used, Totalize operates in so-called Manual Totalize mode.

In this mode RESTART button start counting trigger events, while HOLD/RUN button is used to pause and resume the counting. Sample Interval setting has no effect, samples are generated each 100 ms.

1.5.5.2. Timed Totalize

Setting Start Arming Source to Off and Stop Arming Source to Timer enables so-called Totalize Timed Mode.

In this mode RESTART button start counting trigger events for time duration set by Sample Interval (which defines the length of Totalize Gate). Single sample is generated after the end of the Gate.

1.5.5.3. Armed Totalize

If both Start Arming Source and Stop Arming Source are set, then start and stop arming events define start and stop of Totalize Gate for each Sample (Arm On setting is ignored, the Analyzer uses arming in Sample implicitly).

See 4.6 Arming for details on this Totalize mode.

1.5.6. Voltage

The Analyzer measures the voltage by searching the minimum and maximum signal levels. See 4.2 Voltage measurement principles for details.

Vmin, Vmax and Vpp functions allow measuring voltage on 4 inputs in parallel, Vminmax allows only one input but provides both – min and max – at the same time. Resolution is 1 mV, up to 16 million samples can be acquired in one measurement session.

1.6. Measurement cheat-sheet

1.6.1. Generic hints

  • Whenever you find yourself in trouble while setting up the measurement – use Autoset:
    • Connect the signals,Choose measurement function/inputs,Choose Sample Count and Sample Interval,
    • Press Autoset button,

And it will find proper settings for most cases when measuring continuous signals.

  • Use Auto choice for settings items unless you understand the implications of selecting other option.
  • Settings → User Option → Recall Defaults will reset measurement settings to Defaults.
  • Save complex measurement configurations as Presets (Settings → Measurement Presets or dedicated icon on measurement screen). In this case you can easily recreate the same measurement setup if you need it later.
  • Make sure input circuits are setup appropriately:
    • Use Auto-trigger for signals above 100 Hz, otherwise make sure Absolute trigger level is set. appropriately (prefer using Autoset for low frequency signal – it will set trigger levels for you).Make sure input impedance is set correctly.Use only DC coupling for low frequency signals and rely on Autoset to setup proper trigger levels.Keep Preamp OFF, except for extremely low input signal levels (below 50 mVrms).Keep Attenuation 1x, except for signals with amplitudes above exceeding +/- 5V.
    • Keep Filter OFF, except for low frequency sine wave signals (below 100 kHz).
  • Settings → Advanced → Voltage Mode should be set to Normal, except for signals below 100 Hz. For signals below 100 Hz please use Autoset to let the counter select best voltage mode for you. Set Voltage mode explicitly only if Autoset fails to find appropriate instrument setup (e.g. for not continuous signals)

1.6.2. Measuring 1 PPS

Hints:

  • Set DC on inputs 1 PPS signals are connected to,
  • Select measurement function and inputs,
  • Set Sample Interval to 0,
  • Use Autoset or set Trigger Mode to Manual and set Trigger Level to the middle of 1 PPS signal voltage range.

Same is most of the time true for signals below 100 Hz.

1.6.3. Measuring single cycles or pulses

Hints:

  • Set DC on the inputs, which the signals are connected to,
  • Select:
    • Period Single for measuring single cycle frequency period, or
    • Time Interval Single for measuring intervals between events, or
    • Totalize for counting events, or
    • Any function from Pulse group for measuring pulse characteristics.

Please note: using other functions will not give reliable results for single cycles/pulses.

  • Set Trigger Mode to Manual and set Trigger Level to the middle of signal voltage range.

Please note: auto-trigger won’t work for single cycles/pulses.

1.6.4. Measuring Frequency/Period

See 6.2 Measuring 1 PPS if signal is below 100 Hz.

Hints:

  • The basic setting Sample Interval in the Measurement menu is central to all Frequency related measurement. This setting means the same as Measuring time, or Gate time, used by other counter manufacturers.

A long Sample Interval (Gate time) increases resolution (counting during a longer time) but decreases measurement speed. The Sample Interval is always a compromise between how many digits you want to read, and how fast you want to take your frequency samples. For normal bench use – 200 ms is a good choice, because it is hard for the eye to follow faster changes in the displayed value.

The CNT-104S will give 12-13 digits resolution with 1 s Sample Interval, 9 digits with 1 ms Sample interval, and 6 digits with 1 μs Sample Interval

  • Use AC Coupling because possible DC offset is normally undesirable.
  • Use Trigger Mode Auto and/or Autoset.
  • Use Preamp ON for signals with amplitudes below 200 mVpp.

Please note: amplifying the signal also amplifies the noise.

  • Sample Interval of 200 ms is a reasonable tradeoff between measurement speed and resolution on the bench.

1.6.5. Time measurements of continuous signals

Hints:

  • Use DC coupling.
  • High signal level, and Steep signal edges.

1.6.6. Jitter measurements

Statistics provides an easy method of determining the short term timing instability, (jitter) of pulse parameters.

Note: that the measured pulse parameter should be a single cycle value, whether it is period, or pulse width.

1.6.6.1. Single cycle jitter

Single cycle jitter made on random samples of single periods, is usually specified with its rms value, which is equal to the standard deviation based on single measurements. The Analyzer can then directly measure and display the rms jitter. Jitter can also be expressed as peak-to-peak value, which is also displayed in the Statistics screen.

1.6.6.2. Cycle-to-cycle jitter

Cycle-to-cycle jitter demands zero dead-time measurements without gaps and can be made on input signals with a jitter frequency of up to 20 MHz. There is currently no dedicated measurement function, but the raw data of a Period Average measurement, with Sample Interval of 0 or down to 50 ns, could be exported to e.g. Matlab or Excel for “number crunching” and analysis.

1.6.6.3. Wander measurements

Wander measurements, which is a “slow jitter” measurement with jitter frequencies <10 Hz is made by using the TIE function, which compares the accumulated period phase drift, with the ideal phase from an ideal clock.

1.6.6.4. Deterministic jitter

Deterministic jitter is revealed in the Distribution graph, which will show underlying noise sources in a clear way. For example a sine modulated noise source would give a bathtub shape, a pulse modulated noise source would give a twin peak shape, and a measurement of a source containing not one, but two, fundamental frequencies will be displayed as “double hump”.

1.6.7. Frequency Modulated Signals

A frequency modulated signal is a carrier wave signal (CW frequency = f0) that changes in frequency to values higher and lower than the frequency f0. It is the modulation signal that changes the frequency of the carrier wave.

The Analyzer can accurately measure:

  • f0 = Carrier frequency.
  • fdev = Frequency deviation = (fmax -fmin)/2. And via the timeline graph, you will also get a good indication of the modulation frequency fmod

1.6.7.1. Initial capture settings

The optimum settings is to find a balance between large enough sample intervals to achieve high resolution per individual frequency sample, max. 10% of the Frequency deviation.

And small enough Sample intervals to capture enough frequency samples per modulation cycle for good graph visibility.

A rule of thumb is that the number of samples per modulation cycle should be >10, for good graphical view of the modulation signal, and acceptable error of fmax and fmin

Example: 10 kHz modulation frequency (100 us modulation cycle) of a 200 MHz carrier with 200 kHz deviation (0.1% modulation).

Set Sample interval to 10 μs (10% of the modulation cycle). Set Sample Count (N) to 100 (to cover 10 modulation cycles).

Now every frequency sample will have a resolution of  (10 ps/10 μs) x 200 MHz = 200 Hz.

This resolution is 1000 times better than the frequency deviation.

Start measurement and view the Timeline graph, which will show10 modulation cycles, with 10 samples per modulation cycle.

To improve the graphical experience, lower Sample Interval to 1 μs (1% of the modulation cycle), and increase Sample Count to 1000.

Now each frequency sample has a resolution of (10ps/1μs) x 200 MHz = 2 kHz. Still with a lot of margin to deviation.

You may want to play around with the Sample Interval and Sample Count setting until you have found your optimum view of the FM signal (no of displayed mod. cycles).

1.6.7.2. Carrier Wave Frequency f0

To determine the carrier wave frequency, just look at fmean which is best approximation of f0.

Ideally the sum of all Sample Intervals should be selected to cover an integer number of modulation periods. This way the positive frequency deviations will compensate the negative deviations during the measurement.

Example: If the modulation frequency is 1 kHz, the Sample Interval 10 μs and N = 1000 will make the Analyzer measure exactly 10 complete modulation cycles. A bad combination of Sample Interval and N would worst case mean that exactly half a modulation cycle is uncompensated for, giving a max. error for a sine modulation of:

f0 – fmean = Δfmax / (sample int.) x N x fmod x π

For very accurate measurements of the carrier wave frequency f0, make an extra measurement session and set Sample Interval as close as possible to an integer number of modulation cycles, and increase the number of samples substantially. A worst case error of half a modulation cycle means far less in a million cycles compared to 10 cycles.

1.6.7.3. Frequency deviation fmax - f0

Read the max, min, and mean frequency values from statistics screen or beneath the graph and calculate fdev as either:

  • fmax – fmean
  • fmean – fmin
  • fp-p/2

These three values should be exactly the same for an ideal sine wave or square wave modulation.

1.6.7.4. Modulation frequency fmod

The modulation frequency is easiest found by visual estimate in the graph on screen by using Cursors. Place one cursor on the beginning of the first modulation cycle and the other – on the end of the last modulation cycle. If the end point time difference between cursors is T seconds and the exact integer number of modulation cycles between cursors is M, the modulation frequency is:

fmod = M/T

1.6.7.5. Errors in fmax, fmin, and fp-p

A too large Sample Interval compared to the modulation cycle time leads to an averaging error that will underestimate the true deviation. A Sample interval corresponding to 10% of the modulation cycle, or 36° of the modulation signal, leads to an error of approx. 1.5%.

If that error is not acceptable, decrease the Sample Interval to make more samples than 10 during the modulation cycle.

1.6.8. Frequency profiling

Profiling means measuring and plotting frequency variation versus time. Examples are measuring warm-up drift in signal sources over hours, measuring the linearity of a frequency sweep during seconds, VCO switching characteristics during milliseconds, or the frequency changes inside a “chirp radar” pulse during sub-microseconds.

The Analyzer can handle many profiling measurement situations with some limitations. In profiling applications, the Analyzer acts as a fast, high-resolution sampling front end, storing results in its internal memory. These results are later displayed on screen and/or transferred to the controller for analysis and graphical presentation.

You must distinguish between two different types of measurements called free-running and repetitive sampling.

1.6.8.1. Free-Running Measurements

Free-running measurements are performed over periods down to the sub-microseconds range, e.g., to measure initial drift of a signal generator or oscillator, to plot linearity of a sweep signal ramp, or to measure short-term stability down to microsecond averaging times. In these cases, measurements are performed at user-selected Sample Intervals, and performed as gap-free measurements in the range 50 ns to 1000 s.

Just start the block measurement and view the profile in the graph presentation mode.

1.6.8.2. Repetitive Sampling Profiling

The measurement setup just described will not work when the profiling demands less than 50 ns intervals between samples.

How to do a VCO step response profiling with 50 samples during a time of 1 us.

This measurement scenario means that you need to come to 20 ns between samples (50 points * 20 ns = 1 ms observation time).

You will need a repetitive input step signal, and you have to repeat your measurement 50 times, taking one new sample per cycle. And every new sample should be delayed 20 ns with respect to the previous one.

Profiling can theoretically be done manually, but the best would be to perform this series of measurements with a dedicated program on PC, controlling the Analyzer and collecting data from it remotely.

The following are required to setup a measurement:

A repetitive input signal (e.g., frequency output of VCO). An external SYNC signal (e.g., step voltage input to VCO). Use of start arming delay (20, 40, 60 ns, etc). See Figure 38 for a test setup diagram.

Figure 41. Setup for transient profiling of a VCO.

1.6.8.3. Vrms

When the waveform (e.g. sinusoidal, triangular, square) of the input signal is known, its crest factor, defined as the quotient (QCF) of the peak (Vp) and RMS (Vrms) values, can be used to set the constant K in the mathematical function K*X+L. The display will then show the actual Vrms value of the input signal, assuming that Vpp is the main parameter.

Example: A sine wave has a crest factor of 1.414 (√2), so the constant in the formula above will be 0.354.

1.7. Other features

1.7.1. Hold-off

Hold-off function allows to insert dead-time into input trigger circuit which effectively acts as a digital lowpass filter. Hold-off can be set to 0 (Hold-off OFF) or  in the range [20 ns .. 2.683 s] which correspond to low-pass filter frequency from 100 MHz down to 0.5 Hz.

Setting Hold-off to approx. 75% of the cycle time of the signal allows to inhibit erroneous triggering for noisy signals.

Figure 42. Using hold-off as a Digital LP filter to cope with erroneous triggering on noisy signal

Hold-off is also an effective measure to cope with contact bouncing on the front of the signal under test.

Figure 43. Using Hold-off to cope with switch bounce effect

You should be aware of a few limitations to be able to use the Hold-off feature effectively and nambiguously. First you must have a rough idea of the frequency to be measured. A cutoff frequency that is too low might give a perfectly stable reading that is too low. In such a case, triggering occurs only on every 2nd, 3rd or 4th cycle. A cutoff frequency that is too high (>2 times the input frequency) also leads to a stable reading. Here one noise pulse is counted for each half-cycle.

1.7.2. Timeout

If stop arming is not used, the Analyzer ends measurement when all requested samples have been collected. However, if signal is absent (or lost) on one of the inputs used for the measurement – timestamps from this channel will never come and Analyzer will wait forever unless measurement is stopped explicitly.

However, in many cases this is undesirable behavior. For example in an automated test system when absence of signal can be a result of a wrong test setup or device under test malfunction, it is would be a waste of time to wait until the expected end of a long measurement to discover that one of the signals is just missing.

This is where Timeout function comes to help. If Timeout is ON, the measurement will end in case there are no samples from one of measurement inputs for the time duration set by Timeout Time.

1.7.3. Calibration

1.7.3.1. Internal Calibration

The Analyzer has a possibility to compensate for some internal sources of error by the means of internal calibration. This procedure doesn’t require any external signal, the Analyzer can perform it automatically.

Performing internal calibration before the start of measurement helps getting maximum accuracy and best resolution. However, because internal calibration takes up to 2 s it has impact on measurement speed which might be important in automated test systems. Hence, the Analyzer allows to choose the schedule of internal calibration. Summarizes available options.

ModeDescription
Every 30 minutesThe Analyzer performs internal calibration every 30 minutes between successive measurements or when it is idle. This is the default option which provides the best trade-off between accuracy, resolution and average measurement speed.
Before every measurementThe analyzer performs internal calibration before each timing measurement to ensure best resolution and accuracy. This results in additional time overhead of around 2 s per measurement session. If such overhead is not critical – this is the recommended choice.
Once (after warm-up)The Analyzer performs internal calibration only once – after the instrument has warmed up. This guarantees no calibration overhead, but resolution will deteriorate over time.
Table 4. Internal Calibration Modes

To provide maximum flexibility, the Analyzer also provides the possibility to perform internal calibration implicitly. This is especially useful when Interpolator Calibration Mode is set to Once.

All above can be configured under Settings Advanced section (see Figure 39).

Figure 44. Internal Calibration configuration

1.7.3.2. Timebase Calibration

For increasing measurement accuracy, a good reference source can be used for timebase calibration. Connect the source to Input A, select SettingsTimebase Calibration, choose reference frequency and start the procedure. It is possible to interrupt the process midway, re-apply result from previous calibration or reset to factory calibration setting.

Figure 45. Timebase Calibration menu

1.7.3.3. Voltage Calibration

For increasing accuracy of voltage measurements and manual trigger level setting accuracy, a good  source of DC voltage can be used for voltage calibration. Open Settings Voltage menu, select the input to be calibrated and follow the instructions.

Figure 46. Voltage Calibration menu

Please note: voltage calibration sets inputs to 1 MOhm impedance.

1.7.4. Mathematics

The Analyzer can use five mathematical expressions to process the measurement result before it is displayed:

  • K×X+L
  • K/X+L
  • (K×X+L)/M
  • (K/X+L)/M
  • X/M-1

Select Settings -> Mathematics to enter the mathematics submenu.

Figure 47. Mathematics menu

The default values of K (Scale factor), L (Offset) and M (Reference value) are chosen to 1, 0 and 1 respectively, so that the measurement result is not affected directly after activating Math. Recalling the default setting will restore these values as well.

It is possible to apply Mathematics function to all measurement series or to selected one.

When Mathematics is turned on, the Analyzer status bart shows MATH indicator.

1.7.4.1. Example use cases

If you want to observe the deviation from a nominal frequency, for example 10 MHz, instead of the absolute frequency itself, you can do like this:

  • Select Math
  • Select the expression K×X+L
  • Select K = 1 (if not already set)
  • Select L = -10 MHz
  • Now the display will show the deviation from the value you have just entered.

By changing the constant K you can scale the result instead. Set for example K = 60 to convert Frequency in Hz to RPM (revolutions per minute) from rotation transducers.

Use the expression X/M-1 if you want the result to be displayed as a relative deviation. The result will be displayed as

%, ppm, ppb, or as a dimensionless number like +1.2345E-12

1.7.5. Limits

Limits feature is used for setting numerical limits and selecting the way the instrument will report the measurement results in relation to them.

Figure 48. Limits configuration

Limit Behavior setting defines how the device will react on limits:

  • Off – limits are not checked.
  • Capture – only samples meeting the limit criterion are captured, the rest are discarded. Limit status is displayed.
  • Alarm – all samples are captured; limit status is displayed.
  • Alarm Stop – measurement session stops if measured value doesn’t meet the limit criterion.

Limit Type:

  • Above – results above set Lower Limit will pass.
  • Below – results below set Upper Limit will pass.
  • Range – results within the set limits will pass.

Limits can be applied to all measurement series or to selected one, depending on user’s choice.

When Limit Behavior is not Off, Analyzer status bar shows LIM. It will change to LIM! if at least one sample didn’t meet set Limit criterion during measurement session.

Numeric, Graph and Distribution screens will also have additional Limit indicators displayed.

1.7.6. Pulse Output (option)

Please note: license is needed to unlock Pulse Output functionality in the Analyzer

Figure 50. Pulse Output configuration

Pulse Output is located on rear panel of the Analyzer and can be used for one of the following purposes:

  • Pulse Generator. Pulse period can be selected from the range [10 ns .. 2.147 s] in 2 ns steps, pulse width – in the range [6 ns .. 2.147 s] in 2 ns steps.
  • Gate Open. Indicates if measurement is in progress.
  • Alarm Out. Indicates when Limits Alarm is active. Can be selected between Active High and Active Low

Irrespective to the selected mode, the amplitude of Pulse Output signal is set to TTL levels into 50 Ohm termination

1.7.7. Network

The Analyzer supports wired 10/100/1000 Mbps connection as well as wireless (via external USB Wi-Fi adapter).

It has IPv4 support and can be configured in either Static or Dynamic (DHCP) mode. If Static mode is selected, user is expected to manually enter IP address, Network mask and Gateway. For Dynamic mode, these fields are read-only and display IP address, network mask and gateway that are currently in use.

Figure 51. Network configuration

1.7.7.1. Web Interface

The Analyzer has built in web server that provides Web Interface allowing to see the instrument screen and control it remotely, download files and upgrade firmware.

Figure 52. Web Interface

1.7.7.2. VNC

The Analyzer also exposes VNC server on port 5901 which allows remote access and control. One can use any VNC client software on PC, mobile phone or tablet.

1.7.8. Front USB ports

Front panel USB ports can be used for connecting:

  • Peripherals (PC keyboard and mouse) which complement the touch screen interface.
  • USB storage for saving measurement results, presets or upgrading firmware.
  • Wi-Fi adapter for enabling wireless networking.

1.7.9. File Manager

The Analyzer has built-in File Manager accessible via Settings User Options File Manager or dedicated icon on measurement screen.

1.7.10. Firmware Update

There are 2 ways of updating firmware of the Analyzer:

Update via Web Interface (preferred):

  • Download SW update file (it has .swu extension) to your PC
  • Connect CNT-104S to LAN: either via ethernet cable or use supported Wi-Fi dongle to connect via Wi-Fi
  • On CNT-104S open Settings -> User Options -> Network to check or set current IP address
  • On PC, open web browser and put CNT-104S address to adress field. CNT-104S Web Interface will open
  • Click Software Update link on top right and follow the instructions

Update via USB stick:

  • Copy SW update file (it has .swu extension) to USB stick
  • Insert USB stick to one of the CNT-104S front panel USB ports
  • On CNT-104S Open Settings -> User Options -> Firmware Update to open Firmware Update screen
  • On CNT-104S Firmware Update screen tap/click on SW update file. SW update will start. No progress indication will be displayed – wait until CNT-104S reboots

1.7.11. Installing license

  • Put License File on USB stick
  • Plug it to one of front USB ports
  • Navigate to Settings User Options Import License
  • Select License to be imported

1.8. Performance Check

1.8.1. General Information

WARNING: Before turning on the in­strument, ensure that it has been installed in accordance with the In­stallation Instructions outlined in Chapter 1 of the User’s Manual.

This performance procedure is intended for:

  • checking the instrument’s specification.
  • incoming inspection to determine the ac­ceptability of newly purchased instruments and recently recalibrated instruments.
  • checking the necessity of recalibration af­ter the specified recalibration intervals.

NOTE: The procedure does not check every facet of the instrument’s calibration; rather, it is concerned primarily with those parts of the instrument which are essential for determining the function of the instrument.

It is not necessary to remove the instrument cover to perform this procedure.

1.8.2. Preparations

Power up your instrument at least 30 minutes before checking to let it reach normal operating temperature. Failure to do so may result in certain test steps not meeting equipment specifications.

1.8.3. Test Equipment

Type of EquipmentRequired Specifications
Reference Oscillator  10 MHz, 1×10-8 (e.g. 6688) for calibrating the standard TCXO oscillator
10 MHz, 1×10-9 (e.g. 6689) for calibrating Opt 30 & Opt 40 (OCXO)
Voltage CalibratorDC -50 V to +50 V (e.g. Fluke 5500) for calibrating the built-in voltage ref­erence, alternatively corresponding DC power supply + DVM with uncertainty <0.1 %
LF SynthesizerSquare/ Sine up to 10 MHz, 10 VRMS
Pulse Generator2 ns rise time, 5 V peak, >10 MHz, continuous & one-shot trigger
Oscilloscope1 GHz, <3% voltage uncertainty
RF Signal Generator0.1 to 3, 10, 15, 20, or 24 GHz dep. on RF input, <1dBm level uncertainty, 10 MHz ext.ref.
Power Splitter50 Ohm 6dB BNC
T-pieceBNC
Termination50 Ohm feed through BNC
Low-pass Filter50 kHz (for 1 MOhm) load
BNC CablesApprox. 10 pcs of suitable lengths
Table 5. Recommended equipment for calibration and performance check.

1.8.4. Internal Self-Tests

Internal self-tests are run on every instrument power up. In case of a failure information message box appears described the type of the error.

1.8.5. Front Panel Controls

1.8.5.1. Touch Panel and Keyboard Test

  • Press Settings icon on top right. Open User Options Recall Defaults. Confirmation dialog will appear.
  • Press Yes.
  • Press BACK hard button. Main Settings screen will appear.
  • Press Advanced, then press Signal Source and select Test.
  • Press ABOUT in bottom right corner. About box will appear.
  • Press OK.
  • Press HOME hard button. Measurement screen will appear. Frequency around 1 MHz will be measured.
  • Press HOLD hard button. Measurement will be put in HOLD after current one finishes.
  • Press RESTART hard button. Instrument will perform single measurement.
  • Press Measurement Function name in top left corner. Function selection dialog will appear.
  • Select Period Period Single A, B.
  • Press OK. Measurement screen will appear.
  • Press AUTOSET hard button. Autoset progress dialog will appear followed by “Autoset finished” notification.

1.8.6. Short Form Specification Test

1.8.6.1. Sensitivity and Frequency Range for Inputs A, B, D, E

  • Recall Defaults
  • Select Frequency A.
  • Select 50 Ω input impedance, 1x attenuation, Manual Trigger Levels and Absolute Trigger Level A 0V.
  • Select Preamp ON
  • Connect a signal from a HF generator to a BNC power splitter.
  • Connect the power splitter to Input A of your counter and an oscilloscope. Set the input impedance to 50 Ω on the oscilloscope.
  • Adjust the amplitude according to the following table. Read the level on the oscilloscope. The timer/counter should display the correct frequency.
  • Repeat the measurements and input settings above for Input B, D, and E.
Frequency   MHzLevel  Pass/Fail  
mVrmsdBm
1015-23 
5015-23 
10015-23 
20015-23 
30025-19 
40035-16 
Table 6. Sensitivity for inputs A, B, D & E at various frequencies

1.8.6.2. Sensitivity and Frequency Range for RF Input (Input C)

To verify the specifications of the different RF prescalers, use the following basic test setup:

  • Connect the output of a signal generator covering the specified frequency range to the RF input (C) of the Analyzer.
  • Connect the 10 MHz REF OUT from the generator to the EXT REFon the rear panel of the Analyzer. Choose External in Settings → Advanced → Timebase Reference.
  • Select Frequency C as Measurement Function.
  • Generate a sine wave in accordance with the data in the relevant table (Table 7, Table 8).
  • Verify that the Analyzer is counting correctly. (The last digits will be unstable).
Frequency GHzAmplitude dBm
0.1-0.3-21
0.3-2.5-27
2.5-2.7-21
2.7-3.0-15
Table 7. RF input sensitivity, Option 10 (3 GHz)
Frequency GHzAmplitude dBm
0.15-0.3-15
0.3-0.5-21
0.5-7.5-27
7.5-20-24
20-22-21
22-24-15
Table 8. RF input sensitivity, Option 110 (10, 15, 20 or 24 GHz)

1.8.6.3. Voltage

  • Recall Defaults.
  • Select Vpp A
  • Select DC coupling and Filter 10 kHz. Do not apply an input signal to Input A yet.
  • The display should now indicate (disregard the main parameter Vpp): Vmin= 0 ± 0.015 V and Vmax= 0 ± 0.015 V
  • Adjust the current limit of the DC voltage source to <200 mA.
  • Connect +2.500 Vdc to Input A, using the external 50 kHz low-pass filter on the input.
  • The display should now indicate: Vmin = 2.500 ± 0.040 V and Vmax = 2.500 ± 0.040 V Repeat the measurement with inverted polarity.
  • Select Input A and select 10x.

CAUTION: Before the next step, make sure the input impedance is still 1 MΩ. Applying more than 12 V without proper current limiting may cause extensive damage to the main PCB, if the impedance is set to 50 Ω.

  • Change the DC level to +50.00 V.
  • The display should now indicate: Vmin = 50.00 ± 0.65 V and Vmax = 50.00 ± 0.65 V Repeat the measurement with inverted polarity.
  • Disconnect the DC voltage from Input A. Remove the external low-pass filter.
  • Select Input A and select 1x.
  • Connect the LF generator to Input A, and set an amplitude of 4.000 Vpp and a frequency of 100 kHz. Verify the Amplitude with a good Voltmeter
  • The display should now indicate: 4.000 ± 0.150 Vpp.
  • Select Input A and select 10x.
  • Change the amplitude to 18.00 Vpp.
  • The display should now indicate: 18.00 ± 1 Vpp. Disconnect the LF generator from Input A.
  • Select Input A and select 1x, 50 ohm, and Filter = OFF.
  • Connect the RF generator to Input A and set an amplitude of 4.000 Vpp and a frequency of 100 MHz. Verify the amplitude on an oscilloscope.
  • The display should now indicate: 4.000 ± 0.40 Vpp. Select Input A and select 10x.
  • Change the amplitude to 18.00 Vpp.
  • The display should now indicate: 18.00 ± 2.2 Vpp
  • Proceed by repeating the measurements for Input B, D, and E, as described above for Input A.

1.8.6.4. Reference Oscillators

X-tal oscillators are affected by a number of external conditions like ambient temperature and supply voltage. Aging is also an important factor. Therefore, it is hard to give limits for the allowed frequency deviation. The user himself must decide the limits depending on his application and recalibrate the oscillator accordingly.

To check the accuracy of the oscillator you must have a calibrated reference signal that is at least five times more stable than the oscillator that you are testing. See Table 7-6 and the list of test equipment on page 7-2. If you use a non-10 MHz reference, you can use the mathematics in the timer/counter to multiply the reading.

  • Recall Defaults.
  • Connect the reference to input A
  • Check the readout against the accuracy requirements of your application.

1.8.6.5. Resolution Test

  • Connect the pulse generator to a power splitter.
  • Connect one side of the power splitter to Input A on the Analyzer using a coaxial cable.
  • Connect the other side of the power splitter to Input B on the Analyzer.

Settings for the pulse generator:

  • Amplitude = 4 Vpp, (high level +4 V and low level 0 V) Period = approx. 1 ms
  • Duration = approx. 50 ns
  • Rise time = 2 ns

Settings for the Analyzer:

  • Recall Defaults,
  • Select Time Interval Single A, B,
  • Set for Inputs A & B: 50 Ω, DC coupling, Manual Trigger Levels,
  • Set Absolute Trigger Level A to +1 V,
  • Set Absolute Trigger Level B to +1 V,

The standard deviation (std) should be less than 140 ps, corresponding to a resolution of 7 ps per timestamp.

1.8.7. Rear Inputs/Outputs

1.8.7.1. 10 MHz OUT

  • Connect an oscilloscope to the 10 MHz output on the rear of the Analyzer. Use a coaxial cable and 50 Ω termination.
  • The output voltage should be sinusoidal and >1Vp-p, typically 1Vrms.

1.8.7.2. EXT REF FREQ IN

  • Recall Defaults.
  • Connect a stable 10 MHz signal (e.g REF OUT from another counter/analyzer) to input A. Connect a 10 MHz, 100 mVRMS, (0.28 Vp-p) signal from the LF synthesizer to EXT REF. Select Ext Ref. from the Timebase Oscillator setting menu
  • The display should show 10 MHz.
  • Change the external reference frequency to 5 and 1 MHz.
  • The counting should continue, and the display should still show 10 MHz.

1.8.7.3. EXT ARM IN

  • Proceed from the test above.
  • Settings for the pulse generator:
    • single shot pulse,
    • manual trigger,
    • amplitude TTL = 0 – 2 VPP, and
    • duration = 10 ns.
  • Connect the pulse generator to Ext Arm Input.
  • Set Start Arming to EA on the Analyzer. The Analyzer does not measure.
  • Apply one single pulse to Ext Arm Input.
  • The Analyzer measures once and shows 10 MHz on the display.

1.8.7.4. PULSE OUT

  • Connect an oscilloscope to the pulse output on the rear panel with a 50 Ω coaxial cable terminated at the scope input with 50 Ω (internally or externally).
  • Enter Settings → Pulse Output.
  • Set Mode to Pulse Generator. Select Pulse Period and set the value to 1000 ns. Select Pulse Width and set the value to 500 ns.
  • The output signal should be a pure square wave signal with 1 MHz frequency and 50 % duty cycle. The rise/fall time should be approximately 2.5 ns. The low and the high level should be <0.2 V resp. >2.4 V.

1.8.8. Measuring Functions

  • Recall Defaults
  • Set Settings → Advanced → Signal Source to Test
  • Set Sample Interval to 200 ms
  • Set DC, 50 Ω, Manual Trigger Levels, Absolute Trigger Level to 0.5 V for Inputs A, B, D, E
  • Go through Measurement Functions from the Table 8 and verify the results.

Note that the results in the table are rounded off and very approximate. Test signal is not synchronized to Analyzer timebase and can generate Frequencies far from nominal. No tolerances are given for this test.

Measurement FunctionDisplayPass/Fail
Frequency A,B,D,E1 MHz 
Smart Frequency A,B,D,E1 MHz 
Frequency Ratio A,B,D,E1 
Period Average A,B,D,E1 us 
Smart Period Avg A,B,D,E1 us 
Period Single A,B (D, E)1 us 
Time Interval A,B,D,E>-100 ps, <100ps 
Time Interval Single A,B,D,E>-100 ps, <100ps 
Acc. Time Interval A,B,D,E>-100 ps, <100ps 
Phase A,B (D,E)0° (360°) 
Acc. Phase A,B (D,E)0° (360°) 
TIE0 s 
Pos. Duty Cycle A (B,D,E)0.5 
Neg. Duty Cycle A (B,D,E)0.5 
Pos. Pulse Width A,B (D,E)500 ns 
Neg. Pulse Width A,B (D,E)500 ns 
Rise Time A, B (D,E)< 5 ns 
Fall Time A, B (D,E)< 5 ns 
Rise-Fall Time A (B,D,E)< 5 ns 
Pos. Slew Rate A, B (D,E)>350 MV/s 
Neg. Slew Rate A, B (D,E)<-350 MV/s 
Totalize A,B,D,Eincrements 
Totalize X+Y A,B,D,Eincrements 
Totalize X-Y A,B,D,E0 
Totalize X/Y A,B,D,E1 
Vmin A,B,D,E0 V 
Vmax A,B,D,E2 V 
Vp-p A,B,D,E2 V 
Vminmax A (B,D,E)Vmin=0 V, Vmax=2 V 
Table 10. Measurement Functions check

1.8.8.1. Optional RF Input C

  • With an optional RF input (Input C) you will require an external RF source to verify Input C. A simple functional check can be performed by connecting a 1 GHz, -10 dBm signal after selecting Freq C. No other settings need to be changed.
  • Read 1 GHz on the display

1.8.9. Check of HOLD OFF Function

  • Recall Defaults
  • Select Period Single A
  • Set DC, 50 Ω for Input A
  • Connect the rear panel output marked 10 MHz Out to Input A. The Analyzer will display 100 ns
  • Increase Hold-Off Time setting (Settings → Measurement → Hold-Off Time) in steps from 0 s to 120 ns
  • While Hold-Off Time is below 100 ns the result will be about 100 ns (one period). As soon as Hold-Off Time exceeds 100 ns (e.g. 110 ns), the result displayed will be about 200 ns (two periods)

1.9. Specifications

1.9.1. Measuring Functions

Display modes

Values/Statistics: Numeric display of Measurement values or Statistics parameters with large digits. Values mode also display auxiliary parameter values (with less resolution).

Time-line/Distribution: All measurements are displayed graphically. Multi-channel graphs are colorcoded. Statistics values are also displayed beneath the graphs.

Resolution

Measure up to 4 input signals in parallel with 7 ps resolution per timestamp (Period single, Time Interval, Pulse width, Rise/Fall time, Duty cycle, TIE), or 12 digits/s (frequency and period average).

Smart Frequency/Period avg. calculation mode

Basic resolution for frequency and period average is 12 digits in 1s measuring time. Statistics resolution enhancement algorithm (smart mode) gives up to one extra result digit depending on input signal and measurement setting.

Frequency A, B, D, E

Mode: Parallel measurements on up to 4 inputs. Back-to-back, with or without smart calculation

Range: 0.001 Hz to 400 MHz Aux.

Parameter: Vmax, Vmin, Vp-p

Frequency C (option)

Mode: Back-to-back, with or without smart calculation

Range: See input C

Aux. Parameter: Period C

Frequency Ratio (A,B,C,D, or E) / (A,B,C,D, or E)

Mode: Parallel measurements on 2 or 4 inputs.

Range: (10-9) to 1011

Input Frequency: See input A,B,D,E and C

Aux Parameters: Freq 1, Freq 2

Period A, B, C, D, E average

Mode: Parallel measurements on up to 4 inputs. Back-to-back, with or without smart calculation

Range: See the inverse of Frequency specifications

Aux. Parameter:

  • Ch. A, B, D, E: Vmax, Vmin, Vp-p
  • Ch. C: Frequency C

TIE A, B, C, D, E (Option 151)

TIE = Time Interval Error, calculated as: Accumulated period – Expected (“ideal”) accumulated period

Mode: Parallel measurements on up to 4 inputs. Back-to-back.

Freq range: See Frequency specifications

Aux. Parameter: Ref Frequency

Period A, B, D or E single

Mode: Parallel measurements on 1 or 2 inputs.

Range 2.5 ns to 1000 sec.

Aux. Parameter (A, B): Vmax, Vmin, Vp-p

Time Interval A, B, D, E (single or continuous)

Mode: Parallel timestamping of trigger events on up to 4 channels on continuous or single-shot signals.

Start and stop channel(s): any of A, B, D, E

Note: each input can produce 1 or 2 trigger events with individual trigger level and slope

Accumulated Time Interval: ON or OFF (adding or subtracting one start channel period to the Time Interval, when required)

Range: -1000s to +1000s

Repetition rate: up to 400 MHz or single-shot events

Min. Pulse width: 1.5 ns

Channel-to-channel offset: 100ps rms typ.

Positive and Negative Pulse Width A, B, D, E

Mode: Parallel measurements on 1 or 2 inputs.

Range: 1.5 ns to 1000 sec.

Repetition rate: up to 300 MHz or single-shot events

Resolution: <10 ps per calculated result

Rise / Fall Time A, B, D, E

Mode: Parallel measurements on 1 or 2 inputs of Rise OR Fall time, or

Mode 2: Single input measurement of Rise AND Fall time on the same pulse.

Range: 1.5 ns to 1000 sec.

Aux. Parameters: Slew rate, Vmax, Vmin

Positive and negative Slew Rate A, B, D, E

Mode: Parallel measurements on 1 or 2 inputs

Calculation: (80% of Vp-p) / (Rise or Fall Time)

Aux. Parameters: Slew rate, Vmax, Vmin

Positive and Negative Duty Cycle A, B, D, E

Mode: Single input meaurement

Range: 0.000001 to 0.999999

Repetition rate: up to 300 MHz

Aux. parameters: Period, Pulse width

Phase A Relative B, B Relative A

Mode: Intended for phase shift or delay measurements of two signals with identical frequency

Accumulated Phase: OFF or ON (adding or subtracting 360o to the Phase, when required)

Range: -180° to +180° (Acc. Phase is OFF)

Resolution: 0.00003° to 100 kHz, decreasing to 0.03° >100 MHz. (10k sample statistics averaging)

Freq. Range: up to 300 MHz

Aux. Parameters: Freq (A), Va/Vb (in dB)

Totalize A, B, D, E

Inputs: up to 4 inputs (A, B, D, E)

Mode: Tot A, B, D, E; Tot A+B, D+E; Tot A-B, D-E: Tot A/B, D/E

Range: 1 to 1010 counts

Range: up to 400 MHz

Start control: Manual, start arming

Stop control: Manual, stop arming, timed

Vmax, Vmin, Vp-p A, B, D, E

Range: -5 V to +5 V, -50V to +50V

Freq. Range: DC, 100Hz to 200 MHz

Coupling: Sine (AC or DC), Square (DC only)

Resolution: 1 mV (5V range), 10 mV (50V range)

Uncertainty (5V range):

  • DC, 1Hz to 1kHz: <1% +15 mV
  • 1kHz to 20 MHz sine: 3% +15 mV (typ.)
  • 20 to 100 MHz sine: 10% +15 mV (typ.)
  • 100 to 200 MHz sine: 30% +15 mV (typ.)

(For square waves add 10% to Vmax,/min & 20% to Vp-p) (For 50V range, add 2% + 150 mV)

Aux parameters: Vmin, Vmax, Vp-p

1.9.2. Input Specifications

Inputs A, B, D and E

Frequency Range:

  • DC-Coupled: DC to 400 MHz
  • AC-Coupled: 10 Hz to 400 MHz

Impedance: 1MΩ // 40 pF or 50 Ω (VSWR ≤2:1 typ.)

Trigger Slope: Positive or negative

Channel-channel skew: <50 ps (after calibration)

Sensitivity (typical):

  • DC-400 MHz: <70 mVrms (PreAmp =OFF)
  • DC-100 MHz: 15 mVrms (PreAmp = ON)
  • 100-200 MHz: 25 mVrms (PreAmp = ON)
  • 200-400 MHz: 35 mVrms (PreAmp = ON)

Hysteresis window: approx. 20 mV (PreAmp=OFF)

Attenuation: x1, x10

Dynamic Range (x1):

PreAmp = OFF: 0.04 to 10 Vp-p within ±5V window

PreAmp = ON: 0.01 to 2 V p-p within ±1V window

Trigger Level: Read-out in menu

  • Resolution: 1mV
  • Uncertainty (x1): ±(15 mV + 1% of trigger level)

Trigger Level modes: Manual, Relative (to Vp-p), Auto

AUTO Trigger Level set to:

  • 50% point of input signal’s Vp-p, combined with a wide hysteresis between the 40% and 60% points, for frequency, period average, TIE
  • 10% and 90% points, for Rise/Fall Time, Slew
    rate, combined with minimum hysteresis
  • 50% point with minimum hysteresis for all
    other functions
  • Min. voltage 200 mVp-p

Analog LP Filter: Nominal 10 or 100kHz selectable.

Max Voltage Without Damage:

  • 1MΩ: 350 V (DC + AC pk) to 440 Hz, falling to 12 Vrms at 1MHz.
  • 50 Ω: 12 Vrms

Connector: BNC

Input C (Option 10)

Operating Input Voltage Range opt. 10:

  • 100 to 300 MHz: -21 dBm to +35 dBm
  • 0.3 to 2.5 GHz: -27 dBm to +35 dBm
  • 2.5 to 2.7 GHz: -21 dBm to +35 dBm
  • 2.7 to 3.0 GHz: -15 dBm to +35 dBm

Prescaler Factor: 16

Impedance: 50 Ω nominal, VSWR <2.5:1 typ.

Max Voltage without Damage: +35 dBm

Connector: Type N Female

Input C (Option 110)

Freq. Range: 0.4 to 24 GHz; SW license enabled to 10, 15, 20 or 24 GHz

Operating input voltage range:

  • 400 to 600 MHz: -21 to +27 dBm
  • 0.6 to 17 GHz: -27 to +27 dBm
  • 17 to 19 GHz: -24 to +27 dBm
  • 19 to 21 GHz: -21 to +27 dBm
  • 21 to 24 GHz: -15 to +27 dBm

Prescaler Factor: 64

Impedance: 50 Ω nominal, VSWR <2.0:1 typ.

AM tolerance: > 90% within sensitivity range

Max Voltage Without Damage: +27 dBm

Connector: 2.92 mm, SMA compa ble Female

1.9.3. Rear Panel Inputs and Outputs

Reference Input

Frequency: 1, 5, or 10 MHz; 0.1 to 5Vrms sine

Impedance: 50 Ω (nom.)

Reference Output

Source: External input if used, otherwise internal

Frequency: External ref freq., or 10 MHz (internal)

Output impedance: 50 Ω

Amplitude: 1Vrms sine into 50 Ω (nom.)

Arming Input

Arming of all measuring functions

  • Impedance: Approx. 1kΩ
  • Freq. Range: DC to 200 MHz
  • Trigger level: approx. 1.5V fixed
  • Trigger slope: Pos. or neg. selectable

Programmable Pulse Output (Option 132)

Pulse mode: Pulse generator, Gate open, Alarm

Period range: 10ns-2s in 2ns steps

Pos. Pulse width range: 4ns-2s in 2ns steps

Min negative pulse width: 6ns

Rise time: 2.5 ns (nom.)

Output impedance: 50 Ω (nom.)

Output level: Low <0.4V; High: 4.5-5.25V (open
output); 2.0-2.5V (50 ohm load)

1.9.4. Auxiliary Functions

Trigger Hold-Off

Time Delay Range: 20 ns to 2 s in 10 ns steps

External Start and Stop Arming

Modes:

  • Start Arming
  • Stop Arming
  • Ext. Gate (combined Start and Stop Arming)

Arming channels: A, B, D, E or rear panel ARM

Arming delay to first trigger ready: <5 ns (typ.)

Start/Stop Time Delay Range: 20 ns to 2 sec.

Statistics

Functions: Maximum, Minimum, Mean, Δmax-min, Standard Deviation and Allan Deviation

Display: Numeric or frequency distribution graph

Sample Size: 2 to 16×106 samples

Max. sample rate:

  • up to 140 kSa/s calculated
  • up to 20 MSa/s captured

Limit alarm

Graphical indication of limits with Pass/Fail message on front panel,

Limit Qualifier: OFF or Capture values above, below, inside or outside limits

Sample Interval (Gate time)

The Sample Interval sets the measuring time (gate) in Frequency/Period modes, the timing gate in Totalized timed measurements, and the time between measurements/samples in all other modes.

Range: OFF or 50 ns to 1000 sec.

Mathematics

Functions: OFF, (K*X-L)/M, (K/X-L)/M, X/M-1 X is current reading, and K (Scale factor), L (Nulling value) and M (Reference value) are constants

Other Functions

Timebase Reference: Internal, External or Autoselected

Restart: Aborts current measurement and starts a new

Run/Hold: Switch between RUN (continuous measurements) and HOLD (Freezes result, until a new measurement is initiated via Restart)

Save and Recall Settings and Measurements

Instrument Set-ups can be saved/recalled. Setups saved to internal memory can be user protected.

Measurement results (RAM) can be accessed by connected PC, and/or saved in internal non-volatile memory, and moved to USB stick.

Max. Measurement Speed and Storage size (RAM):

20 MSa/s (1 to 4 inputs): 16k samples

12.5 to 3.125 MSa/s (1 to 4 inputs): 32M samples

Display

Display: Graphic screen for menu control, numerical read-out, status information, plus distribution, trend and time-line graphs

Resolution: 1280×720 pixels

Type: Color Touch 5” TFT LCD display with backlight

Front panel accessible tools: Graph smoothing, pan and zoom, cursor read-out

1.9.5. Remote interfaces

Remote operation

Programmable Functions: All front panel accessible functions

Max. measurement rate (depending on measurement settings):

Block mode: up to 170k readings/s

Individual results: up to 200 readings/s

To Internal Memory: 20M readings/s

Data Output format: ASCII, IEEE double precision floating point, or packed

USB interface

USB version: 2.0

Connectors

Rear panel: 1x Type B; (Device) used for remote communication and data transfer both ways

Front panel: 2x Type A; (Host) used for FW updates, mouse/keyboard connec” on, external result storage, WiFi dongle

Protocol: USBTMC-USB488

LAN & WLAN interface

Speed: 10/100/1000 Mbps

Capabilities:

  • Web server
  • SCPI over HiSLIP protocol, compatibility with VISA

Supported WiFi USB-dongles: TP-Link TL-WN321G, TP-LINK Archer T4U v.2, TPLINK Archer T4U v.3, Netgear A6150 – AC1200, TP-Link TL-WN725N, Asus AC53Nano

1.9.6. Calibration of Timebase Oscillator

Mode: Closed case, electronic calibration, menu controlled. Calibration menu is password protected

Ref. Cal. Frequencies: 1, 5, 10, 1.544 or 2.048 MHz

1.9.7. General Specifications

Environmental Data

Class: MIL-PRF-28800F, Class 3

Installation category: II

Operating Temp:

0°C to +50°C / 5..75%RH bench-top,
0°C to +40°C / 5..75%RH rack-mount

Storage Temp: -40°C to +71°C

Vibration: Random and sinusoidal according to MIL-PRF-28800F, Class 3

Shock: Half-sine 30G per MIL-PRF-28800F; Bench handling

Transit drop test: According to MIL-PRF-28800F

Safety: EN 61010-1:2011, pollution degree 2, installation/over voltage category II, measurement category I, CE, indoor use only
CSA C22.2 No 61010-1-12

EMC: EN 61326-1:2013-06, increased test levels according to EN 61000-6-2:2008, Group 1, Class B, CE

Power Requirements

Max. Version: 100-240 VAC 50-60 Hz (Nom.), <70 W

Dimensions and Weight

Width x Height x Depth: 210 x 90 x 395 mm (8.25 x 3.6 x 15.6 in)

Weight: Net 3 kg (6.6 lb)

1.9.8. Time Base Options

Option modelSTD3040
Time base type:TCXOOCXOOCXO
Uncertainty due to:-Aging per 24h per month per year-Temperature variations: 0˚C to 50˚C 20˚C to 26˚C (typ. values)n/a <2×10-7 (typ.) <1×10-6 <5×10-7 not specified<5×10-10 (1) <1×10-8 <5×10-8 <5×10-9 <1×10-9<3×10-10 (1) <3×10-9 <1.5×10-8 <2.5×10-9 <4×10-10
Short-term stability: τ =1s (root Allan Variance) τ =10s<1×10-9 (typ.)<1×10-11 <1×10-11<5×10-12 <5×10-12
Power-on stability:Deviation vs. final value after 24 h on time, after a warm-up time of:<1×10-6 5 min<1×10-8 10 min<5×10-9 10 min
Typical total uncertainty, for operating temperature 20˚C to 26˚C, at 2σ (95%) confidence interval:
-1 year after calibration
-2 years after calibration
<1.2×10-6 <2.4×10-6<6×10-8 <1.2×10-7<1.8×10-8 <3.5×10-8
1After 1 month of continuous operation

1.9.9. Ordering Information

Basic model

CNT-104S: 4-channel 400 MHz Frequency Analyzer, 7 ps resolution, std. TCXO timebase 1 ppm/year

Input C Frequency Options

Option 10: 3 GHz Input C

Option 110: 10 GHz Input C (HW)

Option 110/15: SW upgrade from 10 to 15 GHz

Option 110/20: SW upgrade from 15 to 20 GHz

Option 110/24: SW upgrade from 20 to 24 GHz

Timebase Oscillator Options

Option 30: Very High Stability, OCXO 50 ppb/year

Option 40: Ultra High Stability, OCXO 15 ppb/year

Other options (SW license enabled)

Option 132: Programmable pulse output

Option 151: TIE measurement function

Included with Instrument:

  • 2 year product warranty1
  • Line cord (dependent on destination country)
  • Link to User documentation (PDF)
  • Certificate of Calibration
  • Important information document

1: Warranty period may be extended to 3 years, at no cost, by registrating the product

Optional Accessories

  • Option 22/90: Rack-Mount Kit- 1 unit
  • Option 22/05: Rack-Mount Kit -2 units
  • Option 27: Carrying Case – soft
  • Option 27H: Heavy-duty Hard Transport Case
  • Option 90/03: Calibration Certificate with Protocol; Standard TCXO oscillator
  • Option 90/06: Calibration Certificate with Protocol; Oven oscillator
  • Option 95/05: Extended warranty 2 extra years
  • OM-100: User’s Manual English (printed)2
  • PM-100: Programmer’s Manual English (printed)2
  • SM-100: Service Manual English
  • GS-100-EN: Getting Started English (printed)2

2: Always available as download from the Pendulum website

1.10. Sales and Service Contacts

For additional product information, customer support and service, please contact Pendulum Instruments at the following addresses:

Pendulum Instruments

SWEDEN
Madviksvägen 4, 370 22 Drottningskär, Sweden
Moravägen 1, 782 31 Malung
Phone: +46 280 41122

UNITED STATES
50 Woodside Plaza # 642, Redwood City, CA 94061
Phone: +1(866) 644-1230  (toll free)

POLAND
Lotnicza 37, 80-297 Banino, Poland
Phone: +48 (58) 681 89 01

CHINA
Room 1208, 12F, Building 2, Fuhai Center Daliushu,
Haidian District, Beijing 100081
Phone: +86 13501221550

General Enquiries
info@pendulum-instruments.com

Request A Quotation
sales@pendulum-instruments.com

Orderdesk
orderdesk@pendulum-instruments.com

Technical Support
service@pendulum-instruments.com

2. CNT-90/91/91R/91RAF/90XL

2.1. GENERAL INFORMATION User Manual CNT-90/91/91R/91RAF/90XL

About this Manual

This manual contains directions for use that apply to the Timer/Counter/Analyzers CNT-90 and CNT-91 as well as the Frequency Calibrator/Analyzer CNT-91R and CNT-91R/AF and the Mi­crowave Counter/Analyzer CNT-90XL.

In order to simplify the references, these instruments are further referred to throughout this manual as the ‘9X’, whenever the information applies to all types. Differences are clearly marked.

Examples:

  • CNT-90 means CNT-90 and CNT-90/XL
  • CNT-90/91 means CNT-90 and CNT-91
  • CNT-91(R) means CNT-91, CNT-91R and CNT-91R/AF

Chapter 8, Specifications is divided into four separate sections to increase legibility. Much of the contents is common, so redundant data is the price in this case.

Warranty

The Warranty Statement is part of the folder Important Information that is included with the shipment.

Declaration of Conformity

The complete text with formal statements concerning product identification, manufacturer and standards used for type testing is available on request.

2.2. Chapter 1: Preparation for Use

2.2.1. Preface

2.2.1.1. Introduction

Congratulations on your choice of instrument. It will serve you well and stay ahead of most competition for many years to come, whether in bench-top or rack system use. It gives significantly increased performance compared to traditional Timer/Counters. The ‘9X’ offers the following advantages:

  • 12 digits of frequency resolution per sec­ond and 50 or 100 ps resolution, as a re­sult of high-resolution interpolating recip­rocal counting.
  • A high measurement rate of up to 250k  readings/s to internal memory.
  • Optional oven-controlled timebase oscilla­tors, except the CNT-91R & CNT-91R/AF, which have an ultra-stable rubidium oscillator.
  • CNT-90, CNT-91(R): A variety of RF prescaler options with up­per frequency limits ranging from 3 GHz to 20 GHz.
  • CNT-91R/AF: Special version of CNT-91R with selected Rubidium oscillator, plus 5 Reference frequency outputs covering 100 kHz, 1 MHz, 5 MHz, and 10 MHz. Model CNT-91R/AF has a 3 GHz input C and CNT-91R/AF/20G has a 20 GHz input C as standard
  • CNT-90XL: A number of microwave inputs with upper frequency limits ranging from 27 to 60 GHz.
  • CNT-90(XL): Optional Pulsed RF for RF pulse characterization up to 60 GHz carrier frequency and down to 30 ns pulse width.
  • Optional built-in Li-Ion battery supply realizes instant high-precision measurements in the field and true UPS operation.
  • Integrated high performance GPIB inter­face using SCPI commands.
  • A fast USB interface that replaces the tra­ditional but slower RS-232 serial interface
  • Optional external GPIB-to Ethernet controller that allows connection to LAN .

2.2.1.2. Design Innovations

2.2.1.3. Remote Control

This instrument is programmable via two in­terfaces, GPIB and USB.

The GPIB interface offers full general func­tionality and compliance with the latest stan­dards in use, the IEEE 488.2 1987 for HW and the SCPI 1999 for SW.

In addition to this ‘native’ mode of operation there is also a second mode that emulates the Agilent 53131/132 command set for easy ex­change of instruments in operational ATE systems. The USB interface is mainly intended for the lab environment in conjunction with the op­tional TimeView™ analysis software. The communication protocol is a proprietary ver­sion of SCPI.

2.2.2. Safety

2.2.2.1. Introduction

Even though we know that you are eager to get going, we urge you to take a few minutes to read through this part of the introductory chapter carefully before plugging the line con­nector into the wall outlet.

This instrument has been designed and tested for Measurement Category I, Pollution Degree 2, in accordance with EN/IEC 61010-1:2001 and CAN/CSA-C22.2 No. 61010-1-04 (in­cluding approval). It has been supplied in a safe condition. Study this manual thoroughly to acquire ade­quate knowledge of the instrument, especially the section on Safety Precautions hereafter and the section on Installation on page 1-7.

2.2.2.2. Safety Precautions

All equipment that can be connected to line power is a potential danger to life. Handling restrictions imposed on such equipment should be observed.

To ensure the correct and safe operation of the instrument, it is essential that you follow gen­erally accepted safety procedures in addition to the safety precautions specified in this manual.

These units are designed for indoor use only.

The instrument is designed to be used by trained personnel only. Removing the cover for repair, maintenance, and adjustment of the instrument must be done by qualified personnel who are aware of the hazards involved.

The warranty commitments are rendered void if unauthorized access to the interior of the instrument has taken place during the given warranty period.

2.2.3. Unpacking

Check that the shipment is complete and that no damage has occurred during transportation. If the contents are incomplete or damaged, file a claim with the carrier immediately. Also notify your local Spectracom sales or service organization in case repair or replacement may be required.

2.2.3.1. Check List

The shipment should contain the following:

  • Counter/Timer/Analyzer CNT-90/91 or Frequency Calibrator/Analyzer CNT-91R or CNT-91R/AF or Microwave Coun­ter/Analyzer CNT-90XL
  • Line cord
  • Brochure with Important Information
  • Certificate of Calibration
  • Options you ordered should be installed. See Identification below.
  • CD including the following documentation in PDF:
    • Getting Started Manual
    • User’s Manual
    • Programmer’s Handbook

2.2.3.2. Identification

The type plate on the rear panel shows type number and serial number. See illustrations on page 2-5 and 2-6. Installed options are listed under the menu User Options – About, where you can also find information on firmware version and calibration date. See page 2-15. The CNT-91R/AF version is identified by a unique identification marking, or UID. This permanent tag contains a barcode and allows customers to track easily their inventory and property.

2.2.3.3. Installation

2.3. Chapter 2: Using the Controls

2.3.1. Basic Controls

A more elaborate description of the front and rear panels including the user interface with its menu system follows after this introductory survey, the purpose of which is to make you familiar with the layout of the instrument. See also the appendix.

2.3.2. Secondary Controls

2.3.2.1. Connectors & Indicators

2.3.2.2. Rear Panel

Pulse Output [CNT-91(R) only]: User definable to serve as output for built-in pulse gener­ator, gate indicator or alarm.

Optional Main Input Connectors (not with Option 23/90): The front panel inputs can be moved to the rear panel by means of an optional cable kit. Note that the input capacitance will be higher.

Type Plate: Indicates instrument type and serial number.

Fan: A temp. sensor controls the speed of the fan. Normal bench-top use means low speed, whereas rack-mount­ing and/or options may result in higher speed.

Protective Ground Terminal: This is where the protective ground wire is connected inside the in­strument. Never tamper with this screw!

Line Power Inlet: AC 90-265 Vrms, 45-440 Hz, no range switching needed.

Reference Output: 10 MHz derived from the internal or, if present, the external reference.

External Reference Input: Can be automatically selected if a signal is present and approved as timebase source, see Chapter 9.

External Arming Input: See page 5-7.

GPIB Connector: Address set via User Options Menu.

Ext. DC Connector: Part of Option 23/90 for CNT-90(XL). Range: 12-18 V Note the polarity.

USB Connector: Universal Serial Bus (USB) for data communication with PC.

2.3.2.3. Rear Panel (CNT-91R/AF)

Pulse Output [CNT-91(R) only]: User definable to serve as output for built-in pulse gener­ator, gate indicator or alarm.

Additional output frequencies Connectors: These connectors provide additional out­put frequencies which are, from left to right, 100kHz, 1MHz, 5MHz and 10MHz.

Type Plate: Indicates instrument type and serial number.

Fan: A temp. sensor controls the speed of the fan. Normal bench-top use means low speed, whereas rack-mount­ing and/or options may result in higher speed.

Protective Ground Terminal: This is where the protective ground wire is connected inside the in­strument. Never tamper with this screw!

Line Power Inlet: AC 90-265 Vrms, 45-440 Hz, no range switching needed.

Reference Output: 10 MHz derived from the internal or, if present, the external reference.

External Reference Input: Can be automatically selected if a signal is present and approved as timebase source, see Chapter 9.

External Arming Input: See page 5-7.

GPIB Connector: Address set via User Options Menu.

USB Connector: Universal Serial Bus (USB) for data communication with PC.

2.3.3. Description of Keys

2.3.3.1. Power

The ON/OFF key is a toggling secondary power switch. Part of the instrument is always ON as long as power is applied, and this standby condition is indicated by a red LED above the key. This indicator is consequently not lit while the instrument is in operation.

CNT-91R and CNT-91R/AF only

While the rubidium oscillator is warming up, an open padlock symbol labeled RB is flash­ing at the top right corner of the display, indi­cating that the control loop is not locked. Normal time to lock is about 5 min. Do not start measuring until the unlock symbol disappears.

New Message Box

Information exchange between the rubidium oscillator and the CPU takes place over a serial bus. Any malfunction in the UART-con-trolled communication link will be reported in a pop-up message box on the display.

CNT-90(XL) w. Option 23/90

The User Interface Screens have two indica­tors near the upper right corner of the display. One is a power supply status indicator, and the other is a battery charging level indicator.

The status indicator shows:

  • a fixed battery symbol when the internal battery is the active power source
  • a charging battery symbol when the in­ternal battery is being charged
  • a power plug symbol when the mains is the active power source
  • a power plug symbol on top of a battery symbol when the instrument has been prepared for UPS operation and charging is not going on

The charging level indicator shows:

  • the relative charging level in percent

2.3.3.2. Select Function

This hard key is marked MEAS FUNC.

When you depress it, one of the menus below will open.

Fig. 2‑1 CNT-90: Select measurement function.
Fig. 2-2    CNT-90XL: Select measurement function.
Fig. 2-3    CNT-91(R): Select measurement function.

The current selection is indicated by text in­version that is also indicating the cursor posi­tion. Select the measurement function you want by depressing the corresponding softkey right below the display.

Alternatively, you can move the cursor to the wanted position with the RIGHT/LEFT arrow keys. Confirm by pressing ENTER.

A new menu will appear where the contents depend on the function. If you for instance have selected Frequency, you can then select between Frequency, Frequency Ratio and Frequency Burst. Finally you have to decide which input channel(s) to use.

2.3.3.3. Autoset/Preset

By depressing this key once after selecting the wanted measurement function and input channel, you will most probably get a measure­ment result. The AUTOSET system ensures that the trigger levels are set optimally for each combination of measurement function and input signal amplitude, provided rela­tively normal signal waveforms are applied. If Manual Trigger has been selected before pressing the AUTOSET key, the system will make the necessary adjustments once (Auto Once) and then return to its inactive condition.

AUTOSET performs the following functions:

  • Set automatic trigger levels
  • Switch attenuators to 1x
  • Turn on the display
  • Set Auto Trig Low Freq to
    • 100 Hz, if fin >100 Hz, or to
    • fin, if 10<fin<100 Hz, or to
    • 10 Hz, if fin <10 Hz

A higher value means faster settling time.

By depressing this key twice within two sec­onds, you will enter the Preset mode, and a more extensive automatic setting will take place. In addition to the functions above, the following functions will be performed:

  • Set Meas Time to 200 ms
  • Switch off Hold-Off
  • Set HOLD/RUN to RUN
  • Switch off MATH/LIM
  • Switch off Analog and Digital Filters
  • Set Timebase Ref to Auto
  • Switch off Arming

Default Settings

An even more comprehensive preset function can be performed by recalling the factory de­fault settings. See page 2-16.

2.3.3.4. Move Cursor

There are four arrow keys for moving the cur­sor, normally marked by text inversion, around the menu trees in two dimensions.

2.3.3.5. Display Contrast

When no cursor is visible (no active menu se­lected), the UP/DOWN arrows are used for adjusting the LCD display contrast ratio.

2.3.3.6. Enter

The key marked ENTER enables you to con­firm a choice without leaving your menu position.

2.3.3.7. Save & Exit

This hard key is marked EXIT/OK. You will confirm your selection by depressing it, and at the same time you will leave the current menu level for the next higher level.

2.3.3.8. Don't Save & Exit

This hard key is marked CANCEL. By de­pressing it you will enter the preceding menu level without confirming any selections made at the current level. If the instrument is in REMOTE mode, this key is used for returning to LOCAL mode, unless LOCAL LOCKOUT has been programmed.

2.3.3.9. Presentation Modes

VALUE

Fig. 2-4    Main and aux. parameters.

Value mode gives single line numerical pre­sentation of individual results, where the main parameter is displayed in large characters with full resolution together with a number of auxiliary parameters in small characters with limited resolution.

Fig. 2-5    Limits presentation.

If Limit Behavior is set to Alarm and Limit Mode is set to Range you can visualize the de­viation of your measurements in relation to the set limits. The numerical readout is now com­bined with a traditional analog pointer-type in­strument, where the current value is represented by a “smiley”. The limits are presented as numerical values below the main parameter, and their positions are marked with vertical bars labelled LL (lower limit) and UL (upper limit) on the autoscaled graph.

If one of the limits has been exceeded, the limit indicator at the top of the display will be flashing. In case the current measurement is out of the visible graph area, it is indicated by means of a left or a right arrowhead.

STAT/PLOT

If you want to treat a number of measurements with statistical methods, this is the key to operate. There are three display modes available by toggling the key:

  • Numerical
  • Histogram
  • Trend Plot

Numerical

Fig. 2-6    Statistics presented numerically.

In this mode the statistical information is dis­played as numerical data containing the fol­lowing elements:

  • Mean: mean value
  • Max: maximum value
  • Min: minimum value
  • P-P: peak-to-peak deviation
  • Adev: Allan deviation
  • Std: Standard deviation

Histogram

Fig. 2-7    Statistics presented as a histo­gram.

The bins in the histogram are always autoscaled based on the measured data. Limits, if enabled, and center of graph are shown as vertical dotted lines. Data outside the limits are not used for autoscaling but are replaced by an arrow indicating the direction where non-displayed values have been recorded.

Trend Plot

Fig. 2-8    Running trend plot.

This mode is used for observing periodic fluc­tuations or possible trends. Each plot terminates (if HOLD is activated) or restarts (if RUN is activated) after the set number of samples. The trend plot is always autoscaled based on the measured data, starting with 0 at restart. Limits are shown as horizontal lines if enabled.

Remote

When the instrument is controlled from the GPIB bus or the USB bus, the operating mode changes to Remote, indicated by the label REM on the display. All front panel keys ex­cept CANCEL are then disabled. See also page 2-8 for more information on this key.

2.3.3.10. Entering Numeric Values

Sometimes you may want to enter constants and limits in a value input menu, for instance one of those that you can reach when you press the MATH/LIMIT key.

You may also want to select a value that is not in the list of fixed values available by pressing the UP/DOWN arrow keys. One example is Meas Time under SETTINGS.

A similar situation arises when the desired value is too far away to reach conveniently by incrementing or decrementing the original value with the UP/DOWN arrow keys. One example is the Trig Lvl setting as part of the INPUT A (B) settings.

Whenever it is possible to enter numeric val­ues, the keys marked with 0-9;. (decimal point) and ± (stands for Change Sign)take on their alternative numeric meaning.

It is often convenient to enter values using the scientific format. For that purpose, the rightmost softkey is marked EE (stands for Enter Exponent), making it easy to switch be­tween the mantissa and the exponent. Press EXIT/OK to store the new value or CANCEL to keep the old one.

2.3.3.11. Hard Menu Keys

These keys are mainly used for opening fixed menus from which further selections can be made by means of the softkeys or the cur­sor/select keys.

Input A (B)

Fig. 2-9    Input settings menu.

By depressing this key, the bottom part of the display will show the settings for Input A (B).

The active settings are in bold characters and can be changed by depressing the correspond­ing softkey below the display. You can also move the cursor, indicated by text inversion, to the desired position with the RIGHT/LEFT arrow keys and then change the active setting with the ENTER key.

The selections that can be made using this menu are:

  • Trigger Slope: positive or negative, indi­cated by corresponding symbols
  • Coupling: AC or DC
  • Impedance: 50 W or 1 MW
  • Attenuation: 1x or 10x
  • Trigger:1 Manual or Auto
  • Trigger Level:2 numerical input via front panel keyboard. If Auto Trigger is active, you can change the default trigger level manually as a percentage of the amplitude.
  • Filter:3 On or Off

Notes: Always Auto when measuring risetime or falltime

The absolute level can either be adjusted using the up/down arrow keys or by pressing ENTER to reach the numerical input menu.

Pressing the corresponding softkey or ENTER opens the Filter Settings menu. See Fig. 2-10. You can select a fixed 100 kHz analog filter or an adjustable digital filter. The equivalent cutoff frequency is set via the value input menu that opens if you select Digital LP Frequency from the menu.

Fig. 2-10    Selecting analog or digital filter.

Input B

The settings under Input B are equal to those under Input A.

Settings

This key accesses a host of menus that affect the measurement. The figure above is valid after changing the default measuring time to 10 ms.

Fig. 2-11     The main settings menu.

Meas Time

Fig. 2-12    Submenu for entering measuring time.

This value input menu is active if you select a frequency function. Longer measuring time means fewer measurements per second and gives higher resolution.

Burst

Fig. 2-13    Entering burst parameters.

This settings menu is active if the selected measurement function is BURST – a special case of FREQUENCY – and facilitates mea­surements on pulse-modulated signals. Both the carrier frequency and the modulating fre­quency – the pulse repetition frequency (PRF) – can be measured, often without the support of an external arming signal.

Arm

Fig. 2-14     CNT-90 & CNT-90XL: Setting arming conditions.
Fig. 2-15    CNT-91(R): Setting arming con­ditions.

Arming is the general term used for the means to control the actual start/stop of a measurement. The normal free-running mode is inhib­ited and triggering takes place when certain pretrigger conditions are fulfilled.

The signal or signals used for initiating the arming can be applied to three channels (A, B, E), and the start channel can be different from the stop channel. All conditions can be set via this menu.

NOTE:   Stop Delay can only be used for realizing the function Timed Totalize in the CNT-91(R).

Trigger Hold-Off

Fig. 2-16    The trigger hold-off submenu.

A value input menu is opened where you can set the delay during which the stop trigger conditions are ignored after the measurement

start. A typical use is to clean up signals gen­erated by bouncing relay contacts.

Statistics

Fig. 2-17    Entering statistics parameters.

In this menu you can do the following:

  • Set the number of samples used for calculation of various statistical measures.
  • Set the number of bins in the histogram view.
  • Pacing

The delay between measurements, called pacing, can be set to ON or OFF, and the time can be set within the range 2 ms – 500 s.

Timebase Reference

Fig. 2-18    Selecting timebase reference source.

Here you can decide if the counter is to use an Internal or an External timebase. A third al­ternative is Auto. Then the external timebase will be selected if a valid signal is present at the reference input. The EXT REF indicator at the upper right corner of the display shows that the instrument is using an external timebase reference.

Miscellaneous

Fig. 2-19    CNT-90: The ‘Misc’ submenu.
Fig. 2-20    CNT-90XL: The ‘Misc’ submenu.
Fig. 2-21     CNT-91(R): The ‘Misc’ submenu.

The options in this menu are:

  • Smart Measure with submenus:
    • Smart Time Interval (valid only if the selected measurement function is Time Interval) The counter decides by means of timestamping which measurement channel precedes the other.
    • Smart Frequency (valid only If the selected measurement function is Frequency or Period Average) By means of continuous timestamping and regression analysis, the resolution is increased for measuring times between 0.2 s and 100 s.
  • Input C Acquisition (CNT-90XL only) Auto means that the whole specified fre­quency range is scanned for valid input signals.

Fig. 2-22   CNT-90XL: The ‘Input C Acqui­sition’ submenu.

Manual means that a narrow band around the manually entered center fre­quency is monitored for valid input sig­nals. This mode is compulsory when measuring burst signals but is also rec­ommended for FM signals, when the ap­proximate frequency is known. An additional feature is that the measure­ment results are presented much faster, as the acquisition process is skipped.

NOTE:   Signal frequencies outside the manual capture range may cause erroneous results. In order to draw the operator’s attention to this eventuality, the sign “M.ACQ” is visible in the upper right corner of the display.

  • Auto Trig Low Freq: In a value input menu you can set the lower frequency limit for automatic trig­gering and voltage measurements within the range 1 Hz – 100 kHz. A higher limit means faster settling time and consequently faster measurements.
  • Timeout: From this submenu you can activate/deactivate the timeout function and set the maximum time the instrument will wait for a pending measurement to finish before outputting a zero result. The range is 10 ms to 1000 s.
  • Interpolatator Calibration: By switching off the interpolator calibra­tion, you can increase the measurement speed at the expense of accuracy.
  • TIE (CNT-91 only): From a submenu you can either let the counter choose the reference frequency automatically (Auto) or enter it manually.

Math/Limit

Fig. 2-23    Selecting Math or Limits pa­rameters.

You enter a menu where you can choose be­tween inputting data for the Mathematics or the Limits postprocessing unit.

Fig. 2-24    The Math submenu.

The Math branch is used for modifying the measurement result mathematically before presentation on the display. Thus you can make the counter show directly what you want without tedious recalculations, e.g. revolutions/min instead of Hz.

The Limits branch is used for setting numerical limits and selecting the way the instrument will report the measurement results in relation to them.

Let us explore the Math submenu by pressing the corresponding softkey below the display.

Fig. 2-25    Selecting Math formula for postprocessing.

The display tells you that the Math function is not active, so press the Math Off key once to open the formula selection menu.

Select one of the five different formulas, where K, L and M are constants that the user can set to any value. X stands for the current non-modified measurement result.

Fig. 2-26    Selecting formula constants.

Each of the softkeys below the constant labels opens a value input menu like the one below.

Fig. 2-27    Entering numeric values for constants.

Use the numeric input keys to enter the man­tissa and the exponent, and use the EE key to toggle between the input fields. The key marked X0 is used for entering the display reading as the value of the constant.

The Limit submenu is treated in a similar way, and its features are explored beginning on page 6-6.

User Options

Fig. 2-28    CNT-90: The User Options menu.
Fig. 2-29   CNT-90XL & CNT-90 with Option 23/90: The User Options menu.
Fig 2-30    CNT-91(R): The User Options menu.

From this menu you can reach a number of submenus that do not directly affect the measurement. You can choose between a number of modes by pressing the corresponding softkey.

Save/Recall Menu

Fig. 2-31     The menu appearance after pressing Save/Recall.

Twenty complete front panel setups can be stored in non-volatile memory. Access to the first ten memory positions is prohibited when Setup Protect is ON. Switching OFF Setup Protect releases all ten memory positions si­multaneously.

The different setups can be individually la­beled to make it easier for the operator to re­member the application.

Fig. 2-32   The memory management menu after pressing Setup.

The following can be done:

  • Save current setup
Fig. 2-33    Selecting memory position for saving a measurement setup.

Browse through the available memory positions by using the RIGHT/LEFT arrow keys. For faster browsing, press the key Next to skip to the next memory bank. Press the softkey below the num­ber (1-20) where you want to save the setting.

  • Recall setup
Fig. 2-34    Selecting memory position for recalling a measurement setup.

Select the memory position from which you want to retrieve the contents in the same way as under Save current setup above. You can also choose Default to restore the preprogrammed factory set­tings. See the table on page 2-19 for a complete list of these settings.

  • Modify labels

Select a memory position to which you want to assign a label. See the descrip­tions under Save/Recall setup above. Now you can enter alphanumeric char­acters from the front panel. See the fig­ure below.

The seven softkeys below the display are used for entering letters and digits in the same way as you write SMS messages on a cell phone.

  • Setup protection

Toggle the softkey to switch between the ON/OFF modes. When ON is ac­tive, the memory positions 1-10 are all protected against accidental overwriting.

Fig. 2-35    Entering alphanumeric charac­ters.

Dataset Menu

Fig. 2-36     The memory management menu after pressing Dataset.

This feature is available in statistics mode only, and if HOLD has been pressed prior to initiating a measurement with RESTART. Up to 8 different datasets can be saved in FLASH memory, each containing up to 32000 sam­ples. If the pending measurement has more than 32000 samples, only the last 32000 will be saved. A default label will be assigned to the dataset. It can be changed in a similar way as the setup labels. See Modify labels above.

  • Save: Select a memory position, accept or change the name, and press OK.
  • Recall: Select a memory position and press OK.
  • Total Reset: The safety screen below will appear. Pressing OK will restore all factory set­tings and erase all user information.

Fig. 2-37    The Total Reset safety screen.

Calibrate Menu

This menu entry is accessible only for calibra­tion purposes and is password-protected.

Interface Menu

Fig. 2-38 Selecting active bus interface. Bus Type

Select the active bus interface. The alterna­tives are GPIB and USB. If you select GPIB, you are also supposed to select the GPIB Mode and the GPIB Address. See the next two paragraphs.

GPIB Mode

There are two command systems to choose from.

  • Native: The SCPI command set used in this mode fully exploits all the features of this instru­ment series.
  • Compatible: The SCPI command set used in this mode is adapted to be compatible with Agilent 53131/132/181.

GPIB Address

Value input menu for setting the GPIB ad­dress.

Test

A general self-test is always performed every time you power-up the instrument, but you can order a specific test from this menu at any time.

Fig. 2-39    Self-test menu.

Press Test Mode to open the menu with avail­able choices.

Fig. 2-40    Selecting a specific test.

Select one of them and press Start Test to run it.

Digits Blank

Jittery measurement results can be made easier for an operator to read by masking one or more of the LSDs on the display.

Place the cursor at the submenu Digits Blank and increment/decrement the number by means of the UP/DOWN arrow keys, or press the soft key beneath the submenu and enter the desired number between 0 and 13 from the keyboard. The blanked digits will be represented by dashes on the display. The default value for the number of blanked digits is 0.

Misc (CNT-90XL & CNT-90 with Op­tion 23/90)

The CNT-90XL without Option 23/90 has a single submenu called Units. By pressing this softkey you get to the submenu Power. Press Power and then select dBm or W as the unit of measurement, when either of the functions Frequency C or Power C is selected from the MEAS FUNC menu.

The CNT-90 with Option 23/90 has a single submenu called Use Battery in Standby. By toggling this softkey you can decide if the in­ternal OCXO will remain powered or not when you turn off the instrument in battery operation mode.

The CNT-90XL with Option 23/90 has a combination of the two submenus mentioned above. See the figure below.

Fig. 2-41     The ‘Misc’ submenu for CNT-90XL with battery option.

Output [CNT-91(R) only]

The rear panel pulse output can be used for three different purposes:

  • pulse generator
  • gate indicator
  • alarm

Press the softkey Output to open the submenu below.

Fig. 2-42 Selecting output mode and pulse parameters.

Off is the default mode and inhibits all activity on the output connector.

The pulse generator parameters Period and Width can be entered by first pressing the corresponding softkeys, then setting the numerical values as usual. By placing the cursor over the parameter, you can also set the values directly in 1-2-5 steps with the UP/DOWN arrow keys.

Press Output Mode to enter the mode selection menu below:

  • Gate Open indicates to external equip­ment when a measurement is in progress.
  • Pulse Generator activates a continuous pulse train having the parameters en­tered in the previous menu.
  • Alarm can be set to be active low or ac­tive high. The MATH/LIM menu is used for setting up the behavior and the nu­merical limits that trigger the alarm.
Fig 2-43    Output Mode selection menu.

The amplitude is fixed at TTL levels into 50 Ω irrespective of the output mode.

About

  • Here you can find information on:
  • model
  • serial number
  • instrument firmware version
  • timebase option & calibration date
    • The CNT-91R reports “Rubidium” in this field.
  • RF input option
    • The CNT-90XL reports the upper frequency limit.

Hold/Run

This key serves the purpose of manual arm­ing. A pending measurement will be finished and the result will remain on the display until a new measurement is triggered by pressing the RESTART key.

Restart

Often this key is operated in conjunction with the HOLD/RUN key (see above), but it can also be used in free-running mode, especially when long measuring times are being used, e.g. to initiate a new measurement after a change in the input signal. RESTART will not affect any front panel settings.

2.3.4. Default Settings

See page 2-16 to see how the following prepro­grammed settings are recalled by a few key­strokes.

PARAMETERVALUE/SETTING
Input A & B
Trigger LevelAUTO
Trigger SlopePOS
Impedance1 MW
Attenuator1x
CouplingAC
FilterOFF
Arming
StartOFF
Start SlopePOS
Start Arm Delay0
StopOFF
Stop SlopePOS
Hold-Off
Hold-Off StateOFF
Hold-Off Time200 ms
Time-Out
Time-Out StateOFF
Time-Out Time100 ms
Statistics
StatisticsOFF
No. of Samples100
No. of Bins20
Pacing StateOFF
Pacing Time20 ms
Mathematics
MathematicsOFF
Math ConstantsK=1, L=0, M=1
Limits
Limit StateOFF
Limit ModeRANGE
Lower Limit0
Upper Limit0
Burst
Sync Delay400 ms
Start Delay0
Meas. Time200 ms
Freq. Limit400 MHz
Miscellaneous
FunctionFREQA
Smart FrequencyAUTO
Smart Time IntervalOFF
Meas. Time200 ms
Auto Trig Low Freq100 Hz
Timebase ReferenceAUTO
Blank Digits0
Interpolator calibrationON
Output (CNT-91(R))OFF

2.4. Chapter 3: Input Signal Conditioning

2.4.1. Input Amplifier

The input amplifiers are used for adapting the widely varying signals in the ambient world to the measuring logic of the timer/counter.

These amplifiers have many controls, and it is essential to understand how these controls work together and affect the signal.

The block diagram below shows the order in which the different controls are connected. It is not a complete technical diagram but in­tended to help understanding the controls.

The menus from which you can adjust the set­tings for the two main measurement channels are reached by pressing INPUT A respectively INPUT B. See Figure 3-2. The active choices are shown in boldface on the bottom line.

Fig. 3-1 Block diagram of the signal conditioning
Fig. 3-2 Input settings menu.

2.4.1.1. Impedance

The input impedance can be set to 1 MΩ or 50 Ω by toggling the corresponding softkey.

CAUTION: Switching the impedance to 50 Ω when the input voltage is above 12 Vrms may cause perma­nent damage to the input circuitry.

2.4.1.2. Attenuation

The input signal’s amplitude can be attenuated by 1 or 10 by toggling the softkey marked 1x/10x. Use attenuation whenever the input signal ex­ceeds the dynamic input voltage range ±5 V or else when attenuation can reduce the influence of noise and interference. See the section deal­ing with these matters at the end of this chap­ter.

2.4.1.3. Coupling

Switch between AC coupling and DC cou­pling by toggling the softkey AC/DC.

Fig. 3-3 AC coupling a symmetrical signal.

Use the AC coupling feature to eliminate un­wanted DC signal components. Always use AC coupling when the AC signal is superim­posed on a DC voltage that is higher than the trigger level setting range. However, we rec­ommend AC coupling in many other measure­ment situations as well.

When you measure symmetrical signals, such as sine and square/triangle waves, AC cou­pling filters out all DC components. This means that a 0 V trigger level is always cen­tered around the middle of the signal where triggering is most stable.

Fig. 3-4 Missing trigger events due to AC coupling of signal with varying duty cycle.

Signals with changing duty cycle or with a very low or high duty cycle do require DC coupling. Fig. 3-4 shows how pulses can be missed, while Fig. 3-5shows that triggering does not occur at all because the signal ampli­tude and the hysteresis band are not centered.

NOTE: For explanation of the hysteresis band, see page 4-3.

Fig. 3-5 No triggering due to AC coupling of signal with low duty cycle.

2.4.1.4. Filter

If you cannot obtain a stable reading, the sig­nal-to-noise ratio (often designated S/N or SNR) might be too low, probably less than 6 to 10 dB. Then you should use a filter. Certain conditions call for special solutions like highpass, bandpass or notch filters, but usu­ally the unwanted noise signals have higher frequency than the signal you are interested in. In that case you can utilize the built-in lowpass filters. There are both analog and dig­ital filters, and they can also work together.

Fig. 3-6 The menu choices after selecting FILTER.

Analog Lowpass Filter

The counter has analog LP filters of RC type, one in each of the channels A and B, with a cutoff frequency of approximately 100 kHz, and a signal rejection of 20 dB at 1 MHz.

Accurate frequency measurements of noisy LF signals (up to 200 kHz) can be made when the noise components have significantly higher frequencies than the fundamental signal.

Digital Lowpass Filter

The digital LP filter utilizes the Hold-Off function described below.

With trigger Hold-Off it is possible to insert a deadtime in the input trigger circuit. This means that the input of the counter ignores all hysteresis band crossings by the input signal during a preset time after the first trigger event.

When you set the Hold-Off time to approx. 75% of the cycle time of the signal, erroneous triggering is inhibited around the point where the input signal returns through the hysteresis band. When the signal reaches the trigger point of the next cycle, the set Hold-Off time has elapsed and a new and correct trigger will be initiated. Instead of letting you calculate a suitable Hold-Off time, the counter will do the job for you by converting the filter cutoff frequency you enter via the value input menu below to an equivalent Hold-Off time.

Fig. 3-7 Value input menu for setting the cutoff frequency of the digital filter.

You should be aware of a few limitations to be able to use the digital filter feature effectively and unambiguously. First you must have a rough idea of the frequency to be measured. A cutoff frequency that is too low might give a perfectly stable reading that is too low. In such a case, triggering occurs only on every 2nd, 3rd or 4th cycle. A cutoff frequency that is too

high (>2 times the input frequency) also leads to a stable reading. Here one noise pulse is counted for each half-cycle.

Use an oscilloscope for verification if you are in doubt about the frequency and waveform of your input signal. The cutoff frequency setting range is very wide: 1 Hz – 50 MHz

Fig. 3-8 Digital LP filter operates in the measuring logic, not in the input amplifier.

2.4.1.5. Man/Auto

Toggle between manual and automatic trigger­ing with this softkey. When Auto is active the counter automatically measures the peak-to-peak levels of the input signal and sets the trigger level to 50% of that value. The attenuation is also set automatically.

At rise/fall time measurements the trigger lev­els are automatically set to 10% and 90% of the peak values.

When Manual is active the trigger level is set in the value input menu designated Trig. See below. The current value can be read on the display before entering the menu.

Speed

The Auto-function measures amplitude and calculates trigger level rapidly, but if you aim at higher measurement speed without having to sacrifice the benefits of automatic trigger­ing, then use the Auto Trig Low Freq func­tion to set the lower frequency limit for volt­age measurement.

If you know that the signal you are interested in always has a frequency higher than a cer­tain value flow , then you can enter this value from a value input menu. The range for flow is 1 Hz to 100 kHz, and the default value is 100 Hz. The higher value, the faster measure­ment speed due to more rapid trigger level voltage detection.

Even faster measurement speed can be reached by setting the trigger levels manually. See Trig below.

Follow the instructions here to change the low-frequency limit:

  • Press SETTINGS->Misc->Auto Trig Low Freq.
  • Use the UP/DOWN arrow keys or the nu­meric input keys to change the low fre­quency limit to be used during the trigger level calculation, (default 100 Hz).
  • Confirm your choice and leave the SET­TINGS menu by pressing EXIT/OK three times.

2.4.1.6. Trig

Value input menu for entering the trigger level manually.

Use the UP/DOWN arrow keys or the nu­meric input keys to set the trigger level. A blinking underscore indicates the cursor po­sition where the next digit will appear. The LEFT arrow key is used for correction, i.e. deleting the position preceding the current cursor position.

Fig. 3-9 Value input menu for setting the trigger level.

NOTE:  It is probably easier to make small ad­justments around a fixed value by us­ing the arrow keys for incrementation or decrementation. Keep the keys de­pressed for faster response

NOTE:   Switching over from AUTO to MAN Trig­ger Level is automatic if you enter a trigger level manually.

Auto Once

Converting “Auto” to “Fixed”

The trigger levels used by the auto trigger can be frozen and turned into fixed trigger levels simply by toggling the MAN/AUTO key. The current calculated trigger level that is visible on the display under Trig will be the new fixed manual level. Subsequent measurements will be considerably faster since the signal levels are no longer monitored by the instrument. You should not use this method if the signal levels are unstable.

NOTE: You can use auto trigger on one input and fixed trigger levels on the other.

2.4.2. How to Reduce or Ignore Noise and Interference

Sensitive counter input circuits are of course also sensitive to noise. By matching the signal amplitude to the counter’s input sensitivity, you reduce the risk of erroneous counts from noise and interference. These could otherwise ruin a measurement.

Fig. 3-10 Narrow hysteresis gives errone¬ous triggering on noisy signals.
Fig. 3-11 Wide trigger hysteresis gives correct triggering.

To ensure reliable measuring results, the coun­ter has the following functions to reduce or eliminate the effect of noise:

  • 10x input attenuator
  • Continuously variable trigger level
  • Continuously variable hysteresis for some functions
  • Analog low-pass noise suppression filter
  • Digital low-pass filter (Trigger Hold-Off)

To make reliable measurements possible on very noisy signals, you may use several of the above features simultaneously. Optimizing the input amplitude and the trigger level, using the attenuator and the trigger con­trol, is independent of input frequency and useful over the entire frequency range. LP fil­ters, on the other hand, function selectively over a limited frequency range.

2.4.2.1. Trigger Hysteresis

The signal needs to cross the 20 mV input hysteresis band before triggering occurs. This hysteresis prevents the input from self-oscil­lating and reduces its sensitivity to noise. Other names for trigger hysteresis are “trigger sensitivity” and “noise immunity”. They ex­plain the various characteristics of the hyster­esis.

Fig. 3-12 Erroneous counts when noise passes hysteresis window.

Fig. 3-10 and Fig. 3-12 show how spurious signals can cause the input signal to cross the trigger or hysteresis window more than once per input cycle and give erroneous counts.

Fig. 3-13 Trigger uncertainty due to noise.

Fig. 3-13 shows that less noise still affects the trigger point by advancing or delaying it, but it does not cause erroneous counts. This trig­ger uncertainty is of particular importance when measuring low frequency signals, since the signal slew rate (in V/s) is low for LF sig­nals. To reduce the trigger uncertainty, it is de­sirable to cross the hysteresis band as fast as possible.

Fig. 3-14 Low amplitude delays the trig¬ger point

Fig. 3-14 shows that a high amplitude signal passes the hysteresis faster than a low ampli­tude signal. For low frequency measurements where the trigger uncertainty is of importance, do not attenuate the signal too much, and set the sensitivity of the counter high.

In practice however, trigger errors caused by erroneous counts (Fig. 3-10 and Fig. 3-12) are much more important and require just the op­posite measures to be taken.

To avoid erroneous counting caused by spuri­ous signals, you need to avoid excessive input signal amplitudes. This is particularly valid when measuring on high impedance circuitry and when using 1 MW input impedance. Under these conditions, the cables easily pick up noise.

External attenuation and the internal 10x attenuator reduce the signal amplitude, includ­ing the noise, while the internal sensitivity control in the counter reduces the counter’s sensitivity, including sensitivity to noise. Re­duce excessive signal amplitudes with the 10x attenuator, or with an external coaxial attenuator, or a 10:1 probe.

2.4.2.2. How to use Trigger Level Setting

For most frequency measurements, the optimal triggering is obtained by positioning the mean trigger level at mid amplitude, using either a narrow or a wide hysteresis band, de­pending on the signal characteristics.

Fig. 3-15 Timing error due to slew rate.

When measuring LF sine wave signals with little noise, you may want to measure with a high sensitivity (narrow hysteresis band) to re­duce the trigger uncertainty. Triggering at or close to the middle of the signal leads to the smallest trigger (timing) error since the signal slope is steepest at the sine wave center, see Fig. 3-15.

When you have to avoid erroneous counts due to noisy signals, see Fig. 3-12, expanding the hysteresis window gives the best result if you still center the window around the middle of the input signal. The input signal excursions beyond the hysteresis band should be equally large.

Auto Trigger

For normal frequency measurements, i.e. without arming, the Auto Trigger function changes to Auto (Wide) Hysteresis, thus wid­ening the hysteresis window to lie between 70 % and. 30 % of the peak-to-peak ampli­tude. This is done with a successive approxi­mation method, by which the signal’s MIN. and MAX. levels are identified, i.e., the levels where triggering just stops. After this MIN./MAX. probing, the counter sets the trig­ger levels to the calculated values. The default relative trigger levels are indicated by 70 % on Input A and 30 % on Input B. These values can be manually adjusted between 50 % and 100 % on Input A and between 0 % and 50 % on Input B. The signal, however, is only ap­plied to one channel.

Before each frequency measurement the coun­ter repeats this signal probing to identify new MIN/MAX values. A prerequisite to enable AUTO triggering is therefore that the input signal is repetitive, i.e., >100 Hz (default). Another condition is that the signal amplitude does not change significantly after the mea­surement has started.

NOTE:   AUTO trigger limits the maximum measuring rate when an automatic test system makes many measurements per second. Here you can increase the measuring rate by switching off this probing if the signal amplitude is constant. One single command and the AUTO trigger function determines the trigger level once and enters it as a fixed trigger level.

Manual Trigger

Switching to Man Trig also means Narrow Hysteresis at the last Auto Level. Pressing AUTOSET once starts a single automatic trigger level calculation (Auto Once). This cal­culated value, 50 % of the peak-to-peak am­plitude, will be the new fixed trigger level, from which you can make manual adjustments if need be.

Harmonic Distortion

As rule of thumb, stable readings are free from noise or interference.

However, stable readings are not necessarily correct; harmonic distortion can cause errone­ous yet stable readings. Sine wave signals with much harmonic distor­tion, see Fig. 3-17, can be measured correctly by shifting the trigger point to a suitable level or by using continuously variable sensitivity, see Fig. 3-16. You can also use Trigger Hold-Off, in case the measurement result is not in line with your expectations.

Fig. 3-16 Variable sensitivity.
Fig. 3-17 Harmonic distortion.

2.5. Chapter 4: Measuring Functions

3. SCPI Guide for CNT-104S

Preface

Please refer to User Manual for general description of instrument operation, measurement principles and concepts.

Introduction to SCPI

What is SCPI?

SCPI (Standard Commands for Programmable Instruments) is a standardized set of text-based commands used to remotely control programmable test and measurement instruments. It defines the syntax and semantics that a controller must use to communicate with the instrument. This manual is an overview of SCPI and shows how SCPI is used in Pendulum CNT-104S instrument. SCPI is based on IEEE-488.2 to which it owes much of its structure and syntax.

Syntax and style

Syntax of Program Messages

In SCPI all messages that you can send to an instrument are divided into two categories: commands (that do not imply getting any response) and queries (that allow to get response back from the instrument). Queries have question mark (‘?’) at the end of command header.

A command or query is called a program message unit. A program message unit consists of a header followed by zero or more parameters:

<header> [parameter [,parameter ,...]]

For example, in the query

FETCH:ARRAY? MAX, A

FETCH:ARRAY is a header and MAX and A are parameters.

One or more program message units (commands) may be sent within a simple program message:

<program message unit>; <program message unit>; <program message unit>...

For example,

:INIT; *OPC?

Common Commands

SCPI standard defines a set of commands that every instrument must support. The common command header starts with the asterisk character (*), for example *RST.

SCPI Commands Tree

SCPI command headers may consist of several keywords (mnemonics), separated by the colon character (:).

Each keyword in a SCPI command header represents a node in the SCPI command tree. The leftmost keyword is the root level keyword, representing the highest hierarchical level in the command tree.
The keywords following represent subnodes under the root node.

Example: :SYST:CONF "Sample Interval=15ms"

In this example first colon (:) referers to the root of the tree. Next, SYST refers to an item under root, and CONF referes to an item under SYST.

SCPI commands syntax description used in this manual

Short and long forms

According to SCPI each command header can have short and long form. In order to distinguish both forms in command syntax description, upper and lower case characters are used. Note, that SCPI is case-insensitive, the usage of upper and lower case characters is done solely for the purpose of syntax definition. You may even mix upper and lower case. There is no semantic difference between upper and lower case in program messages. Same applies for parameters – they may have short and long forms.

Example 1. Let’s consider such syntax description: SYSTem:CONFigure <parameters>
Here SYST and CONF specify the short form, and SYSTem and CONFigure specify the long form. It means that the instrument will accept the following command headers: syst:conf , SYST:CONF , SYSTEM:CONFIGURE, SYST:CONFIGURE, or even sYstEm:cOnFiGuRE. However, SYSTE or CONFIG headers are not allowed and will cause a command error, because they don’t refer to short or long forms.

Example 2. Let’s consider such syntax description :FORMat[:DATA] <format> , where <format> is one of ASCii, REAL or PACKed. Such argument syntax indicates that the argument may be specified as: ASCII, ASC, asc, REAL, real, PACKED, pack, PACK.

Default nodes and arguments

SCPI standard states that some nodes in SCPI commands tree may play role of default nodes. That means that it is not required to specify them in command headers. Same applies for arguments. In this manual optional nodes and arguments are denoted with square brackets.

For example, let’s consider the following syntax description: :FETCh[:SCALar]? [<series name>]

Here square brackets indicate the fact that the node inside them (SCALAR) is default node under its parent node (FETCH). That means that you can specify the header as: :FETCH or :FETCH:SCALAR and result will be same. Same applies for parameters in square brackets. In this syntax <series name> parameter is marked as optional. Exact behavior of a command with omitted parameter is specified separately for each command.

Parameters

Each command defines which type of parameters it accepts.

Numeric Data

  • Decimal data. Numeric values that may contain both a decimal point and an exponent (base 10). Examples: 2.5, 1e-10, 5
  • Integer. Integer numbers.

Keywords

In addition to entering decimal data as numeric values, several keywords can exist. The manual explicitly specify which keywords are allowed by a particular command.

Boolean Data

A Boolean parameter specifies a single binary condition which is either true or false.
Boolean parameters can be one of the following:

  • ON or 1 means condition true.
  • OFF or 0 means condition false.

Other Data Types

  • String data. Always enclosed between single or double quotes, for example “This is a string” or ‘This is a string.’
  • Non-decimal data: For instance, #H3A for hexadecimal data.
  • Block data: Used to transfer any 8-bit coded data. This data starts with a preamble that contains information about the length of the parameter.

Common SCPI commands

SCPI standard requires that all instrument support a set of common commands and queries. Such commands are described in next paragraphs.

*CLS

Clear Status Command

The *CLS common command clears the status data structures by clearing all event registers and the error queue. It does not clear enable registers. It clears any pending *WAI, *OPC, and *OPC?.

Example:

Send: → *CLS

*ESE

*ESE <integer>

*ESE?

Standard Event Status Enable

Sets or reads out the enable bits of the standard event enable register. This enable register contains a mask value for the bits to be enabled in the standard event status register. A bit that is set true in the enable register enables the corresponding bit in the status register. An enabled bit will set the ESB (Event Status Bit) in the Status Byte Register if the enabled event occurs.

Parameters: <integer> = the sum (between 0 and 255) of all bits that are true.

Event Status Enable Register (1 = enable)
BitWeightEnables
7128Reserved
664Reserved
532Reserved
416Reserved
38Reserved
24Reserved
12Reserved
01Operation Complete

Returned Format: <integer> \n

Example:

SEND → *ESE 1

In this example, bit 0 (Operation Complete event) is enabled. This will set the “ESB” bit of the Status Byte Register when long operation completes.
SEND → *ESE?
Reply: 1


*ESR?

Event Status Register.

Reads out the contents of the standard event status register. Reading the Standard Event Status Register clears the register.
Returned Format: <integer> = the sum (between 0 and 255) of all bits that are true.

*IDN?

Identification query

Reads out the manufacturer, model, serial number, and firmware level in an ASCii response data element. The query must be the last query in a program message.

Response is <Manufacturer>, <Model> , <Serial Number>, <Firmware Level>.

Example:

SEND → *IDN?

READ ← Pendulum, CNT-104S, 000024, v1.1.1 2022-11-24

*OPC

Operation Complete

The Operation Complete command causes the device to set the operation complete bit in the Standard Event Status Register when all pending selected device operations have been finished.

*OPC?

Operation Complete Query.

Operation Complete query. The Operation Complete query places an ASCii character 1 into the device’s Output Queue when all pending selected device operations have been finished.

Returned Format: 1 \n

*OPT

Option Identification

Response is a list of all detectable options present in the instrument. When no options are present response is ASCII ‘0’:
<Prescaler option (if present)>, <Oscillator code>, <SW option>, <SW option>…

<Prescaler option> = 10 3GHz / 110 10Ghz / 110/15 15GHz / 110/20 20GHz / 110/24 24GHz.

<Prescaler option> represents maximum frequency that a user is allowed to measure using currently installed HW and SW license option.

<Oscillator code> = TCXO / OCXO30 / OCXO40.

*RST

Reset

The Reset command resets the instrument. The settings will be set to the default, except settings in Network, Date/Time, Display groups. All previous commands are discarded and the counter is prepared to start new operations.

It is a good practice to start working with the instrument by issuing this command to ensure all settings are in known default state.

Example: *RST

Send: → *RST

*SRE

*SRE <integer>

*SRE?

Service Request Enable

The Service Request Enable command sets/reads the service request enable register bits. This enable register contains a mask value for the bits to be enabled in the status byte register. A bit that is set true in the enable register enables the corresponding bit in the status byte register to generate a Service Request.

Parameters: <integer> = the sum (between 0 and 255) of all bits that are true

See table below:

Service Request Enable Register (1 = enable)
BitWeightEnables
7128OPR, Operation Status
664RQS, Request Service
532ESB, Event Status Bit
416MAV, Message Available
38QUE, Questionable Data/Signal Status
24EAV, Error Available
12Reserved
01Reserved

Returned Format: <integer>

Where:

<integer> = the sum of all bits that are set.

Example: *SRE 16

In this example, the counter generates a service request when a message is available in the output queue.

*STB?

Status Byte Query

Reads out the value of the Status Byte. Bit 6 reports the Master Summary Status bit (MSS), not the Request Service (RQS). The MSS is set if the instrument has one or more reasons for requesting service.

Returned Format:

<Integer> = the sum (between 0 and 255) of all bits that are true. See table below:

Status Byte Register (1 = true)
BitWeightNameCondition
7128OPREnabled operation status has occurred
664MSSReason for requesting service
532ESBEnabled status event condition has occurred
416MAVAn output message is ready
38QUEThe quality of the output signal is questionable
24EAVError available
12 Reserved
01 Reserved

See also: If you want to read the status byte with the RQS bit, use serial poll.

*WAI

Wait-to-continue

The Wait-to-Continue command prevents the device from executing any further commands or queries until execution of all previous commands or queries has been completed.

Instrument configuration and control commands

:INITiate

Initiate (start) a measurement

Command syntax:

:INITiate

Description

This command starts a measurement. Measurement settings must be configured before starting a measurement using SYSTEM:CONFIGURE command. After measurement is complete the instrument doesn’t automatically start any new measurement.

:SYSTem:CONFigure

Configure measurement (and other) settings.

Command syntax

:SYSTem:CONFigure <parameters_in_quoted_string>

Where <parameters_in_quoted_string> is a quoted string of key-value pairs like "<param1> = <value1>; <param2> = <value2>; ..."

where param1, param2 are configuration keys and value1, value2 are corresponding configuration values.

Query syntax

:SYSTem:CONFigure? <category>

where <category> is one of

ALL – to get all settings

MEASure – to get only measurement-related settings

NETwork – to get Ethernet interface settings

Query response format

parameters_in_quoted_string in the same format as for command syntax. Only settings belonging to specified category are returned.

Description

Both command parameter and query response represent a quoted string of various settings for the device. The settings are given as key-value pairs separated by semicolon (‘;’) inside quoted string.

When you start programming an instrument that may have unknown configuration, it’s always a good idea to bring the instrument to a default state by sending: *RST; *CLS .This will ensure that all measurement settings are reset to defaults and that error and message buffers are cleared.

SYST:CONF command may be used several times in a raw. The command never changes (adjusts) other (not mentioned) settings implicitly. Neither they are reset to default values. When you want to perform two measurements with very different settings, you may want to use *RST command to reset all settings to known defaults before making new configuration.

If given settings are not compatible with previously configured settings or a command has other problems (e.g. parameters out of allowed range), command execution will result in an error and no new settings will be applied. In other words, the command will either successfully apply all specified settings or will not change instrument configuration at all. Such behavior allows to ensure that the instrument configuration is always in a known predictable state. To check for possible configuration errors use SYSTEM:ERROR? query immediately after configuring the instrument with SYSTEM:CONFIGURE.

Example

SEND → :SYST:CONF "CouplingA=DC; FilterA=100kHz; SampleInterval=500us; SampleCount=10; Function=Positive Pulse Width A"

Configuration parameters for :SYSTEM:CONFIGURE

TriggerMode

This parameter specifies how the instrument selects trigger levels for measurement comparators. Trigger levels can be set automatically by the instrument or specified by the user.

Parameter syntax: TriggerMode<Input>

where <Input> is one of A, B, D, E, for example: TriggerModeA

Possible values: Auto, Relative, Manual

Default value (RST condition): Auto

Description

Auto– Preliminary voltage measurement will be performed to find out signal voltage range and set trigger levels to best values for selected measurement function.

Depending on measurement function selected trigger levels will be automatically set to percentage values of signal voltage range:

  • 10% for the main comparator, 90% for the supplementary comparator for signal edge related functions: RiseTime/FallTime/RiseFallTime/PositiveSlewRate/NegativeSlewRate
  • 70% for the main comparator, 30% for the supplementary comparator for the functions with hysteresis on: Frequency/FrequencyRatio/frequencySmart/PeriodAverage/PeriodAverageSmart/TIE
  • 50% for both main and supplementary comparators for all other functions

Relative– Preliminary measurement is preformed, but you can adjust trigger levels relative to the measured signal voltage range, in percents, using RelativeTriggerLevel parameter.

Manual– Trigger levels are set accordingly to values specified by AbsoluteTriggerLevel parameter. It is recommended to use this mode only in cases when Autoset fails to find the best settings.

Example:

SYST:CONF "TriggerModeA=Auto"

AbsoluteTriggerLevel

Set absolute trigger levels for main and supplementary comparators

Parameter syntax: AbsoluteTriggerLevel<Comparator>

where <Comparator> is one of A, A2, B, B2, D, D2, E, E2. For example: AbsoluteTriggerLevelA2

Possible values:

Any floating point number representing trigger level in Volts, withing voltage measurement range. Voltage measurement range depends on Attenuation and Preamplifier parameters. See description of Attenuation and Preamplifier parameters.

Default value (RST condition): 0

Description

Sets trigger level in volts on main comparator (if numeric index is omitted, for example: A, B, D, E) or on supplementary comparator (if numeric index is 2, for example: A2, B2, D2, E2) of the input. Main comparator is used for all measurements performed on input, generating events to internal measurement core whenever signal crosses set trigger level. Supplementary comparator can be selected explicitly for some measurements from input (e.g. Time Interval A, A2), generating independent events to internal measurement core whenever signal crosses set trigger level. Otherwise it is used implicitly for frequency average and period average measurements (to assure wide hysteresis), for Rise & Fall Time and Slew Rate. 

Example:

SEND → SYST:CONF "TriggerModeA=Manual; AbsoluteTriggerLevelA=-2.5; AbsoluteTriggerLevelA2=2.5; TriggerModeB=Manual; AbsoluteTriggerLevelB=0; AbsoluteTriggerLevelB2=1.35"

RelativeTriggerLevel

Sets relative trigger levels in percents relative to signal voltage range, for main and supplementary comparators.

Parameter syntax: RelativeTriggerLevel<Comparator>

where <Comparator> is one of A, A2, B, B2, D, D2, E, E2. For example: RelativeTriggerLevelB2

Possible values: 0 … 100

Default value (RST condition):

70 for the main comparators

30 for the supplementary comparators

Description

Sets trigger level on main (if comparator index is omitted, e.g. just A) or on supplementary comparator (if comparator index is 2, e.g. A2) of input in percents relative to measured signal voltage range.  0% corresponds to signal min value and 100% corresponds to signal max value. Main comparator is used for all measurements performed on input, generating events to internal measurement core whenever signal crosses set trigger level. Supplementary comparator can be selected explicitly for some measurements generating independent events to internal measurement core whenever signal crosses set trigger level. Otherwise it is used implicitly for frequency average and period average measurements (to assure wide hysteresis), for Rise & Fall Time and Slew Rate.

Example

SEND → SYST:CONF "TriggerModeA=Relative; RelativeTriggerLevelA=65; RelativeTriggerLevelA2=35"

Slope

Specifies signal slope that triggers comparator

Parameter syntax: Slope<Comparator>

where Comparator is one of A, A2, B, B2, C, D, D2, E, E2, EA, ER, G, T

Possible values: Positive, Negative

Default value (RST condition): Positive

Description

Positive– Positive slope is used for corresponding input

Negative – Negative slope is used for corresponding input

Example

SYST:CONF "SlopeA=Positive"

Impedance

Specifies input impedance

Parameter syntax: Impedance<Input>

where <Input> is one of A, B, D, E. For example: ImpedanceA

Possible values: 50Ohm, 1MOhm

Default value (RST condition): 1MOhm

Description

50Ohm – 50 Ohm impedance is used for corresponding input

1MOhm – 1 MOhm impedance is used for corresponding input

Example

SEND → SYST:CONF "ImpedanceA = 50 Ohm"

Coupling

Allows to select AC or DC coupling of an input.

Parameter syntax: Coupling<Input>

where <Input> is one of A, B, D, E. For example: CouplingA

Possible values: DC, AC

Default value (RST condition): AC

Description

AC coupling allows to block unnecessary DC offset that may be present in the signal.

DC – DC coupling is used for corresponding input

AC – AC coupling is used for corresponding input

Example

SEND → SYST:CONF "CouplingA = AC"

Filter

Selects whether low-pass filter is enabled for an input

Parameter syntax: Filter<Input>

where Input is one of A, B, D, E. For example: FilterA

Possible values: Off, 10kHz, 100kHz

Default value (RST condition): Off

Description

Off – Filter is not used for corresponding input

10kHz – 10 kHz low pass filter is used for corresponding input

100kHz – 100 kHz low pass filter is used for corresponding input

Example

SYST:CONF "FilterA = Off"

Attenuation

Enables or disables signal attenuation on an input

Parameter syntax: Attenuation<Input>

where Input is one of A, B, D, E. For example: AttenuationA

Possible values: 1x, 10x, Auto

Default value (RST condition): 1x

Description

This setting allow to enable attenuation for situations when measurement signal amplitude is too big for an input.

1x – 1x attenuation is used for corresponding input (corresponds to no attenuation)

10x – 10x attenuation is used for corresponding input (signal is decreased 10 times).

Auto – Attenuation is auto-selected is used for corresponding input.

Correct auto-trigger operation operation and voltage measurements are possible for the following input signal voltage ranges depending on attenuation and preamplifier settings.

 Preamplifier=offPreamplifier=on
Attenuation=1x-5 … +5 V-1.5 .. +1.5 V
Attenuation=10x-50 … +50 V-15 .. +15 V
Attenuation=Auto-50 … +50 V-1.5 .. +1.5 V

Note! When measuring voltage-related signal characteristics, measurement results displayed on the screen and provided by SCPI queries are not decreased 10 times when attenuation is enabled. Even though the signal is attenuated inside the instrument, resulting data are scaled back to original scale.

Example

SYST:CONF "AttenuationA = 10x"

Preamplifier

Enables or disables signal amplification inside the instrument for an input.

Parameter syntax: Preamplifier<Input>

where Input is one of A, B, D, E. For example: PreamplifierA

Possible values: Off, On

Default value (RST condition): Off

Description

Allows to amplify input signal. It is recommended to turn amplification on only if input signal has low amplitude.

Off – Preamplifier in off for corresponding input

On – Preamplifier in on for corresponding input

Correct auto-trigger operation and voltage measurements are possible for the following input signal voltage ranges depending on attenuation and preamplifier settings.

 Preamplifier=offPreamplifier=on
Attenuation=1x-5 … +5 V-1.5 .. +1.5 V
Attenuation=10x-50 … +50 V-15 .. +15 V
Attenuation=Auto-50 … +50 V-1.5 .. +1.5 V

Example

SYST:CONF "PreamplifierA = On"

ArmOn

When arming is enabled, defines whether sample block or each sample within the block should be armed.

Parameter syntax: ArmOn

Possible values: Block, Sample

Default value (RST condition): Block

Description

When arming is enabled, defines whether sample block or each sample within the block should be armed. Block of samples is a group of samples captured during a measurement (number of samples is defined by SampleCount parameter). This setting is available for modification only when arming is enabled. See StartArmingSource parameter.

Block – Arm on Block mode: entire sample block is being armed. Please note: when arming on Block and stop arming is not Off – the resulting number of samples in the block might be less than SampleCount.

Sample – Arm on Sample mode: each individual sample inside the block is being armed.

Example

SYST:CONF "ArmOn = Block"

Function

Selects measurement function and inputs

Parameter syntax: Function=<function name> <input_or_comparator>[,<input_or_comparator>, ...]

where

<function name> is one of Frequency, SmartFrequency, PeriodAverage, SmartPeriodAverage, PeriodSingle, TimeInterval, TimeIntervalSingle, AccumulatedTimeInterval, Phase, AccumulatedPhase, TIE, PositiveDutyCycle, NegativeDutyCycle, PositivePulseWidth, NegativePulseWidth, RiseTime, FallTime, RiseFallTime, PositiveSlewRate, NegativeSlewRate, Totalize, TotalizeX+Y, TotalizeX-Y, TotalizeX/Y, Vmin, Vmax, Vpp, Vminmax, DC Offset

input_or_comparator is one of A, A2, B, B2, C, D, D2, E, E2, EA, ER, G, T. See description below for limitations.

Possible values:

Note, that this parameter is combination of function name, space character and a list of inputs/comparators, separated by comma. Each measurement function supports different maximum number of inputs or comparators. See description below for possible values, their meanings and limitations.

Default value (RST condition): Frequency A

Description

Allows to select measurement function of the instrument.

<function name>Description
FrequencyAverage frequency over gate time (set by Sample Interval parameter). This is back-to-back measurement (every period of the signal can be captured) for frequencies up to 20 MHz. Up to 4 signals can be measured in parallel. All inputs/comparators can be used.
FrequencyRatioRatio of frequency averages. This mode is just additional math applied over frequency measurements.All inputs/comparators can be used. Minimum two inputs/comparators must be specified. When two inputs/comparators are specified then the frequency ratio of second to first input/comparator is measured. When three inputs/comparators are specified then ratios of 2nd to 1st and 3rd to 1st are measured. When 4 inputs/comparators are specified then ratios of 2nd to 1st and 4th to 3rd are measured.
SmartFrequencySmart Frequency function makes use of regression analysis to increase the resolution of the measurement at the expense of measurement speed. Please, note: this mode assumes signal frequency is static within gate time (set by Sample Interval). All inputs/comparators can be used.
PeriodAverageAverage period over gate time (set by Sample Interval parameter). This is back-to-back measurement (every period of the signal can be captured) for frequencies up to 20 MHz. Up to 4 signals can be measured in parallel. All inputs/comparators can be used.
SmartPeriodAverageSmart Period Average function makes use of regression analysis to increase the resolution of the measurement at the expense of measurement speed. Please, note: this mode assumes signal frequency is static within gate time (set by Sample Interval parameter). All inputs/comparators can be used.
PeriodSingleAllows to capture single signal periods for periods less than 20 MHz at expense of 50 ns dead-time.All inputs/comparators can be used. Maximum is 2 inputs.
TimeIntervalTime Interval between up to 4 periodic signals. Result is normalized to the range of -0.5 to +1 signal period.All inputs except C can be used.
TimeIntervalSingleTime Interval between single events from up to 4 inputs.All inputs except C can be used.
AccumulatedTimeIntervalSame as Time Interval, but the result is not normalized.All inputs except C can be used.
PhasePhase difference between 2 periodic signals. Result is normalized to the range of -180° to +360°.All inputs except C can be used.
AccumulatedPhaseSame as Phase, but the result is not normalized.All inputs except C can be used.
TIETime Interval Error (TIE) between up to 4 independent clock sources.All inputs can be used.
PositiveDutyCycleRatio of a pulse signal Positive Pulse Width to its Period.Inputs A, B, D, E can be used. One input only.
NegativeDutyCycleRatio of a pulse signal Negative Pulse Width to its Period.Inputs A, B, D, E can be used. One input only.
PositivePulseWidthPositive Pulse Width of a pulse signal.Inputs A, B, D, E can be used. Maximum is 2 inputs.
NegativePulseWidthNegative Pulse Width of a pulse signal.Inputs A, B, D, E can be used. Maximum is 2 inputs.
RiseTimeMeasures how much time it takes for the signal to go from 10% to 90% of its voltage range.Inputs A, B, D, E can be used. Maximum is 2 inputs.
FallTimeMeasures how much time it takes for the signal to go from 90% to 10% of its voltage range.Inputs A, B, D, E can be used. Maximum is 2 inputs.
RiseFallTimeMeasures how much time it takes for the signal to go from 10% to 90% of its voltage range and back.Inputs A, B, D, E can be used. One input only.
PositiveSlewRateMeasures how fast signal voltage increases from 10% to 90% of its range.Inputs A, B, D, E can be used. Maximum is 2 inputs.
NegativeSlewRateMeasures how fast signal voltage decreases from 90% to 10% of its range.Inputs A, B, D, E can be used. Maximum is 2 inputs.
TotalizeCounts number of events on up to 4 input channels in parallel.All inputs except C can be used.
TotalizeX+YTotalize with additional maths applied.All inputs except C can be used. Minimum is 2 inputs.
TotalizeX-YTotalize with additional maths applied.All inputs except C can be used. Minimum is 2 inputs.
TotalizeX/YTotalize with additional maths applied.All inputs except C can be used. Minimum is 2 inputs.
VminMinimum voltage level of a signal.Inputs A, B, D, E can be used.
VmaxMaximum voltage level of a signal.Inputs A, B, D, E can be used.
VppSignal maximum and minimum voltage levels difference.Inputs A, B, D, E can be used.
VminmaxMinimum and maximum voltage levels of a signal.Inputs A, B, D, E can be used. One input only.
DC OffsetMeasure DC offset voltage of a signal. Note: DC coupling must be enabled for corresponding input.

Example

:SYST:CONF "Function = Frequency A"

:SYST:CONF "Function=Period Average A,B2,EA"

HoldOff

Dead time between consecutive trigger events

Parameter syntax: HoldOff

Possible values: 0 - 2.683 s

Default value (RST condition): 0 s

Description

Adds dead time between consecutive trigger events. Used to cope with contact bouncing or signal oscillations.

Example

SYST:CONF "HoldOff = 0.555 s"

LimitBehaviour

Enables of disables limits for measurements. Defines instrument behavior when specified limits are exceeded.

Parameter syntax: LimitBehaviour

Possible values: Off, Capture, Alarm, AlarmStop

Default value (RST condition): Off

Description

Defines how the instrument will react on limits. Limit criterion is set by Limit Type, Upper Limit and Lower Limit. For all limit behavior choices except Off the following is true: If measured value has fell off the limit criterion during measurement session then red exclamation mark indicator is displayed.

Off– Limits are disabled.

Capture – Only samples meeting the limit criterion are captured, the rest are discarded. Limit status is displayed

Alarm – All samples are captured, limit status is displayed

AlarmStop – Measurement session stops if measured value doesn’t meet the limit criterion

Example

SYST:CONF "LimitBehaviour = Alarm"

LimitLower

Specifies lower limit.

Parameter syntax: LimitLower

Possible values: any decimal

Default value (RST condition): 0

Description

Lower limit (used if LimitType=Above or LimitType=Range and LimitBehaviour is not Off)

Example

SYST:CONF "LimitLower = 0 Hz"

LimitSeriesName

Specifies name of series for which limit is applies to.

Parameter syntax: LimitSeriesName

Possible values: All, A,B,A/B,A+B,Vmin, etc.

Default value (RST condition): All

Description

Name of the series that the limit is applied to, or “All“ if applied to all series. This parameter can be used only when limits are enabled (LimitBehaviour is not Off)

Example

SYST:CONF "LimitSeriesName = A/B"

LimitType

Specifies limit type.

Parameter syntax: LimitType

Possible values: Above, Below, Range

Default value (RST condition): Above

Description

Above– Results above set Lower Limit will pass

Below – Results below set Upper Limit will pass

Range – Results within the set limits will pass

This parameter can be used only when limits are enabled (LimitBehaviour is not Off)

Example

SYST:CONF "LimitType = Range"

LimitUpper

Specifies upper limit

Parameter syntax: LimitUpper

Possible values: any decimal

Default value (RST condition): 0

Description

Upper limit (used if LimitType=Below or LimitType=Range and LimitBehaviour is not Off)

Example

SYST:CONF "LimitUpper = 24.7 Hz"

MathCoeffK, MathCoeffL, MathCoeffM

Specifies values for coefficients K, L, M, when mathematical formula is enabled.

Parameter syntax: MathCoeff<Coefficient>

where Coefficientis one of K, L, M,. For exampe: MathCoeffL

Default value (RST condition):

MathCoeffK = 1

MathCoeffL = 0

MathCoeffM = 1

Description

K, L, M constants used in Math formula.

Example

SYST:CONF "MathCoeffM = 1"

MathCustomUnit

Overrides result units when mathematical formula is applied.

Parameter syntax: MathCustomUnit

Description

When math formula is applied, measurement results units are usually determined automatically. This parameter allows to override the unit of the value after math formula is applied. The length of the custom unit must not exceed 4 characters

Example

SYST:CONF "MathCustomUnit = Emu"

MathMode

Selects mathematical formula to apply for results

Parameter syntax: MathMode

Possible values: Off, K*X+L, K/X+L, (K*X+L)/M, (K/X+L)/M, X/M-1

Default value (RST condition): Off

Description

Allows to apply math over measurement results. Please note, some of available formulae change unit of original value.

Example

SYST:CONF "MathMode = K/X+L"

MathSeriesName

Select series to apply math formula to.

Parameter syntax: MathSeriesName

Possible values: All, A, B, A/B, A+B, Vmin, etc.

Default value (RST condition): All

Description

Name of the series that MathMode is applied to, or “All“ if applied to all series

Example

SYST:CONF "MathSeriesName = A+B"

PulseOutputMode

Controls the rear Pulse Output of the device.

Parameter syntax: PulseOutputMode

Possible values: Off, PulseGenerator, GateOpen, AlarmOutActiveHigh, AlarmOutActiveLow

Default value (RST condition): Off

Description

Controls the rear Pulse Output of the instrument. The amplitude is set to TTL levels into 50 Ohm irrespective to output mode.

Off– No signal on Pulse Output

PulseGenerator – Continuous pulse train with period and pulse width set in next menus

GateOpen – Indicates when measurement is in progress

AlarmOutActiveHigh – High level output when limits alarm is active, low level otherwise

AlarmOutActiveLow – Low level output when limits alarm is active, high level otherwise

Example

SYST:CONF "PulseOutputMode = AlarmOutActiveLow"

PulseOutputPeriod

Set period of pulses generated on rear Pulse Output of the instrument.

Parameter syntax: PulseOutputPeriod

Possible values: 10 ns .. 2.147 s

Default value (RST condition): 1 ms

Description

Set period of pulses generated on Pulse Output if Mode is set to Pulse Generator.  Resolution for this parameter is 2 ns.

Example

SYST:CONF "PulseOutputPeriod = 12 ns"

PulseOutputWidth

Set width of pulses generated on rear Pulse Output of the instrument.

Parameter syntax: PulseOutputWidth

Possible values: 4 ns .. 2.146999994 s (but at least 6 ns lower than PulseOutputPeriod)

Default value (RST condition): 500 us

Description

Set width of pulses generated on Pulse Output if Mode is set to Pulse Generator.  Resolution for this parameter is 2 ns. Should be at least 6 ns less than PulseOutputPeriod.

Example

SYST:CONF "PulseOutputWidth = 2.1 s"

SampleCount

Defines number of samples to be collected for each measurement series. 

Parameter syntax: SampleCount

Possible values: up to 31999999 samples (depends on selected function and inputs/comparators and other settings)

Default value (RST condition): 1

Description

Defines number of samples to be collected for each measurement series. 

Example

SYST:CONF "SampleCount = 10000"

SampleInterval

Specifies how often measurement samples are generated and/or define gate time.

Parameter syntax: SampleInterval

Default value (RST condition): 10 ms

Description

Defines gate time for Frequency measurement. Please note, that if signal period is larger than this value then actual sample interval will be equal to signal period. 

For Frequency, Sample Interval should be in the range: 1 us .. 10.995 ks  Please note: to allow sample interval below 1 us corresponding license is required.

Example

SYST:CONF "SampleInterval = 10 ms"

SignalSource

Specifies whether to use input signals for measurement or internal test generator.

Parameter syntax: SignalSource

Possible values: Inputs, Test

Default value (RST condition): Inputs

Description

Built-in test signal generator is used for performing internal device calibrations but can also be used for testing purposes. This setting must be used only for testing or demonstrational purposes when there is no possibility to connect external source of signal to instrument’s inputs.

Inputs– Normal operation

Test – Using internal test signal generator instead of inputs on front (back) panel. Output of the internal generator are connected to inputs A, B, D, E and can be measured. Please, note: test generator is using independent coarse time base and is not expected to provide accurate frequency. It is not the same generator which drives rear Pulse Output of the device.

Example

SYST:CONF "SignalSource = Test"

StartArmingDelay

Delay for making measurement after arming event.

Parameter syntax: StartArmingDelay

Default value (RST condition): 0 s

Description

Defines time after start arming event when measurement should be started.  Start Arming Delay should be in the range: 0 s .. 10.995 ks

Example

SYST:CONF "StartArmingDelay = 8.556 ks"

StartArmingSlope

Signal slope to use as arming event.

Parameter syntax: StartArmingSlope

Possible values: Positive, Negative

Default value (RST condition): Positive

Description

Slope which arms measurement

Negative– Negative slope is used for Start Arming

Positive – Positive slope is used for Start Arming

Example

SYST:CONF "StartArmingSlope = Negative"

StartArmingSource

Input or comparator that will be used to detect arming event.

Parameter syntax: StartArmingSource

Possible values: Off, EA, A, B, D, E, A2, B2, D2, E2

Default value (RST condition): Off

Description

Defines whether signal from one of device inputs should be used to arm start of measurement.

Example

SYST:CONF "StartArmingSource = A"

StopArmingDelay

Delay for stopping measurement after stop arming event.

Parameter syntax: StopArmingDelay

Default value (RST condition): 0 s

Description

Defines time after stop arming event when measurement should be stopped.  Stop Arming Delay should be in the range: 0 s .. 10.995 ks

Example

SYST:CONF "StopArmingDelay = 6.652 ks"

StopArmingSlope

Signal slope to use as stop arming event.

Parameter syntax: StopArmingSlope

Possible values: Positive, Negative

Default value (RST condition): Positive

Description

Slope which arms measurement stop

Negative– Negative slope is used for Stop Arming

Positive – Positive slope is used for Stop Arming

Example

SYST:CONF "StopArmingSlope = Negative"

StopArmingSource

Input or comparator to use for stop arming event detection.

Parameter syntax: StopArmingSource

Possible values: Off, EA, A, B, D, E, A2, B2, D2, E2

Default value (RST condition): Off

Description

Defines whether signal from one of device inputs or timer should be used to stop measurement.

Example

SYST:CONF "StopArmingSource = B2"

TestSignalFrequency

Frequency of internal built-in test generator.

Parameter syntax: TestSignalFrequency

Possible values: 1.039 kHz .. 68 MHz

Default value (RST condition): 1 MHz

Description

Sets frequency of built-in test generator.  Please, note: test generator is using independent coarse timebase and is not expected to provide accurate frequency. It is not the same generator which drives rear Pulse Output of the device.  Test Signal Frequency should be in the range: 1.039 kHz .. 68 MHz

Example

SYST:CONF "TestSignalFrequency = 5.555 kHz"

TieReferenceFrequency A, A2, B, B2, D, D2, E, E2, EA, ER

Reference frequency for input or comparator when doing TIE measurements.

Parameter syntax: TieReferenceFrequency<Input>

where Input is one of A, A2, B, B2, D, D2. For example: TieReferenceFrequencyA

Possible values: 100 mHz .. 400 MHz

Default value (RST condition): 10 MHz

Description

Reference frequency for input A, A2, B, B2, D, D2, E, E2, EA, ER. Should be in the range: 100 mHz .. 400 MHz

Example

SYST:CONF "TieReferenceFrequencyB = 101 mHz"

TieReferenceFrequencyC

Reference frequency for input C when doing TIE measurements.

Parameter syntax: TieReferenceFrequencyC

Possible values: 100 mHz .. 24 GHz

Default value (RST condition): 1 GHz

Description

Reference frequency for input C.  Ref Frequency for input C should be in the range: 100 mHz .. 24 GHz

Example

SYST:CONF "TieReferenceFrequencyC = 12 GHz"

TieReferenceFrequencyDetection

Defines if reference frequency is detected automatically or should be set manually

Parameter syntax: TieReferenceFrequencyDetection

Possible values: On, Off

Default value (RST condition): On

Description

Defines if reference frequency is detected automatically or should be set manually

On– Reference frequency for TIE measurement is detected automatically

Off – Reference frequency for TIE measurement is set manually

Example

SYST:CONF "TieReferenceFrequencyDetection = Off"

TieReferenceFrequencyNumberOfDigits

Number of digits detected reference frequency should be rounded to.

Parameter syntax: TieReferenceFrequencyNumberOfDigits

Possible values: 0-10

Default value (RST condition): 5

Description

Defines how many digits detected reference frequency should be rounded to.  Ref Frequency Number Of Digits should be in the range: 0  .. 10

Example

SYST:CONF "TieReferenceFrequencyNumberOfDigits = 9"

TimebaseReference

Specifies which reference clock to use for measurements.

Parameter syntax: TimebaseReference

Possible values: Auto, Internal, External

Default value (RST condition): Auto

Description

Defines which reference clock will be used for measurement.

Internal – Internal timebase reference is used

External – External timebase reference is used if it is connected and within expected parameters, otherwise measurement is not performed.

Auto– External timebase reference is used if it is connected and within expected parameters, otherwise internal

Example

SYST:CONF "TimebaseReference = External"

Timeout

Enable of disable measurement timeout.

Parameter syntax: Timeout

Possible values: On, Off

Default value (RST condition): Off

Description

Used to make measurement session to end if signal is missing for more than specified Timeout Time.

On– Timeout is on

Off – Timeout is off

Example

SYST:CONF "Timeout = Off"

TimeoutTime

Set measurement timeout value.

Parameter syntax: TimeoutTime

Possible values: 10 ms .. 1 ks

Default value (RST condition): 100 ms

Description

If Timeout is On, measurement session ends if signal is missing for more than specified Timeout Time.

Example

SYST:CONF "TimeoutTime = 168 ms"

VoltageMode

* * * * * * * * * * * * * *

Parameter syntax: VoltageMode

Possible values: Normal, VerySlow, Slow, Fast, VeryFast

Default value (RST condition): Normal

Description

Defines minimal signal frequency for which voltage measurements and/or auto-trigger works correctly. Please, note: voltage/auto-trigger for lower frequencies are measured at the expense of measurement speed.  It is recommended to treat this setting as a fallback for the cases where Autoset fails to find best setting automatically.

VerySlow – Used for signals with frequency in range: < 10 Hz

Slow– Used for signals with frequency in range: 10 Hz to 100 Hz

Normal– Used for signals with frequency in range: 100 Hz to 1 kHz

Fast – Used for signals with frequency in range: 1 kHz to 10 kHz

VeryFast – Used for signals with frequency 10 kHz and above.

DC signals can be measured with any mode.

Example

SYST:CONF "VoltageMode = Fast"

InternalCalibrationMode

Defines when to start internal calibration.

Parameter syntax: InternalCalibrationMode

Possible values: Every30Min, BeforeEveryMeasurement, OnceAfterWarmup

Default value (RST condition): Every30Min

Description

Internal calibration is always done on device start-up and after it has warmed up. More frequent calibration can be done in order to improve timing measurement resolution.

Every30Min – Additional calibration every 30 minutes

BeforeEveryMeasurement– Additional calibration before every measurement

OnceAfterWarmup– No additional calibration

Example

SYST:CONF "InternalCalibrationMode = Every30Min"

NumOfBlankDigits

Number of digits to blank on display.

Parameter syntax: NumOfBlankDigits

Possible values: 0 .. 15

Default value (RST condition): 0

Description

Defines the number of least significant digits to be masked. This can be used to help operator to read out the results of jittery measurements.  Please note: it applies only to the current measured value, not statistics.  Digits Blank should be in the range: 0 .. 15

Example

SYST:CONF "NumOfBlankDigits = 12"

ScreenSaverTimeout

Timeout to switch off display.

Parameter syntax: ScreenSaverTimeout

Possible values: 5minutes, 10minutes, 30minutes, 1hour, Never

Default value (RST condition): 10minutes

Description

Inactivity timeout for turning device display off

5minutes – Inactivity timeout set to 5 minutes

105minutes– Inactivity timeout set to 10 minutes

305minutes– Inactivity timeout set to 30 minutes

1hour– Inactivity timeout set to 1 hour

Never– Device display is always on

Example

SYST:CONF "ScreenSaverTimeout = Never"

Brightness

Display brightness.

Parameter syntax: Brightness

Possible values: Minimum, Low, Medium, High, Maximum

Default value (RST condition): Maximum

Description

Inactivity timeout for turning device display off

Minimum – Minimum brightness

Low– Low brightness

Medium– Medium brightness

High– High brightness

Maximum– Maximum brightness

Example

SYST:CONF "Brightness = Minimum"

Wired and Wireless network settings

IPAddress/WirelessIPAddress

Specifies static (manual) IPv4 address in Ethernet network

Parameter syntax: IPAddress, WirelessIPAddress

Possible values: IP address (four numbers, dot-separated)

Default value (RST condition): 192.168.0.99

Description

IP address for Ethernet interface when static IP address mode is enabled in IPMode parameter. When DHCP mode is enabled, the IP is assigned by a DHCP server in network and can be read back with SYST:CONF? query)

IP address for Wireless interface (with DHCP, configured address can be read back)

Example

SYST:CONF "IPAddress = 192.168.0.99"

SYST:CONF "WirelessIPAddress = 192.168.0.99"

IPDNS/WirelessIPDNS

DNS servers

Parameter syntax: IPDNS1, WirelessIPDNS1 and IPDNS2, WirelessIPDNS2

Possible values: IP address (four numbers, dot-separated)

Default value (RST condition): 8.8.8.8

Description

DNS server(s) IP addresses for Ethernet interface when static IP address mode is enabled in IPMode parameter. When DHCP mode is enabled, these settings are assigned by a DHCP server in network and can be read back with SYST:CONF? query)

1st nameserver IP address for Wireless interface (with DHCP, configured address can be read back)

Example

SYST:CONF "IPDNS1 = 8.8.8.8; IPDNS2 = 1.1.1.1"

SYST:CONF "WirelessIPDNS1 = 8.8.8.8; WirelessIPDNS2 = 1.1.1.1"

IPGateway/WirelessIPGateway

Default gateway.

Parameter syntax: IPGateway, WirelessIPGateway

Possible values: IP address (four numbers, dot-separated)

Default value (RST condition): 192.168.0.1

Description

Gateway IP for Ethernet interface when static IP address mode is enabled in IPMode parameter. When DHCP mode is enabled, this setting is assigned by a DHCP server in network and can be read back with SYST:CONF? query)

Gateway IP address for Wireless interface (with DHCP, configured address can be read back)

Example

SYST:CONF "IPGateway = 192.168.0.1"

SYST:CONF "WirelessIPGateway = 192.168.0.1"

IPMode/WirelessIPNetmask

Select whether to configure IP address automatically from DHCP server or manually

Parameter syntax: IPMode, WirelessIPMode

Possible values: DHCP, Static

Default value (RST condition): DHCP

Description

IP configuration mode for Ethernet interface

IP netmask for Wireless interface (with DHCP, configured netmask can be read back)

DHCP– IP settings are aquired via DHCP

Static– Static IP configuration. When this mode is selected you should also configure IPAddress and IPNetmask, IPGateway, IPDNS1 (and optionally IPDNS2) parameters.

Example

SYST:CONF "IPMode = DHCP"

SYST:CONF "WirelessIPMode = DHCP"

IPNetmask/WirelessIPNetmask

IP netmask

Parameter syntax: IPNetmask, WirelessIPNetmask

Possible values: IP mask (four numbers, dot-separated)

Default value (RST condition): 255.255.255.0

Description

IP netmask for Ethernet interface when static IP address mode is enabled in IPMode parameter. When DHCP mode is enabled, this setting is assigned by a DHCP server in network and can be read back with SYST:CONF? query)

IP netmask for Wireless interface (with DHCP, configured netmask can be read back)

Example

SYST:CONF "IPNetmask = 255.255.255.0"

SYST:CONF "WirelessIPNetmask = 255.255.255.0"

Other configuration and control commands

:SYSTem:ERRor

Read the Error/Event Queue

You read the error queue with the :SYSTem:ERRor? query.

Example:

SEND → :SYST:ERR?

READ ← -220,"Parameter error;Wrong enum value '25x' for setting 'AttenuationA'"

The query returns the error number followed by the error description.

If more than one error occurred, the query will return the error that occurred first. When you read an error, you will also remove it from the queue. You can read the next error by repeating the query.

When you have read all errors, the queue is empty, and the :SYSTem:ERRor? query will return:

0, "No error"

When errors occur and you do not read these errors, the Error Queue may overflow. Then the instrument will overwrite the last error in the queue with:

-350, "Queue overflow"

If more errors occur they will be discarded.

It is a good practice to check for errors after instrument configuration and before starting a measurement.

:DISPlay:ENABle

<Boolean>

Display results on-screen On/Off

This command switches displaying measurement results on-screen on or off. Switching off is useful to boost fetching speed for block measurements. If switched off, the user will see a lock screen that can be unlocked by tapping a button, unless the device is in Remote Locked state.

*RST condition: 1

:ROSCillator:STATE

Query reference clocks (time base) statuses.

Query syntax

:ROSCillator:STATE?

Query response format:

<used_ref_status>, <int_ref_status>, <ext_ref_status>

Where

<used_ref_status> is one of INT, EXT or FAIL

<int_ref_status> is one of OK, FAIL

<ext_ref_status> if one of 1MHz, 5MHz, 10MHz, FAIL

Description

This query provides extensive information about currently used reference clocks and the state of internal and external reference clock signals. The response contains 3 fields separated by commas.

First field indicates which time base is currently in use: internal (INT), external (EXT) or none (FAIL).

Second field indicates status of internal time base reference: OK or FAIL.

Third field indicates whether external reference signal is connected (1MHz, 5MHz or 10MHz) or not (FAIL).

Example:

SEND → :ROSC:STATE?

READ ← EXT, INT OK, EXT 10MHz

Acquisition of measurement data

:FETCh[:SCALar]

Fetch one result

Query syntax

:FETCh[:SCALar]? [<series name>]

where <series names> in measurement function dependent series

Query response format

The format of the returned data is determined by the format commands :FORMAT:TINF and :FORMAT:DATA. See description below.

Description

The fetch query retrieves one measurement result for the given series name without making new measurements. Fetch does not work unless a measurement has been made by the :INITiate command. Series name argument is optional. If ommited, the command will default to first series for current measurement. If the counter has made an array of measurements, the query fetches the first measuring results first. The second query fetches the second result and so on. When the last measuring result has been fetched, the query returns empty string.

Measuring result can be fetched as long as the result is valid, i.e. until the following occurs:

– *RST is received.

– an :INITiate command is executed

– any reconfiguration is done.

The format of the returned data is determined by the format commands :FORMAT:TINF and :FORMAT:DATA:

 :FORMAT:DATA ASCii:FORMAT:DATA REAL:FORMAT:DATA PACKED
:FORMAT:TINF OFF<Val>,<Val>,<Val>…#18<Val>,#18<Val>,#18<Val>…#280<Val><Val><Val>…
:FORMAT:TINF ON<Val>,<TS>,<Val>,<TS>,<Val>,<TS>#18<Val>,#18<TS>,#18<Val>,#18<TS>,#18<Val>,#18<TS>…#6000160<Val><TS><Val><TS><Val><TS>….

Val = measurement value (double-precision floating-point format according to IEEE-754 in REAL and PACKed)

TS = timestamp value (double-precision floating-point format according to IEEE-754 in REAL, and 64-bit integer representing the number of picoseconds in PACKed)

#18 and #3160 – are binary data headers. First digit after “#” represent the number of subsequent digits. Those digits specify the size of a binary data (in bytes) that follow the header. For example, in REAL format in the header #18 “1” indicates that there is one more digit to read after “#”. “8” indicates that there will be 8 bytes of binary samples. In PACKED format the header #6000160 shows that there are 6 more digits after ‘#’. 000160 indicates that there will be 160 bytes of binary data.

In some situations, the instrument may not be able to provide valid results because of a measured value exceeds expected range (for example signal has too big amplitude or frequency is too high). In such situations the samples returned by :FETCh[:SCALar] and :FETCh:ARRay will have special ‘infinity’ value. In ASCII format it will be inf string, and for REAL and PACKED formats it will be bit pattern corresponding to infinity according to IEEE 754.

:FETCh:ARRay

Fetch an array of results

Query syntax

:FETCh:ARRay <fetch array size>, [<series name>]

where <fetch array size> is either an integer number or MAX keyword and <series name> is series name.

Query response format

The format of the returned data is determined by the format commands :FORMat and :FORMat:FIXed. See :FETCh[:SCALar] for formats description.

Description

:FETCh:ARRay? query differs from the :FETCh? query by fetching several measuring results at once.

<fetch array size> must be positive integer value or MAX keyword. Data samples in response are present in the order they were created by the measurement core of the instrument (sorted by time, earliest sample is first). Maximum allowed array size for a single fetch is 1000000. Samples are fetched in FIFO-manner. For example, when the instrument has made a measurement and an array of measurements is available for input ‘A’ then :FETCh:ARRay? 10, A fetches the first 10 measuring results from the output queue. The second :FETCh:ARRay? 10, A fetches results 11 to 20, and so on. When the last measuring result has been fetched, :FETCh:ARRay? 10, A returns empty string.

:FORMat[:DATA]

Specifies format of the data samples that are returned in response to FETCH:SCALAR? and FETCH:ARRAY? queries.

Command syntax

:FORMat[:DATA] <format>

where <format> is one of ASCii, REAL or PACKed

Query syntax

:FORMat[:DATA]?

Query response

ASCII, REAL or PACKED

Default value: ASCII

Description

ASCii: Returned data samples are represented as floating point numbers in text, separated by comma (for FETCH:ARRAY? query).

REAL: Returned data samples are represented as binary data with “#18” header. Each sample or timestamp consists of 8 bytes.

PACKed: See REAL.

For more details, see :FETCh[:SCALar] query description.

:FORMat:TINFormation

Specifies whether timestamps are included in data samples that are returned in response to FETCH:SCALAR? and FETCH:ARRAY? queries.

Command syntax

:FORMat:TINFormation <boolean>

where <boolean> is one of 1, 0, ON, OFF

1 or ON enable timestamping

0 or OFF disable timestamping

Default value: OFF

Description

This command turns on/off the time stamping of measurements. The setting of this command will affect the output format of FETCh queries.

For more details, see :FETCh[:SCALar] query description.

Connection to the instrument using SCPI

For controlling the instrument over Ethernet connections, HiSLIP (High-Speed LAN Instrument Protocol) is used. Simplest way to communicate with the instrument from a PC is to make use of VISA software, for example NI VISA. For connecting to the instrument, a connection resource string in the following form will be required:

TCPIP::<IP address>::hislip0::INSTR

Replace <IP address> with IPv4 address of the instrument, for example:

TCPIP::192.168.0.25::hislip0::INSTR

IP address of the instrument can can checked in Settings → User Options → Network page in device’s on-screen interface.

Example of a simple measurement

Send this commands to the instrument to make 200 period measurements of the signal on the input D, averaged over 10 ms intervals with auto-trigger and send results. (Signal is assumed to be present on input D).

Queries (commands with ‘?’ sign) assume reading response from the instrument.

*RST; *CLS SYST:CONF "Function=Period Average D; SampleCount=200; SampleInterval=10ms; VoltageMode=VeryFast" :INIT *OPC? FETC:ARR? MAX

Instrument programming in Python environment

Installing prerequisites

Download and install NI VISA software: NI-VISA Download

Download and install latest Python 3 version: Download Python

Checking Python installation

Open command prompt:

on Windows: press Win+R, type cmd, press Enter. You will see a window where you can type commands:

In command prompt type

python --version

or

python3 --version

followed by Enter to check if python is correctly installed. You should get response indicating installed python version, like this:

Python 3.11.4

On Windows, if Microsoft Store is open when you execute “python” command or the command simply gives no response:

On Windows 11 go to Start Menu → Settings → Apps → Advanced app settings → App execution aliases and disable “python” and “python3” aliases.

On Windows 10 open Start Menu → Settings (“Gear” icon) → Applications → Applications and functions → Link “Application execution aliases”. Disable “python” and “python3” items.

PyVISA library installation

Open source PyVISA library can be used for interaction with NI VISA software which, in turn, provides functionality required to support communication with measurement instruments using protocols such as HiSLIP.

To install PyVisa library open command prompt and type:

pip install pyvisa

If you receive error message saying “’pip’ is not recognized as an internal or external command, operable program or batch file.“, then ensure that Python is correctly installed.

Check if communication with Pendulum CNT-104S device is possible from python (at the very basic level):

  • Ensure your instrument is connected to the network.
  • Start Python in interactive mode by typing in command prompt:

python

  • In python command prompt type the following lines replacing 192.168.0.25 with the actual IP address of your instrument (can be checked in Settings → User options → Network → Ethernet IP address):

import pyvisa as visa rm = visa.ResourceManager() instr = rm.open_resource('TCPIP::192.168.0.25::hislip0::INSTR') instr.query('*IDN?')

The last line executes “*IDN?” query which asks the instrument for identification information. You should get response from the instrument like this:

'Pendulum, CNT-104S, 607017, v1.2.0 2023-07-13\n'

  • Type the following to disconnect from the instrument and exit python:

instr.close() quit()

Examples

More complex scenarios imply using Python in non-interactive mode.

Here is an example showing very basic usage of python programming language to control the instrument.

#!/usr/bin/env python

# REPLACE WITH THE IP ADDRESS OR YOUR INSTRUMENT!
# (See Settings -> Settings -> User options -> Network -> Ethernet IP address)
INSTRUMENT_IP = '192.168.0.25'

import pyvisa as visa

rm = visa.ResourceManager()

def example(resource_str):
instr = rm.open_resource(resource_str) # Connect to the instrument
instr.timeout = 5000 # VISA I/O operations timeout, in milliseconds

idn = instr.query('*IDN?') # Send '*IDN?' and read response.
print('Running example 1 with {} at {}'.format(idn.strip(), resource_str))
print('In this example frequency measurement is performed on input A')

instr.write('*RST;*CLS') # Reset to default settings, clear error and message queues.
# Configure the measurement: simple frequency measurement, with timeout.
# (Pay attention to double and single quotes)
instr.write(':SYSTEM:CONFIGURE "Function=Frequency A; SampleCount=10; SampleInterval=0.01; '
'Timeout=On; TimeoutTime=1.0"')
# It's a good practice to check for errors.
err = instr.query(':SYST:ERR?')
if err.strip() != '0,"No error"':
raise Exception('Error configuring measurement: {}'.format(err))

instr.write(':INIT')

# Waiting (in a blocking manner) for measurement completion.
# *OPC? query responds back only when all pending operations (measurement in this case) are completed.
# Measurement will be complete when all requested samples are collected or if timeout occurs.
instr.query('*OPC?') # No need to use response here, because it is always '1' by SCPI standard.

data_str = instr.query(':FETCH:ARRAY? MAX, A') # Will return a string of comma-separated numbers
data_str = data_str.strip() # to remove \n at the end
if len(data_str) > 0:
data = list(map(float, data_str.split(','))) # Convert the string to python array
else:
data = []

# Display measurement results
print('Results: {}'.format(data if data else 'no data (signal not connected?)'))
instr.close()

if name == 'main':
resource_str = 'TCPIP::{}::hislip0::INSTR'.format(INSTRUMENT_IP)
try:
example(resource_str)
except visa.VisaIOError as e:
print('Error occurred: {}'.format(e))