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).

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.

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.

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.

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.

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=TS_CH3-TS_CH1Period= TS_CH2-TS_CH1

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.

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.