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.