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Sample Clocked Buffered Frequency Measurement

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    Last Modified: February 26, 2018

    Sample clocked buffered point frequency measurements can either be a single frequency measurement or an average between sample clocks. Use CI.Freq.EnableAveraging to set the behavior. For buffered frequency, the default is True.

    A sample clocked buffered frequency measurement with CI.Freq.EnableAveraging set to True uses the embedded counter and a sample clock to perform a frequency measurement. For each sample clock period, the embedded counter counts the signal to measure (fx) and the primary counter counts the internal time-base of a known frequency (fk). Suppose T1 is the number of ticks of the unknown signal counted between sample clocks and T2 is the number of ticks counted of the known timebase as shown in the following figure. The frequency measured is fx = fk * (T1/T2).

    Figure 1. Sample Clocked Buffered Frequency Measurement (Averaging)

    When CI.Freq.EnableAveraging is set to False, the frequency measurement returns the frequency of the pulse just before the sample clock. This single measurement is a single frequency measurement and is not an average between clocks as shown in the following figure.

    Figure 2. Sample Clocked Buffered Frequency Measurement (Non-Averaging)

    With sample clocked frequency measurements, ensure that the frequency to measure is twice as fast as the sample clock to prevent a measurement overflow.


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