Measuring Digital Frequency
The digital frequency of a signal is the inverse of the period of a signal. To get the frequency of the signal, take the inverse of the period. The formula for frequency is Frequency (in Hz) = Counter Timebase Rate (in Hz) / Count.
The Counter Timebase Rate is a known frequency and is usually a built-in time source. If the counter timebase rate is unknown, you only can make measurements only in terms of ticks of the counter timebase. This may be the case if you are using an external signal for the counter timebase, and the frequency of the external signal is unknown or aperiodic.
Digital frequency is an example of a time measurement. Refer to Configuring a Time Measurement in NI-DAQmx and Two Counter Measurement Method for more information about measuring time.