Hardware Average of Counter Measurements over a Period of Time

Updated Jan 8, 2018

Reported In

Driver

  • NI-DAQmx

Issue Details

I would like to measure a signal whose frequency is varying in time around a specific value. I cannot use instantaneous measurements and I would like to perform an average on the frequency or period of the signal. Is there any built in functionality of the NI counter/timer boards that I could use ?  

Solution

The NI Multifunction and counter/timer boards used together with the NI DAQmx driver have an integrated averaging functionality. It can be accessed via the DAQmx Channel property node.

 

For frequency and period measurements using Sample Clock timing, some devices can return an averaged measurement of all periods since the previous Sample Clock pulse, instead of measuring only the period immediately preceding the current Sample Clock pulse. Use the EnableAveraging DAQmx Channel property/attribute, associated with each of those measurement types, to enable averaging.

If you card contains multiple counters, you could use one of them to generate a custom Sample Clock, thus specifying over which period to perform the averaging. The custom Sample Clock signal can be routed internally, using one of the PFI lines, thus eliminating the need for external wiring.


 

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