Difference between CI Freq and CI Pulse Freq

[BikeBandit]

I'm using a NI 9401 to collect counter data for a optical tachometer and a flow meter but I noticed there was a specific subsection of DAQmx counter channels for Pulse measurement.  I think I understand the Pulse time and pulse tick inputs but I'm not getting the Pulse freq.  Namely I don't understand how that is different than the normal CI Freq measurment.

Glancing at the LabVIEW detailed help doesn't seem to offer a clear difference that I can see. I don't suppose anyone can explain the difference or has a link to a resource explaining this in greater detail than the help document?

Thanks,

Richard

[chaka123]

Hello BikeBandit,

The CI Freq measures the frequency of a digital signal, while the CI Pulse Freq returns the frequency and the duty cycle of the signal.

Regards,

Carmen C.

[BikeBandit]

Thanks for the reply Carmen.

So then the frequency measured by both could be the same I imagine?

Richard

[John_P1]

CI Freq predates CI Pulse Freq (which only works on STC3-based devices like X Series and cDAQ other than the 9172).  The frequency measured by each should be the same, but the pulse measurement also computes duty cycle like Carmen mentioned.

The X Series User Manual has diagrams of how each method works.  The CI Pulse Freq method results in twice the data needing to be transferred, but that's really only a concern if you are taking high frequency buffered measurements.

Best Regards,