lowpass filter 9401

[lmrmendes]

i use a NI9401 to count a frequency of a signal

in the signal analysis i detect noise

i'de like to apply a lowpass filter (20hz) no my signal

[Kevin_Price]

You *probably* only need the 2 properties DigFltrEnable and DigFltrMinPulseWidth.  You'll need to read the manual for your cDAQ chassis because the appropriate pulse width setting will depend on what matters more:  rejecting every frequency below 20 Hz or passing every frequency above 20 Hz.   

As I recall, there's generally a factor of 2 between what's certain to pass and what's certain to be rejected.  This arises due to the inevitable quantization that comes with discrete time operations.

-Kevin P