DAQmx counting tach pulses stops counting as speed increases

[nano2nd]

I am trying to count tach pulses using DAQmx 6254 ctr 0 in a PXI. The counter is read in a timed loop and the count value is passed to another slower, lower priority timed loop using a shared var with rtfio enabled.  It counts correctly at lower speeds but stops counting as the speed increases. As the speed comes back down, the counter starts counting again.  Once I get this working I need to run a control loop every time x pulses are counted.

[tbd]

Hi nano2nd,

      What's the magnitude, duration and frequency of shortest expected pulse(s), and, any chance of your sharing some code(?) - even a PNG of the timed-loop is better than nothing.

Have you watched the pulse on a scope - preferably with all the DAQ hardware also connected - to be sure pulse is "behaving"?

Cheers!

Message Edited by tbd on 12-04-2008 09:14 PM

[Jordan F]

Hi nano2nd,

I attached an example (LabVIEW 8.2) that sets up a counter task and uses a shared variable to update an indicator.   I would recommend to try the example I attached to see if it works at a higher frequency (I was able to get 1MHz counting).  Also, I am interested in the answers to the questions in the previous post. 

Message Edited by Jordan F on 12-05-2008 02:21 PM