counter

[James_R]

I am using LV7.1 with a PCI 6025E DAQ.  I am counting pulses from counter 1 using the DAQMX VI's and I get unstable results under 700ms per read.  I should get 342 pulses per second during normal operation and when I go below 700ms the results start to swing and when you get to 100ms per read the results swing from 340 to 350. 

What can I do to get the accuracy i have at 700ms at 100ms where i need it.

I have a 2.5GHz P4 running windows xp pro with 2 GB of RAM

[Tom_W_[DE]]

Hi James-

It looks like you are trying to perform a frequency measurement of your unknown digital signal.  Is this correct?  If so, you may be interested to know that your card supports hardware-timed frequency measurements that will not be susceptible to the O/S jitter you appear to be running into now.

A great example of calculating frequency with NI-DAQmx is "Meas Dig Frequency-Low Freq 1 Ctr.vi" or any of the other examples found in the NI Example Finder (Help>>Find Examples) under Hardware Input and Output>>DAQmx>>Counter Measurements>>Digital Frequency.

Hopefully this helps- please post back if I have missed the point of your application.