Timing problem with counting edges

Question

Hello!
I use a NI PCI-6221 DAQ card with NI-DAQmx to count edges of TTL pulses for a spectrometric application.
It is extremely important that I count the pulses for a well-defined period of time. Typically, I want to count the edges that reach the counter in the period of 400 milliseconds.
Normally, this works quite well, when I use a WHILE loop that reads and restarts the counter every 400 milliseconds. Things change when the PC I run the VI on has other programs running in the background. Expecially computing-time intensive programs delay the 400 milliseconds of the WHILE loop for up to several 100 percent, resulting in an wrong counter read.
I tried to use a timed WHILE loop but this din't change anything, regardless of the timimg source (onboard clock or PCI-6221 counter) I applied.
Has anyone encountered similar problems and found a solution? Isn't there a possibility to control the counting time by hardware?
Thanks in advance!
EresthorMessage Edited by Eresthor on 04-07-2005 08:17 AM

Answer 1

Hej Lynn,
of course your idea works, thank you. It works extremely well this way, too.
My problem with this approach is that I need both counters on the PCI-6221 to count data from my spectrometer simultaneously on two channels. That's why I would like to trigger the counter in a different way, for example with a clock.
Is there no way to trigger the counter with the timebase of a hardware clock on the card? Or ist there another possibility without wasting a counter?
Eresthor