DAQ-6601 Hardware Buffered Input

[vikg]

Hi, we are trying to sample a input (basically pulses) using an edge-counting counter task.
Recently, we discovered that not all pulses were being read, or some were being dropped.

So, we added a DAQmx Timing block, however getting it to work has proven difficult. We are using the sample clock setting, but setting the rate at 1000 and the sample clock as the 20MHz timebase is not allowed as
"Sample Clock Rate must match the frequency of the internal timebase specified as the Sample Clock Source."

Changing the rate to 20,000,000 (20MHz) results in "Data was overwritten before it could be read by the system."

It seems impossible to clock in at the default timebase, or even at a fraction of the time base

[Erik_J]

Hi vikg,

You shouldn't use a DAQmx Timing VI with a Counter Input task.  This is because you don't need to set a sampling rate, the counter will simply count the edges up to the maximum frequency it is able to count.

At what frequency are the pulses being generated?  And what card are you using to count the edges?  Our E-Series cards can count edges on a pulse train of up to 20 MHz and our M-Series cards can count edges on a pulse train of up to 80 MHz.

What is generating the pulses?  Have you tried generating a pulse train on another device at the same rate and counting those edges?  You could even generate a pulse train on the output of counter 0 on your DAQ card and count the edges on counter 1 on the DAQ card.  This way you can see if there is a problem with the card or the hardware generating the pulses.

I hope this helps!

Regards,
Erik J
Applications Engineer
National Instruments