Sampling rate issues in Labview

[THERMAN]

Hi Everybody,

I'm trying to measure an oscillating pressure signal using an Endevco 8530C through a NI 9237 module. 

For start, I'm trying acquire 1024 samples in a rate of 1024/sec, which should take a full second to complete. For some reason when I use the DAQ assistant, it only measures for about 0.6 second instead of a full second. Changing the number of samples or the rate does not help, and it still doesn't take the full measurement.

Nevertheless, when I do the same thing using the DAQmax, it works fine.

Any ideas as to what I'm missing here?

Two screenshots are attacked.

Thanks! 

[crossrulz · Accepted solution]

Your problem is you need to read the data sheet.  On page 8 you will see a section on Data Rates.  In it, you will see that the slowest the 9237 can sample at is 1613 S/sec.  So that is the rate the task is actually running at.  So (1024 S)/(1613 S/sec) = 0.635 sec, which corresponds with what you are seeing with the DAQ Assistant.  Your other graph is showing sample numbers, not time, so that is not a valid comparison.