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cDAQ reporting 0.000000V reading


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I have a program that reads a cDAQ NI 9221 Analog input card. Occasionally (1 in 3Billion), one of the values is 0.000000V.


Using an NI 9189 chassis with an NI 9221 Analog input card. The task is set up to capture at an 8k rate and read n samples at a time. My program reviews the values and records a 2000 point chunk to excel if there is an error with the voltages. The program needs to run for 45hrs at a time, so over a billion readings per run.

Once in a while, maybe once every three 45hr cycles, one of the errors logged is because of a 0.000000V reading. Adjacent readings are perfectly fine, and do not ramp in or out to 0. And since the 0 value is absolutely 0V I am suspicious that it is not coming from the DAQ but is instead a memory issue in the PC.

Has anyone else experienced this?

Here is an example of readings:

23.731911
23.762417
23.792923
0.000000
23.792923

 

1 occurrences in 3Billion is very good for consistency, but I am curious why.
If the SW is stable looping for 3Billion readings, I don't think its anything with my code. 
 

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  • 4 weeks later...

Is it still an issue or have you solved it?

  • It's not entirely clear that the error is random, or occurs "reliably" after the 3x45 hours.
  • How is your time sampled? Is it possible that the hardware clock and software clock not being perfectly synchonized causes the problem?
  • Is there any middle data processing bewteen DAQ and voltage checking?
  • The 0.0000 is in the middle of a DAQ read chuck or at the begining/end? Or maybe a whole chunk, so for some reason the buffer is not ready when you read it?

Sorry, I'm no expert in NI DAQ, for little quircks like this (and it seams to have a "soul") we are not using NI for DAQ...

Edited by Lipko
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