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Data Logging Time Skips?

Hello all,

 

I am logging data to disk using TDMS write in a producer-consumer architecture. I noticed in my test data that there are few instances where there is irregular data intervals. For example, when I set my data logging rate to 1 per 10 seconds, there are few spots where data is taken at 10.1 seconds. See the attached images to get an idea of what I mean. In the example, data1 is written at 21.204 seconds and data2 is written at 31.214 seconds, while my data logging rate is set to once every 10 seconds. This also starts drifting the data longer and longer. I usually run day long tests, so this drift could be very bad. 

 

Any idea what causes this? It seems to me to be some hardware timing limitation. I am, however, running LabVIEW on my laptop using a simulated PXIe 6361.

 

Thank you for your time

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At the moment, I'm inclined to think it is due to simulating the hardware (therefore, you have software timing involved).


GCentral
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@crossrulz is probably correct.

 

That being said, some suggestions.

  1. Use a notifier for your display and a queue for writing to the disk. Notifiers are lossy, if you miss one, then you only lose the display, queues are not lossy, thus your file never misses a point.
  2. Since you are writing TDMS files, just use the built in lugging function, no producer-consumer necessary and much better.

mcduff

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