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Analog DAQ Readings with cDAQ9179

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I am using a cDAQ-9179 with NI 9205 AI cards in slots 1-10. Card 1 is wired to signals coming from DUT 1, card 2 is wired to signal from DUT 2, and so on. When I set up an analog input task (differential) with 1 ai channel from a few of the cards (cDAQ1Mod1/ai3,cDAQ1Mod3/ai3,cDAQ1Mod5/ai3,cDAQ1Mod7/ai3,cDAQ1Mod9/ai3), set up the timing to a sample clock (rate: 44100Hz, # of samples: 4410, sample mode: finite) and then start and read (# of samples: 4410, analog multi-channel, multi-sample, 1D waveform), I get a timeout error on the read saying "Some or all of the samples requested have not yet been acquired".


If I use the same code to read from 2 channels of each card, I get no timeout error on the read.


Whether I am reading 1 signal or 10 signals from each of the cards, I would expect to be able to read the amount of samples I specified in the timing node. Changing the timeout on the read VI to -1 (indefinite) does not solve the problem.


Does anyone have an idea on what is going on here?

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If you wire a -1 to the timeout terminal of the DAQmx Read VI, does it just hang forever? It seems like the acquisition is stopping before it acquires all of the samples requested. What happens if you set the samples to read per channel to a smaller value?


J. Calvert

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If I wire a -1 to the timeout terminal of the DAQmx read, the VI hangs forever. I can lower the number of samples per read to a smaller value and fix the issue, but I have no thresholded this to see when the issue appears again.


I would still like to know why this behavior occurs when reading 1 channel from each card and not when reading more than 1 channel from each card.

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It looks like you have a service request open with another Applications Engineer. I am going to keep working with him to figure out what is causing this problem. If you are able to find a solution working on that service request, please post the solution here in case other people run into this problem.

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Message 4 of 5
Accepted by topic author mattb1
07-28-2016 01:36 PM

I was pointed to some Knowldege Base articles by NI support that lead to the solution. There is a bug with DAQmx 15.1.1 and the cDAQ-9179 chassis that I am using.



An update to DAQmx 15.5 solved the issue.

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