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USB 9219 repeated data values

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We are using a USB 9219 to read and log Analog Voltage data at 100 Hz, (high speed mode) with no problems until today.

 

Suddenly the data being returned consists of exactly 50 consecutive repeated values at a time, as if the data was latching every 1/2 second but was being read at 100 Hz.  This is only happening on a single device - we have several in use - but it is in the middle of a long term test.

 

Screenshots of the Acquisition loop and the Init Task.vi are attached.  Sample rate is set to 100 (Hz) and Number of Samples is set to 10.

 

Thanks for your ideas.

 

David

 

 

 

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It looks like you have a large application and have posted part of it. Can you verify the module is working properly by itself? Try it in Measurement and Automation Explorer as well as open an example. If this works, then it is something with the way the application is written.

When you do a read, how many samples are you pulling at a time? You say it looks like your are latching every 1/2 second, how do you know this - are you determining this from the time information stored in the waveform data? What is your sample rate set to on the first image? Can you post a sample of your waveformdata?

 

 

--Michelle

PXI Software R&D
National Instruments
PXI
Machine Vision
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Thanks Michelle, we got it.  All the other tests were done with a USB 9219 in the single USB 9216 carrier.  For the problem test they had put the 9219 in a cDAQ chassis 9172.

 

To work in the chassis the timing mode had to be explicitly set to high speed with a property node.  I didn't see that in the documentation - I must have missed it - perhaps you can point me to the correct passage so I can read it for the future.

 

The module worked as desired in MAX, but had the same problem when run with the shipped example "TDMS Streaming - Cont Log and Read Data.vi".

 

They were taking 10 samples at a time, the 2 Hz was based on the time stamps stored in the waveform data, and the sample rate was set to 100 Hz.

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