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Streaming provides different results for analog inputs


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#1 simon51

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Posted 29 June 2012 - 08:43 AM

Hello all, I'm using a U6-pro to acquire analog data with Labview. I noticed that using streaming of using the easy functions doesn't yield the same results. I'm using the easy functions with the highest resolution, and the streaming with the lowest. It looks like an offset or gain mismatch. My question is: is the build-in factory calibration in use when I use streaming? If not, how can I apply it myself (with Labview)? Regards, Simon

#2 LabJack Support

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Posted 29 June 2012 - 10:11 AM

You will often see small changes when you change gain, as the their is a calibration for each gain. There is also a calibration for each converter, so you might see the same reading for resolutions 1-8 and the same for 9-12, those those 2 groups are slightly different. If you are seeing the readings change as you increment resolution from 1 to 2 to 3 ... and so on, that is often a sign that there is a problem with the signal (e.g. too much source impedance). Do you see this with a known low-impedance signal, or just your signal? For example test with a jumper from the channel to GND. DF just makes calls to the UD driver, and the UD driver uses the calibration. As an alternative to DF, you can test with LJLogUD and LJStreamUD.

#3 simon51

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Posted 29 June 2012 - 11:13 AM

Hello and thank you for the quick answer I didn't know there are 2 different converters according to the resolution. The issue probably comes from here. I should be using the first in one case and the second in the other. I will check again. Simon


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