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U12 Offset calibration


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#1 Guest_James Dorsey_*

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Posted 12 August 2005 - 08:00 AM

I am trying to measure a Diff signal in the range of 0 to 25mV. Even with the AI0 & AI1 shorted together I get ~ 2mv offset. I have verified using a Fluke 87 the input is indeed 0 but the device is reporting 2mv. I have selected the 1V range for gain. Is there a way to "Calibrate" the Zero Offset out of the LabJack U12?

#2 LabJack Support

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Posted 12 August 2005 - 08:12 AM

That is one of the great things about PC-based data acquisition. You just enter your 2 mV offset in software to subtract it off. You could do the re-calibration procedure described in Section 3.7 of the U12 User's Guide, but I would not bother. The voltage resolution at the +/-1 volt range is 2/4096 = 0.5 mV/count, so your 2 mV of offset is only 4 counts and not unusual. Also note that each channel on the U12 has individual signal conditioning, so each channel might have a different offset. Also also note that since the resolution is 0.5 mV/count, you will only get about 50 counts across your entire 25 mV range.



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