Large offset voltage in NI 6011E

[rgentry]

I have an older data acquisition system that has performed flawlessly for 5+ years.  Now I am experiencing a DC offset voltage of 0.1394 volts on the NI 6011E on each channel of the system (this is on the +- 10 volt scale).  If I switch to a +- 1 volt scale, the DC offset voltage is 0.01394 volts.  I call this an offset voltage because this is the voltage I read when I short the two leads connected to a floating channel together.

This system has never been calibrated.  Do I need to calibrate the board or replace it?

I have a large number of new systems using Labview 8 with newer hardware.  This system is a legacy system and is not used that frequently.  If I upgrade one component -- I will need to replace the entire system (computer, operating system, data acquisition, MAX, Labview, etc.).  So, I am trying to get it corrected without replacing anything.

I could do something very kludgy like putting the offset voltage into Labview as a constant and then subtracting this value from every measured result. 

[Brian F.]

Hello rgentry.  The board does seem to be exhibiting behavior that indicates the need for calibration.  The fact that the board is still taking readings that are close to the expected value, but not precise is a great indication that the accuracy of the board has drifted a bit.  Luckily, NI does offer calibration services for a large number of its boards including the 6011E.  For information about this process, please refer to:

Calibration Solutions from National Instruments

http://www.ni.com/support/calibrat/

For a list of Calibration Service Partners, please visit:

Calibration Services

http://www.ni.com/support/calibrat/calcert.htm

I hope this is informative!  If you need any further guidance, please let us know!

Brian F

National Instruments

[rgentry]

Thanks Brian.  So if I send the board in to NI, it will be calibrated and the new calibration constants will be stored on the board.  Is that correct? 

If the board, is toast, I assume that the calibration procedure will indicate this and that there will be no cost for the calibration ( I will of course then be purchashing a new board! ). 

Thanks again for your help.

[Brian F.]

Hi rgentry.  If you send the board back, only calibration will be done at your request.  If you wish to have the board fully tested, there probably will be an additional cost for that testing as well.  However, I believe that since your card is still taking fairly good readings with a DC offset, all that needs to be done is some calibration.  For the best level of support regarding cost associated with the testing, I would recommend contacting our customer service representatives.  This process, specifically tailored to calibration requests, is outlined at the following link

Sending a National Instruments Board in for Repair or Calibration

http://digital.ni.com/public.nsf/websearch/5b6448ed65ea711186256a3700800c67

Please follow these steps and a customer service representative will be able to give you more specifics on this process, price considerations, and shipping specifics.  We look forward to hearing from you!

Brian F

National Instruments