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How correctly using USB 6251 to measure DC voltage

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Hi all

I have encounter a problem like in the topic http://forums.ni.com/ni/board/message?board.id=170&message.id=404676&query.id=250408.

I'm sorry for repeating of topic but I've read all of your advices and have not yet resolved problem. 

My task very simply: I use USB 6251, differential mode to measure voltage of battery Energizer 1.5V. But result shows >10V ??? Mean.vi shows bigger 4V (see the attached picture)

I don't understand what happed with my task?

Please help me!

Thank so much!

MC

 
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Accepted by topic author nguyenmanhcuong

Hello,

Thank you for posting to the NI Forums!

 

How do you have your battery connected? Are you using bias resistors? This could be a grounding problem and may be fixed if bias resistors are used. Check out Table 1 in this document and the differential configuration for a floating source.

Regards,
Margaret Barrett
National Instruments
Applications Engineer
Digital Multimeters and LCR Meters
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Thank Flaugher

I did not connect bias resistors. But now I do another way: connect possitive pole of battery to the AI0 and other to the AI GRD, choose input configuration "RSE" and get good results. 

 

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