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AI SENSE used for offset cancelling

I am planning to use a LEM CASR 6N current transducer and a NI USB6218 to measure current in 32 channels. The LEM CASR 6N has a 2,5V offset voltage I want to remove before ADC measuring. This could be done by 32x differential amplifiers, but it seams to be much easier to use the NRSE measurement mode and a 2,5V offset on the Analog Input Sense (AI SENSE).

 

In the Field Wiring and Noise Considerations for Analog Signals - NI it is stated: the potential at this node(AI SENSE) can vary with respect to the measurement system ground (AI GND). But I can't fin any specification of how much the AI SENSE potential can vary from AI GND. Is 2,5V OK?

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Based on the simplified circuit, AISENSE should have the same electrical specifications as the AI channels as it just replaces all the AIx- channels with one AISENSE

santo_13_2-1635259141385.png

 

santo_13_1-1635259113302.png

I believe you will be calibrating this 2.5V offset somehow as the actual offset on each current transducer will definitely vary based on accuracy specifications.

 

Santhosh
Soliton Technologies

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Thank you very much Santhosh

Actually the 32 LEM CASR 6-NP can run on the same external 2,5V reference, but they will be individual calibrated as well.

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