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AD7982_Eval Board  not Correct?

Question asked by Victor_sg on Jan 20, 2017
Latest reply on Feb 12, 2017 by Victor_sg

I am evaluate AD7982 performance with AD7982 evaluation board with Eval-SDP-CB1Z communication board. But the reading seems not correct.

Case 1: Without any input,  DC reading seems correct. Its output due to zero differential input should be zero too. But Reading is 2.501V(first photo). IN+=2.5V, IN-=2.5V.

Case 2: Vin+=3.5VDC (1VDC overlap on 2.5V VCM), Vin-=2.5VDC (actually no input). Output reading should be 1V. But actual reading is around 3V. (second photo). IN+=3.5V, IN-=2.5V.

Case 3: Vin+=1.5V (-1VDC overlap on 2.5V VCM), VIN-=2.5VDC (no input). Output reading should be -1V. But actually reading is  near 2V. (3rd photo). IN+=1.5V, IN-=2.5V


We plan to use AD7982 to measure DC current in our application.  Last photo is the board set up. Could any one help on this?