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AD5940 (Ramp example & Calcuration Rtia in Amperometry)

Dear all,

I have a little problem during testing the Ramp example. I used ad5940,adicup3029 (Evaluation board)  and crocodile clip cable.

I  configured hardware by referring to this site(AN-1563 (Rev. 0) (

I constructed the circuit & coding like a picture 

and the result is the following picture.

This is the same result as connecting resistance only.

 I think this is a problem caused by cap and diode or ad5940's hardware configuration.

How this could be fixed?

+ The link mentioned earlier contains the Rtia formula for all examples except amperometry. What should I refer to?