Dear Bob, You are right about the power supply noise. Our SMPS was very noisy we replace it and all problems were resolved. Also the STATUS register which we were getting spurious values also stopped. Found very stable readings and spurious zero voltage given by adc also stopped. Have attached our schematic for your reference do give your suggestion if any change is required. One more point is when we give -0.34volt to TP2 we get -1.68volt (gain of 5 of opamp stage 2) at E1 point . But output given by ADC is -0.3131volt. i.e. we are getting offset of 0.028volt. Same for positive voltage. Please advice why this offset of 20-30milli volt is seen. Thank you.
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