QUsing unity gain as your data sheet RevB page 5 Figure 5. Vin in the range 0 to
+5v, have attenuated battery voltage with a potentiometer. Concerned for
overvoltage protection, is there any protection built into the Ad202 ? Have
tried a clamp diode Pin 1 to 2. In concept this works, but have seen the
linearity worsen from 0.1% to about 0.7% in the range 0 to 5v, for a 10v clamp
using Panjit's Sa10CA transient suppressor. With a 5v clamp using the Sa5SC
this linearity worsens to 10%.
AThe AD202 module does not provide any Input protection. Input protection (if
needed) must be provided by the user.
Based on your information, it sounds like the protection that you are providing
has leakage currents that vary with signal in the 0 to 5V range.
You could try to reduce the impedance of the resistive divider to see if this
improves the problem.