In an attempt to develop an automated potentiometer measuring device I have implemented the following op-amp based voltage controlled current source, controlled by the output of a DAC. The voltage across two terminals of the potentiometer is then measured using a differential ADC (not pictured) from which one of the resistances is found.
I'm having a problem with this circuit in that the DC offset introduced in the op-amp is causing problems when the potentiometer resistance is low. The measured voltage goes negative instead of positive, or remaining at 0V.
To correct this I am thinking of using a chopper-stabilized op amp to minimise the DC offset. This would also need to be rail-to-rail as the supply it is driven from is a single supply +15V. Do these exist?
My question is: would this suitably reduce the DC offset? Or is there a compensation technique I could use in this circuit to reduce the offset?