In-situ monitoring during processing of a substrate includes processing a conductive film on a substrate in a semiconductor processing apparatus and generating a signal from an eddy current sensor during processing. The signal includes a first portion generated when the eddy current sensor is adjacent the substrate, a second portion generated when the eddy current sensor is adjacent a metal body and not adjacent the substrate, and a third portion generated when the eddy current sensor is adjacent neither the metal body nor the substrate. The second portion of the signal is compared to the third portion of the signal and a gain is determined based at least on a result of the comparing, and the first portion of the signal is multiplied by the gain to generate an adjusted signal.