Metal detection process includes calibration operations to determine a plurality of gain settings and a plurality of model parameters, each corresponding to a region through which a moving metal door travels as it traverses a predefined motion path. Thereafter, a corresponding one of the plurality of gain settings is selected, and a corresponding set of the model parameters are selected. The selected gain setting control AFE gain so as to maintain the output of the AFE within a predetermined valid operating range. The model parameters are used to cancel the influence of the moving metal door from output controlled AFE signal.