A method for pre-processing electrical sensing signals for compensating for common mode to differential mode conversion caused by signal transfer function nonlinearities. Linearization functions are applied to the input signals to counter the nonlinearities. The method includes a calibration process in which a plurality of sets of standardized test signals are applied to the input channels of the measurement operation, and corresponding test outputs measured for each test signal set. The parameters of the linearization functions are set based on the obtained dataset of test outputs.