A substrate support apparatus for a plasma processing system includes a layer of dielectric material having a top surface and a bottom surface. A calibration circuit receives each uncorrected digital value and outputs a corrected digital value. In this storage system, a write process that writes write data to the first storage area is executed. When the control signal is utilized to selectively enable or disable a soft-mute function of the demodulator, the calibration module can be utilized to calibrate or determine the soft-mute function of the demodulator.