Abstract: A signal conversion system wherein variable amplitude alternating current signals from instrument sensors, which represent the magnitude of measured physical variables or control signals by amplitude modulated alternating current voltage signals, are converted to variable amplitude direct current or voltage signals (FIG. 1). The input signal is filtered for normal mode noise and capacitor isolated for common mode noise. The conversion process also includes magnitude scaling of the variable amplitude input signal, including but not limited to, square root extraction and linear amplitude adjustment.