Circuitry is presented for the measurement of surface potential changes upon adsorption of gases on a metal foil or film by the static capacitor method. The circuit operates in the usual manner applying a backing off potential which opposes the flow of current from the cell comprised of the foil or film and a reference surface. The advantages of the present circuit include simplicity, low cost, fast response time, no moving parts, and the requirement of only one low voltage, dual‐polarity power supply.