The Electroquasistatics of the Capacitive Touch Panel

Abstract

The capacitive touch panel is a high-resolution position sensor intended for computer displays. A practical panel must be safe and inexpensive and must sense position accurately in spite of electrical noise, dirt, or direct electrostatic discharge. The implementation discussed here uses a quasi-static electric field, applied to a semiconducting coating on the panel surface. A touch draws current from the surface. This current can be used to compute position. If the computation is performed properly, the computed position is independent of touch current and panel coating resistivity. The electroquasistatic basis for position measurement with a capacitive touch panel, and a system to implement it, will be described. © 1990 IEEE