Surface Capacitive Sensor Materials Glass substrate, transparent metal oxide coating Principle of Operation •Voltage is applied to the corners of the touch screen. •A pattern of electrodes around the periphery of the touch screen distribute the voltage to form a uniform electric field across the conductive surface. •A finger touch draws a minute amount of current from the surface and is measured by the controller. •The relative magnitude of current is inversely proportionate to the distance from the contact point to the touch screen corners. •Ratios of the four corner currents are calculated to determine the X,Y coordinate.