The sensor pads of CapSense connect to the PSoC pins through low resistance traces of a printed circuit board or flex circuit. This electrical connection needs to be under direct control of the PSoC for CapSense to work correctly. A DC voltage placed at this point will interfere with the operation of CapSense, so prevent an DC voltage from directly driving the CapSense sensor pad. The touch surface is normally covered by a millimeter or more of plastic or glass, so this provides insulation between the finger and the sensor pads. A DC voltage on the finger has no effect on the performance of CapSense, even up to many kilovolts.