Patent ID: 7375536

Claim:
A touch switch device with an electric circuit for at least one capacitive sensor element, wherein: the circuit is designed as a switch capacitor circuit for the sensor element and is provided with a micro controller, the circuit is provided with at least one sensor branch, the sensor branch contains the sensor element and a charging capacitor, the sensor element has a non-triggered state and a charged state, the charging capacitor is charged with a charge of the sensor element responsive to a touch by a user on the touch switch until it reaches a switching voltage, wherein the sensor element is repeatedly charged to a first charge in a first step, and the charging capacitor is in turn charged with the first charge in a second step; the sensor branch is connected with the micro controller, the micro controller is provided with a reference circuit, wherein the reference circuit has a reference charging capacitor and a reference capacitance which are in a known ratio with a capacitance of the sensor element in the non-triggered state, wherein the reference capacitance is repeatedly charged to a reference charge in a first reference step, and the reference charging capacitor is in turn charged with the reference charge in a second reference step, and the micro controller compares a number of charge processes in the sensor branch associated with repeatedly transferring the first charge from the sensor element to the charging capacitor with the number of the charge processes in the reference circuit associated with repeatedly transferring the reference charge from the reference capacitance to the reference charging capacitor until said switching voltage is reached; wherein the reference capacitance corresponds approximately to the capacitance of the non-triggered sensor element, and wherein the reference capacitance is provided in the micro controller.