Patent ID: 8410932

Claim:
Capacitive sensor array with a sensor electrode, by which the intrusion of an object into a space in front of the sensor electrode is detected, a control and evaluation circuit coupled with the sensor electrode that detects a change in the capacitance of the sensor electrode in comparison to a reference potential, in that the sensor electrode, at a given frequency, periodically and repeatedly couples with a given first potential, and that evaluates at least one parameter of a current and voltage profile dependent on the periodic charging and discharging of the sensor electrode, for the detection of the capacitance change, at least one background electrode located a distance behind the sensor electrode, and a shield electrode which is arranged between the sensor electrode and the at least one background electrode and which is coupled with the sensor electrode through the control and evaluation circuit so that it has no influence on the measured capacitance of the sensor electrode in comparison to the reference potential and its potential essentially adjusts to the potential of the sensor electrode, wherein the background electrode, or at least one of the background electrodes, is coupled with the control and evaluation circuit and is controlled in such a way that its potential is periodically switched at the given frequency between the reference potential and a second potential which has the same polarity compared to the reference potential as the first potential, wherein the background potential is placed on the reference potential at least during a part of those times in which the sensor electrode is coupled with the first potential, and is placed on the second potential at least during a part of those times in which the sensor electrode is not coupled with the first potential.