A capacitive sensor array including a sensor electrode which detects the intrusion of an object, a shield electrode and a background electrode. A control and evaluation circuit is coupled to the sensor electrode which detects a change in the capacitance of the sensor electrode. The sensor electrode periodically evaluates at least one of a current and voltage profile to detect the capacitance change. The shield electrode is coupled to the sensor electrode through the control and evaluation circuit such that it has no influence on the measured capacitance. The background electrode is controlled such that its potential is periodically switched between the reference potential and a second potential. When the sensor electrode is coupled with the first potential, the background electrode may be located on the reference potential. When the sensor electrode is not coupled with the first potential, the background electrode may be located on the second potential.