Capacitive proximity sensor

An elongated sensor electrode assembly (4) has sensor and auxiliary electrodes (5,6) arranged at a predetermined minimum distance. Electrode assembly is connected to a control circuit. Sensor electrode is connected respectively to low electric potential node and capacitor at specific time periods. Auxiliary electrode is connected to a high electric potential node. An insulator cover (10) is arranged on a cover (2) for hermetically sealing the electrode assembly. Distances (12,13) of sensor electrode from outer surface (11) and front surface of cover are about 10 mm.