A capacitive sensor with at least one reference impedance and at least one measuring condenser (5), with at least one electrical alternating signal source (6), with a current supply network as well as with an analysis unit (7) in which the reference impedance and the measuring condenser (5) are connected...http://www.google.de/patents/US7724002?utm_source=gb-gplus-sharePatent US7724002 - Capacitive sensor
