Patent ID: 7920122

Claim:
A control knob of a motor vehicle, said control knob comprising: an electromechanical transducer ( 31 ); a mobile part ( 25 ) coupled to the electromechanical transducer ( 31 ) and rotatably about a vertical axis ( 27 ) with the electromechanical transducer ( 31 ) disposed below the mobile part ( 25 ); a metal surface ( 37 ) surrounding the electromechanical transducer ( 31 ) and coupled to and disposed below the mobile part ( 25 ); a dish ( 39 ) disposed below the mobile part ( 25 ) and supporting the metal surface ( 37 ) with the dish ( 39 ) comprising a metal-coated joint ring ( 47 ) abutting the metal surface ( 37 ); and means to measure the capacitance ( 63 ) of the metal surface ( 37 ) with the metal surface ( 37 ) electrically connected to the capacitance measurement means ( 63 ) through the joint ring ( 47 ).