Capacitive position sensor

US5077635A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Heins-Erdam Bollhagen · Leonberg, DE
• Siegbert Steinlechner · Leonberg, DE
• Berthold Wocher · Gaiberg, DE

Key dates

• Filing date: Apr 8, 1991
• Grant date: Dec 31, 1991
• Expiry date: Apr 8, 2011

Classification

• Technology area (CPC G): Physics
• CPC primary: G01D5/2412
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A capacitive position sensor includes a capacitor arrangement assembled of a stator (5) and a rotor (6). The stator supports at least three coplanar electrodes (21, 22, 23) having the shape of circle sectors 120.degree.. The rotor supports at least a counterelectrode (25) having the shape of a circle sector of 240.degree.. An oscillator (30) applies two a.c. voltage (u1, u2) of equal amplitude and opposite phase to two of the stator electrode (21, 22). The range of rotation of the rotor is such that the remaining third electrode on the stator is always overlapped by the counterelectrode. Voltage induced on the counterelectrode by means of the a.c. voltages on the stator electrodes is inverted and fed back as a neutralizing voltage (uR) to the third stator electrode (23) until the induced voltage on the counterelectrode reaches zero value. The neutralizing voltage is rectified and integrated into a d.c. voltage (UA) which serves as a measure of the angular position of the rotor (6).