A variable-capacitance transducer detects the angular position of a rotatable member. The transducer includes a first capacitance plate having a plurality of electrically conductive capacitance electrodes, a second capacitance plate spaced therefrom, and a dielectric element located between the plates....http://www.google.com.tw/patents/US5099386?utm_source=gb-gplus-share專利 US5099386 - Variable-capacitance position transducing
