A variable capacitance type encoder for measuring the length of an object to be measured on the basis of detecting the amount of movement of a probe as a function of the variation of electrostatic capacity between a rotary disk which is secured to a shaft and a pair of fixed disks which are secured to...http://www.google.de/patents/US4843387?utm_source=gb-gplus-sharePatent US4843387 - Variable capacitance type encoder
