Remote Power Sourceless Encoder Using Resonant Circuit with Loop-type Coil

Abstract

Implantable encoder for angle or position detection is one of the most required devices especially in the medical field. Power source and connecting wires are necessary for conventional optical or magnetic type encoders. Because direct connection from the implant devices to outside devices causes necrosis around the wiring points on skin, it is difficult to apply those conventional method to implantable devices. In this study, new remote rotary and linear encoders, which consist of an LC circuit with a loop type coil and a parallel-plate capacitor, are proposed. In this system, the capacitance of the parallel-plate capacitor varies with rotation or displacement, and the change of the resonant frequency is remotely measured by a dip meter. A method for linearization of resonant frequency to displacement is also developed. Several experiments with trial devices show validity of the encoder system.