Prototyping of flexible capacitive encoder with un-tethered slider using electrostatic induction

This paper describes a capacitive linear encoder that is characterized by its un-tethered sensor slider. The main components are made of flexible printed circuit films measuring only 0.2 mm in thickness that allows the sensor to be set up in thin interspaces or on curved surfaces. The sensor consists of a long receiver film and a short transmitter film, respectively containing four-phase and two-phase electrode; the transmitter is used as a slider and the receiver as a stator. To realize an un-tethered slider, the sensor employs a unique approach; electric power is supplied to the transmitter film by electrostatic induction, thus removing electric wires from the slider. This un-tethered slider can facilitate the sensitive applications where mechanical disturbance caused by an electric wire can be a problem. The principle was verified using a prototype encoder, which showed a linearity error of +/- 10 micrometers.