An accurate smart capacitive angular-position sensor with a full circle range

A novel high-performance smart capacitive angular-position sensor with a full circle measurement range is presented. It is mainly composed of three parts: the capacitive sensing element, a signal processor and a microcontroller. A modified algorithm is used to calculate the position from the capacitor´s values. With this algorithm the effect of the main undesired influences is eliminated or strongly reduced and the measurement range of the sensor is extended to 360°. The structure of the sensing element is optimised to reduce the influence of the electric-field bending effect and the nonflatness of electrodes. The signal processor has multi-capacitance input and one period-modulated output and includes a very linear capacitance/period converter. The microcontroller acquires output data of the processor, calculates the positions and optionally communicates with the outside world. The resolution of the smart capacitive angular-position sensor is 0.58 arcsec and the nonlinearity is less than ±90 arcsec (13.8 bits) over 0-360° range for a measurement time of 100 ms