An accurate low-cost capacitive absolute 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. The sensor is mainly composed of three parts: the capacitive sensing element, a signal processor and a microcontroller. Using an appropriate algorithm, the effects of the main undesired influences are eliminated or strongly reduced. The measurement range covers the full-circle range (360°). The structure of the sensing element is optimized to reduce the influence of the electric-field-bending effect and the mechanical errors. The signal processor has a multicapacitance input and a single period-modulated output, and includes a nearly linear capacitance/period converter. The microcontroller acquires output data from the processor, calculates the positions and optionally communicates with the outside digital world. The resolution of the smart capacitive angular-position sensor is 1.5 arcsec, and the nonlinearity is less than ±58 arcsec over the 0-360° range for a measurement time of 140 ms