A SMART CAPACITIVE ABSOLUTE ANGULAR-POSITION SENSOR

This paper describes a novel low-cost smart accurate capacitive absolu te angular-position sensor with high accuracy and high resolution (18 bits r.m.s.). One of the novelties of this sensor is that, for each me asurement, it uses all 24 segment electrodes along the circumference, each of them ranging from 0 to 0.3 pF. The capacitance values between these electrodes have a lot of redundancy with respect to the position to be measured. The electronic processing uses this redundancy to com pensate for mechanical errors in the sensor in order to obtain an accu rate measurement and to reduce the mechanical demands on the sensor. T his novel approach can also be applied directly to capacitive absolute linear-position sensors. A simple and cheap oscillator is used to mea sure the various sensor capacitances. The oscillator converts the anal og capacitance information into the time domain and is directly digiti zed by a microcontroller, eliminating the need for an expensive AD con verter.