Abstract: A new design scheme of proximity capacitive sensor used for automatic car wiper control system is presented. It aims to develop a low-cost sensor with high sensitivity and robustness. The principles of sensing technique based on optical, piezoelectric and capacitive sensors are introduced respectively. Three types of proximity capacitive sensors are designed, and their performances are simulated by using COMSOL and Matlab under the same conditions. The key parameters of the sensor design are discussed and determined. An impedance analyzer is used to measure the fringe capacitance between each electrodes pair. At the last, the system noise occurring in measurement is discussed and the solving method is given. The experimental results indicate the validity and importance of the capacitance-based sensing technique which can be used in an automatic car wiper control system.

Key words: Fringe effect, Impedance analysis, Proximity capacitance sensor, Sensor design