Abstract: A process and a system for controlling a windshield wiper, in particular on a motor vehicle, employs a sensor which recognizes the intensity of the rain. The sensor gives off a signal whereby the windshield wiper is automatically controlled as a function of the intensity of the rain. A variation in the signal of the sensor is effected by random signals produced by the continuous movements of drops of water, and serves as measure for the intensity of the rain. In order to assure an optimal and reliable control of the windshield wiper as a function of the intensity of the rain, there is a monitoring of the time between a first sudden change of the signal and a second sudden change. When the time exceeds a given value, the windshield wiper is controlled as a function of at least an earlier one of the sudden changes in the sensor signal which precedes the aforementioned first sudden change.

Abstract: In a wetness sensor for a window of a motor vehicle, a heating resistor arranged in the window and powered by DC current can be connected to a measuring device for measuring an AC impedance of the heating resistor, in particular the capacitive portion thereof. The impedance varies with the amount of wetness and, thereby, serves as a measure of the wetness. A capacitor is used to bring the sensor near resonance for improved sensitivity.

Abstract: A process and a system for controlling a windshield wiper, in particular on a motor vehicle, in which a rain sensor is located on the glass to be wiped and within the region of the windshield wiper. The sensor outputs a sensor signal as a function of the amount of moisture. The signal is detected periodically and, when a reference degree of moisture is reached during a measurement cycle, the system produces a triggering signal and the windshield wiper is activated. The wiping process takes place even when the windshield wiper is wetted with moisture only to a slight but nevertheless disturbing extent. In the process, when a degree of moisture below a reference degree of moisture is present at the end of the measurement cycle, this degree of moisture is included additively to the degree of moisture of a further measurement cycle. Thereupon, the degree of moisture of the further measurement cycle is compared with the reference degree of moisture.