Patent ID: 7208962

Claim:
A device for detecting environmental change of an automobile windshield, comprising: a plane capacitor including two electrodes disposed on a common plane on an inner surface of said windshield, the electrodes having a total area of less than 100 cm 2 , environmental change of said windshield effecting a change in capacitance of the plane capacitor; and a sensor circuit operatively coupled with the plane capacitor and adapted to couple test signals to the plane capacitor and receive said test signals therefrom modified in relation to said change in capacitance so as to develop change signals corresponding to environmental change of said windshield, such that equipment working on said windshield in response to the change signals operates in closed-loop fashion to affect said environmental change of said windshield; said sensor circuit including a signal generator adapted to generate said test signals, a programme-controlled analog signal magnifier and filter circuit adapted to receive the test signals as modified and output DC voltage signals in relation thereto, an analog-to-digital conversion circuit to convert the DC voltage signals to digital signals, and a micro-processor adapted to digitally process the digital signals and output change signals for control of said equipment.