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US 5,672,976 AGranted
Wetness sensor for a window of a motor vehicle
AssigneeVDO Adolf Schindling AG
InventorsArmin Egger, Reinhold Berberich, Dieter Busch
Life of this patent
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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.
Claims7
A wetness sensor for a window of a motor vehicle, comprising:
- a heating resistor disposed in the window for removal of frost, said resistor comprising a grid of a plurality of wires extending across the window from a first terminal connected to a first end of each wire to a second terminal connected to a second end of each wire;
- a measuring device connected to the heating resistor via said first terminal and said second terminal for measuring a capacitive portion of an impedance of the heating resistor;
- and
- wherein the capacitor portion of the impedance varies in accordance with an amount of wetness of the window, thereby enabling the measuring device to sense the wetness.
1 more element
Dependencies are inferred from the claim text.