| 摘要 |
The invention concerns rainwater sensors for windshields. In one embodiment, a first, inner, conductive film is applied to the inner surface of the windshield, and a second film, of same size and shape as the first, is applied to the outer surface. However, a narrow strip is removed from the second film, forming a gap which divides the second film into parts 1 and 2. The resulting structure forms two capacitors, namely: (1) inner film plus part 1, and (2) inner film plus part 2. The impedance of one capacitor is monitored. When rain occurs, it falls into the gap between parts 1 and 2, and acts as a resistor, bridging part 1 to part 2. This bridging adds a new impedance in parallel with the first capacitor, thereby changing the effective impedance. This change indicates the presence of rain.
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