| 摘要 |
A sensor electrode is capacitively coupled to the environment. Electric charges carried by surrounding objects induce corresponding electric charges on the sensor electrode. A high input impedance circuit senses change in charge on the electrode and provides a first varying signal indicative of that change. A second circuit compares the first signal against a threshold level and provides a second signal indicative of the movement. A pair of sensors may be included to cancel out extraneous environmental chasrges. Difference between charges on each sensor electrode of the pair is compared in a circuit which provides signal indicative of the difference. The varying signal is compared against a threshold to provide a signal indicative of the movement.
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