| 摘要 |
<p>A capacitive field sensor (14) employs a single coupling plate (12) to detect change in capacitance to ground. The apparatus comprises a circuit (46, 62) for charging a sensing electrode (12) and a switching element (50) to remove charge from the sensing electrode (12) and to transfer it to a charge detection circuit (56). The time intervals employed for the charging and discharging steps can vary widely and can be selected to be less than a characteristic conduction time associated with a shunting conductor, such as a sheet of water. Thus, the sensor (14) can detect the presence of an object or user near the plate without being subject to measurement artifacts arising from standing water such as may occur in a controller for a water basin.</p> |
