| 摘要 |
A capacitive proximity sensor comprising an emitter electrode ( 104 ) capacitively coupled to receive an electrode ( 102 ). A first active guard electrode ( 110 ), driven by the output of a unity gain amplifier ( 108 ), is provided in respect of the receive electrode ( 102 ), to shield parts thereof not facing a potential obstacle ( 122 ), and a grounded shield ( 126 ) is provided in respect of the emitter electrode ( 104 ) to shield parts thereof not facing a potential obstacle ( 122 ). A second active guard electrode ( 103 ) is provided between the emitter and receiver electrodes ( 104, 102 ), just behind the cover ( 106 ), which is also driven by the output of the amplifier ( 108 ). The second active guard electrode ( 103 ) acts to block shortened electric field lines ( 124 ) between the emitter and receiver electrodes ( 104, 102 ), thereby improving accuracy and reliability of the sensor.
|
