| 摘要 |
A capacitive sensor comprises a sensing electrode having a capacitance to be measured, a first switching arrangement configured to switch the sensing electrode, in the manner of a switched capacitor, alternately to a first node and to a second node, and a measurement circuit having the second node as an input node and being configured to measure the capacitance of the sensing electrode. The sensor comprises a shielding electrode and a driven shield circuit, which is configured to maintain the shielding electrode substantially at the same voltage level as the sensing electrode when the sensor is operating. The driven shield circuit comprises a second switching arrangement and a buffer amplifier. The second switching arrangement is configured to operate in synchronism with the first switching arrangement, in such a way as to alternately switch the shielding electrode, in the manner of a switched capacitor, to the first node each time when the sensing electrode is switched to the first node and to a third node each time when the sensing electrode is switched to the second node. The buffer amplifier is connected between the second node and the third node to copy the voltage of the second node to the third node.
|
