Patent ID: 7863909

Claim:
A capacitive proximity sensor device, the capacitive proximity sensor device comprising: a sensing electrode, the sensing electrode having an associated measurable capacitance that varies with object proximity; a storage capacitor; a charging circuit, the charging circuit configured to selectively couple the storage capacitor and to selectively charge the storage capacitor to a predetermined level, thereby storing a set amount of charge on the storage capacitor; a charge transfer circuit, the charge transfer circuit configured to controllably transfer charge from the storage capacitor to the sensing electrode while measuring voltage on the sensing electrode and, where the charge transfer circuit is configured to cease controllably transferring charge responsive to the measured voltage on the sensing electrode reaching a defined level, with a residual voltage remaining on the storage capacitor after the transfer; and a measurement circuit coupled to the storage capacitor, the measurement circuit configured to measure the residual voltage remaining on the storage capacitor to determine the measurable capacitance associated with the sensing electrode from the measured residual voltage.