Patent ID: 8493054

Claim:
A circuit, comprising: a voltage sensor having a housing for detachably coupling the sensor to a wire; a first voltage sensing conductor integrated in the housing for providing a first output indicative of a voltage on the wire, wherein the first voltage sensing conductor does not make electrical contact with the wire; a second voltage sensing conductor integrated in the housing for providing a second output indicative of the voltage on the wire, wherein the second voltage sensing conductor does not make electrical contact with the wire; a selector circuit coupled to the first voltage sensing conductor and coupled to the second voltage sensing conductor for selecting between a measurement mode and a calibration mode, wherein in the calibration mode, the selector circuit couples the first voltage sensing conductor to a voltage source that applies a calibration voltage of predetermined magnitude to the first voltage sensing conductor; and an AC voltage measuring circuit having an input with a predetermined input impedance coupled to the second voltage sensing conductor, wherein in the calibration mode, the AC voltage measuring circuit measures a voltage present on the second voltage sensing conductor to determine a voltage measurement calibration value, and wherein in measurement mode, the selector circuit couples the first voltage sensing conductor and the second voltage sensing conductor in parallel to the input of the AC voltage measuring circuit and measures a voltage present on parallel combination of the first voltage sensing conductor and the second voltage sensing conductor to obtain a voltage measurement value, and wherein the voltage measuring circuit adjusts the voltage measurement value in conformity with the voltage measurement calibration value.