Calibration of non-contact voltage sensors
First Claim
1. 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.
1 Assignment
0 Petitions
Accused Products
Abstract
Calibration of a non-contact voltage sensor provides improved accuracy for measuring voltage on a conductor such as an AC branch circuit wire. In a calibration mode, a predetermined voltage is imposed on a first voltage sensing conductor integrated in the non-contact voltage sensor, while a voltage on a second voltage sensing conductor is measured using a circuit of predetermined input impedance. The capacitance between the wire and each of the voltage sensing conductors may be the same, so that in measurement mode, when the first and second voltage sensing conductors are coupled together, the effective series capacitance provided in combination with the predetermined input impedance is four times as great. The results of the voltage measurement made in the calibration mode can thereby be used to adjust subsequent voltage measurements made in measurement mode with the first and second voltage sensing conductors combined in parallel.
-
Citations
11 Claims
-
1. 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A circuit, comprising:
-
a voltage sensor having a cylindrical housing forming a clamshell from two half-cylinder housing portions coupled by a hinge, for detachably coupling the voltage sensor to a wire; a first voltage sensing conductor forming a half-cylinder plate integrated a corresponding one of the half-cylinder housing portions 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 forming a half-cylinder plate integrated a corresponding one of the half-cylinder housing portions 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, wherein the first voltage sensing conductor and the second voltage sensing conductor have substantially equal capacitance to the wire, and wherein the voltage measurement circuit adjusts the voltage measurement value according to an increase in the capacitance acting in series with the predetermined input impedance by a factor of four when the measurement mode is selected.
-
Specification