Calibration of non-contact current sensors
First Claim
1. A circuit, comprising:
- a current sensor having a housing for detachably coupling the current sensor to a wire;
a current sensing device integrated in the housing for providing a first output indicative of a current conducted through the wire;
a voltage sensing conductor integrated in the housing having a first terminal for providing a second output indicative of an electric potential on the wire and a second terminal, wherein the voltage sensing conductor and the current sensing device do not make electrical contact with the wire;
a selector circuit coupled to the voltage sensing conductor for selecting between a measurement mode and a calibration mode, wherein in the calibration mode, the selector circuit couples the first terminal and the second terminal of the voltage sensing conductor to a current source that causes a calibration current of predetermined magnitude to be conducted through the voltage sensing conductor; and
a current measuring circuit that measures the first output of the current sensing device to obtain a current measurement calibration value when the selector circuit selects the calibration mode, and wherein in the measurement mode, the current measuring circuit adjusts a value of the first output in conformity with the current measurement calibration value.
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Accused Products
Abstract
Calibration of a non-contact current sensor provides improved accuracy for measuring current conducted through a conductor such as an AC branch circuit wire. In a calibration mode, a predetermined current is injected through a voltage sensing conductor integrated in the non-contact current sensor. The magnitude of the magnetic field is measured using a sensing element of the non-contact current sensor. Then, when operating in measurement mode, a current conducted in a wire passing through the non-contact current sensor is determined by correcting the output of the non-contact current sensor using the result of the measurement made in the calibration mode. The voltage sensing conductor is used to provide an indication of the magnitude and/or the phase of the electrostatic potential on the wire. The calibration current may be a DC current, and calibration may be performed while the conductor is carrying an AC current.
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Citations
22 Claims
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1. A circuit, comprising:
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a current sensor having a housing for detachably coupling the current sensor to a wire; a current sensing device integrated in the housing for providing a first output indicative of a current conducted through the wire; a voltage sensing conductor integrated in the housing having a first terminal for providing a second output indicative of an electric potential on the wire and a second terminal, wherein the voltage sensing conductor and the current sensing device do not make electrical contact with the wire; a selector circuit coupled to the voltage sensing conductor for selecting between a measurement mode and a calibration mode, wherein in the calibration mode, the selector circuit couples the first terminal and the second terminal of the voltage sensing conductor to a current source that causes a calibration current of predetermined magnitude to be conducted through the voltage sensing conductor; and a current measuring circuit that measures the first output of the current sensing device to obtain a current measurement calibration value when the selector circuit selects the calibration mode, and wherein in the measurement mode, the current measuring circuit adjusts a value of the first output in conformity with the current measurement calibration value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A circuit, comprising:
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a current sensor having a housing for detachably coupling the current sensor to a wire and providing a first output indicative of a magnitude of a current conducted in the wire, wherein the current sensor does not make electrical contact with the wire; at least two ferrite cylinder portions disposed within the housing, wherein when the housing is coupled to the wire, the wire passes through a central void defined by the ferrite cylinder portions extending through a central axis thereof, and wherein a gap is defined along a circumference of a cylinder formed by the ferrite cylinder portions; a semiconductor magnetic field sensor disposed within the gap, wherein the first output is a voltage output of the semiconductor magnetic field sensor; a voltage sensing conductor forming a conductive metal cylinder having a radius smaller than and disposed within the ferrite cylinder portions, and having a first terminal and a second terminal located at opposing ends of the conductive metal cylinder, wherein the voltage sensing conductor does not make electrical contact with the wire; a selector circuit coupled to the voltage sensing conductor for selecting between a measurement mode and a calibration mode, wherein in the calibration mode, the selector circuit couples the first terminal and the second terminal of the voltage sensing conductor to a current source that causes a calibration current of predetermined magnitude to be conducted through the voltage sensing conductor; and a current measuring circuit that measures the first output of the current sensing device to obtain a calibration current measurement when the selector circuit selects the calibration mode, and wherein in the measurement mode, the current measuring circuit adjusts a value of the first output in conformity with the calibration current measurement. - View Dependent Claims (17, 18)
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14. A method for calibrating a non-contact current sensor, comprising:
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selecting between a calibration mode and a measurement mode in a circuit connected to the non-contact current sensor; responsive to selecting the measurement mode, first measuring a first magnitude of a first magnetic field generated by current conducted in a wire passing through the non-contact current sensor using an output of a sensing element within the non-contact current sensor; responsive to selecting the measurement mode, second measuring at least one of a second magnitude or phase of an electrostatic field generated by the wire by measuring the voltage of a voltage sensing conductor included within the non-contact current sensor; responsive to selecting the calibration mode, conducting a calibration current of predetermined magnitude through the voltage sensing conductor and third measuring a second magnitude of a second magnetic field generated by the predetermined current in the voltage sensing conductor using the output of the sensing element to obtain a current measurement calibration value; and correcting a result of the first measuring in conformity with the current measurement calibration value. - View Dependent Claims (15, 16, 19, 20, 21, 22)
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Specification