Calibration of non-contact current sensors
First Claim
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1. A circuit, comprising:
- a current sensor having a housing for detachably coupling the sensor to a wire;
a current sensing device integrated in the housing for providing a current sensor output indicative of an AC current conducted through the wire;
a calibration conductor that does not make electrical contact with the wire and extends through the housing;
a DC current source coupled to the calibration conductor for providing a DC current through the calibration conductor; and
a current measuring circuit that measures the current sensor output of the current sensing device to obtain a current calibration value by filtering and measuring a DC component of the current sensor output, wherein the current measuring circuit further measures an AC component of the current sensor output to obtain an AC current measurement value and adjusts a value of the AC current measurement value in conformity with the current calibration value.
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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 DC current is injected through a 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.
44 Citations
20 Claims
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1. A circuit, comprising:
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a current sensor having a housing for detachably coupling the sensor to a wire; a current sensing device integrated in the housing for providing a current sensor output indicative of an AC current conducted through the wire; a calibration conductor that does not make electrical contact with the wire and extends through the housing; a DC current source coupled to the calibration conductor for providing a DC current through the calibration conductor; and a current measuring circuit that measures the current sensor output of the current sensing device to obtain a current calibration value by filtering and measuring a DC component of the current sensor output, wherein the current measuring circuit further measures an AC component of the current sensor output to obtain an AC current measurement value and adjusts a value of the AC current measurement value in conformity with the current calibration value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for calibrating a non-contact current sensor, comprising:
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detachably coupling the non-contact sensor to a wire; first measuring a first magnitude of a first AC magnetic field generated by an AC current conducted in the wire using an output of a sensing element within the non-contact current sensor; conducting a DC calibration current of predetermined magnitude through a calibration conductor passing through the non-contact current sensor; second measuring and filtering a second magnitude of a second DC magnetic field generated by the predetermined current in the calibration 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 (14, 15, 16, 17, 18, 19)
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20. A non-contact current sensor, comprising:
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a housing for detachably coupling the sensor to a wire; a current sensing device comprising 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 integrated in the housing; a semiconductor magnetic field sensor disposed within the gap; a calibration conductor that does not make electrical contact with the wire and extends through the housing; a DC current source coupled to the calibration conductor for providing a DC current through the calibration conductor; and a current measuring circuit that measures a current sensor output of the semiconductor magnetic field sensor to obtain a current calibration value by filtering and measuring a DC component of the current sensor output while the wire conducts an AC current, wherein the current measuring circuit further measures an AC component of the current sensor output to obtain an AC current measurement value and adjusts a value of the AC current measurement value in conformity with the current calibration value.
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Specification