Calibration of non-contact current sensors

A circuit, comprising:

• 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.

A method for calibrating a non-contact current sensor, comprising:

• 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.