Differential dual sensor contactless magnetic-mode electrical current sensors with tamper detection

An electrical circuit, comprising:

• a pair of magnetic sensors placed adjacent to an electrical conductor, each magnetic sensor providing a respective output signal responsive to electrical current flowing through a respective portion of the electrical conductor adjacent to the magnetic sensor;
• a first electrical circuit that processes the respective output signals from the pair of magnetic signals to output a first signal indicative of the electrical current flowing through the electrical conductor;
• a second electrical circuit that processes the respective output signals from the pair of magnetic signals to output a second signal indicative of magnitude and polarity of the external magnetic field imposed upon the pair of magnetic sensors;
• and
• a comparator having a first input receiving the second signal and a second input receiving a tampering threshold and a comparison output providing a signal indicative of a comparison between the second signal and the tampering threshold.

An electrical utility meter for a building, comprising:

• a pair of magnetic sensors placed adjacent to an electrical conductor providing a source of electrical power to the building, each magnetic sensor providing a respective output signal responsive to electrical current flowing through a respective portion of the electrical conductor adjacent to the magnetic sensor;
• a first electrical circuit that processes the respective output signals from the pair of magnetic signals to output a first signal indicative of the electrical current flowing through the electrical conductor;
• a second electrical circuit that processes the respective output signals from the pair of magnetic signals to output a second signal indicative of the external magnetic field imposed upon the pair of magnetic sensors;
• a comparator having a first input receiving the second signal and a second input receiving a tampering threshold and a comparison output providing a signal indicative of a comparison between the second signal and the tampering threshold;
• and
• an output circuit communicating at least a meter signal, based on the first signal, indicative of an amount of electrical power provided to the building over a period of time, and an alarm signal, based on the signal provided by the comparison output, indicative of the external magnetic field including a tampering magnetic field.

A system for measuring an electrical current in an electrical conductor while detecting presence of an external magnetic field, comprising:

• means for generating a first measurement signal in response to a first magnetic field induced by an electrical current in the electrical conductor at a first location along the electrical conductor and a second measurement signal in response to a second magnetic field induced by the electrical current in the electrical conductor at a second location along the electrical conductor where the second magnetic field is complementary to the first magnetic field;
• means for processing the first and second measurement signals to generate a first signal indicative of the electrical current in the conductor;
• means for processing the first and second measurement signals to generate a second signal indicative of any external magnetic field;
• means for comparing the second signal to a tampering threshold to generate an alarm signal indicative of whether the external magnetic field exceeds the tampering threshold, wherein the tampering threshold is indicative of an unacceptable magnetic field interference directed at the system;
• means, responsive to the alarm signal, for persistently storing event information describing instances of interference directed at the system;
• and
• means for reading the persistently stored event information.

An electrical utility meter for a building, comprising:

• a pair of magnetic sensors placed adjacent to an electrical conductor providing a source of electrical power to the building, each magnetic sensor providing a respective output signal responsive to electrical current flowing through a respective portion of the electrical conductor adjacent to the magnetic sensor;
• a first electrical circuit that processes the respective output signals from the pair of magnetic signals to output a first signal indicative of the electrical current flowing through the conductor;
• a second electrical circuit that processes the respective output signals from the pair of magnetic signals to output a second signal indicative of the external magnetic field imposed upon the pair of magnetic sensors;
• and
• an output circuit communicating at least a meter signal, based on the first signal, indicative of an amount of electrical power provided to the building over a period of time, and an alarm signal, based on the second signal, indicative of any detected external magnetic field,
• wherein the programmable function comprises comparing the second output signal to a threshold to generate the alarm signal, wherein the threshold is set to a value indicative of an external magnetic field at least two times larger than Earth's ambient magnetic field.

An electrical utility meter for a building, comprising:

• a pair of magnetic sensors placed adjacent to an electrical conductor providing a source of electrical power to the building, each magnetic sensor providing a respective output signal responsive to electrical current flowing through a respective portion of the electrical conductor adjacent to the magnetic sensor;
• a first electrical circuit that processes the respective output signals from the pair of magnetic signals to output a first signal indicative of the electrical current flowing through the electrical conductor;
• a second electrical circuit that processes the respective output signals from the pair of magnetic signals to output a second signal indicative of the external magnetic field imposed upon the pair of magnetic sensors;
• and
• an output circuit communicating at least a meter signal, based on the first signal, indicative of an amount of electrical power provided to the building over a period of time, and an alarm signal, based on the second signal, indicative of any detected external magnetic field,
• wherein the programmable function comprises comparing the second output signal to a threshold to generate the alarm signal,
• wherein the threshold is set to a value indicative of an external magnetic field between Earth's magnetic field and a value at which the pair of magnetic sensors are subject to either saturation or damage.

An electrical utility meter for a building, comprising:

• a pair of magnetic sensors placed adjacent to an electrical conductor providing a source of electrical power to the building, each magnetic sensor providing a respective output signal responsive to electrical current flowing through a respective portion of the electrical conductor adjacent to the magnetic sensor;
• a first electrical circuit that processes the respective output signals from the pair of magnetic signals to output a first signal indicative of the electrical current flowing through the electrical conductor;
• a second electrical circuit that processes the respective output signals from the pair of magnetic signals to output a second signal indicative of the external magnetic field imposed upon the pair of magnetic sensors;
• and
• an output circuit communicating at least a meter signal, based on the first signal, indicative of an amount of electrical power provided to the building over a period of time, and an alarm signal, based on the second signal, indicative of any detected external magnetic field,
• wherein the external magnetic field comprises a tampering field greater than an ambient magnetic field due to Earth's magnetic field and any additional ambient magnetic field produced by electrical circuitry operating in proximity to the magnetic sensors.