High accuracy non-invasive current sensor system

A non-intrusive current monitoring system with closed loop configuration, comprising:

• two magnetic field sensors configured for differential sensing of a magnetic field generated around a current carrying conductor;
• analog frontend circuitry for each of the sensors, wherein the analog front end circuitry for each sensor is configured to remove direct current (DC) offset of a corresponding magnetic field sensor, upconvert the output of the corresponding magnetic field sensor, and filter out undesirable frequency components from the up-converted signal;
• and
• a processor configured to:
• measure a differential sensor output based on output signals received from the analog front-end circuitry;
• generate control signals to cause a coil winding on the current carrying conductor to cancel effective magnetic field acting on the magnetic field sensors;
• determine a measurement of the current flowing through the conductor based on the differential sensor output;
• and
• output data comprising the current flow measurement.

A method for non-intrusive current monitoring, comprising:

• performing calibration to remove, from the output of a magnetic field sensor proximate to a current carrying wire, a direct current (DC) offset caused by external magnetic field not generated by the current carrying wire;
• causing output switching circuitry to switch between differential outputs of the magnetic field sensor and generate a combined output signal;
• receiving a first filtered signal from a high-gain bandpass filter that receives the combined output signal;
• receiving a second signal from a low-gain bandpass filter that receives the combined output signal;
• selecting one of the first filtered signal or the second filtered signal to avoid saturation;
• calculating the phase angle between the selected signal and an internal reference signal to determine the current flowing direction;
• and
• outputting the phase angle.