High linearity, low offset interface for hall effect devices

Abstract

A Hall effect sensor or device may be used in a variety of embodiments, such as measuring current within an associated conductor by helping to measure flux density within a gap of a ferromagnetic power meter core, such as in a power meter. A high linearity interface for a Hall effect device is provided for minimizing offset effects without using complicated electronic circuits. First and second levels of modulation relative to line frequency are used to synchronize Hall effect device input switching circuits and feedback loops for improved elimination of offset signals or noise from the ultimate system output. The substrate of the Hall effect device may be connected electrically to an output pin of the Hall device or to a separate virtual ground to eliminate any effects caused by asymmetry of the voltage appearing in the channel relative to the substrate. The net effect of the high linearity interface is to eliminate any adverse effects to linearity of the system, especially at low magnetic flux levels where the output voltage of the Hall device would be relatively small compared to the offset voltage levels involved. The interface virtually eliminates adverse effects from operational amplifier input offset voltages, Hall effect device output offset voltages, and any common mode voltages.