A Novel Closed Loop Current Sensor Based on a Circular Array of Magnetic Field Sensors

Abstract

During the last years, coreless current sensors based on circular arrays of magnetic field sensors have been investigated. These sensors were limited in bandwidth and accuracy by the magnetic field sensors used to realize the circular arrays. Thus, this paper applied the well-known “closed loop” principle to circular array-based current sensors to overcome these limitations. This paper gives a comparison between circular arrays built from Hall and Fluxgate magnetic field sensors in both the closed loop and open loop operation. If closed loop configuration Fluxgate sensors are used, instead of Hall sensors, the measurement error can be reduced by a factor of two due to their intrinsic characteristics. Moreover, it is shown that the closed loop operation of the circular arrays results in a significant reduction of the temperature drift of the sensitivity for Fluxgate and Hall sensor-based circular arrays. If Hall sensors are used for the circular array, the reduction of the temperature drift of the sensitivity achieved by closed loop operation is about a factor of 10. If Fluxgate sensors are used, a significant reduction of the nonlinearities like hysteresis and a substantial reduction of the temperature drift of the sensitivity was observed.