Design and Development of a Differential Current Probe With High Misalignment Tolerance

Abstract

A modified, simple, and reliable core-less differential Hall-Effect current probe is presented in this paper. The proposed probe has a high tolerance to typical misalignments of the conductor position that otherwise affects the accuracy. The conventional anti-differential probe has two magnetic sensing elements, with an axis of sensitivity. The current carrying conductor is kept between these elements, and the output is a function of the gap between the conductor and the sensing element. In practice, it is very difficult to ensure the correct positioning of the conductor, during the installation and throughout the operation, such that the gap is maintained the same for both the sensing elements. A recent sensor configuration presented partially corrects for the associated errors. This paper presents a modified probe with sensing elements that are sensitive to two directions that are in quadrature. In the modified probe, the current is computed in a special manner that provides accurate output even if the conductor is moved away from the ideal position in any direction. This ensures high reliability as the output significantly reduces the effect of positional error owing to mechanical movement, deformation, and vibration of the conductor in vertical and horizontal directions. A prototype of the proposed probe has been developed in the laboratory using commercially available Hall-Effect sensors and tested for a wide range of vertical and horizontal misalignments. The maximum error noted from the prototype probe showed more than 20 times improvement compared to the conventional probe when the same misalignment, mentioned above, was introduced to both the probes. The results from the experimental studies conducted using the developed probe proved the practicality.