CORELESS CURRENT PROBE AND A METHOD OF MEASURING DIRECT CURRENT

摘要

A coreless current probe has a U-shaped body with arms, an open end and a cross piece forming a closed end. The opening formed in the U-shaped body has a length not less than the width between the arms. The U-shaped body can engage around a conductor carrying a current to be measured. The U-shaped body has a number of coreless single point magnetic field sensors, usually Hall devices, distributed around the opening. An arrangement with six sensors has two sensors at the ends of the arms of the U-shaped body, two sensors at the closed end, and two sensors mid-way along the arms. Sensing circuitry applies factors to the outputs of the sensors and sums the results to produce a measured current value. The factors are selected so that the summed result is zero in any externally generated homogeneous magnetic field.

主权项

1. A coreless current probe comprising a U-shaped body having arms, an open end, and a cross piece forming a closed end opposite to said open end, said U-shaped body defining an opening having a width between the arms and a length from said closed end to said open end, wherein said length is not less than said width, said width and said length defining a plane of said opening and a central line normal to said plane, whereby a conductor carrying a current to be measured can be engaged by said body of said probe so as to extend through said opening parallel to said central line;
a plurality of coreless single point magnetic field sensors distributed in said body around said opening including a respective said sensor at an end of each of said arms on each side of said open end of said body and at least one said sensors at said closed end of said body, said sensors each having a respective axis of magnetic field sensitivity and being arranged in said body so that each of said axes is not co-planar with said central line; and sensing circuitry connected to said sensors which is operative to produce for each of said sensors a respective sensor signal which is a measure of the angle component of magnetic field at the sensor aligned with the respective axis of magnetic field sensitivity of the sensor, said sensors being arranged such that there are values of cr for which, in any homogeneous magnetic field,∑r=1ncrhr=0, where n is the number of said magnetic field sensors,
hr is said measure of said magnetic field component for the rth sensor, and cr is a constant factor for the rth sensor, said sensing circuitry being further operative to combine said measures hr to produce a measured current value representing current following in a conductor engaged by said body of said probe.