Measurement of electrical conductivity in nonferromagnetic tubes and rods at low frequencies

Abstract

We present a simple and precise method to measure the azimuthal electrical conductivity in nonferromagnetic tubes and rods at low frequencies. The results are readily obtained by analyzing the eddy currents in the sample when it is subjected to an axial harmonic magnetic field. The information about the eddy currents can be obtained from a measurement of the phase of the induced voltage in a short probe coil located inside the tube or around the rod when the sample is axially excited by a long primary coil. At low frequencies, the eddy currents are distributed over the full depth of the sample and any irregularities can be detected when the probe coil is moved along the sample axis.