Measurement of the Conductivity of Metallic Cylinders by Means of an Inductive Method

Abstract

The method of measuring conductivities by observing the decay of eddy currents induced in metallic cylinders is analyzed exactly. We consider the case where the primary coil wound around the sample is connected to a circuit that has an arbitrary time constant, and where the sample partially fills the primary coil. Results derived by other authors are shown to be incorrect. The theoretical predictions are checked against experimental results for cylinders of copper,aluminum, and brass. The experiments are done both at room temperature and at the temperature of liquid nitrogen. The experimental results agree with the theory to within ±5%.