Simultaneous Measurement of Conductivity and Diameter of an Infinite Length Metallic Rod Using the Phase Signature of Induced Eddy Current

This article proposed an eddy current testing (ECT) method to simultaneous measure conductivity and diameter of metallic rod using phase feature. The eddy current sensor with single coil encircles metallic rod during measurement. It is well known that the parameter coupling between the conductivity and the metallic rod will affect the response signal. In this investigation, we have found that the impedance phase at peak frequency is only related with rod diameter, not conductivity. Meanwhile, the logarithm of peak frequency is linear with the logarithm of rod diameter. Specifically, the slopes of linear fitting are the same for different materials, and the intercept is associated with conductivity. Hence, the diameter and conductivity can be retrieved by the phase at peak frequency and the intercept of linear fitting. The related experiments have been conducted on metallic rods with different materials and diameters, and the results indicate that the average error is less than 1.7%.