Accuracy Evaluation of an Electromagnetic Method for Conductive Tube Inspection

Eddy-current nondestructive testing of metallic tubes, includes measurement of tube inner diameter and electromagnetic properties - magnetic permeability and electrical conductivity. In our previous work we have developed a procedure for simultaneous measurement of inner diameter and permeability-to-conductivity ratio by minimizing difference between measured impedance of a coil excited at only one frequency and prediction of a two-parameter impedance model. In this paper we evaluate the errors that rise from the usage of the two-parameter model and requirements for accuracy of the coil impedance measurement. Our findings show that the errors and required coil impedance accuracy are within limits acceptable for practical implementation of the procedure.