SYMPOSIA PAPER Published: 01 January 1958

Introduction to Eddy Current Methods and Techniques


The eddy current test is an electromagnetic test applicable to the examination of electrically conducting test specimens for detecting irregularities in structure and composition. Such irregularities must affect the flow of eddy currents within the test specimen, for it is the inductive effect of the flow of these eddy currents on the test coil which is observed and used as an indication of the presence of irregularities. Eddy current tests are generally nondestructive, and thus are adaptable to 100 per cent inspection. Applications include metal sorting, detection of cracks transverse to current flow, determination of electrical conductivity, detection of voids and inclusions, measurement of plate or tubing thickness, determination of cladding depth, and measurement of depth of nonconducting films on electrically conducting bases. Eddy current tests are generally most effective near the surface, with sensitivity for irregularities falling off as depth below the surface increases. Like most nondestructive tests, the eddy current test is an indirect evaluation of the characteristics of the test specimen, and care must be taken to prove the correlation between the measured quantities and the structural or serviceability characteristics in question (1)

Author Information

Libby, H., L.
Hanford Atomic Products Operation, Richland, Wash.
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Developed by Committee: E07
Pages: 13–28
DOI: 10.1520/STP41978S
ISBN-EB: 978-0-8031-5948-8
ISBN-13: 978-0-8031-6102-3