Eddy-current inspection is a nondestructive evaluation method based on the principles of electromagnetic induction. Eddy-current methods are used to identify or differentiate a wide variety of physical, structural, and metallurgical conditions in electrically conductive ferromagnetic and nonferromagnetic metals and metal parts. Giving a brief introduction on the uses of eddy-current inspection, this article discusses the operating principles and the principal operating variables encountered in eddy-current inspection, including coil impedance, electrical conductivity, magnetic permeability, lift-off and fill factors, edge effect, and skin effect. It further describes different aspects of eddy current testing such as the selection of inspection frequencies and...