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INTRODUCTION Eddy current testing is one of the standard nondestructive testing methods. It uses electromagnetic fields and is very aenaitive to many material and geometric variables. Because it is an electromagnetic test, its signals move with the speed of light, and its measurements can be made very quickly. Being electrical in nature, eddy current testing can easily be auto~ted and its signals can be used to control other electrical devices. Because the sensing devices are coupled to the test specimens through electromagnetic fields, the devices do not have to contact the test specimen. Eddy current testing can even be used in a vacuum. For these and other reasons, eddy current testing is extensively used throughout the industrial world.

This chapter provides the fundamental principles and guides associated with eddy current testing. It includes the theory of operation, the type of equipment, the advantages and disadvantages of method, various applications and standards, and guides for specific disciplines. The information contained in chapter 1 should be included with this chapter for general guidelines to the employment of all NDT methods and for a more complete understanding of eddy current testing as it compares with other basic methods.