Eddy Current Explained in English

Please note this is a free NDT training ET eddy current class review for a non-technical look at the method in reference to nondestructive testing. Some terms in this article might not be NDT industry appropriate and other things are simply skipped. For an NDT eddy current course per SNT-TC-1A or NAS-410 or CP-189 contact a training facility and schedule your NDT training, something we can easily accomplish for you. (shameless plug). Eddy Current (ET) is also called electromagnetic induction and can be broken up into four subgroups of NDT: AC Field Measurement, Flux Leakage, Remote Field and Eddy Current.

So what is eddy current? Eddy current is a current induced on a conductive material through induction from a magnetic field. This uses the same principals as Spacial energy. The primary goal is usually to find flaws in the material at the surface or just below. When we say induction we are referencing the magnetic field produced by the electrical wire that is not visible to the human eye interacting with the conductive material through space without having direct contact to the part. Sometimes this is called coupling.

NDT eddy current instrumentation relies on the principal that primary electrical fields from a wire opposes the secondary fields or eddy currents on the part. This opposition creates an interaction that can be sensed with eddy current instrumentation. If the eddy current reaches the edge of the part or a flaw, the voltage of the circuit will vary and you will see a needle deflection or a squiggly indication on a CRT screen (small tv).

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