Eddy current methods are based on analysis of the interaction between an external electromagnetic field and the electromagnetic field of eddy currents induced by the excitation coil in the electro conductive test object. Density of eddy currents in the object depends on the geometric and electromagnetic parameters of the object, as well as positional relationship of the measuring eddy current transducer or probe and the object. Induction coils (one or several) are usually used as eddy current transducers. However, eddy-current testing can detect very small cracks in or near the surface of the material, the surfaces need minimal preparation, and physically complex geometries can be investigated. It is also useful for making electrical conductivity measurements.

The main advantage of Eddy Current Testing it is Quick, simple, and reliable inspection technique to detect surface and near-surface defects in conductive material. Can be used to measure material electrical conductivity. Measurement of nonconductive coating. Hole inspection with the use of high-speed rotating scanner and surface probe. Drastically reduces inspection time. Covers a large area in one single pass. High  speed inspection.

Eddy current test can readily detect very shallow and tight surface fatigue cracks and stress corrosion cracks. High temperature and on-line testing is possible, even in shop floors.