Eddy Current Testing (ECT)

Eddy currents were identified by James Maxwell in 1864. The term “eddy currents” resulted from the similarity in the movement of these circulating electrical currents to the whirlpool activity of so-called “eddies” in liquids. Eddy currents are defined as circulating electrical currents indirectly induced in an isolated conductor by an alternating magnetic field. The alternating magnetic field is developed through and around a coil connected to the AC generator output of an eddy current instrument. When the alternating magnetic field is brought near a metallic material, its flux lines affect the atoms of the material in such a way that electrons are passed from one atom to the next. However, in contrast to electricity conducted along the length of a wire, the electricity generated by the test coil’s lines of force has a circular eddy-like pattern.