5. Eddy current testing

5.1 Excitation phase analysis

The part to be tested is subjected to the action of a time-varying magnetic field, so as to induce currents in the material. A sine wave is generally used. Its frequency can vary from a few hertz to several megahertz, depending on the nature of the applications envisaged and the products inspected.

The sensitivity of the method for each application is closely linked to the choice of frequency, which conditions the penetration of induced currents: this is the "skin effect", extending to a depth that depends on the absolute magnetic permeability of the material and...