Eddy Current (ECT)
Eddy Currents technology is relatively simple and low cost.
A transducer includes an electronical circular coil; which generates an electromagnetic field. If the circular coil and its magnetic field are placed in proximity to an electrically conductive material, a circular flux of electrons, called Eddy Currents, will then be inducted in the material. Eddy Currents generates its own magnetic field, which interact by mutual inductance with the circular coil and its magnetic field. Every flaw in the material will disturb Eddy Currents flux and their magnetic field, modifying the electrical impedance of the circular coil. This disturbance is measured, amplified, and displayed on the instrument screen.
This technology offers the advantage to be extremely sensible to surface defaults, and works also for defaults that are right under the surface, a few millimeters away. Eddy Currents are indicated to rapidly inspect large surfaces, and the technique does not require couplant using. As well as detecting small cracks, Eddy Currents can also be used to control hardness and metal conductivity when these attributes are necessary. In certain cases, this technology is combined to ultrasounds, like two complementary techniques: Eddy Currents offer the advantage of a rapid surface inspection, and ultrasounds will take care to inspect the volume in depth.