The Eddy Currents Test (ET), when AC current is passed through a winding, creates a magnetic field around that winding. When this winding is brought closer to an electrically conductive material surface, the variable magnetic field of the winding creates induction currents on the material surface. These currents flow in a closed circuit and are called eddy currents. Eddy currents also create their own magnetic fields. By measuring this secondary magnetic field created, surface defects can be found, parameters of the material such as conductivity, permeability can be determined.