Eddy Current Testing (ECT) works on the principle of electromagnetic induction. In ECT a probe is excited with sinusoidal alternating current to induce eddy current in an electrically conducting material such as stainless steel, aluminium etc. The change in coil impedance that arises due to distortion at regions of discontinuities and associated magnetic flux leakage is measured. This is a surface technique and can readily detect very shallow surface defect and sub-surface defects. ECT is a simple, high-speed, high sensitive, versatile and reliable NDT technique and is popularly used in many engineering industries.