Eddy current testing is a non-destructive method used for a variety of purposes, including flaw detection,material and coating thickness measurements, material identification and establishing the heat treatment condition of certain materials. 

Eddy current uses the principle of electromagnetic induction to detect flaws in conductive materials. An exciting coil is placed in proximity to the component to be inspected, the changing in voltage across the coil will affect the material being scanned and allow the eddy current instrument to measure surface and subsurface discontinuities.