Working principle
Eddy current detection uses the principle of electromagnetic induction to excite the probe coil with a sinusoidal current. When the probe approaches the metal surface, the alternating magnetic field around the coil generates an induced current on the metal surface. For flat metal, the direction of the induced current is a circular circle concentric with the coil, shaped like a vortex, called eddy current. At the same time, the eddy current also produces a magnetic field of the same frequency, the direction of which is opposite to the direction of the coil magnetic field.