Principle of Eddy Current Testing: Eddy current testing uses the principle of electromagnetic induction to excite the probe coil with sinusoidal current. When the probe is close to the metal surface, the alternating magnetic field around the coil generates induced current on the metal surface. For flat metal, the flow of the induced current is a concentric circle of coils, shaped like a vortex, called an eddy current. The eddy also generates a magnetic field of the same frequency, in the opposite direction of the coil's magnetic field. The loss resistance of the eddy current channel and the anti-magnetic flux generated by the eddy current are reflected back to the probe coil, changing the current magnitude and phase of the coil, that is, changing the impedance of the coil. Therefore, when the probe moves on the metal surface and encounters defects or changes in material and size, the reaction of eddy current magnetic field to the coil is different, resulting in changes in coil impedance. By measuring such changes with eddy current testing instruments, the metal surface can be identified with defects or other physical property changes. There are many factors that affect the eddy current field, such as the degree of coupling between the probe coil and the material under test, the shape and size of the material, electrical conductivity, magnetic permeability, and defects. Therefore, the problems of flaw detection, thickness measurement and sorting of metal materials can be solved by using eddy current principle
Technical parameters: flaw detection sensitivity: from the workpiece surface to the metal extending depth ≥ 0.05mm, length ≥2 mm crack, defect; When the thickness of the metal between the top edge of the crack and the surface of the workpiece is ≤ 0.2mm, the crack with a depth of ≥0.20mm and a length of ≥ 1mm can be detected.