| 摘要 |
PURPOSE:To obtain a sufficient current for detection of flaws and to improve both sensitivity and S/N, by providing ferrite core electrodes to generate 2 pairs of magnetic fluxes to the surface of a material to be checked. CONSTITUTION:A knife edge is formed at the area where ferrite core electrodes 1 and 1' wound with coil windings 2 and 2' face a material 3 to be checked, and the distance between a pair of knife edges is set equal to the minimum distance between a pair of electrodes. As a result, the magnetic fluxes are easily concentrated between knife edges to increase the efficiency. Therefore two units of electrodes are used to generate 2 pairs of magnetic fluxes, and a differential connection is given between the coils 2 and 2'. Then a current is flowed to the coils, and the material 3 is shifted toward an arrow mark. Thus the balance of coil impedance is lost when surface flaws 6 orthogonal to an eddy current 5 pass through. As a result, flaw signals are detected. In such a constitution, the sensitivity is increased, and at the same time the S/N is improved since the magnetic fields are concentrated at the knife edge part. |
