| 摘要 |
PURPOSE:To expand a flaw sampling area to be close to the surface of an object to be inspected by feeding a signal as detection output to a monitor with a compensation coil provided to remove or reduce leakage waves due to a direct induction from a transmission coil. CONSTITUTION:An eddy current develops on the surface of an object 1 to be inspected with a pulse current fed to a transmission coil 31 from a pulse generator 4. Since a magnetic field is applied to the surface of a sample 1 from a magnetic generator comprising a magnetic pole 21, an exciting coil 22 and a d.c. power source 23, a Lorentz's force is generated along the surface of the sample 1 and vertical to a current vector and a transversal wave advances the thickness-wise direction of the sample 1. The transversal wave is reflected back on a bottom defect 11 of the sample 1 produces an eddy current on the surface of the sample 1 due to an interaction with the magnetic field, entailing the gneration of an induced power in a receiving coil 32. A compensation coil 33 is provided outside the transmission coil 31 and differentially connected with the receiving coil 32 to offset and remove inductive noise voltage. |
