| 摘要 |
PURPOSE:To achieve quick and accurate measurement employing nondestructive inspection, by providing a differential type magnetic sensor along the surface of a low magnetic-permeability material to be tested. CONSTITUTION:As a powerful magnetic field Ho is continuously applied to a pipe 1 from a permanent magnet 2 as advanced from the surface to back of a paper turning circumferentially and a magnetic moment M is detected with a differential magnetic sensor 4 to measure variations in the magnetic permeability of the pipe 1. If there is only change in the composition of the pipe 1, the output of the magnetic sensor 4 varies on the spot according to the change thereby enabling decision on the propriety of the pipe 1 depending on the degree of the change. |
