| 摘要 |
<p>The device enables eddy current testing of metal tubing whose external surface is covered by a thin layer with magnetic or electrical properties differing from those of the underlying metal. The device is made up of a measuring head with a measuring coil (14) to encircle the tube and means of supplying the coil with high frequency power in excess of 100 kHz and of analysing the coil's impedance. The head contains a magnet (22) to surround the coil and magnetic flow guides (24) that frame the coil axially and, together with the magnet, form a magnetic circuit that creates a maximum-intensity magnetic field within the coil and in proximity to it.</p> |
