| 摘要 |
Apparatus for measuring, and indicating, the thickness of non-metallic coatings over a metallic surface, such as in sheathing of an electrical cable or similar structure, has a number of measuring heads, for example four, of electrical inductance type, spaced around the structure. A probe in each head has a profiled surface for presentation to the surface of the coating, the profile such as to offset any variation in inductance effects on the probe resulting from variation in diameter of the cable, without affecting the inductance effects of any variation in coating thickness. The measuring head is flexibly mounted and the signals from circuits associated with the probes are arranged to give visual indication of variation in coating thickness, and also any eccentricity. Particularly the indication can be a visual one representative of the cross section of the cable or the like.
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