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Publication of GB668411ApublicationCriticalpatent/GB668411A/en
Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means
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Abstract
668,411. Magnetic device for measuring thickness. BRITISH IRON & STEEL RESEARCH ASSOCIATION. July 14, 1950 [July 15, 1949], No. 18703/49. Class 37. A device for measuring the thickness of a magnetic body of which only one face is accessible comprises an electromagnet 16 with pole faces 19, 20 which can be brought into contact with a surface of the body to produce a saturation flux therein, the flux circuit having a narrow non-magnetic gap 22 across which is a further magnetic circuit comprising pole faces 24 in which is an energized moving coil 23. The flux developed across the gap 24, 24 varies inversely with the thickness of the plate bridging 19, 20 so that the moving coil 23 is deflected in relation to the thickness. The flux passing from pole 16 to pole 19 comprises the flux through the plate under test together with the air or stray flux; this latter flux varies with the current .through the coil 17 and its effect is eliminated by a winding 27 on the shunt circuit including the moving-coil gap, so that the coil deflection is dependent only on the thickness of the plate.