GB1261393A - Inductive transducers - Google Patents

Abstract

1,261,393. Inductive transducers. ASSOCIATED ENG Ltd. June 23, 1970 [March 28, 1969], No. 16505/69. Heading G1N. An inductive transducer responsive to the spacing of a rotating shaft 26 from its working face 23 is provided with a dummy transducer to give temperature compensation. In Fig. 1, a non-ferromagnetic casing 11 having a dividing wall 12 houses axially aligned ceramic spools 13, 14 with sector-shaped feet 18 abutting wall 12, on which are wound the active pick-up coil 19 and dummy coil 20 of ceramic-insulated silver or silver-palladium wire. Magnetic cores 21, 22 of bundles of soft iron wire through the hollow centres of the spools are bent round between feet 18 to lie parallel to the spool axis outside coils 19, 20 and are located in slots spaced around the circumference of spool flanges 16, 17. Both ends of the wires 21 end in the working face 23. The ends of the wires 22 end at face 24. A dummy armature 28 of the same material as shaft 26 is separated from face 24 by a ceramic spacer 27 of thickness equal to the average working gap between face 23 and shaft 26. Both coils are sealed against ingress of gas or vapour: a tensioned non-ferromagnetic diaphragm 25 is welded to casing 11 at the working face 23 and places spool 13 under compression; three leads 29 pass through ceramic sleeves 30 in slots in the periphery of spool 14 to connect the coils 19, 20 in adjacent arms of a bridge circuit, Fig. 2 (not shown), the leads being welded in hollow tubes 31 of nickel iron sealed in a sintered alumina plug 32 coated with molybdenum brazed to member 33 of nickel electron-beam welded to casing 11. An A.C. bridge circuit, Fig.2 (not shown), is described having zero adjust components (R2, L2), the output being fed via a synchronous detector (D) and filter (F) to an indicator, recorder or C.R.O.