GB1071578A - Devices for exploring the surfaces of objects to determine dimensional variations - Google Patents

Abstract

1, 071, 578. Measuring displacement electrically. PHYSICAL SCIENCES CORPORATION. June 23, 1964, No. 28225/66. Divided out of 1, 071, 577. Heading G1N. A displacement transducer for examining a plane surface comprises a differential inductance 216 (Fig. 1) fixed in a telescopic tubular casing 210, 214 associated with a core 218 fixed to a sapphire probe head 222 by a plunger 226 supported in a gas bearing and forward biased by gas pressure in a chamber 240. The transducer head is carried by part 214 of the casing which is connected to the other part 212 by a screw thread 246 adjustable by a motor 268 through reduction gearing 254 and a yielding clutch mechanism 262, until the coil 216 is centrally located with respect to the core 218. The motor 268 is also coupled to a pulse generator 278, 280 whose output is fed to a counter giving an indication of the zero position of the coil 216. The transducer unit is made to scan the surface 225 under test, the centre-tapped coil 216 being connected in a bridge circuit whose output is recorded and indicates the variations in the surface level. Variations in the torque load on the unit are measured by a fixed symmetrical coil arrangement 305 (Fig. 3) at the other end of the tubular casing 212, and an armature 306 attached to the casing 212 by a rod 302 Fig. 2 (not shown), whereby the angular twist at this end of the casing can be measured. Two transducer units may be used to examine the two surfaces of a wall and derive thickness measurements Fig. 4 (not shown).