GB1069435A - Electromechanical transducer device - Google Patents

Abstract

1,069,435. Pressure-sensitive resistors. G. V PLANER Ltd. Aug. 18, 1964 [May 21, 1963; Nov. 19, 1963], Nos. 20109/63 and 45582/63. Heading H1K. [Also in Division G1] A pressure transducer comprises an elastic support, such as a vitreous silica tube 1 (Fig. 1), of elliptical section and closed at one end, having terminal strips 2 . . . 6 deposited longitudinally on the exterior surface of the tube, and thin films 7, 8 of strain-sensitive semi-conductor material, such as intrinsic or doped germanium, deposited around the circumference of the tube, as shown. The pressure to be measured is introduced into the tube, and tends to distort the latter towards a circular cross-section, thus differentially stressing areas X and Y of film 7. X and Y are connected in a bridge circuit, Fig. 2 (not shown), with resistances (A, B), the reading on a meter (V) being indicative of the test pressure; film 8 (forming resistance Z), is connected in series with the meter to compensate for variation of temperature. Alternatively, film 8 may be shunted across a potentiometer (C, Fig. 3, not shown), in a balanced-bridge arrangement. Further temperature compensating films may be added to the circuit. The support may alternatively be made of sapphire, glass, ceramic, glazed metal, or plastics. The strain-sensitive material may alternatively be silicon, and is preferably deposited on the support by evaporation in a vacuum, although other methods such as sputtering may be used. A layer of protective material, e.g. silicon monoxide, silicon nitride, or silica, may be applied between the support and the films of strainsensitive material, and a similar layer may be applied over the films. Reference has been directed by the Comptroller to Specification 757,597.