GB773677A - Improvements in or relating to fluid pressure gauges - Google Patents

Abstract

773,677. Fluid-pressure gauges. GENERAL ELECTRIC CO., Ltd., MASON, M. T., and MATTHEWS, A. Feb. 14, 1955 [Feb. 15, 1954], No. 4394/54. Class 40 (1). [Also in Group XIX] A fluid pressure gauge comprises: (i) two pressure chambers separated by a flexible diaphragm, (ii) a movable magnetic member in one of the chambers and mechanically coupled to the diaphragm, (iii) one or more inductance coils disposed outside the pressure chambers. In use of the gauge movement of the magnetic member due to displacement of the diaphragm by the pressure to be measured causes a variation of the self or mutual inductance of the coil or coils. This change in inductance is measured by a suitable instrument. In the embodiment shown in Fig. 1, two inductance coils 5, 6 surround two fixed magnetic cores 26, 27, air-gaps 28, 29 and a central axially movable magnetic core 7 enclosed in a non-magnetic tube 19. The latter is secured to a short tube 14 which supports a flexible capsule 13 (e.g. of beryllium-alloy) in a pressure chamber 4. The tube 19 is sealed at its upper end by a plug 21 so that the second pressure chamber 24 comprises the interior of capsule 13. The movable core 7 is secured to a rod 30 into which is screwed a rod 32 extending from the lower wall of capsule 13. The fluid whose pressure is to be measured is fed into pressure chamber 4 via inlet conduit 25 and movement of the wall of capsule 13 in accordance with the differential pressure between the two chambers 4, 24 moves magnetic core 7 so as to vary the widths of the air-gaps 28, 29 and thus vary the self-inductance of the two coils 5, 6 differentially. The coils 5, 6 may be connected in the circuit disclosed in Specification 759,041 in order to give an indication of the pressure to be measured. The apparatus shown in Fig. 1 comprises a zero adjuster described and claimed in Specification 773,678. The zero adjuster comprises a bolt 34 threaded into the end of rod 32 and passing through a U-shaped cross-section member 33. By rotating the bolt 34 the wall of capsule 13 enclosed by member 33 is distorted and this moves magnetic member 7 to adjust the air gaps 28, 29. In a modification, Fig. 2, not shown, the fluid whose pressure is to be measured feeds into the capsule interior. One of the pressure chambers may be evacuated.