GB626624A - Improvements in or relating to measuring devices such as barometers - Google Patents

Abstract

626,624. Indicating apparatus; barometers. LIQUIDOMETER CORPORATION. Sept. 18, 1945, No. 24063. Convention date, March 7. [Classes 106 (ii) and 106 (iv)] A device for measuring a change of a variable comprises a control member arranged to be displaced in response to a change of said variable, a permanent magnet rotatably mounted on said control member and arranged so that a line connecting the poles of said magnet is transverse of the axis of rotation thereof, a magnetic system for producing two stationary opposed magnetic fields in substantially parallel planes equally spaced axially on opposite sides of a normal position of the magnet and adjacent and perpendicular to the axis of rotation of the magnet, said magnet being displaceable bodily along its axis of rotation relative to said two opposed magnetic fields by a displacement of said control member, and an indicating element fixed relative to said magnet to indicate a bodily displacement thereof by a rotational deflection corresponding to the angular position of said magnet. A chamber of a pocket barometer is formed between a diaphragm 14 and housing 13 and may be evacuated or filled with a gas under pressure. A dial 26, the ends 59 of which may be sprung together during assembly, is mounted on a opal support 22 which rests on a diaphragm guide 12 and carries a setting gear 20 which may be a forced fit thereon, or formed integrally therewith. The setting gear 20 may be rotated by a knob 50. Three fingers of an adjusting spring 24 are engaged in slots in the dial support 22 and the centre of the spring is threaded to engage a bushing 17 mounted upon the diaphragm. A permanent magnet 31 and a pointer 32 are mounted on a shaft rotatably supported by the bushing 17 and an adjustable bracket 33 carried thereby. Associated with the magnet 31 are two stationary permanent magnets or electromagnets 40, 401 mounted in opposition on a housing 41 and located by ears 42. The vertical position of these magnets may be adjusted initially by rotating a screw 46 which engages a plate 44, a spring washer 45 pressing the magnets against this plate. The apparatus is housed in a casing 61 having a transparent cover 62. In operation, movement of the diaphragm causes a vertical movement of the magnet 31 which rotates due to the varying field of the stationary magnets, the amount of rotation being limited by stops 38, 39. The dial and spring 24 are then rotated by the knob 50 until the diaphragm returns to its initial position as indicated, it is stated, by the return of the pointer to its zero position shown by an index 58. The pressure may then be read from the dial 26, the indication remaining until a further observation is made.