GB661944A - Improvements in or relating to apparatus for measuring or indicating a physical condition such as temperature, gas pressure or density - Google Patents

Abstract

661,944. Thermometers; specific-gravity determining apparatus. KALLE, K. T. July 14, 1949, No. 18616/49. Class 97 (iii). Apparatus for determining a physical quantity such as temperature pressure or density of a gas by causing the gas to pass through a capillary opening and measuring the small pressure variations of the gas produced under standard conditions owing to the change of the density of the gas with variation in pressure or temperature at the capillary opening, the said pressure variations being magnified by means of a pressure pump operating at constant volume with a mixture of the gas and a liquid comprises a hollow member 12 having a capillary inlet 9 through which gas is caused to flow by a compressor pump, e.g. a gear-wheel compressor 3, 25, connected to the member 12 by a gas conduit 8 which terminates in an inlet passage 5 for liquid on the suction side 13 of the pump so as to provide for the pump a mixture of gas and liquid which is discharged from the discharge side 14 of the pump through a restricted outlet 15 and a pressure indicating instrument 17 communicating with the discharge side of the pump, the inlet passage 5 being so dimensioned as to compensate for variation in viscosity of the liquid by causing frictional resistance which is related to the resistance in the restricted outlet 15. Variations in the speed of the pump are compensated by means of a centrifugal pump 7 or similar device which sets up a centrifugal force which the liquid to the input of the compressor pump has to overcome. In the arrangement shown the liquid inlet passage to the compression pump 3, 25 includes a rotor 27 in a cylindrical casing 28 which rotor 27 is integral with the wheel 25 of the pump so as to rotate in synchronism therewith and the rotor 27 is provided with projecting vanes to cause rotation of a ring of liquid in the space 6 between the rotor 27 and the cylindrical casing. The rotor has an axial channel 29 and radial channels 7 in communication therewith to allow liquid to pass from the rotating ring of liquid to the suction side 13 of the compression pump. The gas conduit 8 terminates at the centre of the rotor 27. The compressor pump 3, 25 is placed in a closed container 4 partly filled with liquid and to compensate for any variation in the static pressure at the inlet of the conduit 5 a suction pump 21 is arranged to exhaust gas from the upper part of the container 4 and a gas inlet tube 24 adjustably ends below the liquid level 18 in the container. For measuring temperature the tube 12 is enclosed within a tubular casing 10 closed at one end and is in communication at the other end with a gas supply, e.g. the atmosphere, by means of an inlet 11. This feeler member so formed is inserted into the body or space, the temperature of which is to be measured so that the gas drawn into the space between the tubes 10 and 12 is heated to the temperature. Variations in the density of a gas caused, e.g. by changes in composition of the gas as in the proportion of C0 2 in air or waste gas or of S0 2 in the gases at pulp mills can be indicated by maintaining constant the temperature of the gas passing through the capillary inlet 9. Specification 661,943 is referred to.