GB191418495A - Improvements in Means for Measuring and Regulating Temperature Differences. - Google Patents

Abstract

18,495. Wilson, J. C., and Packard, H. N. Aug. 16, 1913, [Convention date]. Thermometers and pyrometers; anemometers. -In apparatus particularly applicable to steam, gas, and like meters, such as are described in Specification 30,405/09, for measuring the difference in temperature between two given points, or maintaining a predetermined difference in temperature between such points, by means of the changes in electric resistance due to temperature changes, one or both of the resistances is formed of substances so selected both as to nature and quantity that through a wide range of temperature a certain difference in resistance always corresponds to a fixed temperature difference. In the gas-meter shown, the gas flows through a conduit 1 and is heated by a resistance 2, its temperature before and after heating affecting resistance thermometers 3, 4, of equal resistance at equal temperatures, arranged in two adjacent arms of a wheatstone bridge, which is adapted to be initially balanced by an adjustable resistance 10. A constant temperature difference between the thermometers 3, 4 is automatically maintained by means of a rheostat 7 adapted to be controlled by suitable means from the wheatstone bridge to vary the heating-current, which is measured by a watt-meter, whereby the flow of gas is also measured. When the gas is being heated, the difference in the resistances of the thermometers 3, 4, which are preferably formed of nickel wire, is balanced by a resistance 11, which is formed, for example, of nickel and manganese so proportioned as to compensate for the differences in the temperature-resistance coefficient of the nickel thermometers at different temperatures. Variations in the specific heat and moisture content of the gas may be similarly compensated.