GB828730A - Improvements in or relating to measuring instruments - Google Patents

Abstract

828,730. Electric measuring systems. GENERAL ELECTRIC CO. Ltd. Dec. 31, 1957 [Dec. 31, 1956], No. 39666/56. Class 40 (1). [Also in Group XXXVI] Apparatus for measuring the gravimetric rate of flow of a fluid comprises a dynamometer instrument, the moving coil of which is supplied with current proportional to the volumetric rate of flow of the fluid, and the fixed coil(s) of which produce(s) a magnetic field proportional to the density of the fluid. As shown, the volumetric rate of flow of petrol in a pipe 3 of an aircraft fuel system determines the frequency of the output of a pulse generator 1 which comprises a turbine wheel 2, carrying a bar magnet 4 and mounted in the pipe 3, and a pick-up coil 5 located outside the pipe adjacent the turbine 2. The pulses from generator 1 are amplified at 6 and passed to a frequency discriminator 7, the output I of which is fed to the moving coil 12 of an iron-cored dynamometer 11. The dielectric constant, K, of the fuel is sensed by using the fuel as the dielectric of a capacitor 9 which is connected to an A.C. voltage generating and rectifying circuit 10, the output I 2 of which is applied to a fixed coil 13 of the dynamometer 11. Since the density of petrol equals BK - C, where B and C are constants, and as K=EI 2 , where E is the constant of proportionality, the field due to I 2 is modified by supplying a current I 3 , equal to C/BE, from a source 15 to a second fixed coil 14 of the dynamometer 11, so that indication may be given directly in gravimetric units.