GB991736A - Densimetering systems - Google Patents

Abstract

991, 736. Measuring fluid density electrically. SOC. DE PROSPECTION ELECTRIQUE SCHLUMBERGER. Feb. 20, 1963 [March 6, 1962], No. 6870/63. Heading G1N. Apparatus for measuring the density and viscosity of a fluid flowing in a conduit comprises a resilient element in the conduit, torsionally vibrated at its resonant frequency at a constant amplitude,and it is shown that (a) this frequency is indicative of the density of the fluid, and (b) the current required to maintain the amplitude of vibration at a constant value is indicative of the viscosity of the fluid. Construction. (Figs. 1, 9). A cylinder 34 is mounted on a torsion shaft 42 inside the fluidcarrying conduit 10 by radial blades 38 connected to a hub 40, the ends of the shaft 42 being rigidly attached to the conduit 10 by radial blades 22, 31. The lower end of shaft 42 carries a diametrically polarized permanent magnet 64 which is magnetically coupled to an A.C. -energized electromagnet 50, 52, to produce torsional oscillations in shaft 42. The extent and frequency of the oscillations are sensed by coils 74, 76 coupling with permanent magnets 66, 68 attached to the other end of the shaft 42. Circuitry (Fig. 2). The amplitude of the signal Vd developed in coils 74, 76 is compared at 96 with a reference value, and any difference is amplified at 100 and determines the gain of an amplifier 90 controlling the excitation current i in coil 52, whereby the amplitude of the signal Vd is maintained constant. A phase shifting network 104 produces a #/4 phase shift between i and Vd, and it is shown that under these circumstances the frequency of oscillation, measured at 82, is indicative of the density of the fluid in the conduit 10, and the mplitude of the oscillatory current i, measured at 108, is indicative of its viscosity. The values of density, viscosity and temperature, as measured by a thermocouple, are recorded by an automatic printer.