GB1073461A - Measuring composition of liquid mixtures - Google Patents

Abstract

1,073,461. Analyzing liquid mixtures electrically. NATIONAL RESEARCH DEVELOPMENT CORPORATION. April 27, 1965 [Jan. 27, 1964], No. 3467/64. Heading G1N. The ratio of two liquids in a mixture is determined by noting the dielectric constant, using the mixture as the dielectric of a capacitor in a tuned circuit and measuring the resonant frequency. As shown (Fig. 1), a sealed metal tube 11 with a central electrode 17 and filled with a reference liquid, is surrounded by a second metal tube 13, electrode 17 and tube 11 forming a reference capacitor and tubes 11, 13 with the test liquid as dielectric forming a test capacitor. Each capacitance forms a tuned circuit with half of a coil 18, and the two resonant circuits are fed with A. C. of cyclically varying frequency via coil 22. The voltage induced in a pick-up winding 23 is minimum when either circuit is resonant. Thus the time between resonances in each cycle of frequency scanning is indicative of the difference between the capacitances, dielectric constants and mixture ratios. Non-linearity is the variation of dielectric constant of the mixture can be compensated by suitable variation in the rate of change of frequency during the scanning cycle.