Fluid density and concentration measurement using noninvasive in situ ultrasonic resonance interferometry

A method of noninvasively measuring the density of fluids contained within pipes, cans, tanks, and bottles has been developed. The container-fluid system is interrogated using an ultrasonic transducer. A second transducer is used to observe transmitted energy as the input frequency is swept through an appropriate range determined by the geometry. Resonance peaks are observed in the transmitted energy. The periodicity of the resonant peaks is determined by analyzing the response data using a fast Fourier transform. The technique is tested using known NaCl concentration standards within a stainless steel pipe. The concentration of unknown NaCl solutions is measured in situ with an accuracy of ±0.15 M over a range of 0.4 to 3.4 M corresponding to an accuracy of ±0.02 specific gravity (SG) units over a range of 1.000 to 1.134 SG units