3B-2 Ultrasonic Density Measurement of Liquids - A Novel Method using a Generalized Singular Value Decomposition based System Identification

Electrical conductance of an ultrasonic transducer depends on the applied acoustic load. Provided one mechanical port charged with known impedance, and the other port exposed to a fluid, the resulting load is determined by the acoustic impedance of the liquid. This work applies generalized singular value decomposition (GSVD) to determine the transfer function of a pulsed transducer attached to a reference by analyzing the reverberating voltage at the electrical port. The transfer function gives the conductance spectrum as a function of acoustic load. The Butterworth-van-Dyke equivalent circuit is used to derive load impedance from conductance. With acoustic impedance being the product of sound velocity and density, speed of sound recording permits a density measurement of liquids. The proposed method has been successfully tested for water- and oil-based liquids. This work shows experimental results and discusses the influence of temperature and liquid inhomogeneities