CHARACTERIZATION OF SUSPENSIONS BY ULTRASONIC REFLECTION MEASUREMENTS

The ultrasonic attenuation and the ultrasonic backscatter coefficient from suspensions are known to be correlated with the concentration of particles and the particle size distribution. However, for suspensions with a very low particle concentration (<500 ppm) the effect of the p articles on the attenuation or backscatter coefficient is in general n ot significant. In this paper a new ultrasonic technique is presented, which can be applied to characterize suspensions with a very low conc entration of particles. The method is based on ultrasonic reflection f rom individual particles passing through a small measurement volume. S uch a small volume is achieved by applying a focused transducer and wi ndowing of the time signal. The amplitude of a received reflection dep ends on the position of the reflecting particle in the measurement vol ume and on the dimensions and shape of the particle. A forward analyti cal model describes the relations between the suspension properties (p article size distribution and particle concentration) and the measured histogram of amplitudes. The particle size distribution and concentra tion are obtained from the measurements via numerical inversion of the forward model. Results of measurements on a well-controlled suspensio n demonstrate the feasibility of this technique. (C) 1998 Elsevier Sci ence B.V.