Ultrasonic measurement of density of liquids

This paper presents two methods to measure the density of liquids based on the measurement of the reflection coefficient and propagation velocity, using a novel double-element transducer. The measurements can be made in liquids, stationary or in motion. The main factors that affect the precision of the measurements are analyzed. The effect of acoustic diffraction is eliminated by using the double-element transducer, where the receiver is somewhat larger in diameter than the emitter. The effect of short- and long-term stability of the electronics and piezoelectric ceramics employed in the system is also eliminated. A system was implemented and measurements of several liquids, stationary and in motion, were conducted.