A Microwave–Ultrasonic Cell for Sound-Speed Measurements in Liquids

In this work preliminary results obtained in developing a prototype cylindrical ultrasonic cell designed to apply a microwave resonance technique to the determination of its iInternal dimensions are described. Since the apparatus is iIntended for speed-of-sound measurements in pressurized liquid-phase media, the cell design is such that a double reflector pulse-echo technique can be used for time-of-flight measurements. The main absorption and dispersion effects that influence the acoustic measurement in this iInterferometer-like configuration and the values of the corresponding corrections are considered and discussed. The performance of the experimental apparatus and method in terms of achievable precision and accuracy was tested by measuring the speed of sound in water on a single isotherm at 325K between 0.1 and 90MPa.