Ultrasonic cell with IDT's for measurement of liquid acoustic velocity

Abstract

AbstractThis paper proposes a measuring system for the small changes of sound velocity, using the leaky surface wave excited by the interdigital transducer (IDT) on a piezoelectric substrate. The ultrasonic cell was fabricated and an experimental investigation was made. It is shown that the sound velocity change of the order of 2 ppm can be measured. When the propagation surface is loaded by a liquid, the elastic surface wave excited by IDT is converted into the leaky surface wave, which excites the ultrasound into the liquid. By constructing the measuring system utilizing this ultrasound excitation in the water, little spurious wave is excited, and a differential measurement can be successfully performed in the present system. The characteristics of the fabricated ultrasonic cell are examined and the measurement limit and accuracy are discussed. As examples, the change of sound velocity in KCL solution by concentration and some other measurements are discussed, indicating the usefulness of the proposed measuring system.