An application of A0 mode Lamb wave devices employing ZnO-film/Al-foil composite structures to mass density sensors for liquids is discussed. By using the variational technique, the effect of liquid-loading upon A0 mode Lamb wave propagation in the device is analyzed, and a simple relation between the A0 mode Lamb wave velocity and physical conditions is derived. The results suggest that the mass density sensor could be realized by measuring the fractional change in A0 mode Lamb wave velocity. It is experimentally shown that the center frequency of the fabricated A0 mode Lamb wave device distinctly shifts due to various liquid-loading. The fractional change in the velocity is almost proportional to the mass density of liquids. The error of the measured mass density for seven different liquids is within about 5%
Published in:
Ultrasonics Symposium, 1992. Proceedings., IEEE 1992
Date of Conference: 20-23 Oct 1992