Improvement of Lamb waves sensors

Anti-symmetrical Lamb wave mode A0 presents a large sensitivity to mass loading and can be used in contact with liquids with a small attenuation. In a practical use point of view, the main problem of this kind of sensor is its temperature sensitivity. The influence of stress on temperature sensitivity has been studied. A first experiment is based on a stress compensation produced by differential thermal dilatation. The results showed a poor repeatability. Then, a completely different method has been developed. On the same membrane, two different waves with perpendicular propagating directions are produced. Experimentally, temperature sensitivity is rather different depending on the propagation direction but mass sensitivity is almost the same, which allows to distinguish temperature effects and effects due to mass loading on the frequency shift measurements.