Improvement of Lamb waves sensors temperature sensitivity compensation

Anti-symmetrical Lamb wave mode A₀ present a large sensitivity to mass loading and can be used in contact with a liquid with a small attenuation. It can be, at least, expected a sensitivity 10 times greater than for an AT quartz cut using bulk waves. Nevertheless, for a practical use, the main problem is the temperature sensitivity of this sensor. A first attempt is based on a compensation of stress produced by a differential thermal dilatation. We obtain a important variation of the temperature sensitivity. Nevertheless, the results showed a poor repeatability. Then, a completely different method has been developed. On the same membrane two different waves with perpendicular propagating direction are produced. Experimentally, it has been shown that the temperature sensitivity is rather different according to the propagation direction but the mass sensitivity is almost the same. With the frequency variation, it is possible to take into account the temperature influence. In the present case, with a non-optimized device the reduction of the temperature sensitivity can be about a factor ten.