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Les capteurs à ondes élastiques de surface : applications pour la mesure des basses pressions et des hautes températures

Abstract : The thesis deals with the application of SAW sensors for low pressure and high temperature measurements. The first chapter is devoted to the history of SAW devices, from 1965. The principles of SAW sensors are described, as well as their industrial and economical potentials. The second part is devoted to the theoretical tools, used to model the basic properties of elastic waves as well as their sensitivity to external disturbances. Formulas for calculating the sensitivity of devices under strain or temperature changes are inferred. The approaches of Nalamwar/Epstein and Tiersten to take into account the effect of strain fields are both presented. The third part is devoted to the study of a new SAW pressure sensor concept (suggested by the author), for the accurate measurement of primary and secondary vacuum. The experimental results confirm the theoretically predicted sensor parameters: measuring range, sensitivity, precision and response time. A patent is pending for this innovation. A more efficient MEMS-type design is elaborated to maximize the level of performances. Finally, the thesis deals with wireless passive SAW sensor as a very promising solution for measurement at high temperature. The issue of materials is discussed, as well as the classical way to calculate the Temperature Coefficient of Delay (TCD) for multilayered structures. The effect of the strain field induced in the SAW structure by the differential thermal expansion of the different layers is taken into account to improve the accuracy of TCD calculations. This original theoretical approach is supported by experimental and theoretical results.
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https://hal.univ-lorraine.fr/tel-01748241
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Pascal Nicolay. Les capteurs à ondes élastiques de surface : applications pour la mesure des basses pressions et des hautes températures. Autre. Université Henri Poincaré - Nancy 1, 2007. Français. ⟨NNT : 2007NAN10096⟩. ⟨tel-01748241⟩

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