GENERATION ET DETECTION D'ONDES DE LAMB A L'AIDE DE P(VF rVFJ) :APPLICATION A LA MESURE DE DENSITES DE LIQUIDES
In this work, we accomplished a theoretical and experimental study of a Lamb wave device based on P(VF2-VF3). It is intended to measure liquids densities for industrial applications. Ibis device is composed of two identical piezo-polymer P(VF2-VF3) plates of 110~m thickness, coated on both sides with aluminum, and coupled to an aluminum media 90~m thick. The electrodes (a pair of single-phase transducers) were etched on the upper aluminum face of the piezo-polymer. The presence ofa liquid on one side of the aluminum plate change the device's synchronism frequency. To measure this variation, we developed an electronic system dedicated to the control of the signal generation and detection. Equations for generation, propagation and detection of the Lamb wave are presented, and permit the evaluation of the liquid density as function of the measured variation on the synchronism frequency. If the longitudinal velo city into the liquid is known, therefore we can use this device to measure the absolute density of liquids with an accuracy of about 5%.