The attenuation of ultrasound in air depends on the

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Unformatted text preview: crystals, piezoelectrical materials, which are widely distributed under the trade name Piezoxide (e.g. by Valvo), are used to generate ultrasound. These materials are made of lead-zirconate-titanate. 180 © Festo Didactic GmbH & Co. KG • FP 1110 11. Physical fundamentals Figs. 11.3.4 and 11.3.5 illustrate the dependence of speed of sound in air on the temperature and relative air humidity. 360 m/s 350 345 v 340 335 330 0 0 5 10 15 20 25 30 °C 40 t Fig. 11.3.4: Speed of sound in dry air as a function of temperature v = v 0 + 0.58 v 0 = 331.6 mT ⋅ s °C m s 1.5 % 40 °C Percentage increase in v 1.0 30 °C 0.5 20 °C 0 °C -10 °C 0 0 50 % 100 Relative air humidity Fig. 11.3.5: Percentage change in speed of sound as a function of relative air humidity © Festo Didactic GmbH & Co. KG • FP 1110 181 11. Physical fundamentals 11.3.2 Attenuation of ultrasound in air When selecting ultrasonic proximity sensors, the frequency of the emitter should be taken into account. The attenuation of ultrasound in air depends on the ultrasonic frequency and as such also...
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This note was uploaded on 11/01/2012 for the course CHEMICAL 102 taught by Professor Jamesrodriguez during the Spring '12 term at Universidad Politécnica de Cartagena.

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