DEVELOPMENT OF A BROAD-BAND ULTRASONIC TRANSDUCER FOR HIGH-TEMPERATURE APPLICATIONS

The construction and test of a broad-band transducer designed to work in the temperature range from 20 degrees C to 250 degrees C are report ed. The variation of acoustic and piezoelectric properties of differen t active and passive materials were measured in order to select the ap propriate materials and to simulate the transducer behaviour at differ ent temperatures by using a numerical model based on the KLM equivalen t circuit. The comparison between theoretical and experimental results shows that the characteristics of the transducer such as centre frequ ency and bandwidth remain stable in the operating temperature range, a nd that the variations of echo amplitude with temperature are mainly d ue to the modification of the couplant acoustic properties.