Abstract: An ultrasonic converter unit (10) includes a disc-shaped piezo-ceramic element (11) which is provided on its upper side with a &lgr;/4 adaptation body (13) and with an attenuating mass (14) and a decoupling layer (17) on the lower side. To avoid conducting leads and the problems associated therewith, the plastic parts (13, 14, 17), which surround the piezo-ceramic oscillator (11), are made electrically conductive and are used for direct contacting of the piezo-ceramic element (11). The adaptation body (13) preferably comprises metallized micro glass balls which are mixed with the synthetic resin. The attenuating mass (14) and the decoupling layer (17) can be made to have low resistance by adding conductive carbon black and function as electric contacts. With the addition of ferromagnetic particles, the shielding attenuation against magnetic alternating fields is improved.

Abstract: In ultrasound flow rate meters, an acoustical short circuit between ultrasonic transducers is a special problem. Such a short circuit results in an ultrasonic signal being propagated through a wall of a measuring tube from a sending to a receiving transducer and not being influenced by a medium in the measuring tube. Sealing off a gas path around the ultrasonic transducers is also problematic. In order to solve the problem, the ultrasonic transducers are sheathed with an elastomer molded body. From 25% to 60% of an outer surface of the ultrasonic transducer, which is constructed as a cup-type transducer, is lined with the elastomer molded body, beginning at a cup edge thereof. Contact of the holder with the ultrasonic transducer is minimal and occurs only in an acoustically quiet zone.