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.

Abstract: A piezoelectric bending transducer includes two piezoceramic layers each having two sides and electrodes on both of the sides. A graphite fiber layer is glued between the piezoceramic layers with an epoxy resin. The graphite fiber layer has a greater length than the two piezoceramic layers defining an exposed part of the graphite fiber layer. A copper foil is glued to the exposed part. The copper foil has an area for disposition of a solder contact. A process for producing a bending transducer includes placing a graphite fiber layer impregnated with incompletely hardened epoxy resin between two polarized piezoceramic layers. The graphite fiber layer is glued between the piezoceramic layers upon hardening of the epoxy resin. A copper foil is glued onto the graphite fiber layer, preferably simultaneously with the gluing of the two piezoceramic layers.

Abstract: An ultrasonic transducer for measuring the travel time of ultrasonic pulses in a gas, in particular for a gas flow rate meter, includes a piezoelectric radial oscillator, which is preferably formed a piezoceramic and which has two sides and electrodes each being disposed on a respective one of the sides for receiving a spike pulse voltage. A first adaptation layer is applied to one of the sides of the radial oscillator. The first adaptation layer has a thickness being less than one-fourth of a characteristic wavelength of the transducer. A second adaptation layer is applied to the first adaptation layer. The second adaptation layer also has a thickness being less than one-fourth of the characteristic wavelength of the transducer. A damping body is mounted on the other of the sides of the radial oscillator. The radial oscillator and the adaptation layers form a sandwich executing a thickness oscillation as a consequence of a radial-thickness coupling, as soon as the spike pulse voltage is applied.

Abstract: Disclosed is a broad beam ultrasonic transducer of sandwich construction, having piezoceramic laminae (2), fitted with electrodes, and plates/films (3, 13) in the shape of a parallelepiped with a width (B) to length (L) ratio of 0.42 and in which the relative thicknesses of the piezoceramic laminae and the plates/films are chosen such that one side surface of the parallelepiped undergoes an in-phase oscillation behavior.