Siemens Aktiengesellschaft

Thomas Mockl

Valentin Magori

Christian Stein

Karl Spendel

Thomas Siebenhaar

Jurgen Loschberger

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.

Holder for ultrasonic transducers

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.

Bonded piezoelectric bending transducer and process for producing the

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. The characteristic wavelength of the transducer is a wavelength resulting from natural resonance in the thickness oscillation.

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Coburg, Germany

Thomas Mockl