Abstract: The invention relates to an apparatus for determining and/or monitoring the viscosity of a medium in a container, having a unit which can oscillate, having a drive/reception unit and having a control/evaluation unit, in which case the unit which can oscillate is arranged at a defined measurement position within the container and/or in which case a unit which can oscillate is fitted such that it is immersed as far as a defined immersion depth in the medium, and in which case the drive/reception unit excites the unit which can oscillate to oscillate and/or in which case the drive/reception unit receives the oscillations from the unit which can oscillate. The control/evaluation unit uses the frequency/phase curve (&phgr;=g(f)) of the unit which can oscillate to determine the viscosity (&eegr;) of the medium.

Abstract: The invention relates to an electromechanical drive or a sensor element composed of piezoelectric elements arranged in the form of a stack. The drive or the sensor element is intended for measurement instruments and operates even at very high temperatures. The new drive or the new sensor element (10) for this purpose comprises a number of piezoelectric ceramic layers (12a-f), with electrode layers (16a-e) in each case being arranged between two mutually facing surfaces of directly adjacent piezoelectric ceramic layers. Connectors (18a,b) in the form of wires run in grooves (14a-d) in the electrode layers (16a-e) in order to make electrical contact with the electrode layers (16a-e), and are passed out of the electrode layers (16a-e).

Abstract: The invention relates to a device for determining and/or monitoring filling of a product or the position of the boundary surface between two media or phases in a container. Said device comprises a signal generating unit (2) that generates high-frequency measuring signals, an injection unit (3) and a surface waveguide (4), wherein the measuring signals are injected into the surface waveguide (4) by means of the injection unit (3) and directed toward the filling product via the surface waveguide (4). The device also comprises a receiver/evaluation unit (5, 6), which directly or indirectly determines filling of the product or the position of the boundary surface in the container during the running time of the measuring signals reflected on the surface or boundary surface of the filling product. The invention aims at providing a device which is configured in such a way that parasitic voltages are effectively diverted.

Abstract: A device for determining and/or monitoring the level of a medium in a container or for ascertaining the density of a medium in the container embodied as a vibration detector. According to the invention the vibration detector still functions reliably even under extreme process conditions and upon abrupt changes in process conditions. The vibration detector has a tubular inner part provided, which is dimensioned such that it is positioned between the housing wall and a drive/receiving unit, and that the tubular inner part is connected to the housing or to the diaphragm.

Abstract: The invention relates to at microwave-operated level meter with a small blind zone, comprising an antenna (15, 35) for transmitting or for transmitting and receiving microwaves, a microwave generator (23, 45, 59, 61, 91) directly located on said antenna (15, 35), and a transmitter or transmitter and receiver element (25, 47, 60, 85, 93) pointing into the antenna (15, 35) and directly linked with the microwave generator (23, 45, 91), said transmitter or said transmitter and receiver element (25, 47, 60, 85, 93) being an extension of the connection.

Abstract: The invention relates to a vibration detector (1) for determining and/or monitoring the level of a medium in a container or for ascertaining the density of a medium in the container.

Abstract: In order to excite Lamb waves in a plate or container wall, an IDT transducer (interdigital transducer) is employed. The IDT comprises a layer composed of piezoelectric material, and on one of whose surfaces two electrodes which engage in one another like fingers are applied. The IDT is acoustically coupled to the plate or container wall by means of the surface facing away from the electrodes. If a radio-frequency AC voltage is applied to the connections of the electrodes, then a thickness vibration is initiated in the piezoelectric layer. If the speed of propagation or speed of sound of the longitudinal waves which result in this thickness vibration in the piezoelectric layer is matched to the phase velocity with which a s0 mode Lamb wave propagates in the material of the plate or of the container wall then only s0 mode Lamb waves are initiated by the resonance effect in the plate or container wall, by virtue of the acoustic coupling between the piezoelectric layer and the plate or container wall.

Abstract: The invention relates to an apparatus for determining and/or monitoring the viscosity of a medium in a container, having a unit which can oscillate (2), having a drive/reception unit (4, 5, 6) and having a control/evaluation unit (8), in which case the unit which can oscillate (2) is arranged at a defined measurement position within the container and/or in which case a unit which can oscillate (2) is fitted such that it is immersed as far as a defined immersion depth in the medium, and in which case the drive/reception unit (4, 5) excites the unit which can oscillate (2) to oscillate and/or in which case the drive/reception unit (4, 6) receives the oscillations from the unit which can oscillate (2).

Abstract: The piezoelectric vortex sensing element (3, 3′, 3″, 3+) of this vortex flow sensor (1) can be assembled from individual components in a simple manner; if its piezoelectric element (34, 34′, 34″, 34*, 34+, 34++) should be faulty, it can be easily replaced. Also, the vortex sensing element can be made largely insensitive to vibrations acting from outside. The vortex flow sensor (1) serves to measure the flow velocity and/or the volumetric flow rate of a fluid flowing through a measuring tube (2). A bluff body (4) generating Kármán vortices is disposed along a diameter of the measuring tube and fixed to the measuring tube at at least one fixing point (41). The vortex sensing element responds to vortex-induced pressure fluctuations and either is installed in a wall (22) of the measuring tube down-stream of the bluff body in a tight manner or extends into a main bore (46) extending through the measuring tube into the bluff body.

Abstract: The invention relates to an electromechanical drive or a sensor element composed of piezoelectric elements arranged in the form of a stack. The drive or the sensor element is intended for measurement instruments and operates even at very high temperatures.

Abstract: An assembly for monitoring a predetermined level of a material in a container comprises two ultrasonic transducers mounted on the container in line with the level to be monitored, such that an interspace exists between the ultrasonic transducers into which the material enters on attaining the level to be monitored. The one ultrasonic transducer is an emitter transducer which at predetermined points in time for emitting ultrasonic pulses is energized by a frequency which is so low that the ultrasonic pulses are transmitted through the interspace to the detector transducer even when the interspace is filled with air. The other ultrasonic transducer is a detector transducer which converts detected ultrasonic pulses into electrical detection signals.

Abstract: In order to excite Lamb waves in a plate (8) or container wall (8), it is proposed that an IDT transducer (interdigital transducer), which is known per se and comprises a layer (1) composed of piezoelectric material, and on one of whose surfaces two electrodes (2, 3) which engage in one another like fingers are applied, be acoustically coupled to the plate (8) or container wall (8) by means of the surface facing away from the electrodes (2, 3). If a radio-frequency AC voltage is applied to the connections (6, 7) of the electrodes (2, 3), then a thickness vibration is initiated in the piezoelectric layer (1).

Abstract: An arrangement for establishing and/or monitoring a predetermined filling level is described, in which a fixed phase difference (.DELTA..phi..sub.R), which is independent of the oscillation quality of the arrangement, exists between a transmission signal and a reception signal (E) at the resonant frequency of the mechanical oscillatory structure. This arrangement comprises a mechanical oscillatory structure (1) at least one transmitter (3), which excites the oscillatory structure (1) to produce oscillations, and two piezoelectric elements as receivers (24a, 24b). In accordance with a first variant, a first signal line (241a) of the first receiver (24a) is connected to an electrode which is arranged on a surface which bounds the first receiver (24a) in a direction opposite to its polarization. A second signal line (241b) of the second receiver (24b) is connected to the transmission signal line (5) via an electrical impedance (Z).

Abstract: Sensing the level of a liquid in a vessel by the pulse transit time technique is done by means of an ultrasonic transducer mounted above the highest-permissible level in the vessel which emits ultrasonic transmission pulses to the surface of the liquid and receives the ultrasonic echo pulses reflected from the liquid surface. The level in the vessel is established from the transit time of the ultrasonic pulses. To detect an overfill when the ultrasonic transducer is immersed in the liquid the decaying output signal of the ultrasonic transducer generated by the ringing of the ultrasonic transducer following the end of the each ultrasonic transmission pulse is analyzed. In this arrangement the fact is exploited that due to the better coupling of the ultrasonic transducer to the liquid than to air the ringing duration is shorter when the ultrasonic transducer is covered by the liquid.

Abstract: An apparatus for establishing and/or monitoring a predetermined filling level in a container is described, in which a fixed phase difference (.DELTA..phi..sub.R), which is independent of the oscillation quality of the apparatus, exists between a transmission signal and a reception signal (E) at the resonant frequency (f.sub.r) of the mechanical oscillatory structure. This apparatus comprises a mechanical oscillatory structure (1), an electromechanical transducer (2) having at least one transmitter (23) and a receiver (24), an evaluation unit (9), which determines the frequency of the reception signal (E), compares it with a reference frequency (f.sub.R) and generates an output signal which indicates that the mechanical oscillatory structure (1) is covered by a charge material if the frequency has a value which is less than the reference frequency (f.sub.

Abstract: An assembly for sensing and/or monitoring the level of a material in a vessel includes a level sensor mounted in the vessel so that it comes into contact with the material when the material has attained a predetermined level. The level sensor contains a low-frequency sensing system and a high-frequency sensing system. The low-frequency sensing system is formed by a mechanical vibrator system induced to vibrate at its natural resonant frequency, and establishing whether the mechanical vibrator system is in contact with the material or not is achieved by evaluating the frequency and/or amplitude of the mechanical vibrations. For forming the high-frequency sensing system high-frequency elastic vibration is induced in a component of the level sensor, and establishing whether this component is in contact with the material or not is achieved by evaluating an electric signal generated as a function of the high-frequency elastic vibration.

Abstract: An apparatus for establishing and/or monitoring a pre-determined filling level in a container is provided, in which the reception signal (E) corresponds to the desired measurement signal and in which a fixed phase difference (.DELTA..phi..sub.R), which is independent of the oscillation quality of the apparatus, exists between the transmission signal and the reception signal (E) at the resonant frequency (f.sub.r) of the mechanical oscillatory structure (1).

Abstract: An apparatus for establishing and/or monitoring a predetermined filling level in a container is provided, in which a reception signal (E) is equal to the measurement signal, and in which a fixed phase difference (.DELTA..phi..sub.R), which is independent of the oscillation quality of the apparatus, exists between a first transmission signal (S.sub.1), and a reception signal (E) at a resonant frequency (f.sub.r).

Abstract: For monitoring a predetermined level of a liquid in a container an ultrasonic transducer is fitted on the outer surface of the container wall at a measurement point situated at the height of the level to be monitored. The ultrasonic transducer contains a piezoelectric element which generates, when excited by an alternating voltage pulse having a given transmission frequency, an ultrasonic transmission pulse which is transferred via a diaphragm to the container wall and which converts ultrasonic vibrations transferred from the container wall to the ultrasonic transducer into electrical reception signals. So that the piezoelectric element for given dimensions can be operated in a large frequency range, and so that a good adaptation to the diaphragm is achieved, the piezoelectric element consists of a porous piezoelectric ceramic having a type 3--3 connectivity.

Abstract: A description is given of a sturdy device for establishing and/or monitoring a predetermined filling level in a container, which device exhibits a housing (1), two oscillating rods (3, 4) projecting into the container, a first diaphragm (2) which is fixedly clamped, at its border, into the housing (1), a second diaphragm (6, 6') which is arranged parallel to said first diaphragm in the interior of the housing (1), a piezoelectric element (7, 7') which is arranged on the second diaphragm (6, 6') and is intended for receiving and converting oscillations into an electric output signal and for inducing bending oscillations in the second diaphragm (6, 6'), and in the case of which device the mode of oscillation produced by the piezoelectric element (7, 7') corresponds to the mode of oscillation utilized for inducing oscillation in the oscillating rods (3, 4).