DE102016115199A1 - Ultrasonic sensor for determining or monitoring a process variable of a medium in automation technology - Google Patents

Abstract

The invention relates to an ultrasonic sensor (4) for determining or monitoring a process variable of a medium (2) in automation technology with a transmitting / receiving unit (9) for transmitting and / or receiving ultrasound signals, with a coupling unit (8) via which the transmitted ultrasound signals from the transmitting / receiving unit (9) to an amplitude transformation unit (10) and the received ultrasonic signals from the amplitude transformation unit (10) are coupled to the transmitting / receiving unit (9), wherein the amplitude transformation unit (10) comprises a first amplitude transformation component (11 ) with a first cone (14) widening in cross-section in the emission direction of the ultrasonic signals and at least one second amplitude transformation component (12) having a second cone (15) tapering in cross-section in the emission direction of the ultrasonic signals, the second cone (15) being within the first cone (14) angeo rdnet is and wherein a front membrane (13) at the end pointing in the direction of radiation end portions (16, 17) of the first cone (14) and of the second cone (15) is provided.

Description

The invention relates to an ultrasonic sensor for determining or monitoring a process variable of a medium in automation technology.

Ultrasonic sensors come i.a. used in Ultrasachall flowmeters. Ultrasonic flowmeters determine or monitor the volume and / or mass flow of a fluid medium that passes through a pipeline in a defined flow direction. The fluid medium is a liquid or a gas. Furthermore, ultrasonic test sensors for the acoustic inspection of workpieces have become known.

A time-of-flight ultrasonic flowmeter consists of at least two ultrasonic sensors, each mounted in an opening in the wall of a measuring tube. In this so-called in-line flowmeter, the measuring tube is fitted in the pipeline. At least two ultrasonic sensors are placed offset to one another in the flow direction of the medium in such a way that the ultrasonic signals or ultrasonic waves emitted by one ultrasonic sensor are received by the other ultrasonic sensor. The ultrasonic sensors are operated alternately as a transmitting and receiving unit. A control / evaluation unit, usually at least one microcontroller with appropriate software determines the volume and / or mass flow of the fluid in the pipe or in the measuring tube based on the transit time difference of the ultrasonic signals in the flow direction and against the flow direction. Corresponding ultrasonic flowmeters are offered and distributed by the applicant in different versions for different applications. Applicants' flowmeters have the name Prosonic Flow 92F, 93C or B200, for example. Next also working on the Doppler principle ultrasonic flowmeters are known, which can only work with an ultrasonic sensor.

The transmitting and / or receiving unit used is an electromechanical converter, which is usually at least one piezoelectric element. The electromechanical transducer is arranged in a cup-shaped housing, whose end face facing the medium is closed by an end-side membrane. An impedance matching between the ultrasonic sensor and the medium takes place via at least one suitably configured matching layer.

The invention has for its object to propose an ultrasonic sensor with an improved impedance matching.

The object is achieved by an ultrasonic sensor for determining or monitoring a process variable of a medium in automation technology with a transmitting / receiving unit for emitting and / or receiving ultrasonic signals, with a coupling unit, via which the transmitted ultrasonic signals from the transmitting / receiving unit to a Amplitude transformation unit and the received ultrasonic signals from the amplitude transformation unit are coupled to the transmitting / receiving unit. The amplitude transformation unit comprises a first amplitude transformation component having a first cone which widens in cross section in the emission direction of the ultrasound signals and at least one second amplitude transformation component with a second cone tapering in cross section in the emission direction of the ultrasound signals, the second cone being arranged inside the first cone. A front membrane is arranged on or in the end regions of the first cone and of the second cone pointing in the emission direction. The front membrane, which is coupled to the end regions, is preferably a thin and rigid membrane which has comparable properties to a loudspeaker membrane. The usual thickness to diameter ratio is less than 1: 5 in these membranes; Preferably, the ratio is less than 1:20. The amplitude transformation unit is in contact with the medium, that is, in contact with the fluid medium to be measured.

• – Mittels der erfindungsgemäßen Amplitudentransformationseinheit lässt sich die an der Frontmembranfläche abgestrahlte Wellenfront der Ultraschallsignale so beeinflussen, dass das Verhältnis von Transmission zu Reflexion maximal oder zumindest näherungsweise maximal ist.
• – Aufgrund des hohen Transmissionsanteils der Ultraschallsignale durch die Frontmembran, wird der Körperschall, also der Anteil der Ultraschallsignale, die sich nicht über das Medium sondern über die Wandung des Messrohres/der Rohrleitung ausbreiten und die Messsignalerfassung stören, reduzieren. Erfindungsgemäß lässt sich daher ein optimiertes Signal-/Rauschverhältnis realisieren.
• – Über die Ausgestaltung und/oder die Materialwahl von erstem Konus und zweitem Konus lässt sich eine gewünschte Wellenfront im Nahfeld der abstrahlenden Frontmembran erreichen. In vielen Anwendungen ist die Abstrahlung einer ebenen Wellenfront vorteilhaft, da diese eine maximale Energiedichte aufweist. Bei Messrohren mit kleinem Messrohr- zu Sensor-Durchmesser, d.h. bei einem Messrohr- zu Sensor-Durchmesser von kleiner als 10:1 bzw. bevorzugt 3:1 kann eine Fokussierung der Wellenfront oder eine Kugelwelle von Vorteil sein. Durch den ersten Konus wird die Schallwelle amplitudentransformiert und erreicht die Frontmembran. Über den zweiten Konus wird die Amplitude der Schallwelle weiter erhöht und an das zu messende Medium bezüglich der Impedanz angepasst. Durch die Dimensionierung der Konen und/oder die Wahl der Materialien (materialabhängige Schallgeschwindigkeit), aus denen die Konen gefertigt sind, lässt sich die Laufzeit der Schallwellen in den Konen so variieren, dass die gewünschte Form der Wellenfront in das Medium abgestrahlt bzw. aus dem Medium empfangen wird.
• – Da die beiden Konen der Amplitudentransformationseinheit lediglich in zwei ringförmigen Bereichen mit der Membran in Verbindung stehen, ist die Impedanz geringer als bei den bislang bei Ultraschallsensoren zur Impedanzanpassung eingesetzten Anpassschichten. Daher erlaubt es die erfindungsgemäße Amplitudentransformationseinheit, die Ultraschallsignale nahezu ungedämpft mit einer hohen Amplitude über die Frontmembran in das Medium aussenden bzw. aus dem Medium empfangen.
• – Ein weiterer Vorteil der erfindungsgemäßen Amplitudentransformationseinheit ist darin zu sehen, dass sie sich auf jedes zu messende Medium durch entsprechende Materialwahl und/oder Dimensionierung der Konen einfach anpassen lässt und auch nachträglich an einen Ultraschallsensor mit einem topfförmigen Gehäuse und Sende-/Empfangseinheit angebracht werden kann. Bevorzugt – aber keineswegs ausschließlich – ist der erfindungsgemäße Ultraschallsensor bzw. das Durchflussmessgerät mit dem erfindungsgemäßen Ultraschallsensor zur Messung der Laufzeit von Ultraschallsignalen in gasförmigen Medien geeignet.

The ultrasonic sensor according to the invention is distinguished by a multiplicity of advantages:

• By means of the amplitude transformation unit according to the invention, the wavefront of the ultrasonic signals radiated on the front membrane surface can be influenced such that the ratio of transmission to reflection is maximal or at least approximately maximum.
• - Due to the high transmission component of the ultrasonic signals through the front membrane, the structure-borne noise, ie the proportion of the ultrasonic signals that do not propagate through the medium but over the wall of the measuring tube / pipe and interfere with the measurement signal detection, reduce. According to the invention, therefore, an optimized signal / noise ratio can be realized.
• - About the design and / or the choice of material of the first cone and second cone can be a desired wavefront in the near field of the radiating front membrane can be achieved. In many applications, the radiation of a planar wavefront is advantageous because it has a maximum energy density. With measuring tubes with Small measuring tube to sensor diameter, ie at a measuring tube to sensor diameter of less than 10: 1 or preferably 3: 1 may be a focus of the wavefront or a spherical wave advantage. The first cone amplifies the sound wave and reaches the front membrane. Via the second cone, the amplitude of the sound wave is further increased and adapted to the medium to be measured with respect to the impedance. By dimensioning the cones and / or the choice of materials (material-dependent speed of sound) from which the cones are made, the duration of the sound waves in the cones can be varied so that the desired shape of the wavefront radiated into the medium or from the Medium is received.
• Since the two cones of the amplitude transformation unit communicate with the membrane only in two annular regions, the impedance is lower than in the case of the matching layers hitherto used in the case of ultrasonic impedance matching sensors. Therefore, the amplitude transformation unit according to the invention allows the ultrasound signals to be emitted almost unattenuated with a high amplitude across the front membrane into the medium or received from the medium.
• Another advantage of the amplitude transformation unit according to the invention is the fact that it can be easily adapted to any medium to be measured by appropriate choice of material and / or dimensioning of the cones and can also be retrofitted to an ultrasonic sensor with a cup-shaped housing and transmitting / receiving unit , Preferably, but by no means exclusively, the ultrasonic sensor according to the invention or the flow measuring device with the ultrasonic sensor according to the invention is suitable for measuring the transit time of ultrasonic signals in gaseous media.

The ultrasound signals transmitted or received by the transceiver unit are influenced by the first amplitude transformation component with the cross-section widening cone, e.g. focused. The acoustic adaptation of the ultrasound measuring signals takes place via the second amplitude transformation component, which has a cone which tapers in cross-section in the emission direction. It goes without saying that, depending on the design and application, also amplitude transformation units with more than two cones can be used.

According to a preferred embodiment of the ultrasonic sensor according to the invention, at least one pressure equalization opening is provided on the amplitude transformation component. This is particularly advantageous when using the ultrasonic sensor for measuring the volume or flow measurement of a gas in a pipeline, since possible pressure surges or a temporary or continuous overpressure or underpressure does not lead to the destruction of the amplitude transformation unit. Despite the filigree structure of the amplitude transformation unit, it is distinguished by its high pressure resistance.

An advantageous embodiment of the ultrasonic sensor according to the invention provides that the end regions of the first cone and / or the second cone pointing in the emission direction of the ultrasonic signals have a serrated crown structure. Preferably, only the tips of the serrated crown structure / crown structures are connected to the front membrane. Despite the filigree structure of the crown structure of the amplitude transformation unit, it is possible according to the invention to achieve a pressure resistance and / or a stability which is greater than in a corresponding amplitude transformation unit with a closed configuration of the cones.

As already mentioned above, provides an advantageous development of the ultrasonic sensor according to the invention that the first cone and the second cone with respect to the structural dimensions and / or the speed of sound of the materials used the cones are coordinated so that the on the front membrane in the Medium radiated ultrasound signals or the ultrasound signals received from the medium substantially form a planar wavefront and / or a wavefront, which is adapted to the requirements of the particular application. The use of ultrasonic sensors can be arranged in a measuring tube which has an arbitrary shape and / or an arbitrary diameter. Furthermore, the medium to be measured can be arbitrary; every medium, whether gas or liquid, has a defined speed of sound, which is also influenced by the T and the pressure in the case of gases. Incidentally, in the context of the invention, an application is understood to mean that the ultrasonic sensor is installed on a measuring tube having a defined diameter, the measuring tube being traversed by a defined medium. For all possible applications or groups of applications which have comparable properties, the ultrasonic sensor according to the invention can be easily adapted by means of the variable amplitude transformation unit according to the invention.

It is regarded as particularly advantageous if the amplitude transformation unit according to the invention is configured in one piece. In a simple way can be a one-piece Amplitude transformation unit via a selective laser sintering method or a 3-D printing method manufacture. In addition, the amplitude transformation unit and the cup-shaped housing or the sensor pot of the ultrasonic sensor can be made in one piece by means of the selective laser sintering method or the 3-D printing method.

An alternative embodiment proposes that the amplitude transformation unit is manufactured from a plurality of interconnected individual components. The individual components are connected to one another via conventional joining techniques, such as welding, soldering (hard or soft solder) or gluing.

Preferably, however, at least the front membrane with one of the two cones - preferably integrally formed - preferably with the second cone. Again, the previously mentioned production process can be used again.

Advantageous developments of the ultrasonic sensor according to the invention relate to the design of the front membrane. For increased stability, the front membrane may have a honeycomb hexagonal reinforcement structure. It preferably consists of an inhomogeneous material or foam, such as open-cell PU foam, glued glass hollow spheres in epoxy matrix or aluminum foam. The advantage of these designs is the low density of the front membrane.

Alternatively, the front membrane is made of a perforated material, such as a perforated plate, wherein the diameter of the perforations is small compared to the respective shorter wavelength of the ultrasonic signals or ultrasonic waves - membrane or medium - is. In addition to the advantage of a low density, this solution also has the advantage that there is simultaneously an alternative possibility for pressure equalization. In this embodiment, the at least one pressure equalization opening in the front membrane is provided. Further design possibilities were eg in the DE 10 2004 059 524 A1 or the DE 10 2007 027 277 A1 described.

According to an advantageous embodiment, the front membrane is made of a ceramic. Ceramic is very durable and is not attacked by most aggressive media. A ceramic front membrane can be produced using a ceramic injection molding (CIM) process as a combination of membrane and inner cone. Alternatively, an ev. Processed ceramic plate material may be used, which is provided for the purpose of soldering with a metallic layer.

An advantageous embodiment provides that the front membrane has a curvature in the direction of the medium and / or is diluted in the curved area towards the center. By this measure, on the one hand, the acoustic coupling to the measuring tube and thus the unwanted structure-borne noise can be reduced while, on the other hand, the pressure resistance of the amplitude transformation unit is increased.

In order to protect the sub-region of the ultrasonic sensor coming into contact with the medium from abrasive damage or a chemical change due to medium or environmental influences, a protective coating is advantageously provided. This may be metallic, polymeric or ceramic nature. When using individual components, the application of the protective coating, for example, after their assembly and thus protects in particular also the joints.

Additively or alternatively, the protective coating can be applied by way of a galvanic coating method, and is therefore suitable both for the connection of the individual components and for protection against medium and environmental influences.

An advantageous embodiment of the ultrasonic sensor according to the invention provides that it is at the transmitting / receiving unit, which generates the ultrasonic signals, sends and receives, is at least one disc-shaped piezoelectric element, which is fixed non-positively on the inner surface of a cup-shaped housing final end membrane , wherein the end-side membrane is configured such that it forms the coupling unit between the transmitting / receiving unit and the amplitude transformation unit.

Alternatively, it is proposed that the transmitting / receiving unit which generates, transmits and receives the ultrasonic signals is a plurality of disk-shaped piezoelectric elements, which is fixed in a non-positive manner to the inner surface of a cup-shaped housing-terminating membrane by means of a pressure mechanism end membrane is configured such that it forms the coupling unit between the transmitting / receiving unit and the amplitude transformation unit

As already mentioned above, the ultrasonic sensor according to the invention, which has previously been described in different embodiments, preferably in an ultrasonic flowmeter for determining or monitoring the flow of a medium through a pipe with a measuring tube and with used at least one arranged in an opening of the wall of the measuring tube ultrasonic sensor. In addition to the flowmeter described above, which determines the flow of the medium on the basis of the transit time difference of ultrasonic signals in and against the flow direction of the medium, the ultrasonic sensor according to the invention can of course also be used in a flow meter that determines the flow on the basis of a double shift.

The invention will be explained in more detail with reference to the following figures. It shows:

1 : A schematic representation of an inline ultrasonic flowmeter 1 Partly in longitudinal section,

2 FIG. 4: a perspective view of a first embodiment of an ultrasonic sensor according to the invention, FIG.

2a a longitudinal section according to the marking AA by the in 2 shown ultrasonic sensor,

3 a perspective view of a second embodiment of an ultrasonic sensor according to the invention and

3a a longitudinal section according to the marking AA by the in 3 shown ultrasonic sensor.

1 shows a schematic representation of an in-line ultrasonic flowmeter according to the invention 1 - partly in longitudinal section. The inline flowmeter is over in 1 not shown separately flanges mounted in a pipe not shown separately. In two openings 6 the wall of the measuring tube 3 are in a known manner ultrasonic sensors 4 positioned. It should be noted that in addition to this so-called. Single-channel flowmeter 1 Also multi-channel flowmeters have become known. For multichannel flowmeters, the ultrasonic sensors are 4 arranged in pairs, also measuring paths MP are present, which are the longitudinal axis L of the measuring tube 3 do not cut. In such an embodiment, in the determination of the flow, the influence of the flow profile of the in the measuring tube 3 flowing medium 2 be taken into account.

In the case shown, the two ultrasonic sensors 4 in opposite areas of the measuring tube 3 arranged, wherein the two areas are offset parallel to the longitudinal axis L. Both ultrasonic sensors 4 are in their medium 2 facing end region in contact with the medium.

The measuring tube 3 is from a fluid medium 2 which is essentially a liquid or gaseous medium 2 acts in the flow direction S flows through. The two ultrasonic sensors 4 are from the control / evaluation unit 5 alternately switched to a transmit mode and a receive mode. In transmit mode, one of the two ultrasonic sensors transmits 4 a sound wave or an ultrasonic signal in the direction of the opposite ultrasonic sensor 4 out. The sound wave or the ultrasonic signal is from the ultrasonic sensor operated in the reception mode 4 after passing through the measuring path MP received. Subsequently, the modes of the two ultrasonic sensors 4 exchanged.

The the medium 2 transverse sound waves preferably run on the marked measuring path MP, the shortest connection between the two ultrasonic sensors 4 features. Sends the upper ultrasonic sensor 4 an ultrasonic signal, this is from the flowing medium in the flow direction S. 2 taken along and has on the measuring path MP one of the control / evaluation unit 5 determined duration. Sends the lower ultrasonic sensor 4 , so a longer transit time is measured on the measuring path MP, since the ultrasonic signal counter to the flow direction S of the medium 2 spreads. The difference between the two transit times depends on the speed with which the medium 2 through the measuring tube 3 or flows through the pipeline.

2 shows a perspective view of a first embodiment of an ultrasonic sensor according to the invention. In 2a is a longitudinal section according to the label AA by the in 2 to see the ultrasonic sensor shown. The ultrasonic sensor 4 for determining and / or monitoring a process variable of a fluid medium 2 in automation technology has an electromechanical transducer unit 9 for transmitting and / or receiving ultrasound signals. The electromechanical transducer unit 9 is designed in the case shown as a piezoelectric disc-shaped element, which frictionally with the end-side membrane 8th connected is. The end-side membrane 8th closes the pot-shaped housing 7 against the medium 2 ,

About the membrane 8th acting as a coupling unit, the ultrasonic signals or ultrasonic waves generated by the electromechanical transducer element become the amplitude transformation unit 10 coupled. Accordingly, the received ultrasonic signals and ultrasonic waves, respectively, from the amplitude transformation unit 10 on the electromechanical transducer element 9 coupled.

The amplitude transformation unit 10 has two components: a first amplitude transformation component 11 with a first cone which widens in cross section in the emission direction of the ultrasonic signals 14 and at least a second amplitude transformation component 12 with a second cone which tapers in cross-section in the direction of emission of the ultrasonic signals 15 having. The cross sections of the cones can be arbitrary: circular, angular, oval, etc. The second cone 15 is inside the first cone 14 arranged. At the end pointing in the direction of radiation end 16 . 17 from the first cone 14 and second cone 15 is a front membrane 13 intended. Incidentally, in the case shown, end regions are the circular end faces of the two cones 14 . 15 ,

As already described above, the first cone 14 and the second cone 15 with respect to the structural dimensions and / or the speed of sound of the materials used are coordinated so that the on the front membrane 13 into the medium 2 radiated ultrasound signals or from the medium 2 received ultrasonic signals having a defined wavefront. Typically, the defined wavefront is essentially a planar wavefront. Depending on the application - which medium flows through which measuring tube diameter - the wavefront can also have a wavefront deviating from the plane wavefront. Possibly. the effect can still by a special expression of the front membrane 13 get supported. Possible embodiments of the front membrane 13 have already been described in previous passage. A repetition at this point is therefore omitted.

Will he be an ultrasonic sensor 4 used for measurement in a fluid medium, for example in a gas which is at least temporarily under pressure, so by attaching a pressure equalization opening of the risk of destruction of the amplitude transformation unit 10 be prevented. The pressure equalization opening consists in the simplest case of an opening in the outer cone 14 and possibly also in the inner cone 15 , A preferred embodiment of the pressure equalization openings 18 is in the figures 3 and 3a to see. Alternatively, the pressure compensation opening 18 also in the memberan 13 be provided.

3 shows a perspective view of a second embodiment of an ultrasonic sensor according to the invention. In 3a is a longitudinal section according to the label AA by the in 3 shown ultrasonic sensor shown. The construction of in 3 shown ultrasonic sensor 4 corresponds to the pressure equalization openings 18 the in 2 shown ultrasonic sensor 4 , Therefore, a repeated description of the identical parts is omitted.

While in the first embodiment ( 2 ) the cones 14 . 15 have closed conical surfaces is in the embodiment ( 3 ) in the end areas 16 . 17 the cones 14 . 15 a jagged crown structure 19 intended. The pointing in the direction of emission of the ultrasonic signals peaks of the two serrated crown structures 19 are with the front membrane 13 connected. Preferably, this embodiment is used in the determination of the speed of sound of gases. As previously stated, the shape of the at least one pressure equalization opening plays 18 for the fulfillment of the task of pressure equalization irrelevant.

The methods for manufacturing the amplitude transformation unit 10 , if necessary in conjunction with other components of the ultrasonic sensor 4 have already been described in previous passage.

LIST OF REFERENCE NUMBERS

1

 Ultrasonic flowmeter

2

 medium

3

 measuring tube

4

 ultrasonic sensor

5

 Control / evaluation unit

6

 opening

7

 pot-shaped housing

8th

 membrane

9

 electromechanical transducer element

10

 Amplitude transformation unit

11

 first amplitude transformation component

12

 second amplitude transformation component

13

 front membrane

14

 expanding cone

15

 tapering cone

16

 end

17

 end

18

 Pressure equalization port

19

 crown structure

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004059524 A1 [0016]
• DE 102007027277 A1 [0016]

Claims (20)

Ultrasonic sensor ( 4 ) for determining or monitoring a process variable of a medium ( 2 ) in automation technology with a transceiver unit ( 9 ) for emitting and / or receiving ultrasound signals, with a coupling unit ( 8th ) via which the transmitted ultrasound signals from the transceiver unit ( 9 ) to an amplitude transformation unit ( 10 ) and the received ultrasound signals from the amplitude transformation unit ( 10 ) to the transceiver unit ( 9 ), wherein the amplitude transformation unit ( 10 ) a first amplitude transformation component ( 11 ) with a first cone which widens in cross-section in the emission direction of the ultrasound signals (US Pat. 14 ) and at least one second amplitude transformation component ( 12 ) with a second cone which tapers in cross-section in the emission direction of the ultrasound signals (US Pat. 15 ), wherein the second cone ( 15 ) within the first cone ( 14 ) and wherein a front membrane ( 13 ) at the end regions pointing in the direction of radiation ( 16 . 17 ) of the first cone ( 14 ) and second cone ( 15 ) is provided. An ultrasonic sensor according to claim 1, wherein at the amplitude transformation component ( 10 ) at least one pressure equalization opening ( 18 ) is provided. Ultrasonic sensor according to claim 1 or 2, wherein the end regions pointing in the emission direction of the ultrasonic signals ( 16 . 17 ) of the first cone ( 14 ) and / or the second cone ( 15 ) a serrated crown structure ( 19 ) and wherein preferably the tips of the serrated crown structure / crown structures ( 19 ) with the front membrane ( 13 ) are connected. An ultrasonic sensor according to claim 1, 2 or 3, wherein the first cone ( 14 ) and the second cone ( 15 ) with regard to the structural dimensions and / or the speed of sound of the materials used in the cones ( 14 . 15 ) are matched to one another in such a way that they reach over the front membrane ( 13 ) into the medium ( 2 ) radiated ultrasound signals or from the medium ( 2 ) received ultrasonic signals substantially form a planar wavefront and / or a wavefront, which is adapted to the requirements of the respective application. Ultrasonic sensor according to at least one of the preceding claims, wherein the amplitude transformation unit ( 10 ) is made in one piece and is made by a selective laser sintering process or a 3-D printing process. Ultrasonic sensor according to claim 5, wherein the amplitude transformation unit ( 10 ) and the housing ( 7 ) of the sensor via the selective laser sintering process or the 3-D printing process are integrally connected together. Ultrasonic sensor according to at least one of claims 1-4, wherein the amplitude transformation unit ( 10 ) is made of several interconnectable individual components. Ultrasonic sensor according to claim 7, wherein the individual components ( 14 . 15 . 13 ) are welded together, soldered or glued together. Ultrasonic sensor according to claim 7 or 8, wherein at least the front membrane ( 13 ) and one of the at least two cones ( 15 ; 14 ) are integrally formed. Ultrasonic sensor according to one or more of the preceding claims, wherein the front membrane ( 13 ) has a honeycomb reinforcing structure. Ultrasonic sensor according to at least one of claims 1-10, wherein the front membrane ( 13 ) is made of an inhomogeneous material or foam, such as open-cell PU foam, bonded hollow glass spheres in epoxy matrix or aluminum foam. Ultrasonic sensor according to at least one of claims 1-10, wherein the front membrane ( 13 ) made of a perforated material, such as perforated plate, wherein the diameter of the perforations is small compared to the wavelength of the ultrasonic signals. An ultrasonic sensor according to claim 12, wherein the diameter of the perforations, for example, less than a half wavelength, preferably less than one-tenth of the wavelength of the ultrasonic waves. Ultrasonic sensor according to one or more of the preceding claims, wherein the front membrane ( 13 ) is made of a ceramic. Ultrasonic sensor according to one or more of claims 1 to 14, wherein the front membrane ( 13 ) and / or at least individual components of the amplitude transformation unit ( 10 ) is produced via a ceramic injection molding (CIM) process. Ultrasonic sensor according to one or more of the preceding claims, wherein a protective coating ( 20 ) is provided, the at least a portion of the outer surface of the ultrasonic sensor ( 4 ) covered. An ultrasonic sensor according to claim 16, wherein the protective coating ( 20 ) is applied via a galvanic coating process. Ultrasonic sensor according to at least one of claims 1-17, wherein it is in the transceiver unit ( 9 ) which generates, transmits and receives the ultrasound signals, is at least one disk-shaped piezoelectric element, which is frictionally connected to the inner surface of a cup-shaped housing (FIG. 7 ) final end-face membrane ( 8th ), wherein the end-side membrane ( 8th ) is configured so that it the coupling unit between the transmitting / receiving unit ( 9 ) and the amplitude transformation unit ( 10 ). Ultrasonic sensor according to at least one of claims 1-17, wherein it is in the transceiver unit ( 9 ), which transmits, transmits and receives the ultrasonic signals, which are a plurality of disc-shaped piezoelectric elements, which are non-positively connected via a pressure mechanism to the inner surface of a cup-shaped housing (FIG. 7 ) final end-face membrane ( 8th ), wherein the end-side membrane ( 8th ) is configured so that it the coupling unit between the transmitting / receiving unit ( 9 ) and the amplitude transformation unit ( 10 ) Ultrasonic flowmeter for determining or monitoring the flow of a medium ( 2 ) through a pipeline with a measuring tube ( 3 ) and at least one in an opening ( 6 ) of the wall of the measuring tube ( 3 ) arranged ultrasonic sensor ( 4 ), wherein the ultrasonic sensor ( 4 ) is described in at least one of claims 1-19.

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