WO2011051006A1

WO2011051006A1 - Ultrasonic flow and particle measuring system

Info

Publication number: WO2011051006A1
Application number: PCT/EP2010/061950
Authority: WO
Inventors: Beat Kissling; Yaoying Lin
Original assignee: Endress+Hauser Flowtec Ag
Priority date: 2009-10-29
Filing date: 2010-08-17
Publication date: 2011-05-05
Also published as: DE102009046159A1; EP2494316A1

Abstract

The invention relates to an ultrasonic flow and particle measuring system (1), comprising a first ultrasonic transducer (2) and at least one further, second ultrasonic transducer (3), wherein the first ultrasonic transducer comprises at least one first ultrasonic transducer element (4) and at least one first coupling element (5), wherein acoustic signals can be emitted and received by the first ultrasonic transducer element (4) during operation via the first coupling element (5). The first and second ultrasonic transducers (2, 3) are arranged in a measuring tube (8) for determining the flow such that the acoustic signals propagate along at least one signal path (9) in the measuring tube (8) between the first and the second ultrasonic transducers (3), wherein at least the first coupling element (5) is designed as an acoustic lens. The ultrasonic flow and particle measuring system (1) comprises an evaluation unit, which is suited to analyze the amplitude of reflection signals of acoustic signals reflected by particles to the first ultrasonic transducer (2), wherein in a predetermined time interval a number of amplitudes of the reflection signals can be counted using the evaluation unit, which are greater than a predetermined threshold value. The invention further relates to a method for determining the flow of a measuring medium through a measuring tube (8) and for detecting particles in the measuring medium using an ultrasonic flow and particle measuring system (1) according to the invention.

Description

Ultrasonic flow and particle measuring system

The present invention relates to an ultrasonic flow and Partikelmesssystenn, with a first ultrasonic transducer and at least one further, second

Ultrasonic transducer, wherein the first ultrasonic transducer at least a first

Ultrasonic transducer element and at least a first coupling element, wherein the first ultrasonic transducer element in operation acoustic signals via the first coupling element can be emitted and received, which first and second

Ultrasonic transducers are arranged in a measuring tube for determining the flow over a transit time difference principle so that propagate the acoustic signals along at least one signal path in the measuring tube between the first and the second ultrasonic transducer.

Ultrasonic flowmeters are widely used in process and process

Automation technology used. They allow in a simple way, the

Determine volume flow and / or mass flow in a pipeline.

The known ultrasonic flowmeters often work after the Doppler or after the transit time difference principle. When running time difference principle, the different maturities of ultrasonic pulses are evaluated relative to the flow direction of the liquid. For this purpose, ultrasonic pulses are sent at a certain angle to the pipe axis both with and against the flow. The runtime difference can be used to determine the flow velocity and, with a known diameter of the pipe section, the volume flow rate.

In the Doppler principle, ultrasonic waves of a certain frequency are coupled into the liquid and the ultrasonic waves reflected by the liquid are evaluated. From the frequency shift between the coupled and reflected waves can also determine the flow rate of the liquid. Reflections in the liquid occur when air bubbles or

Contaminants are present in this, so this principle is mainly used in contaminated liquids use. The ultrasonic waves are generated or received with the help of so-called ultrasonic transducers. For this purpose, ultrasonic transducers are firmly mounted in the pipe wall of the respective pipe section. More recently, clamp-on ultrasonic flow measurement systems have become available. In these systems, the ultrasonic transducers are pressed against the pipe wall only with a tension lock. A big advantage of clamp-on ultrasonic flow measuring systems is that they do not touch the measuring medium and on an existing one

Piping be installed. Such systems are for. B. from EP 686 255 B1, US 4,484,478 or US 4,598,593.

Another ultrasonic flowmeter that operates on the transit time difference principle is known from US 5,052,230. The transit time is determined here by means of short ultrasonic pulses, so-called bursts. A burst signal is a limited number of oscillations of predetermined frequencies, given duration and thus determined bandwidth.

The ultrasonic transducers normally consist of an electromechanical transducer element, e.g. a piezoelectric element, also called piezo for short, and a coupling layer, also known as a coupling wedge or a rare lead body. The coupling layer is usually made of plastic, the piezoelectric element is in industrial process measurement usually from a

Piezoceramic. In the piezoelectric element, the ultrasonic waves are generated and passed over the coupling layer to the pipe wall and passed from there into the liquid. Since the speeds of sound in liquids and plastics are different, the ultrasonic waves are refracted during the transition from one medium to another. The refraction angle is determined to a first approximation according to Snell ^'s Law. The angle of refraction is thus dependent on the ratio of the propagation velocities in the media. Between the piezoelectric element and the coupling layer, a further coupling layer may be arranged, a so-called adaptation layer. The

Adaptation layer assumes the function of transmission of the

Ultrasonic signal and at the same time the reduction of one by different acoustic impedances caused reflection at interfaces between two materials.

Now also methods and measuring devices for determining the concentration and / or size of particles in a fluid have become known as a measuring medium, which are based on an ultrasonic measuring principle. No. 6,481,268 shows such a measuring device with at least one ultrasonic transducer. The ultrasound signal emitted by the ultrasound transducer is reflected by particles in the measuring medium to the transducer and registered there as an echo. One embodiment shows two

opposed ultrasonic transducer on a measuring tube, which the

Transmit and / or receive ultrasonic signals substantially perpendicular to the measuring tube axis. Another embodiment shows a single ultrasonic transducer with a coupling element, which is designed as a lens to focus the ultrasonic signal in the measuring tube. A measurement of the flow is not provided in this document.

In another prior art patent, US 5,251,490, there is shown an ultrasonic flowmeter which monitors flow through a flow meter

Measuring tube determined with the Doppler measuring principle. Ultrasound signals are emitted in the form of waves, focused by an acoustic lens and reflected by particles in the measuring medium. Reflections are greatest in the immediate vicinity of the focus. From the frequency shift between the coupled and

reflected waves, the flow velocity of the liquid is determined. US 5,533,408 discloses an ultrasonic flowmeter having a

Combination of transit time difference principle and Doppler principle. For this, however, each configured sensors are provided. Between the sensors of the two measuring principles is switched when exceeding or falling below a predetermined reading.

In WO 03/102512 A1 we proposed a method for

Duration difference measurement of a flowing fluid, wherein additionally the reflections of the ultrasonic signal to particles in the fluid are determined, to derive the Determine the concentration of the particles. For this purpose, two ultrasonic transducers are proposed in the usual arrangement for a transit time difference measurement, wherein at least one of these ultrasonic transducers is so quickly switched from a transmitting state to a receiving state that he knows the reflections of his

can receive received signal to the particles in the fluid or additional ultrasonic transducers are provided, which are arranged so that they can receive the reflections. To determine the concentration and the size of the particles in the measurement medium, it is proposed to evaluate the Doppler shift of the moving particles. A measurement in stationary medium is therefore not possible.

The object of the invention is to provide a simple ultrasonic flow measuring system with which the number of particles per

Volume unit and / or the particle size, from a predetermined order of magnitude, of particles in a measuring medium can be determined.

The object is achieved by an ultrasonic flow and particle measuring system, with a first ultrasonic transducer and at least one further, second

Ultrasonic transducer, wherein the first ultrasonic transducer at least a first

Ultrasonic transducers are arranged in a measuring tube for determining the flow over a transit time difference principle that propagate the acoustic signals along at least one signal path in the measuring tube between the first and the second ultrasonic transducer, for example at an angle less than 90 ° to the measuring tube axis, wherein at least the first coupling element is designed as an acoustic lens, and wherein the ultrasonic flow and particle measuring system has an evaluation unit, suitable for amplitude analysis of reflection signals of the reflected from the particles to the first ultrasonic transducer acoustic

Signals, wherein the evaluation unit, the amounts of the amplitudes of the reflection signals received from the first ultrasonic transducer can be determined, and wherein the evaluation unit, the number of amplitudes in a predetermined time interval are counted, which are greater than a predetermined threshold value.

The evaluation unit is suitable for detecting and evaluating amplitudes of signals of the acoustic reflection signals received by the first ultrasound transducer element, which reflection signals reflected back from particles in the measurement medium to the first ultrasound transducer, are acoustic signals emitted by the first ultrasound transducer. With the evaluation so the amplitudes of these, received by the first ultrasonic transducer, reflection signals are analyzed, at least their amounts which are greater than a predetermined threshold, can be determined and wherein at least their number in one

predetermined time interval are counted. From the amplitudes of

received reflection signals which are greater than a predetermined

Threshold, the particle sizes of the particles are determined in the medium. This is done via an assignment of the amplitude amounts to particle sizes. Thus, only particles of a given size can be determined. There is both one

Minimum size, as well as a maximum size of the particles. If the particles are larger than the maximum size, they can no longer be differentiated in size. The maximum size is essentially due to the focusing of the lens. From the number of amplitudes, which amplitudes are greater than a predetermined threshold, of the received reflection signals in a predetermined time interval, the particle concentration of particles of a predetermined

Minimum size determined in the measuring medium. At least the first coupling element is designed as an acoustic lens,

for example, as a plano-concave acoustic lens or as an acoustic Fresnel lens. The first coupling element has a first contact surface, which contacts the measuring medium during operation, and at least one further, second contact surface, on which the first ultrasonic transducer element is arranged and fastened. The first contact surface has, for example, a contour with an acoustically effective radius of curvature greater than 5 mm. In particular, this acoustically effective radius of curvature is greater than 10 mm. According to one embodiment, the acoustically effective radius of curvature is at most 150 mm, in particular at most 50 mm. The radius of curvature depends on the measuring tube diameter and / or the

Distance between the two ultrasonic transducers to each other and the material of the first coupling element and the chemical composition and the physical properties of the measured medium, since in particular the propagation velocity of the acoustic signal is dependent on the substance in which the acoustic signal propagates.

Lenses are conventionally limited by at least one ellipsoidal surface or sphere. A sphere has the same curvature everywhere, which is why lenses are definable over the curvature. The same applies to an ellipsoid. One exception is, for example, the Fresnel lenses. Fresnel lenses are divided into a plurality of, for example, annular sections, which can be approximated by prisms in cross section through the Fresnel lens. Ideally, the annular sections of a Fresnel lens form a section of a

conventional lens with a predetermined radius of curvature. This is then advantageously equal to the acoustically effective radius of curvature.

Of course, the acoustically effective radii of curvature and the focal lengths of a lens are linked together via the refractive indices. These in turn depend on the speed of sound in the measuring medium or in the coupling element.

An advantage of a Fresnel lens may be the small thickness of the lens compared to conventional lenses. As a result, the first coupling element is designed to be very thin, as a result of which it can act as an adaptation layer between the measuring medium and the ultrasound transducer element, by detecting the impedances of both

Contact partner adapts each other. Another advantage results from a special embodiment of the Fresnel lens. It has individual steps of a respective height, each approximately η ^* λ / 2, with n being a natural number and λ being the wavelength of the acoustic signal in the lens. The lens is thus designed as a kind of λ / 2 matching layer, which results in an improved transmission of the acoustic signal compared to a conventional lens. Both the first ultrasonic transducer and the second ultrasonic transducer can be fixed in the measuring tube, wherein the coupling elements of the ultrasonic transducer then touch the measuring medium during operation. It is therefore a so-called inline ultrasonic flow and particle measuring system. Both

Ultrasonic transducers are aligned with each other, and the lens of the first

Ultrasonic transducer is designed so that propagates an acoustic signal between the two ultrasonic transducers on at least a first signal path. Therefore, this inline ultrasonic flow and particle measuring system is suitable, the flow of the medium through the measuring tube by means of a

Determine transit time difference method.

Used is an inventive ultrasonic flow and

Particle measuring system, in particular in a plant of the process industry,

in particular in a pipeline system behind a particle filter, for

Monitoring the function of the filter, e.g. for diagnosis, whether e.g. there are small leaks or how high the permeability of the filter is for particles of a certain size, e.g. from a diameter of 1 μηη, is. The diameter of the particles is based on a model concept. Actually, the reflective surface is crucial to the reflection signal. However, the particles are assumed to be spheres in the model. The particles are not larger

Ι ΟΟμηη, in particular they have a diameter not greater than 10μηη, and the measuring medium is not cloudier than 100FNU, or the turbidity of the measuring medium is e.g. less than 10FNU. If the measurement signal is very dim, the acoustic signal may be absorbed and flow measurement is no longer possible. Therefore, only measuring media should be measured which are still clear to the human eye. Here is no highly accurate

Turbidity measurement needed. A first indication of a malfunction can provide the already existing ultrasonic flowmeter, if it

designed according to the invention and / or retrofitted. Another one

The inventive method is the retrofitting of an existing ultrasonic flow measuring system with at least one first coupling element, which is designed as a lens. In this case, it is possible to replace a complete ultrasound transducer without a lens with a first ultrasound transducer according to the invention, or the coupling element is replaced. In further embodiments of the

Invention is the height of the predetermined threshold in operation adjustable and / or when exceeding the predetermined threshold, an alarm can be output. In contrast to turbidity measurement system can with an inventive

Ultrasonic flow and particle measuring not the turbidity of the medium to be determined according to one of the specified standards for turbidity measurement, but only, as already described, the frequency of occurring in the medium from a certain size particles. It is more a particle counter than a turbidimeter. The flow rate is determined by means of a transit time difference method. Since the amplitudes of the reflections on the particles are evaluated for the flow measurement and for the particle measurement, which are simultaneously or temporally offset from one another, without calculating a Doppler shift, the particles are also very slowly flowing, and theoretically also when the medium is stationary still measurable.

Due to the focusing by means of the acoustic lens, the particles are determined only in a small volume of the flow of the measuring medium in the measuring tube. This volume depends on the acoustically effective radius of curvature of the lens ROC, the speed of sound in the lens Ci_ens and in the measuring medium CMedium and the wavelength of the acoustic signal A _M edium- The volume can be assumed to be cylindrical, for example, and is then referred to as a focal tube. The radius of this focal tube around the focal point is calculated, for example, as r ₀ =

, with a the radius of the ultrasonic transducer element and

a / '«With

a ROC of 5 mm and a length of the focal tube of 0.5 mm and a

Radius of the focal tube of 0.26 mm results in a volume 0.1 1 mm ³ .

Assuming the ROC is 50 mm, length and radius are 50.1 mm and 2.6 mm, the volume is already 1064 mm ³ . In these examples, the

Ultrasonic transducer element assumed as circular. The radius of the

Ultrasonic transducer element, such as a piezoelectric element limited of course the acoustic signal across its direction of propagation at the moment of transmission. In this volume, the acoustic signals are reflected on the particles, which could also be referred to as the measurement volume. In this volume, a very large proportion of the energy of the acoustic signal

concentrated. Only particles can be measured at which the acoustic signals are sufficiently reflected. This is the case, for example, for most solid particles. In addition to the angle of incidence of the acoustic signal on the surface of a particle, the acoustic impedance of particles and measuring medium or the velocities of sound in their materials play a major role in the reflection. If the measuring medium and the particles have an identical acoustic impedance, no reflection results. The acoustic impedances must therefore be far enough apart that sufficient reflections result. With an increase or decrease of the threshold value, from which the amplitudes of the reflection signals are considered in more detail, it is thus also possible to adjust which type of particles should be taken into account.

According to a first development, the ultrasonic flow and

Particle measuring a control unit, such as a microprocessor, suitable for exciting the first ultrasonic transducer element for emitting an acoustic signal of a first form, in particular a first burst signal sequence, and suitable for excitation of the first ultrasonic transducer element for emitting an acoustic signal of a second form, in particular a second Burst signal sequence, which is different from the first form, in particular which first burst signal sequence is thus different from the second burst signal sequence. In addition to continuous signals, so-called continuous waves, burst signals are used for measuring transit time. Here now both for flow measurement by means of a transit time difference measurement, as well as for particle determination. The same signals can be used for both flow and particle measurement, or, with simultaneous flow and particle measurement, the same signal. In this development, however, the signals for flow measurement differ from those for particle measurement. The differences may be in the number of individual bursts in the burst bursts and / or in the spacing of the individual bursts in the burst bursts and / or in the pulse shapes of the burst bursts be based on individual burst signals. With only a few bursts in a burst burst, the signal energy is lower than many bursts. To one

To obtain sufficient amplitude of the reflection must be correspondingly much

Signal energy are transmitted to the measuring medium. On the other hand, if very many bursts of fast order are sent to the measurement medium, this results in a narrowband signal, similar to a narrowband continuous signal.

The ultrasonic flow and particle measuring system is further developed in this way

configured such that the ratio of focal length of the acoustic lens in aqueous measuring media to a diameter of the measuring tube is at least 0.2. According to one embodiment of the solution, the ratio is between 0.4 and 0.6. The

Ultrasonic transducers are mounted in the measuring tube. In order not to influence the flow too much, they protrude, if at all, only to a small extent into the flow

Measuring tube into it. They have a fixed distance to each other, which with the

Diameter of the measuring tube correlated. Through the lens and its focus, the first acoustic is bundled; a first signal cone is modeled. In the signal propagation direction after focusing, the acoustic signal is fanned out again, it widens. This creates a second model

Signal cone, which with its tip the tip of the first signal cone in

Focal point of the lens touched - it creates, in the model, a double cone. So that enough signal energy arrives at the second ultrasonic transducer, the ratio of the focal length of the acoustic lens to the distance between the two should

Ultrasonic transducers are not less than 0.2, in particular not less than 0.4, wherein the distance between the first and the second ultrasonic transducer is measured in particular between the medium-contacting surfaces.

With radii of curvature of the acoustic lens of the first ultrasonic transducer of 5 mm to 50 mm and sound velocities of about 2000 m / s to about 3000 m / s in the coupling elements of the ultrasonic transducer, in particular in the first

Coupling element of the first ultrasonic transducer, which as an acoustic lens

focal lengths of 15 mm to 60 mm, for measuring media with sound velocities in the measuring medium of 1 100 m / s to 1900 m / s. A further development of the invention provides that at least the first

Coupling element made of a polymer, e.g. made of PEEK or PVC.

Ultrasonic transducer elements consist of e.g. from a piezoceramic. In this case, according to one embodiment, a piezoceramic disk is glued to a first contact surface of the first coupling element as the first ultrasonic transducer element. On a customarily arranged between the coupling element and the ultrasonic transducer element matching layer is omitted. The piezoceramic disk is thus in direct contact with the coupling element, with only an adhesive layer in between.

On the other hand, liquid couplings, e.g. conceivable with grease or high-viscosity oil instead of the glue.

According to a further development, at least the first

Ultrasonic transducer element with a transmission frequency of at least 5 MHz excitable. Most ultrasonic transducer elements are excited at a certain resonant frequency. They have a relatively narrow usable frequency range. Therefore, the reception frequency is usually in an area around the

Transmitting frequency, whereby, for example, both ultrasonic transducer elements

be operated approximately at the same transmission frequency. An advantage of a high transmission frequency are the small wavelengths of the resulting acoustic signal which increases the resolution during the particle measurement - small particles are registered, since these also reflect back an echo.

In a further development of the ultrasonic flow and particle measuring system according to the invention, it is provided that the measuring tube has an approximately circular cross section, with a diameter of at least 20 mm, in particular at least 30 mm. At the most it is

Measuring tube diameter, for example 150mm or e.g. even only 120mm. The

Ultrasonic transducers, in particular their lenses, are selected accordingly. The object underlying the invention is further achieved by a

Method for determining the flow of a measuring medium through a measuring tube and for detecting particles in the measuring medium, with a first

Ultrasonic transducer and at least one further, second ultrasonic transducer, which are arranged in a measuring tube so that the acoustic signals along at least one signal path in the measuring tube between the first

Spread ultrasonic transducer and the second ultrasonic transducer, wherein acoustic signals from the first ultrasonic transducer both for determining the flow of the measured medium through the measuring tube by means of a transit time difference measurement, as well as for detecting particles in the measuring medium by means of an amplitude analysis of reflection signals of the particles to the first ultrasonic transducer reflected acoustic Signals, ie the reflections of the acoustic signal to the particles, are generated. The acoustic signals generated by the first ultrasonic transducer are focused according to the invention via an acoustic lens. The acoustic lens has at least one focal point, which lies in a volume in the measuring tube. Acoustic signals are modeled along a straight signal path. In reality, their spread depends on many factors and is e.g. lobar.

According to a first development of the method according to the invention, the particle sizes of the particles in the measuring medium at which these reflection signals were reflected are determined from the amplitudes of the received reflection signals, which are greater than a predefined threshold value. The particle size is thus determined by the amount of the received amplitude of the reflection signal, or otherwise called the echo.

In one embodiment of the invention, for example, an alarm is output, when a predetermined threshold value and / or alarm is exceeded when exceeding a predetermined number of particles greater than a predetermined threshold value in a predetermined time interval.

In a further embodiment of the invention, the height of the predetermined threshold value is adaptable in operation, e.g. by the user or it is automatically adjusted depending on process parameters such as e.g. the

Measuring medium and the particles contained in the medium, in particular their acoustic impedance compared to the acoustic impedance of

Measuring medium. In a further development of the method according to the invention

suggested that from the number of amplitudes of the received

Reflection signals in a given time interval, ie from their

Frequency, which amplitudes are greater than a predetermined threshold, the particle concentration is determined in the measuring medium. The first

Ultrasonic transducer element provides a voltage signal, which in one

Processing unit is processed. Of course, the first ultrasonic transducer element also picks up noise which is referred to as noise in the voltage signal. If a threshold value analysis of the signal is now carried out, only those values are processed further and thus recognized as particles which are above this predetermined threshold value. These amplitudes or peaks are counted on the one hand and thus closed on the frequency of particles and on the other hand on the amount determines the particle size. A further development of the invention provides that the first ultrasonic transducer is excited to a first burst signal sequence for transit time difference measurement and is excited to particle measurement to a second burst signal sequence, wherein the first burst signal sequence is different from the second burst signal sequence. Thus, two different burst signal sequences for flow measurement, so the

Runtime difference measurement, and the particle measurement can be used. In principle, both measurements can also be carried out in parallel with the same signal.

In a further process development, at least the first

Ultrasonic transducer excited to a transmission frequency greater than 5 MHz. The

Transmitting frequency may also be higher than 10 MHz, e.g. also 20 MHz. As for the

Wavelength of the acoustic signal is: λ = c / f, with c the speed of sound and f the transmission frequency, the wavelength is smaller at a higher transmission frequency and otherwise the same conditions. As a result, smaller particles are detectable. If the transmission frequency is much larger than 20 MHz, the absorption of the acoustic signal in the measuring medium is very high, even if only a few particles are contained in the measuring medium. A sufficiently strong acoustic signal for flow measurement then seems very difficult to realize. The invention will be explained in more detail with reference to the following figures, in each of which an embodiment is shown. Identical elements are provided in the figures with the same reference numerals.

Fig. 1 shows an inventive ultrasonic flow and particle measuring system, Fig. 2 shows an ultrasonic transducer of an ultrasonic flow and particle measuring system according to the invention.

In Fig. 1 inventive ultrasonic flow and particle measuring system 1 is shown schematically. Two ultrasonic transducers 2, 3, which each emit and / or receive acoustic signals via a coupling element, are fastened in a measuring tube 8 at an angle to the measuring tube axis. This is a so-called inline measuring system with which the flow of a measuring medium, not shown, through the measuring tube 8 can be determined. The central axis through both ultrasonic transducers 2, 3 is intended to model a signal path

indicate along which ultrasonic signals between the two

Ultrasonic transducers 2, 3 spread.

Both ultrasonic transducers 2, 3 each have an acoustic lens 10 here. By this ultrasonic signals between the two ultrasonic transducers 2, 3 are focused in the measuring tube 8. In the following, only the first ultrasonic transducer 2 will be considered in more detail. In this exemplary embodiment, both ultrasonic transducers 2, 3 are configured identically, so that the statements apply to both ultrasonic transducers 2, 3. However, only the first ultrasonic transducer 2 may be equipped with an acoustic lens 10.

The focal point of the acoustic lens 10 of the first ultrasonic transducer 2 is in the volume for particle measurement 11. This volume 1 1 results from the focusing of the lens. It is here drawn in a rotationally symmetrical manner about the signal path 9 and in the illustrated cross-section substantially elliptical. In this

Volumes become particles through reflections of the acoustic signal to the

Particles registered. With this very simply constructed ultrasonic flow and

Particle measuring system 1 can be used to measure flow in parallel or sequentially and to count particles; united in a measuring device. The structure is not significantly different from a conventional ultrasonic flowmeter. Therefore, it is inexpensive to manufacture. Due to the simple amplitude analysis, the particles can be registered for flow measurement without much extra effort.

A proper use of the ultrasonic flow and particle measuring system according to the invention is e.g. in a piping system

downstream of a filter, ie in the flow direction of the medium to be measured through the piping system after the filter, e.g. to monitor the function of the filter.

Fig. 2 illustrates the structure of a first invention

Ultrasonic transducer 2. This comprises a first ultrasonic transducer element 4, e.g. a high-frequency piezoceramic. This ultrasonic transducer element 4 can convert both electrical signals into mechanical vibrations and thus into acoustic signals, as well as acoustic signals in electrical. It thus acts as a sensor and as an actuator. The ultrasonic transducer element 4 transmits and receives acoustic signals via a first coupling element, which is designed as an acoustic lens 10. The coupling element or the acoustic lens 10 has a plurality of surfaces, a first contact surface 6, which contacts the measuring medium in the measuring tube during operation and a second contact surface 7, which is in contact with the ultrasound transducer element 4. For example, the ultrasonic transducer element 4 is glued directly to the second contact surface 7 of the acoustic lens 10, without another

Adjustment layer in between. However, this should not be excluded here.

The ultrasonic transducer element 4 is connected via two cables 13 and a plug-in connection 14 with a transmitter, not shown. In the connection space 12 in the first ultrasonic transducer 2 behind the ultrasonic transducer element 4, a so-called backing may be provided, a vibration damper, which is connected directly to the ultrasonic transducer element 4. The lens 10 is here designed as a plano-concave lens, with a first contact surface 6, which has a predetermined radius of curvature, here for example 14 mm, and a flat second contact surface 7. Similarly, the lens 10 could be considered

Fresnel lens be configured with a, having a contour, so a contoured first contact surface 6, which has a similar acoustically effective radius of curvature. A Fresnel lens is in several segments or

Divided sections, which together form this contour with the acoustically effective radius of curvature. The acoustically effective radii of curvature and the focal lengths of the lenses are linked to one another via the refractive indices, these being determined by the

Depending on the speed of sound in the measuring medium or in the coupling element. The step height of a Fresnel lens is given, for example, by η ^* λ / 2, where λ is the wavelength of the acoustic signal in the coupling element and n is a natural number.

LIST OF REFERENCE NUMBERS

1 ultrasonic flow and particle measuring system

2 First ultrasonic transducer

3 Second ultrasonic transducer

4 First ultrasonic transducer element

5 first coupling element

6 First contact surface of the first coupling element

7 second contact surface of the first coupling element

8 measuring tube

9 signal path

10 Acoustic lens

1 1 volume for particle measurement

12 connection space in the first ultrasonic transducer

13 cables

14 plug connection

Claims

claims

1 . Ultrasonic flow and particle measuring system (1), with a first

Ultrasonic transducer (2) and at least one further, second

Ultrasonic transducer (3), wherein the first ultrasonic transducer at least a first ultrasonic transducer element (4) and at least a first coupling element (5), wherein the first ultrasonic transducer element (4) in operation acoustic signals via the first coupling element (5) can be emitted and received, which first and second ultrasonic transducers (2, 3) in one

Measuring tube (8) are arranged to determine the flow so that the acoustic signals propagate along at least one signal path (9) in the measuring tube (8) between the first and the second ultrasonic transducer (3), characterized

that at least the first coupling element (5) is designed as an acoustic lens, and that the ultrasonic flow and particle measuring system (1) has an evaluation unit, suitable for the amplitude analysis of

Reflection signals of the particles to the first ultrasonic transducer (2) reflected acoustic signals, wherein the evaluation unit, a number of amplitudes of the reflection signals in a predetermined temporal

Interval are counted, which are greater than a predetermined threshold.

2. ultrasonic flow and particle measuring system (1) according to claim 1,

characterized,

that the ultrasonic flow and particle measuring system (1) a

Control unit, suitable for the excitation of the first

Ultrasonic transducer element (4) for emitting a first burst signal sequence as an acoustic signal and suitable for exciting the first

Ultrasonic transducer element (4) for emitting a second burst signal sequence as an acoustic signal, which first burst signal sequence is different from the second burst signal sequence.

3. ultrasonic flow and particle measuring system (1) according to claim 1 or 2, characterized,

in that the ultrasonic flow and particle measuring system (1) is designed so that the ratio of the focal length of the acoustic lens in aqueous measuring media to a diameter of the measuring tube is at least 0.2.

4. Ultrasonic flow and particle measuring system (1) according to one of

Claims 1 to 3,

characterized,

that at least the first coupling element (5) is designed as a plano-concave acoustic lens.

Ultrasonic flow and particle measuring system (1) according to one of

Claims 1 to 3,

characterized,

that at least the first coupling element (5) is designed as an acoustic Fresnel lens.

Ultrasonic flow and particle measuring system (1) according to one of

Claims 1 to 5,

characterized,

that at least the first coupling element (5) is made of a polymer.

Ultrasonic flow and particle measuring system (1) according to one of

Claims 1 to 6,

characterized,

in that a piezoceramic disk is adhesively bonded to a first contact surface (6) of the first coupling element (5) as the first ultrasound transducer element (4).

Ultrasonic flow and particle measuring system (1) according to one of

Claims 1 to 7,

characterized,

that at least the first ultrasonic transducer element (4) with a

Transmission frequency of at least 5 MHz can be excited.

9. Ultrasonic flow and particle measuring system (1) according to one of

Claims 1 to 8,

characterized,

that the measuring tube (8) has an approximately circular cross section, with a diameter of at least 20mm.

10. A method for determining the flow of a measuring medium through a measuring tube (8) and for detecting particles in the measuring medium, with a first ultrasonic transducer (2) and at least one further, second

Ultrasonic transducer (3), which in a measuring tube (8) are arranged so that the acoustic signals propagate along at least one signal path (9) in the measuring tube (8) between the first ultrasonic transducer (2) and the second ultrasonic transducer (3) acoustic signals from the first ultrasonic transducer (2) both for determining the flow of the

Measuring medium through the measuring tube by means of a transit time difference measurement, as well as for the detection of particles in the measuring medium by means of a

Amplitude analysis of reflection signals of the reflected from the particles to the first ultrasonic transducer acoustic signals are generated,

characterized,

in that at least the acoustic signals generated by the first ultrasonic transducer (2) are focused via an acoustic lens.

1 1 .Method according to claim 10,

characterized,

in that the particle sizes of the particles in the measuring medium are determined from the amplitudes of the received reflection signals, which are greater than a predefined threshold value. 12. The method according to claim 10 or 1 1,

characterized,

that of the number of amplitudes of the received reflection signals in a predetermined time interval, which amplitudes are greater than a predetermined threshold value, the particle concentration is determined in the measuring medium.

13. The method according to any one of claims 10 to 12,

characterized,

in that the first ultrasound transducer (2) is excited to a first burst signal sequence during transit-time difference measurement and is excited to a second burst signal sequence for particle measurement, the first burst signal sequence being different from the second burst signal sequence.

14. The method according to any one of claims 10 to 13,

characterized,

that the first ultrasonic transducer (2) is excited to a transmission frequency greater than 5 MHz.

15. Use of an ultrasonic flow and particle measuring system (1) according to one of claims 1 to 9,

characterized,

that the ultrasonic flow and particle measuring system (1) in one

Pipe system is arranged after a particle filter.