Ultrasonic measuring cell and method for measuring the volumetric flow rate of a liquid in a tube

Abstract

An ultrasonic measurement cell for measuring the volumetric flow rate of a fluid flowing through the tube, comprising a fluid transport tube and a continuous central recess for receiving at least six ultrasonic transducers. The first and second ultrasonic transducers are arranged on a first side of the central recess, and the third and fourth ultrasonic transducers are arranged on a second opposite side of the central recess, arranged to emit measurement signals obliquely to the flow direction. The first and second inlay regions are arranged on the first and second sides of the central recess, respectively, between the central recess and the corresponding pair of ultrasonic transducers. The fifth and sixth ultrasonic transducers are arranged parallel to the central recess and opposite each other. The measurement cell is configured to measure the propagation time of the ultrasonic signal in the first inlay region and / or the second inlay region.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) The present invention provides an ultrasonic measurement cell for measuring the volumetric flow rate of a fluid flowing in a pipe, the ultrasonic measurement cell comprising a continuous central recess, longitudinally extended to receive a fluid transport pipe, at least six ultrasonic transducers, at least two inlay regions, and optionally at least two ultrasonic blocking regions, where at least a first and a second ultrasonic transducer are arranged on a first side of the central recess and at least a third and a fourth ultrasonic transducer are arranged on a second side of the central recess, the first and second sides being opposite each other, and where the first and the second ultrasonic transducers are arranged such that the first and / or the second ultrasonic transducers can radiate a measurement signal obliquely to the direction of fluid flow in the pipe to the third and / or the fourth ultrasonic transducer, and can receive a measurement signal radiated obliquely to the fluid flow in the pipe by the third and / or the fourth ultrasonic transducer. A first inlay region is disposed on a first side of the central recess between the first and second ultrasonic transducers such that ultrasonic signals received or emitted by the first and / or second ultrasonic transducers pass at least partially through the first inlay region. Further, a second inlay region is disposed on a second side of the central recess between the third and fourth ultrasonic transducers such that ultrasonic signals received or emitted by the third and / or fourth ultrasonic transducers pass at least partially through the second inlay region. A fifth ultrasonic transducer is disposed on the first side of the central recess, the first inlay region is located between the fifth ultrasonic transducer and the central recess, and a sixth ultrasonic transducer is disposed on the second side of the central recess, the second inlay region is located between the sixth ultrasonic transducer and the central recess. The fifth and sixth ultrasonic transducers are disposed parallel to the central recess and opposite each other. The measurement cell is configured to measure a time of flight of an ultrasonic signal in the first inlay region and / or the second inlay region. To this end, the invention further provides a suitable method.

[0002] Ultrasonic measuring devices are used, inter alia, to measure the volume flow rate in pipes. In known devices, for this purpose, the travel time t of the ultrasonic wave in the direction of the moving fluid is calculated. FWD , and the travel time t of a second ultrasonic wave in the opposite direction. BWD is typically determined. The respective travel times increase or decrease due to the drag effect described by the vector addition of the liquid's sound speed and the liquid flow velocity. The travel time difference Δt can be determined by the following formula:

number

[0003] From the difference in travel time Δt between the first and second ultrasonic waves, the volumetric flow rate Q of the liquid in the tube can be determined by multiplying it by the so-called Geo factor.

number

[0004] The Geo factor depends on the properties of the measuring cell and of the fluid used and is usually determined in a calibration stand for the measuring cell under precisely defined conditions. For all subsequent measurements with the calibrated measuring cell, the Geo factor is assumed to be constant.

[0005] However, in general, the Geo factor is not constant. in , and the distance l that the sound wave travels between the inner walls is a constant quantity, but the speed of sound in the fluid, C fl and the angle β depends on the temperature of the components of the measuring cell.

[0006] Ultrasonic measuring cells for measuring volumetric flow rates are generally used as clamp-on measuring cells, in the center of which a fluid transport tube is fixed. At least one ultrasonic transducer is arranged on a first side of the tube, and at least one second ultrasonic transducer is arranged on a second side of the tube. The ultrasonic transducers are fixed to the housing of the measuring cell. Then, during the measurement of the travel time, an ultrasonic signal is emitted by the first ultrasonic transducer, passes through a part of the housing (distance from the first ultrasonic transducer to the tube), the tube wall, the fluid in the tube, the tube wall, a part of the housing (distance from the tube to the second ultrasonic transducer), and is received by the second ultrasonic transducer. The physical angle β through which the ultrasonic signal passes through the fluid depends not only on the sound speed of the fluid, but also on the sound speed in the housing.

[0007] The further away the actual measurement conditions are from those under which the measurement cell was calibrated and therefore the constant Geo factor was determined, the less accurate the measurement results of said measurement cell will be. In view of the ever increasing requirements for measurement accuracy and flexibility of such measuring devices, it is desirable to take into account the effect of temperature on the Geo factor and the effect of changes in the sound speed of the fluid due to changes in the fluid, and not to consider it as constant.

[0008] For this purpose, it is necessary to know the properties of the measuring cell used, which is the speed of sound in the components through which the sound waves used for the measurement pass, which speed of sound is a function of the prevailing temperature in said components. In particular, the speed of sound in the fluids in the housings and tubes needs to be known as a function of temperature. However, the measuring cells and measuring methods known from the prior art do not take the properties of the respective measuring cell into account at all or only insufficiently.

[0009] EP 3489634 A1 discloses an ultrasonic measuring device for measuring the speed of sound in a fluid and taking into account the effects of the pipe walls. The device comprises four ultrasonic transducers mounted in a cross shape, two ultrasonic transducers arranged on a first side of a fluid transport pipe and two further ultrasonic transducers arranged on a second side of the fluid transport pipe. Each ultrasonic transducer is arranged at an angle to the direction of flow of the fluid in the pipe and is provided for measuring the difference in travel time (Δt).

[0010] The effect of the pipe wall is determined by an ultrasonic signal emitted by a first ultrasonic transducer, reflected in the pipe wall, and received by a second ultrasonic transducer. Optionally, a damping element can be placed between the ultrasonic transducers to prevent the ultrasonic waves from traveling directly from the first ultrasonic transducer to the second ultrasonic transducer. Alternatively, the effect of the pipe wall can be determined by ultrasonic transducers placed perpendicular to the flow direction of the fluid. The speed of sound in the medium is measured by a pair of ultrasonic transducers placed perpendicular to the flow direction.

[0011] The four ultrasonic transducers are arranged in the housing at an angle to the fluid flow direction, so that they are not directly adjacent to the fluid transport pipe. Thus, the emitted ultrasonic waves necessarily pass through a part of the housing before impinging on the pipe and the fluid. Thus, the housing and the general sound speed in the housing influence the Geo factor. However, EP 3489634 A1 does not take into account this effect of the housing, and therefore cannot provide a sufficiently high measurement accuracy for many measurement tasks. This means that the measurement device can only be used to a limited extent.

[0012] US 2006 / 0174717 A1 discloses measuring the propagation velocity of ultrasonic waves within mounting bases on either side of a flow tube. Summary of the Invention [Problem to be solved by the invention]

[0013] Based on the state of the art, the object of the present invention is therefore to provide an ultrasonic measuring device, in particular for measuring volumetric flow rates in fluid transport pipes, and a method which achieves high measurement accuracy under all external measurement conditions (different temperatures of the fluid, different ambient temperatures), with the aim of broadening the scope of application of the ultrasonic measuring device whilst maintaining a high measurement accuracy. [Means for solving the problem]

[0014] Thus, there is provided an ultrasonic measuring cell for measuring a volumetric flow rate of a fluid flowing in a pipe, the ultrasonic measuring cell comprising: a continuous central recess extending longitudinally such that the central recess can receive the fluid transport tube; At least 6 ultrasonic transducers; At least two inlay areas; Optionally, with at least two ultrasound blocking regions; at least first and second ultrasonic transducers are disposed on a first side of the central recess and at least third and fourth ultrasonic transducers are disposed on a second side of the central recess, the first side and the second side of the central recess being opposite each other; the first and / or second ultrasonic transducers are arranged such that they can radiate measurement signals to the third and / or fourth ultrasonic transducers obliquely relative to a flow direction of the fluid in the pipe, and receive measurement signals radiated obliquely by the third and / or fourth ultrasonic transducers relative to the flow of the fluid in the pipe; no ultrasonic coupling gel or grease is present between the fluid transport tube and the ultrasonic measurement cell; Features include: a first inlay region disposed on the first side of the central recess between the central recess and the first and second ultrasonic transducers such that ultrasonic signals received or emitted by the first and / or second ultrasonic transducers pass at least partially through the first inlay region; a second inlay region disposed on the second side of the central recess between the central recess and the third and fourth ultrasonic transducers such that ultrasonic signals received or emitted by the third and / or fourth ultrasonic transducers pass at least partially through the second inlay region; a fifth ultrasonic transducer disposed on a first side of the central recess, the first inlay region being between the fifth ultrasonic transducer and the central recess; a sixth ultrasonic transducer disposed on the second side of the central recess, the second inlay region being between the sixth ultrasonic transducer and the central recess; the fifth and sixth ultrasonic transducers are disposed parallel to the central recess and opposite one another; The fifth and sixth ultrasonic transducers have a natural resonant frequency range of 0.5 MHz to 5 MHz and a natural resonant frequency range of 6.5×10 6 Ns / m 3 ~30×10 6 Ns / m 3 and The ultrasonic measurement cell is configured to measure a time of flight of an ultrasonic signal through the first inlay region and / or the second inlay region.

[0015] Further, a method for determining a characteristic parameter of an ultrasonic measuring cell according to the invention is provided, the method comprising: measuring reflections of ultrasonic signals at an interface between a first inlay region and an adjacent vessel wall and reflections from an inner surface of the vessel wall adjacent the first inlay region and from fluid within the vessel, and associated propagation times; The sound velocity of the first inlay region 1 c inlay, calculating a propagation time t2 of an ultrasonic signal propagating vertically through the first inlay region, and a propagation time t4 of an ultrasonic signal propagating vertically through the vessel wall adjacent to the first inlay region; measuring reflections of ultrasonic signals at the interface between a second inlay region and an adjacent vessel wall and reflections from an inner surface of the vessel wall adjacent the second inlay region and the fluid within the vessel, and associated propagation times; - sound speed in said second inlay region 2 c inlay , calculating a propagation time t3 of an ultrasonic signal propagating vertically through the second inlay region, and a propagation time t5 of an ultrasonic signal propagating vertically through the vessel wall adjacent to the second inlay region; measuring a time of flight t1 of an ultrasonic signal propagating vertically through the first inlay region, the vessel wall adjacent to the first inlay region, the fluid within the vessel, the vessel wall adjacent to the second inlay region, and the second inlay region; calculating a time of flight t6=t1-t2-t3-t4-t5 of an ultrasonic signal propagating vertically through the fluid in the pipe; ·Sound velocity c in the fluid fl and / or calculating the angle of incidence β of the sound wave into the fluid.

[0016] Detailed Description Measuring Cell The ultrasonic measuring cell according to the invention comprises a continuous central recess, which is extended in the longitudinal direction so that the central recess can receive the fluid transport tube. According to ultrasonic measuring cells known in the art, the measuring cell according to the invention is a clamp-on cell, which means that the flexible tube is clamped in the central recess of the measuring cell. Due to the strong contact force between the fluid transport tube and the ultrasonic measuring cell, a high quality acoustic coupling is achieved, which does not require the use of additional ultrasonic coupling gel or grease between the tube and the ultrasonic measuring cell, in particular between the inlay area and the tube. Therefore, there is no ultrasonic coupling gel or grease between the fluid transport tube and the ultrasonic measuring cell, in particular between the tube and the first and second inlay areas. Furthermore, the tube is preferably a plastic tube having the following typical characteristics: Shore hardness range: Shore A20~Shore A95; Sound speed range: 700m / s~3000m / s; Density: 0.9~2.5g / cm 3 ; Attenuation value: 0.05~5dB / mm / MHz; Tube outer diameter: 3~66mm.

[0017] In one embodiment of the invention, the tubing is selected from the group including silicone tubing, perfluoroalkoxyalkane (PFA) tubing, and TYGON tubing, which represents a family of flexible polymeric tubing made from a variety of materials.

[0018] In a further embodiment of the invention, coupling pads are used between the tube and the measuring cell, which are made of a solid material. Preferably, the coupling pads are located between the fluid transport tube and the first inlay area and between the fluid transport tube and the second inlay area. This allows a hard plastic tube with a high Shore hardness to be used with the measuring cell described, which has a contact area with the inlay area that would otherwise be too small for sufficient sound wave transmission. Due to the high contact force, the coupling pads are placed around the tube without the need for ultrasonic coupling gel or grease between the tube and the coupling pad or between the coupling pad and the ultrasonic measuring cell, in particular between the first and second inlay areas and the coupling pad. Suitable coupling pads have the following acoustic properties: Shore hardness range: Shore A20~Shore A95; Sound speed range: 700m / s~2500m / s; Density: 0.9~2.0g / cm 3 ; Attenuation value: 0.05~5dB / mm / MHz; Thickness: 0.2~15mm.

[0019] In the context of the present invention, a rigid plastic pipe is a plastic pipe having the following characteristics: Shore hardness range: Shore A95 and above; Sound speed range: 700m / s~3000m / s; Density: 0.9~2.5g / cm 3 ; Attenuation value: 0.05~5dB / mm / MHz; Tube outer diameter: 3~66mm.

[0020] Examples of rigid plastic tubing include perfluoroalkoxyalkane (PFA) tubing, polyvinylidene fluoride (PVDF) tubing, and PE (polyethylene) tubing.

[0021] Here, the thickness represents the dimension of the coupling pad between the tube wall and the respective inlay area. Preferably, coupling pads are used on both sides of the tube.

[0022] The measurement cell comprises at least six ultrasonic transducers, which are attached to the first or second inlay area by adhesive using a homogeneous zero-gap bonding method. This allows for an adhesive layer thickness of less than or equal to one wavelength of the acoustic signal. The adhesive layer therefore does not affect the acoustics. At least the first and second ultrasonic transducers are arranged on a first side of a central recess, and at least the third and fourth ultrasonic transducers are arranged on a second side of the central recess, the first and second sides of the central recess being opposite each other. Furthermore, the first and second ultrasonic transducers are arranged such that the first and / or the second ultrasonic transducers can radiate a measurement signal obliquely to the flow direction of the fluid in the tube to the third and / or the fourth ultrasonic transducer, and can receive a measurement signal radiated obliquely to the flow direction of the fluid in the tube by the third and / or the fourth ultrasonic transducer.

[0023] Preferably, the first ultrasonic transducer is disposed on a first side of the central recess, and the fourth ultrasonic transducer is disposed on a second side of the central recess, and both ultrasonic transducers are disposed so that an ultrasonic signal emitted by the first ultrasonic transducer can be received by the fourth ultrasonic transducer, and vice versa. Furthermore, the second ultrasonic transducer is disposed on a first side of the central recess, and the third ultrasonic transducer is disposed on a second side of the central recess, and both ultrasonic transducers are disposed so that an ultrasonic signal emitted by the second ultrasonic transducer can be received by the third ultrasonic transducer, and vice versa. Thus, the first to fourth ultrasonic transducers are disposed in a cross-shaped arrangement, obliquely with respect to the central recess, and therefore obliquely with respect to the flow direction of the fluid in the tube.

[0024] The measurement cell further comprises at least two inlay regions: a first inlay region is disposed on a first side of the central recess between the first and second ultrasonic transducers such that ultrasonic signals received or emitted by the first and / or second ultrasonic transducers pass at least partially through the first inlay region, and a second inlay region is disposed on a second side of the central recess between the third and fourth ultrasonic transducers such that ultrasonic signals received or emitted by the third and / or fourth ultrasonic transducers pass at least partially through the second inlay region.

[0025] Preferably, the at least two inlay regions have the following acoustic characteristics: Sound speed range: 1500~3000m / s; Acoustic impedance range: 1×10 6 ~5×10 6 Ns / m 3 ; Density: 0.9~2.0g / cm 3 ; Attenuation value: 0.05~5dB / mm / MHz.

[0026] According to one embodiment of the present invention, the at least two inlay regions comprise a material from the group including ABS (acrylonitrile-butadiene-styrene-copolymer), PEEK (polyetheretherketone), and PMMA (polymethylmethacrylate), polycarbonate (PC), polyethylene (PE), polyethylene terephthalate (PET), polyoxymethylene (POM), polypropylene (PP), polyphenylene sulfide (PPS), polystyrene (PS), and polyvinyl chloride (PVC).

[0027] A fifth ultrasonic transducer is disposed on a first side of the central recess, and a first inlay region is located between the fifth ultrasonic transducer and the central recess, and a sixth ultrasonic transducer is disposed on a second side of the central recess, and a second inlay region is located between the sixth ultrasonic transducer and the central recess.

[0028] The fifth and sixth ultrasonic transducers are arranged parallel to the central recess and opposite each other, i.e., an ultrasonic signal emitted by the fifth or sixth ultrasonic transducer passes through the first inlay region, the tube containing the fluid, and the second inlay region, and is received by an ultrasonic transducer on the opposite side of the fifth or sixth ultrasonic transducer. Furthermore, the fifth and sixth ultrasonic transducers are configured to emit ultrasonic signals and receive ultrasonic signals, either reflected ultrasonic signals or signals emitted by an ultrasonic transducer.

[0029] Preferably, the fifth ultrasonic transducer is disposed between the first and second ultrasonic transducers, and the sixth ultrasonic transducer is disposed between the third and fourth ultrasonic transducers.

[0030] According to the present invention, the fifth and sixth ultrasonic transducers have a natural resonant frequency range of 0.5 MHz to 5 MHz and a 6.5×10 6 Ns / m 3 ~30×10 6Ns / m 3 In a preferred embodiment, the fifth and sixth ultrasonic transducers comprise a piezoelectric composite material. By using ultrasonic waves according to the invention, the fifth and sixth ultrasonic transducers can emit short burst signals. For 1-2 bursts, this corresponds to 1-2 times the period of the corresponding transducer frequency, i.e. 0.3-1 μs (in the range of 3-2 MHz). In a preferred embodiment of the invention, the burst signal has a length of 1-2.5 μs. A short burst signal has the advantage that the time window during which the ultrasonic transducer emits a signal and therefore cannot receive an ultrasonic signal is correspondingly short. In the state of the art, ultrasonic transducer measuring cells are used that comprise piezoelectric ceramics. With standard piezoelectric ceramics, the signal length until the wave is completely attenuated is about twice as long compared to the described ultrasonic transducers.

[0031] In a preferred embodiment of the present invention, the ultrasonic transmitter emits a burst signal with a frequency of 1 MHz to 4 MHz. By using the ultrasonic transducer according to the present invention, the ultrasonic signal can be received by the ultrasonic transducer immediately after the burst signal is emitted. This allows the reflected echo signal to be received and detected by the ultrasonic transducer with a shorter runtime than ultrasonic transducers including piezoelectric ceramics.

[0032] In one embodiment of the invention, the extension of the first inlay region between the fifth ultrasonic transducer and the central recess is 4-12 mm, preferably 4-8 mm, more preferably 5-6 mm, and the extension of the second inlay region between the sixth ultrasonic transducer and said central recess is equal. The extensions of the first and second inlay regions are selected such that the excitation signal of the ultrasonic transducer is attenuated and thus the same ultrasonic transducer receives unobstructed echoes.

[0033] Depending on the design of the measurement cell, a fifth and / or sixth ultrasonic transmitter may be used to measure ultrasonic signals reflected by the inner and outer tube walls, whereby the inner tube wall is defined as the interface between the tube wall and the fluid within the tube, and the outer tube wall is defined as the interface between the inlay area and the tube in the central recess.

[0034] In one embodiment of the present invention, an ultrasonic signal is emitted by a fifth ultrasonic transducer. The ultrasonic signal is reflected by the outer and inner walls of the tube, and the reflected ultrasonic signal is received by the fifth ultrasonic transducer. This allows the runtime of the ultrasonic signal in the tube wall and in the first inlay region to be detected. According to the present invention, all dimensions of the measurement cell are known. Thus, the sound speed of the ultrasonic wave in the tube wall and in the first inlay region can be calculated.

[0035] In a further embodiment of the present invention, an ultrasonic signal is emitted by a sixth ultrasonic transducer. The ultrasonic signal is reflected by the outer and inner walls of the tube, and the reflected ultrasonic signal is received by the sixth ultrasonic transducer. This allows the runtime of the ultrasonic signal in the tube wall and in the second inlay region to be detected. Thus, the speed of sound in the tube wall and in the second inlay region can be calculated.

[0036] The measurement of these ultrasonic echoes is only possible if, on the one hand, an ultrasonic transducer according to the invention is used, for example a piezoelectric composite material that allows short burst signals, and, on the other hand, an inlay area is located between the fifth and sixth ultrasonic transducers, providing a clearly defined pre-travel distance for the ultrasonic signal before it enters the tube in the central recess, so that the received reflected ultrasonic signal can be separated from the emitted burst signal.

[0037] Additionally, a fifth and sixth pair of ultrasonic transducers can be used to measure ultrasonic signals emitted by either the fifth or sixth ultrasonic transducer, passing through the first inlay area, passing through the tube containing the fluid, passing through the second inlay area, and received by either the sixth or fifth ultrasonic transducer. In one embodiment, the ultrasonic signal is emitted by the fifth ultrasonic transducer and received by the sixth ultrasonic transducer. In a further embodiment, the ultrasonic signal is emitted by the sixth ultrasonic transducer and received by the fifth ultrasonic transducer. This measurement path allows for detection of the run time of ultrasonic waves that are not affected by fluid flow as they propagate perpendicular to the fluid in the tube.

[0038] The first and second ultrasonic transducers are preferably arranged at an angle δ′ with respect to the central recess such that the first ultrasonic transducer can emit a measurement signal that is reflected at an interface between the first inlay area and the pipe wall and at an interface between the pipe wall and a fluid in the pipe, the reflected signal being received by the second ultrasonic transducer; and / or The second ultrasonic transducer may emit a measurement signal that is reflected at an interface between the first inlay region and a vessel wall and an interface between the vessel wall and a fluid within the vessel, the reflected signal being received by the first ultrasonic transducer; and / or a third and fourth ultrasonic transducer are disposed at an angle δ′ with respect to the central recess such that the third ultrasonic transducer can emit a measurement signal that is reflected at an interface between the second inlay region and the tube wall and at an interface between the tube wall and a fluid in the tube, the reflected signal being received by the fourth ultrasonic transducer; and / or The fourth ultrasonic transducer can emit a measurement signal that is reflected at the interface between the second inlay region and the vessel wall and at the interface between the vessel wall and a fluid within the vessel, the reflected signal being received by the third ultrasonic transducer.

[0039] Furthermore, the first to fourth ultrasonic transducers are disposed at an angle δ' relative to the central recess, δ' being 55° to 75°, preferably 60° to 70°, and most preferably 65°.

[0040] With this setup, it is possible to measure the run time of the ultrasonic signal reflected off the inner canal wall at the central recess, and the run time of the ultrasonic signal reflected off the outer canal wall at the central recess. Because the distances the ultrasonic waves travel during these run times are known, the speed of sound in the inlay and in the canal wall can be calculated. If the speed of sound is known, the run time of the ultrasonic waves in the inlay and / or in the canal wall can be calculated at any distance.

[0041] Using the first and second ultrasonic transmitters, the speed of sound in the first inlay region and the speed of sound in the canal wall can be measured. Using the third and fourth ultrasonic transmitters, the speed of sound in the second inlay region and the speed of sound in the canal wall can be measured.

[0042] Due to the design of the ultrasonic measurement cell, it is configured to measure the propagation time of the ultrasonic signal in the first inlay region and / or the second inlay region, which can be done by utilizing at least one of the ultrasonic transducers arranged parallel to the central recess, or by utilizing the first and second ultrasonic transducers or the third and fourth ultrasonic transducers.

[0043] If the ultrasonic measurement cell comprises coupling pads between the tube and the first inlay area and between the tube and the second inlay area, the propagation time of the ultrasonic signal in the coupling pads can also be measured by using at least one of the ultrasonic transducers arranged parallel to the central recess, or by using the first and second ultrasonic transducers or the third and fourth ultrasonic transducers.

[0044] In one embodiment, the ultrasonic measurement cell further comprises at least one ultrasonic blocking region, which is arranged either on a first side of the central recess between the first and second ultrasonic transducers, or on a second side of the central recess between the third and fourth ultrasonic transducers; the blocking region is arranged such that an ultrasonic signal emitted by the first or second ultrasonic transmitter and reflected at the interface between the first inlay region and the tube wall in the central recess propagates to the second or first transducer without being attenuated by the blocking region, or such that an ultrasonic signal emitted by the third or fourth ultrasonic transmitter and reflected at the interface between the second inlay region and the tube wall in the central recess propagates to the fourth or third transducer without being attenuated by the blocking region.

[0045] In a further embodiment of the invention, the measurement cell comprises two ultrasonic blocking areas, a first ultrasonic blocking area arranged on a first side of the central recess between the first and second ultrasonic transducers, and a second ultrasonic blocking area arranged on a second side of the central recess between the third and fourth ultrasonic transducers. The first blocking area is arranged such that an ultrasonic signal emitted by the first or second ultrasonic transmitter and reflected at the interface between the first inlay area and the tube wall in the central recess propagates to the second or first transducer without being attenuated by the first blocking area; the second blocking area is arranged such that an ultrasonic signal emitted by the third or fourth ultrasonic transmitter and reflected at the interface between the second inlay area and the tube wall in the central recess propagates to the fourth or third transducer without being attenuated by the second blocking area.

[0046] Thus, the reflected ultrasonic signal is not attenuated by the ultrasonic blocking area. Advantageously, however, the blocking area prevents ultrasonic signals that are not reflected at the interface between the inlay area and the tube wall from being received by the ultrasonic transmitter on the same side of the central recess. This means that ultrasonic signals are not transmitted directly from the first ultrasonic transducer to the second ultrasonic transducer or vice versa, nor from the third ultrasonic transmitter to the fourth ultrasonic transmitter or vice versa. This feature improves the signal quality and eliminates undesired overlap of the signal coming directly from the emitting ultrasonic transmitter with the reflected signal.

[0047] The at least one ultrasound blocking region comprises a material from the group consisting of air, cork and metal. In principle, all materials are suitable whose acoustic characteristic impedance is significantly different from the acoustic characteristic impedance of the material of the inlay region or which have a particularly high acoustic attenuation.

[0048] According to the present invention, the first to fourth ultrasonic transmitters have a natural resonant frequency range of 0.5 MHz to 5 MHz and a frequency of 6.5×10 6 Ns / m 3 ~30×10 6 Ns / m 3 Preferably, the first to fourth ultrasonic transmitters comprise a piezoelectric composite material. Suitable piezoelectric composite materials have been described above. In a preferred embodiment of the present invention, the ultrasonic transmitter emits a burst signal at a frequency of 1 MHz to 4 MHz, most preferably at a frequency of 3 MHz.

[0049] In a further embodiment of the invention, the ultrasonic measurement cell further comprises a seventh and / or eighth ultrasonic transducer, the seventh transducer being arranged on a first side of the central recess, a first inlay area being between the seventh transducer and the central recess, and the eighth transducer being arranged on a second side of the central recess, a second inlay area being between the eighth transducer and the central recess. The seventh and eighth transducers have a natural resonant frequency range of 0.5 MHz to 5 MHz and a natural resonant frequency range of 6.5×10 6 Ns / m 3 ~30×10 6 Ns / m 3 In a preferred embodiment, the fifth and sixth ultrasonic transducers comprise a piezoelectric composite material.

[0050] In a further embodiment of the invention, the ultrasonic measurement cell further comprises seventh and eighth ultrasonic transducers, the seventh transducer being arranged on a first side of the central recess, a first inlay area being between the seventh transducer and the central recess, the eighth transducer being arranged on a second side of the central recess, and a second inlay area being between the eighth transducer and the central recess. The seventh and eighth transducers are arranged parallel to the central recess and opposite each other.

[0051] Preferably, the seventh ultrasonic transducer is disposed between the first and second ultrasonic transducers, and the eighth ultrasonic transducer is disposed between the third and fourth ultrasonic transducers.

[0052] The function of the seventh and eighth ultrasonic transducers corresponds to that of the fifth and sixth ultrasonic transducers. Therefore, all features described for the fifth and sixth ultrasonic transducers also apply to the seventh and eighth ultrasonic transducers. Further ultrasonic transducers arranged parallel to the central recess allow the already described measurement of reflected echoes at further positions of the ultrasonic measuring cell. This allows the sound speed in the inlay area and in the tube wall to be determined at two different positions in the ultrasonic measuring cell. This allows the temperature gradient in the measuring cell, which is caused, for example, by nearby electronic components, to be taken into account.

[0053] In one embodiment of the invention, the ultrasonic measurement cell comprises at least one ultrasonic blocking region arranged between the fifth and seventh ultrasonic transducers. In a further embodiment of the invention, the ultrasonic measurement cell comprises at least one ultrasonic blocking region arranged between the sixth and eighth ultrasonic transducers.

[0054] In a further embodiment of the invention, the ultrasonic measuring cell further comprises at least one temperature sensor. The temperature sensor is configured to measure the temperature of the fluid in the tube. The temperature sensor is therefore preferably arranged at the interface between the first or second inlay region and the central recess. Preferably, the temperature sensor is not present in the propagation path of the ultrasonic signal emitted by any ultrasonic transducer of the ultrasonic measuring cell. Suitable temperature sensors are for example PT100, PT1000 and thermocouples. The temperature sensor should be compatible with a temperature range of -20 to 100 °C.

[0055] The ultrasonic measuring cell further comprises an electronic miniature sensor comprising means for signal amplification and propagation time measurement, allowing post-amplification of the ultrasonic signal, and further comprising a switch for enabling pulse-echo measurements.

[0056] In a preferred embodiment, the electronic miniature sensor is adapted to further process the measurement data. In particular, the electronic miniature sensor is configured to perform calculations according to the method of the present invention. This is advantageous in that the ultrasonic measuring cell according to the present invention provides a miniature device for measuring the flow of a fluid in a pipe, whereby a correction of external measurement conditions is performed. Advantageously, in this embodiment, no further data processing is required, for example on an external computing device. Furthermore, in an embodiment, the ultrasonic measuring cell is provided with a current output and / or a digital output, and the measurement and / or calculation data can be output via said current output and / or said digital output.

[0057] In a further embodiment of the present invention, the ultrasonic measuring cell comprises at least one interface with an external computing device. A suitable external computing device may be, for example, a PC, a tablet or a smartphone. The external computing device is adapted to further process the data measured by the ultrasonic measuring cell. In particular, the external computing device is configured to perform calculations according to the method of the present invention. The external computing device may comprise a display for visualizing the measured and / or calculated data.

[0058] method The invention further comprises a method for determining a characteristic parameter of a measuring cell according to the invention, wherein a fluid transport tube is arranged in the measuring cell, the method comprising the steps of: measuring reflections of ultrasonic signals at an interface between a first inlay region and an adjacent vessel wall and reflections from an inner surface of the vessel wall adjacent the first inlay region and from fluid within the vessel, and associated propagation times; The sound velocity of the first inlay region 1 c inlay , calculating a propagation time t2 of an ultrasonic signal propagating vertically through the first inlay region, and a propagation time t4 of an ultrasonic signal propagating vertically through the vessel wall adjacent to the first inlay region; measuring reflections of ultrasonic signals at the interface between a second inlay region and an adjacent vessel wall and reflections from an inner surface of the vessel wall adjacent the second inlay region and the fluid within the vessel, and associated propagation times; - sound speed in said second inlay region 2 c inlay , calculating a propagation time t3 of an ultrasonic signal propagating vertically through the second inlay region, and a propagation time t5 of an ultrasonic signal propagating vertically through the vessel wall adjacent to the second inlay region; measuring a time of flight t1 of an ultrasonic signal propagating vertically through the first inlay region, the vessel wall adjacent to the first inlay region, the fluid within the vessel, the vessel wall adjacent to the second inlay region, and the second inlay region; calculating a time of flight t6=t1-t2-t3-t4-t5 of an ultrasonic signal propagating vertically through the fluid in the pipe; ·Sound velocity c in the fluid fl and / or calculating the angle of incidence β of the sound wave into the fluid.

[0059] All the features described for the ultrasonic measuring cell of the invention also apply to the method of the invention and vice versa.

[0060] In accordance with the present invention, reflections of ultrasonic signals at the interface between the first inlay region and the adjacent vessel wall, reflections from the inner surface of the vessel wall adjacent the first inlay region and the fluid within the vessel, and the associated propagation times of the ultrasonic signals are measured.

[0061] With the aid of the measuring cell according to the invention the following measuring paths can be used: (a) a fifth ultrasonic transducer emits an ultrasonic signal, which is reflected and received by the fifth ultrasonic transducer; (b) if a seventh ultrasonic transducer is present, the seventh ultrasonic transducer emits an ultrasonic signal, which is reflected and received by the seventh ultrasonic transducer; (c) a first ultrasonic transducer emits an ultrasonic signal that is reflected and received by a second ultrasonic transducer; (d) the second ultrasonic transducer emits an ultrasonic signal that is reflected and received by the first ultrasonic transducer.

[0062] All measurement paths can be used alone or in combination with each other.

[0063] Furthermore, the sound velocity in the first inlay region 1 c inlay A propagation time t2 of an ultrasonic signal propagating vertically through the first inlay region, and a propagation time t4 of an ultrasonic signal propagating vertically through the vessel wall adjacent to the first inlay region are calculated.

[0064] By using measurement paths (a) and / or (b), the echo signal received by the ultrasonic transducer directly contains the propagation times t2 and t4.

number

[0065] The speed of sound in the first inlay region and in the vessel wall adjacent to the first inlay region can be calculated by the relationship v=s / t, where the path length through the first inlay region and the vessel wall thickness are known parameters.

[0066] By using measurement paths (c) and / or (d), as previously described, the detected echo signals can be used to calculate the speed of sound in the first inlay region and in the vessel wall adjacent to the first inlay region analog, resulting in the following equation:

number

[0067] In accordance with the method of the present invention, reflections of ultrasonic signals at the interface between the second inlay region and the adjacent vessel wall, as well as reflections from the inner surface of the vessel wall adjacent the second inlay region and the fluid within the vessel, and associated propagation times are measured.

[0068] With the aid of the measuring cell according to the invention the following measuring paths can be used: (e) a sixth ultrasonic transducer emitting an ultrasonic signal, the ultrasonic signal being reflected and received by the sixth ultrasonic transducer; (f) if an eighth ultrasonic transducer is present, the eighth ultrasonic transducer emits an ultrasonic signal, which is reflected and received by the eighth ultrasonic transducer; (g) a third ultrasonic transducer emits an ultrasonic signal, which is reflected and received by a fourth ultrasonic transducer; (h) the fourth ultrasonic transducer emits an ultrasonic signal that is reflected and received by the third ultrasonic transducer.

[0069] Likewise, all measurement paths can be used alone or in combination with each other.

[0070] Using the measured propagation time, the sound velocity in the second inlay region is calculated. 2 c inlay, the propagation time t3 of the ultrasonic signal propagating vertically through the second inlay region, and the propagation time t5 of the ultrasonic signal propagating vertically through the canal wall adjacent to the second inlay region can be calculated. This can be done by using the parameters 1 c inlay , t2, and t4 are calculated as described above.

[0071] Advantageously, the method of the present invention is tube This allows the measurement of the sound speed in the inlay region as well as in the inlay region, so that the sound speed in both inlay regions is measured independently, thus allowing for consideration of material inhomogeneities or temperature gradients in the inlay region that affect the sound speed therein.

[0072] In one embodiment of the invention, measurement paths (a), (b), (e) and (g) can be used, which also allows for temperature gradients in an inlay region to be taken into account by measuring the sound speed in the inlay region at two different positions in the inlay region.

[0073] Thus, in one embodiment of the invention, reflections of ultrasonic signals at the interface between the first inlay region and the adjacent vessel wall and reflections from the inner surface of the vessel wall adjacent to the first inlay region and the fluid within the vessel, and associated propagation times, are measured with an ultrasonic transducer parallel to the central recess; and Reflection of the ultrasonic signal at the interface between the second inlay region and the adjacent vessel wall and reflection from the inner surface of the vessel wall adjacent the second inlay region and the fluid within the vessel, and the associated propagation times, are measured by a further ultrasonic transducer parallel to the central recess.

[0074] In a further embodiment of the invention, reflections of ultrasonic signals at the interface between a first inlay region and an adjacent vessel wall and reflections from the inner surface of the vessel wall adjacent to the first inlay region and fluid within the vessel, and associated propagation times, are measured using first and second ultrasonic transducers, and reflections of ultrasonic signals at the interface between a second inlay region and an adjacent vessel wall and reflections from the inner surface of the vessel wall adjacent to the second inlay region and fluid within the vessel, and associated propagation times, are measured using third and fourth ultrasonic transducers.

[0075] Additionally, a propagation time t1 of an ultrasonic signal propagating vertically through the first inlay region, the vessel wall adjacent to the first inlay region, the fluid within the vessel, the vessel wall adjacent to the second inlay region, and the second inlay region is measured.

[0076] Using the measuring cell according to the invention, a pair of ultrasonic transmitters arranged parallel to the central recess can be used for the measurement, in a preferred embodiment the fifth and sixth ultrasonic transducers form a suitable pair and / or the seventh and eighth ultrasonic transducers form a suitable pair.

[0077] Based on these measurements, we can calculate the propagation time t6 = t1 - t2 - t3 - t4 - t5 of the ultrasonic signal propagating vertically through the fluid in the pipe. The speed of sound in the fluid, c, is given by the known relationship v = s / t. fl The path length through the fluid corresponds to the inner diameter of the tube, a known parameter.

[0078] Therefore, this method uses the sound speed c in the fluid fl , sound speed in the tube wall c tube , and the sound velocities of the first and second inlay regions 1 c inlay and 2 c inlay This allows for the measurement of

[0079] In one embodiment of the invention, the method further comprises calculating an angle of incidence β' of the ultrasonic signal into the fluid in the tube. The sum of the angle of incidence β' and the angle of entry β of the sound wave into the fluid is 90°. Thus, one angle can be calculated from the other.

[0080] formula

number

number

[0081] Advantageously, the angle of incidence of the ultrasonic signal incident on the tube from the first inlay region and the angle of incidence of the ultrasonic signal incident on the tube from the second inlay region can be calculated independently. If the speed of sound in the first and second inlay regions is different, for example due to a temperature gradient, the method of the present invention takes this into account. This improves the accuracy of the measurement.

[0082] Therefore, in this method, the sound speed in the fluid, c, is measured using different measurement paths. fl , sound speed in the tube wall c tube , and the sound velocities of the first and second inlay regions 1 c inlay and 2 c inlay This allows for redundant measurements, thereby improving measurement accuracy.

[0083] In one embodiment of the invention, the ultrasonic measurement cell comprises coupling pads between the tube and the first inlay region and between the tube and the second inlay region. 1 c pad and the sound velocity in the coupling pad between the tube and the second inlay region. 2 c padcan be measured and calculated similarly to the steps already described.

[0084] In one embodiment of the invention, the method comprises: The propagation time t of the ultrasonic signal emitted by the first ultrasonic transducer, passing through the fluid in the pipe, and reaching the fourth ultrasonic transducer FWD 1→4 , and a propagation time t of an ultrasonic signal emitted by the fourth ultrasonic transducer through the fluid in the pipe to reach the first ultrasonic transducer. BWD 4→1 , and / or the propagation time t of the ultrasonic signal emitted by the second ultrasonic transducer through the fluid in the pipe to the third ultrasonic transducer. FWD 3→2 , and the propagation time t of the ultrasonic signal emitted by the third ultrasonic transducer through the fluid in the pipe to reach the second ultrasonic transducer. BWD 2→3 measuring the Calculating the volumetric flow rate Q of fluid in the tube.

[0085] If the incidence angle β'1 is equal to the incidence angle β'2, the volumetric flow rate is given by the formula

number

number

number

number

[0086] C fl cal and β cal is determined during the calibration of the ultrasonic measuring cell. This is done under well-defined conditions using a known medium, e.g. water, at a known temperature. The calibration factor Geo cal will also be determined in this regard.

[0087] The method of the invention therefore allows for variations in the sound speed or angle of incidence of the fluid, caused for example by temperature changes, to be taken into account by the calculation of the volumetric flow rate, whereby the calculated volumetric flow rate is more accurate compared to volumetric flow rates measured and calculated by state-of-the-art measuring cells and methods.

[0088] Advantageously, it is also possible to take into account the case where, for some reason, the incidence angle β'1 is not equal to the incidence angle β'2. In this case, the volume flow rate is calculated as follows:

number

number

number

number

[0089] β' 1,cal and β' 2,cal represents the angle of incidence measured during calibration of the ultrasonic measurement cell with a known fluid of well-defined temperature. cal1 , Geo cal2 , Geo 1,cal , Geo 2,cal , β' 1,cal , β' 2,cal , and c fl,cal are determined during this calibration step and therefore these values ​​are considered constants in the method of the present invention.

[0090] In one embodiment of the invention, the method further comprises the step of calibrating the measurement cell with a known medium of well-defined temperature, e.g. water. cal1 , Geo cal2 , Geo 1,cal , Geo 2,cal , β' 1,cal , β' 2,cal , and c fl,cal The value of is determined.

[0091] In a preferred embodiment, the calculation according to the invention is carried out by an electronic miniature sensor of an ultrasonic measuring cell. In one embodiment of the invention, the ultrasonic measuring cell is provided with a current output and / or a digital output.

[0092] Thus, in one embodiment, the method of the present invention further comprises the step of outputting the measured and / or calculated data by means of a current output and / or a digital output.

[0093] In a further embodiment, the calculation according to the invention is carried out by an external computing device. Suitable external computing devices have been described above. In this embodiment, the method according to the invention further comprises a step of transferring the measurement data to the external computing device, which can be performed by the electronic miniature sensor.

[0094] In one embodiment, the method comprises: Measuring the temperature of the fluid in the tube.

[0095] The temperature of the fluid in the fluid transport tube can be measured by a temperature sensor in the ultrasonic measurement cell, providing additional information regarding the condition of the fluid. [Brief description of the drawings]

[0096] The present invention will now be further illustrated by seven figures and five examples.

[0097] [Figure 1] FIG. 1 illustrates one embodiment of an ultrasonic measuring cell according to the invention. [Diagram 2] FIG. 2 illustrates a further embodiment of an ultrasonic measuring cell according to the invention. [Diagram 3] FIG. 3 illustrates a further embodiment of an ultrasonic measuring cell according to the invention. [Figure 4] FIG. 4 illustrates a portion of one embodiment of the present invention and the angles of incidence of ultrasonic signals at different interfaces. [Diagram 5] 5(A) to 5(C) illustrate ultrasonic signals received by an ultrasonic transducer of a measuring cell. [Figure 6] 6(a)-6(f) illustrate the results of one example of the present invention. [Figure 7] FIG. 7 illustrates the results of a further example of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0098] The flow direction of the fluid in the tube is shown by arrows in the following figures. Of course, the flow direction may be reversed. The method of the invention is equally applicable. FWD and t BWDOnly the measurement paths for measuring flow direction need to be exchanged. For the sake of brevity, in the following only one flow direction will be described in detail. Figures 1 to 3 illustrate an embodiment of the invention in a schematic manner, however, for the sake of brevity, the influence of the refraction law is not taken into account in the drawings.

[0099] FIG. 1 illustrates an embodiment of an ultrasonic measuring cell 100 according to the invention. The measuring cell comprises six ultrasonic transducers 11-16, the first ultrasonic transducer 11, the second ultrasonic transducer 12 and the fifth ultrasonic transducer 15 being arranged on a first side 70 of a central recess. A tube 20 is located in the central recess. The third ultrasonic transducer 13, the fourth ultrasonic transducer 14 and the sixth ultrasonic transducer 16 are arranged on a second side 80 of the central recess. The first side 70 and the second side 80 of the central recess are opposite each other.

[0100] The first and / or second ultrasonic transducers 11, 12 are arranged such that the first and / or second ultrasonic transducers 11, 12 can radiate measurement signals to the third and / or fourth ultrasonic transducers 13, 14 obliquely to the flow direction of the fluid in the pipe 20, and such that the third and / or fourth ultrasonic transducers 13, 14 can receive the measurement signals radiated obliquely to the flow of the fluid in the pipe 20.

[0101] Furthermore, the first inlay region 30 is disposed on a first side 70 of a central recess between the tube 20 and the first and second ultrasonic transducers 11, 12. Ultrasound signals emitted or received by the first and / or second ultrasonic transmitters 11, 12 pass through at least a portion of the first inlay region 30. The second inlay region 40 is disposed on a second side 80 of a central recess between the tube 20 and the third and fourth ultrasonic transducers 13, 14. Ultrasound signals emitted or received by the third and / or fourth ultrasonic transmitters 13, 14 pass through at least a portion of the second inlay region 40.

[0102] The fifth ultrasonic transducer 15 is disposed on a first side 70 of the central recess, with the first inlay region 30 located between the fifth ultrasonic transducer 15 and the central recess containing the tube 20. The sixth ultrasonic transducer 16 is disposed on a second side 80 of the central recess, with the second inlay region 40 located between the sixth transducer 16 and the central recess containing the tube 20. Furthermore, the fifth and sixth ultrasonic transducers 15, 16 are disposed parallel to the central recess and opposite each other.

[0103] Reference numerals 1 to 9 denote some of the possible paths of the measurement signal. The table below gives an overview of the paths of the ultrasonic signal of the sixth ultrasonic transducer 16.

[0104] [Table 1]

[0105] A similar signal can be measured using a fifth ultrasonic transducer 15. In this case, the speed of sound in the first inlay area 30 can be measured and detected. For clarity, the path is not illustrated in the drawing.

[0106] By using an ultrasonic transducer with well-defined inlay areas 30, 40 and a piezoelectric composite material, it is possible to distinguish between the signals received as echoes by the ultrasonic transducer emitting ultrasonic signals (paths 2-5). In state-of-the-art measuring cells, these signals at least partially overlap each other, so that their propagation times cannot be separated from each other and therefore cannot be detected.

[0107] The following table shows an overview of the paths of the ultrasonic signals of the first to fourth ultrasonic transducers 11 to 14.

[0108] [Table 2]

[0109] Paths 6 and 7 can be measured in a similar manner using third and fourth ultrasonic transmitters 13, 14. For clarity, the paths are not illustrated in the drawings.

[0110] Fig. 2 illustrates a further embodiment of the present invention. In addition to the components of the ultrasonic cell 100 illustrated in Fig. 1, the ultrasonic measurement cell 100 comprises a first ultrasonic blocking area 90 and a second ultrasonic blocking area 91. The first ultrasonic blocking area 90 is arranged on a first side 70 of the central recess between the first and second ultrasonic transducers 11, 12, and the second ultrasonic blocking area 91 is arranged on a second side 80 of the central recess between the third and fourth ultrasonic transducers 13, 14. The first ultrasonic blocking area 90 is arranged so that the ultrasonic signal emitted by the first or second ultrasonic transmitter 11, 12 and reflected at the interface between the first inlay area 30 and the tube wall 21 in the central recess propagates to the second or first transducer 11, 12 without being attenuated by the first blocking area 90. Furthermore, the second blocking region 91 is positioned so that an ultrasonic signal emitted by the third or fourth ultrasonic transmitter 13, 14 and reflected at the interface between the second inlay region 40 and the tube wall 22 in the central recess propagates to the fourth or third transducer 12, 14 without being attenuated by the second blocking region 91.

[0111] FIG. 3 illustrates a further ultrasonic measurement cell 100 according to the invention. The measurement cell 100 further comprises seventh and eighth ultrasonic transducers 17, 18. The seventh ultrasonic transducer is arranged on a first side 70 of the central recess, and the first inlay area 30 is between the seventh ultrasonic transducer 17 and the central recess. The eighth ultrasonic transducer 18 is arranged on a second side 80 of the central recess, and the second inlay area 40 is between the eighth ultrasonic transducer 18 and the central recess. The seventh and eighth ultrasonic transducers 17, 18 comprise a piezoelectric composite material and are arranged parallel to the central recess and opposite each other. The seventh and eighth ultrasonic transducers 17, 18 can thus be utilized for a similar measurement function as the fifth and sixth ultrasonic transducers 15, 16. Thereby, advantageously, the sound speed of the first and second inlay areas 30, 40 can be measured and calculated at two different positions in the measurement cell. Therefore, the incidence angle β' cal can also be calculated at different positions in the measurement cell. Preferably, the seventh ultrasonic transducer 17 is placed between the first and second ultrasonic transducers 11, 12 and the eighth ultrasonic transducer 18 is placed between the third and fourth ultrasonic transducers 13, 14, as shown in FIG.

[0112] FIG. 4 illustrates a schematic of a tube 20 having tube walls 21, 22, a first ultrasonic transducer 11, a second ultrasonic transducer 12, a fifth ultrasonic transducer 15, and a first inlay region 30. FIG. 4 illustrates an ultrasonic signal emitted by the first ultrasonic transducer 11 and propagating through the first inlay region 30, the tube wall 21, and the fluid within the tube. The refraction angles at the interfaces are shown. Additionally, the distance d between the inner and outer tube walls is shown. in , and the distance l that the sound wave travels between the inner walls of the tube. Also shown are the angles of incidence β' and approach β of the sound wave into the fluid. Furthermore, σ=δ'.

[0113] 5(A) to 5(C) show examples of ultrasonic signals received by the ultrasonic transducer of the measurement cell.

[0114] 6 and 7 illustrate the results of measurements from Examples 4 and 5, which are further explained below. EXAMPLES

[0115] Example 1 A measurement cell with a sixth ultrasonic transducer was utilized to measure the reflected ultrasonic signal. The expansion of the first inlay area between the fifth ultrasonic transducer and the central recess and the expansion of the second inlay area between the sixth ultrasonic transducer and the central recess were each 6.1 mm. The sixth ultrasonic transducer, which was positioned parallel to the central recess, was used to emit an ultrasonic burst signal. The reflected echo signal was received by the sixth ultrasonic transducer. This measurement was performed using the following method: (i) with the central recess empty and no tube present in the measuring cell; (ii) the tube is empty and no fluid is flowing through it; (iii) A tube was placed in the central recess and water was flowing through the tube.

[0116] The measured signal is shown in FIG. 5(A). First a burst signal is shown, and the second echo can be assigned to a reflection at the interface between the second inlay area and the tube wall (corresponding to path 2 in FIGS. 1-3). The signal is more prominent in the signal of measurement (i) compared to the signals of measurements (ii) and (iii), which overlap each other. The following echo is due to an echo of a reflection at the interface between the inner tube wall and the medium in the tube (corresponding to path 3 in FIGS. 1-3). The signal is most prominent in the empty tube (ii), but can also be read in the water-filled tube (iii). This measurement shows that the measuring cell according to the invention allows the detection of an ultrasonic signal reflected at the interface between the inlay area and the tube wall, as well as a signal reflected at the inner tube wall and the fluid in the tube, both reflected signals being able to be separated from each other and from the burst signal in the detected signal.

[0117] Based on measurement (ii), the second inlay area 2 cinlay Calculate the speed of sound in accordance with the present invention; 2 c inlay = expansion of first inlay / (t*2 / 2).

[0118] [Table 3]

[0119] The second echo can be assigned to a reflection at the interface between the inner pipe wall and the fluid adjacent the second interlay region, and therefore the speed of sound in the pipe wall can be calculated as follows:

[0120] [Table 4] Where:

number

[0121] Example 2 A pipe through which water flows was inserted into the measurement cell according to Example 1. Ultrasonic signals reflected at the interface between the first inlay region and the pipe wall and at the interface between the inner wall of the pipe and the fluid within the pipe were measured using the first and second ultrasonic transducers.

[0122] FIG. 5(B) illustrates the post-amplified measurement signal. After the burst, a first echo is seen, which can be assigned to the ultrasonic signal reflected at the interface between the second inlay area and the tube wall (corresponding to path 6 in FIGS. 1-3). The second echo can be assigned to the reflection at the interface between the inner tube wall and the water in the tube (corresponding to path 7 in FIGS. 1-3). The third echo is due to the reflection of the ultrasonic signal at the interface between the water in the tube and the tube wall adjacent to the first inlay area. Advantageously, the reflected signal and the burst signal can be clearly separated from each other.

[0123] FIG. 5(C) illustrates the same measurement signal with a shifted time scale. The burst signal is not visible, so all reflected ultrasound signals are shown. Again, the first echo can be assigned to the ultrasound signal reflected at the interface between the second inlay region and the tube wall (corresponding to path 6 in FIGS. 1-3). The second echo can be assigned to the reflection at the interface between the inner tube wall and the water in the tube (corresponding to path 7 in FIGS. 1-3). The third echo is due to the reflection of the ultrasound signal at the interface between the water in the tube and the tube wall adjacent to the first inlay region. The fourth echo is due to the reflection of the ultrasound signal at the interface between the tube wall and the first inlay region.

[0124] Example 3 Using the setup of Example 3, the sound speed of three different fluids was measured at different temperatures. (a) IPA at 19°C (b) Water at 23°C (c) 53°C water

[0125] t7 is the propagation time of the ultrasonic signal emitted by the first ultrasonic transducer, reflected at the interface between the canal wall and the first inlay region, and received by the second ultrasonic transducer. The propagation time t1 of the ultrasonic signal propagating vertically through the first inlay region, the canal wall adjacent to the first inlay region, the fluid in the canal, the canal wall adjacent to the second inlay region, and the second inlay region was measured by the fifth and sixth ultrasonic transducers. The sound speeds in the inlay and canal were calculated according to the following formula:

number

[0126] The sound velocities in the first and second inlay regions were assumed to be equal. According to the relationship c=s / t, times t2, t3, t4, and t5 were calculated using the following dimensions: Expansion of the first / second inlay area: 6.1mm Tube cross section: 1.6mm.

[0127] The propagation time of the ultrasonic signal propagating vertically through the fluid in the pipe is calculated using the formula t6 = t1 - t2 - t3 - t4 - t5, and the sound velocity c of the fluid is calculated using the relationship c = s / t. fl,cal was calculated using s = 6.35 mm.

[0128] Comparison of the calculated results with literature values ​​(L. Bergmann: Der Ultraschall; 5. Auflage; S. Hirzel Verlag Stuttgart 1949 and http: / / www.ddbst.com / en / EED / PCP / SOS_C95.php) and with values ​​measured with state-of-the-art equipment shows that the method according to the invention provides very good data quality.

[0129] [Table 5]

[0130] Example 4 Using the setup of Example 4, the sound speed of water was measured at three different temperatures. (a) 35°C water (b) 45°C water (c) 60°C water

[0131] The volumetric flow rate of water is (i) a Coriolis flow sensor acting as a reference sensor; (ii) An apparatus according to the invention, comprising: ii. 1 The volumetric flow rate is calculated using the Geo factor correction “enabled”; and ii. 2 Volumetric flow rates were measured by the device, calculated using the "nulled" Geo factor correction.

[0132] For volumetric flow calculations with Geo factor correction "enabled" (ii.1), the Geo factor was used according to the formula given in the explanation. For volumetric flow calculations with Geo factor correction "disabled" (ii.2),

number

[0133] The propagation time through the inlay was determined by pulse echo using path 2, and from this value the sound speed in the inlay (c inlay The sound speed in the tube (c tube ) was determined by measuring the transit time of the reflection at the interface between the inlay and the tube from the first transducer to the second transducer. From this, the transit time in water, and therefore the speed of sound in water (c fl ), and hence the angle β, was determined in real time by measuring the flight time of the vertical acoustic path.

[0134] The device according to the invention was calibrated in water at a temperature of 23°C.

[0135] Figures 6(a)-6(c) illustrate measurement results, all at different water temperatures. The absolute deviation of the volumetric flow rate calculated based on measurements by the device of the invention with respect to the volumetric flow rate measured by the Coriolis sensor is plotted in these figures versus the volumetric flow rate. Results are shown for volumetric flow rates calculated based on measurements by the device of the invention with Geo factor correction enabled and with Geo factor correction disabled, where enabled correction represents Geo factor correction enabled and disabled correction represents Geo factor correction disabled. Figures 6(d)-6(f) illustrate the same measurements, but plotting the relative deviation.

[0136] It can be seen that without the correction being enabled, an increase in temperature of the medium accompanied by a change in the sound speed in the medium leads to an increasing deviation of the volume flow rate from that measured by the Coriolis sensor.

[0137] At a volumetric flow rate of 2500 ml / min, the relative deviation (with correction disabled) was:

[0138] [Table 6]

[0139] With the correction enabled, the volume flow measurement of the ultrasonic measuring cell according to the invention is nearly identical to the volume flow measurement of the Coriolis sensor.

[0140] At a volumetric flow rate of 2500 ml / min, the relative deviation (with correction enabled) was:

[0141] [Table 7]

[0142] Example 5 The settings according to Example 4 were used. In this example, the flow rate correction for changes in water temperature occurring continuously in a very short time was measured. The water temperature was changed from 23 ° C to 60 ° C within a few minutes. As in Example 4, the volumetric flow rate measurements were recorded simultaneously with enabled and disabled Geo factor correction. The Coriolis sensor was operated at the same time as a reference measurement. As the water temperature increased, the difference in the flow rate measurements of the ultrasonic sensor with disabled Geo factor correction increased compared to the volumetric flow rate measured by the Coriolis sensor, while the flow rate measurements of the ultrasonic sensor with enabled Geo factor correction were almost the same. As the temperature increased, the deviation of the volumetric flow rate measurements of the ultrasonic sensor with disabled Geo factor correction increased compared to the volumetric flow rate measured by the Coriolis sensor. Even after the medium temperature reached the target value of 60 ° C, the deviation increased because the inlay temperature continued to change until it finally reached equilibrium. With the Geo factor correction enabled, the maximum deviation of the volumetric flow rate values ​​of the ultrasonic sensor and the Coriolis sensor was clearly less than 1% over the entire time range.

[0143] The measurement results are Coriolis flow sensor, A device according to the invention with Geo factor correction enabled (correction enabled); and FIG. 7 illustrates the volume flow rate versus time for the volume flow rate measured with a device according to the invention with Geo factor correction disabled (correction disabled).

[0144] List of reference numbers Routes 1-9 11 First ultrasonic transducer 12 Second ultrasonic transducer 13 Third ultrasonic transducer 14 Fourth Ultrasonic Transducer 15 5th ultrasonic transducer 16 6th Ultrasonic Transducer 17 Seventh Ultrasonic Transducer 18 8th ultrasonic transducer 20 tubes 21, 22 Pipe wall 30 First inlay area 40 Second Inlay Area 70 First side of central recess 80 Second side of central recess 90 First ultrasonic blocking area 91 Second ultrasonic blocking area 100 Ultrasonic measuring cell l The distance that the sound wave travels between the inner walls of the tube d in Distance between inner walls of pipes

Claims

1. 1. An ultrasonic measuring cell (100) for measuring a volumetric flow rate of a fluid flowing through a pipe (20), comprising: - a continuous central recess extended longitudinally so as to receive the fluid transport tube (20); At least six ultrasonic transducers (11-18); - at least two inlay regions (30, 40); - Optionally, with at least two ultrasound blocking regions (90, 91); at least first and second ultrasonic transducers (11, 12) are disposed on a first side (70) of the central recess, and at least third and fourth ultrasonic transducers (13, 14) are disposed on a second side (80) of the central recess, the first side and the second side of the central recess being opposite each other; the first and / or second ultrasonic transducers (11, 12) are arranged such that they can radiate measurement signals to the third and / or fourth ultrasonic transducers (13, 14) obliquely to a flow direction of the fluid in the pipe (20) and receive measurement signals radiated obliquely to the flow of the fluid in the pipe (20) by the third and / or fourth ultrasonic transducers (13, 14); no ultrasonic coupling gel or grease is present between the fluid transport tube (20) and the ultrasonic measurement cell (100); Features include: a first inlay area (30) is disposed on the first side (70) of the central recess between the central recess and the first and second ultrasonic transducers (11, 12) such that ultrasonic signals received or emitted by the first and / or second ultrasonic transducers (11, 12) pass at least partially through the first inlay area (30); a second inlay region (40) is disposed on the second side (80) of the central recess between the central recess and the third and fourth ultrasonic transducers (13, 14) such that ultrasonic signals received or emitted by the third and / or fourth ultrasonic transducers (13, 14) pass at least partially through the second inlay region (40); a fifth ultrasonic transducer (15) disposed on a first side (70) of the central recess, the first inlay region (30) being located between the fifth ultrasonic transducer (15) and the central recess; a sixth ultrasonic transducer (16) disposed on the second side (80) of the central recess, the second inlay region (40) being located between the sixth ultrasonic transducer (16) and the central recess; the fifth and sixth ultrasonic transducers (15, 16) are disposed parallel to the central recess and opposite each other; The fifth and sixth ultrasonic transducers (15, 16) have a natural resonant frequency range of 0.5 MHz to 5 MHz and a natural resonant frequency range of 6.5×10 6 Ns / m 3 ~30×10 6 Ns / m 3 and The ultrasonic measurement cell (100), wherein the ultrasonic measurement cell (100) is configured to measure the propagation time of an ultrasonic signal in the first inlay area (30) and / or the second inlay area (40).

2. the first and second ultrasonic transducers (11, 12) are arranged at an angle δ' with respect to the central recess such that the first ultrasonic transducer (11) can emit a measurement signal that is reflected at an interface between the first inlay area (30) and a pipe wall (21) and at an interface between the pipe wall (21) and the fluid in the pipe (20), the reflected signal being received by the second ultrasonic transducer (12); and / or the second ultrasonic transducer (12) can emit a measurement signal that is reflected at an interface between the first inlay area (30) and the vessel wall (21) and at an interface between the vessel wall (21) and the fluid within the vessel (20), the reflected signal being received by the first ultrasonic transducer (11); and / or the third and fourth ultrasonic transducers (13, 14) are arranged at an angle δ' with respect to the central recess such that the third ultrasonic transducer (13) can emit a measurement signal that is reflected at an interface between the second inlay area (40) and the pipe wall (22) and at an interface between the pipe wall (22) and the fluid in the pipe (20), the reflected signal being received by the fourth ultrasonic transducer (14); and / or 2. The ultrasonic measurement cell (100) of claim 1, characterized in that the fourth ultrasonic transducer (14) is capable of emitting a measurement signal that is reflected at the interface between the second inlay area (40) and the pipe wall (22) and at the interface between the pipe wall (22) and the fluid in the pipe (20); the reflected signal is received by the third ultrasonic transducer (13).

3. 3. The ultrasonic measuring cell (100) according to claim 1 or 2, characterized in that the first to fourth ultrasonic transducers (11-14) are arranged at an angle δ' with respect to the central recess, δ' being between 55° and 75°, preferably between 60° and 70°, most preferably 65°.

4. 2. The ultrasonic measuring cell (100) according to claim 1, characterized in that the extension of the first inlay area (30) between the fifth ultrasonic transducer (15) and the central recess is between 4 and 12 mm, preferably between 4 and 8 mm, more preferably between 5 and 6 mm, and the extension of the second inlay area (40) between the sixth ultrasonic transducer (16) and the central recess is equal.

5. at least one ultrasonic blocking region (90, 91) disposed either on the first side (70) of the central recess between the first ultrasonic transducer (11) and the second ultrasonic transducer (12) or on the second side (80) of the central recess between the third ultrasonic transducer (13) and the fourth ultrasonic transducer (14); the blocking region (90, 91) is radiated by the first or second ultrasonic transmitter (11, 12) and the first inlay region (30) in the central recess; 2. The ultrasonic measuring cell (100) according to claim 1, characterized in that an ultrasonic signal emitted by the third or fourth ultrasonic transmitter (13, 14) and reflected at the interface between the second inlay area (40) in the central recess and the pipe wall (22) is arranged to propagate to the second or first transducer (12, 13) without being attenuated by the blocking area (90), or an ultrasonic signal emitted by the third or fourth ultrasonic transmitter (13, 14) and reflected at the interface between the second inlay area (40) in the central recess and the pipe wall (22) is arranged to propagate to the fourth or third transducer (13, 14) without being attenuated by the blocking area (91).

6. comprising two ultrasonic blocking regions (90, 91), a first ultrasonic blocking region (90) being disposed on the first side (70) of the central recess between the first ultrasonic transducer (11) and the second ultrasonic transducer (12) and a second ultrasonic blocking region (91) being disposed on the second side (80) of the central recess between the third ultrasonic transducer (13) and the fourth ultrasonic transducer (14); the first blocking area (90) is arranged such that an ultrasonic signal emitted by the first or second ultrasonic transmitter (11, 12) and reflected at an interface between the first inlay area (30) in the central recess and a tube wall (21) propagates to the second or first transducer (11, 12) without being attenuated by the first blocking area (91); and 6. The ultrasonic measuring cell (100) according to claim 5, characterized in that the second blocking area (91) is arranged such that an ultrasonic signal emitted by the third or fourth ultrasonic transmitter (13, 14) and reflected at the interface between the second inlay area (40) in the central recess and the tube wall (22) propagates to the fourth or third transducer (13, 14) without being attenuated by the second blocking area (91).

7. 7. The ultrasonic measurement cell (100) according to claim 5 or 6, characterized in that the at least one ultrasonic blocking area (90, 91) comprises a material from the group comprising air, cork and metal.

8. Further comprising a seventh and / or eighth ultrasonic transducer (17, 18); the seventh ultrasonic transducer (17) is disposed on the first side (70) of the central recess, and the first inlay area (30) is between the seventh ultrasonic transducer (17) and the central recess; and the eighth ultrasonic transducer (18) is disposed on the second side (80) of the central recess, and the second inlay region (40) is between the eighth ultrasonic transducer (18) and the central recess; and The seventh and eighth ultrasonic transducers (17, 18) have a natural resonant frequency range of 0.5 MHz to 5 MHz and a natural resonant frequency range of 6.5×10 6 Ns / m 3 ~30×10 6 Ns / m 3 2. The ultrasonic measuring cell (100) according to claim 1, characterized in that it has an impedance range of:

9. 9. The ultrasonic measuring cell (100) according to claim 8, further comprising seventh and eighth ultrasonic transducers (17, 18), the seventh and eighth ultrasonic transducers (17, 18) being arranged parallel to the central recess and opposite each other.

10. The ultrasonic measurement cell (100) according to claim 1, further comprising at least one temperature sensor.

11. 11. The ultrasonic measurement cell (100) according to claim 10, characterized in that the temperature sensor is selected from the group comprising PT100, PT1000 and thermocouple.

12. 2. The ultrasonic measurement cell (100) of claim 1, characterized in that coupling pads are located between the fluid transport tube (20) and the first inlay area and between the fluid transport tube (20) and the second inlay area (40).

13. 2. The ultrasonic measuring cell (100) according to claim 1, characterized in that the ultrasonic transducers (11-18) emit burst signals at frequencies between 2 MHz and 4 MHz.

14. 2. The ultrasonic measuring cell (100) according to claim 1, characterized in that the at least two inlay regions (30, 40) comprise a material from the group comprising ABS (Acrylonitrile-Butadiene-Styrene-Copolymer), PEEK (Polyetheretherketone), and PMMA (Polymethylmethacrylate), polycarbonate (PC), polyethylene (PE), polyethylene terephthalate (PET), polyoxymethylene (POM), polypropylene (PP), polyphenylene sulfide (PPS), polystyrene (PS), and polyvinyl chloride (PVC).

15. 2. A method for determining a characteristic parameter of an ultrasonic measurement cell (100) according to claim 1, comprising: disposing a fluid transport tube (20) in the ultrasonic measurement cell (100); - measuring reflections of ultrasonic signals at the interface between the first inlay area (30) and the adjacent vessel wall (21) and reflections from the inner surface of the vessel wall (21) adjacent the first inlay area (30) and the fluid within the vessel (20) and the associated propagation times; - sound speed in the first inlay region (30) 1 c inlay , the propagation time t of an ultrasonic signal propagating vertically through the first inlay region (30) 2 , and the propagation time t of an ultrasonic signal propagating vertically through the canal wall (21) adjacent to the first inlay region (30). 4 calculating measuring reflections of ultrasonic signals at the interface between the second inlay area (40) and the adjacent vessel wall (22) and reflections from the inner surface of the vessel wall (22) adjacent the second inlay area (40) and the fluid within the vessel (20) and associated propagation times; - sound speed in the second inlay region (40) 2 c inlay , the propagation time t of the ultrasonic signal propagating vertically through the second inlay region (40) 3 , and a propagation time t of an ultrasonic signal propagating vertically through the canal wall (22) adjacent to the second inlay region (40). 5 calculating a propagation time t of an ultrasonic signal propagating vertically through the first inlay region (30), the vessel wall (21) adjacent to the first inlay region (30), the fluid within the vessel (20), the vessel wall (22) adjacent to the second inlay region (40), and the second inlay region (40); 1 measuring the The propagation time t of an ultrasonic signal propagating vertically through the fluid in the pipe (20) 6 = t 1 -t 2 -t 3 -t 4 -t 5 calculating ・Sound velocity c in the fluid fl and / or calculating an incidence angle β of the sound wave into the fluid.

16. 16. The method of claim 15, further comprising the step of calculating an angle of incidence β' of an ultrasonic signal onto the fluid in the tube (20).

17. The propagation time t of an ultrasonic signal emitted by the first ultrasonic transducer (11), passing through the fluid in the pipe (20) and reaching the fourth ultrasonic transducer (14). FWD 1→4 , and the propagation time t of the ultrasonic signal emitted by the fourth ultrasonic transducer (14) through the fluid in the tube (20) to reach the first ultrasonic transducer (11). BWD 4→1 , and / or the propagation time t of the ultrasonic signal emitted by the second ultrasonic transducer (12) through the fluid in the tube (20) to reach the third ultrasonic transducer (13). FWD 3→2 , and the propagation time t of the ultrasonic signal emitted by the third ultrasonic transducer (13) through the fluid in the tube (20) to reach the second ultrasonic transducer (12). BWD 2→3 measuring the 16. The method according to claim 15, further comprising the step of: calculating the volumetric flow rate Q of the fluid in the tube (20).

18. 16. The method according to claim 15, characterized in that the reflection of ultrasonic signals at the interface between the first inlay area (30) and the adjacent vessel wall (21) and at the interface between the inner surface of the vessel wall (21) adjacent to the first inlay area (30) and the fluid in the vessel (20) and the associated propagation times are measured by an ultrasonic transducer parallel to the central recess; and the reflection of ultrasonic signals at the interface between the second inlay area (40) and the vessel wall (22) adjacent to the second inlay area (40) and at the interface between the inner surface of the vessel wall (22) adjacent to the second inlay area (40) and the fluid in the vessel (20) and the associated propagation times are measured by a further ultrasonic transducer parallel to the central recess, the ultrasonic transducer parallel to the central recess and the further ultrasonic transducer parallel to the central recess being preferably the fifth and sixth ultrasonic transducers.

19. 16. The method of claim 15, characterized in that reflections of ultrasonic signals at an interface between the first inlay area (30) and the adjacent vessel wall (21) and at an interface between an inner surface of the vessel wall (21) adjacent to the first inlay area (30) and a fluid in the vessel (20) and the associated propagation times are measured using the first and second ultrasonic transducers (11, 12), and reflections of ultrasonic signals at an interface between the second inlay area (40) and the vessel wall (22) adjacent to the second inlay area (40) and at an interface between an inner surface of the vessel wall (22) adjacent to the second inlay area (40) and a fluid in the vessel (20) and the associated propagation times are measured using the third and fourth ultrasonic transducers (13, 14).

20. The method of claim 15, further comprising the step of: measuring the temperature of the fluid in the tube (20).

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