Measuring tube and flowmeter

Abstract

The invention relates to a measuring tube (1) for use in an ultrasonic flowmeter, comprising: - a measuring tube body (2), wherein the measuring tube body (2) has a measuring portion (MA), the measuring tube body (2) has, in the measuring portion (MA), first, second, and third outer planar surfaces (PF1, PF2, PF3), in particular for attaching transducer elements, and the first, second and third surfaces (PF1, PF2, PF3) are not parallel to one another. The invention further relates to an ultrasonic flowmeter (10) having a measuring tube (1) according to the invention.

Description

[0001] Measuring tube and flow meter

[0002] The invention relates to a measuring tube for use in an ultrasonic measuring device and an ultrasonic measuring device for determining a medium property.

[0003] There are numerous ultrasound-based measuring devices. Lamb wave technology occupies a special position among them. It enables the generation and reception of ultrasound by transducer elements located outside the process, thus protecting these elements from aggressive media and eliminating the need for bores, pockets, or recesses in the measuring tube. Furthermore, the large-area vibration excitation of the tube wall, compared to conventional ultrasound technology, couples the acoustic energy into a correspondingly large area of ​​the adjacent medium, making the resulting sound beam relatively robust against particles (solids) and bubbles (gas inclusions) contained in the flow.

[0004] For certain measuring instruments, especially flow meters, it is advantageous to have off-center measuring paths. Such measuring paths allow, firstly, better coverage of the different areas of the measuring cross-section (outer, transition, inner regions), and secondly, reduce sensitivity to changes in the flow profile due to Reynolds number-dependent effects and upstream flow disturbances.

[0005] To implement such off-center measurement paths, especially those based on Lamb waves, cost-effectively, ideally with only two ultrasonic transducers, the measuring tube requires flat, parallel outer surfaces. Therefore, it is necessary to design at least parts of the measuring tube with flat sections.

[0006] Several ultrasonic flowmeters are already known in which measuring tubes with planar sections are used. For example, DE 198 23 165 A1 discloses an ultrasonic flowmeter with a measuring tube that has a square or rectangular inner cross-section in one measuring range. The end flanges of the ultrasonic flowmeter each have an opening with a quasi-conical shape that tapers towards the square or rectangular inner cross-section. DE 198 23 165 A1 aims to provide a measuring tube that can be fully emitted by clampable ultrasonic transducers. Furthermore, by selecting the appropriate tube wall geometry, a number of parallel ultrasonic beams can be generated to radiate the flow within the measuring tube in such a way that parallel summation is possible instead of Gaussian chord summation of individual paths.DE 10 2017 115 431 A1 discloses a measuring device with a measuring tube which has a substantially rectangular internal cross-section in a measuring section and a non-rectangular internal cross-section in a connecting section. A transition section located between the measuring section and the connecting section has an internal cross-section identical to that of the measuring section at one end and an internal cross-section identical to that of the connecting section at the other. The internal cross-section of the transition section changes continuously along its entire length between the two ends. Thus, the transition between areas with different internal cross-sections is smooth and without hard, abrupt transitions or steps.This prevents increased flow separation and thus uneven flow profiles, high turbulence and pressure losses, which can distort measurements.

[0007] Furthermore, EP 3 388 794 A1 describes a measuring device for measuring the flow velocity of a fluid using a measuring tube. This tube has a rectangular measuring section, an inlet section with a first superelliptical transition shape, and an outlet section with a second superelliptical transition shape. The purpose of EP 3 388 794 A1 is to provide a measuring tube with a particularly homogeneous transition geometry from the circular section to the rectangular measuring section, thus preventing flow separation and achieving improved flow velocity measurement quality despite its short overall length.

[0008] Numerous manufacturing technologies exist for producing measuring tubes with planar outer surfaces, such as conventional internal machining (milling), wire EDM of an internal profile, extrusion of an internal profile, additive manufacturing, or investment casting combined with abrasive polishing. All these methods share the common characteristics of long production times and / or the need for a large amount of raw material to achieve the desired measuring cross-section. The transitions from the process connections, which are typically circular, to the section containing the ultrasonic measuring paths represent the most critical and complex part of the measuring tube, as a continuous and therefore fluid-mechanically efficient geometric transition must be created. Consequently, the production of such measuring tubes is expensive and often not competitive.

[0009] Ultrasonic flowmeters are known that operate using a so-called two-path arrangement. This measurement is performed using two or more pairs of ultrasonic transducers. This arrangement has the advantage that measurement inaccuracies in flow profiles that are not completely symmetrical, especially not completely rotationally symmetrical, can be partially compensated for. Such disturbances are caused by components that are connected to a pipeline and subsequently form part of the pipe or are defined as pipe elements. This includes, among others, elbows, valves, and pumps. Depending on the type of disturbance, it is therefore recommended to maintain a certain minimum distance when positioning the ultrasonic flowmeter, as otherwise a device-specific upper limit for measurement accuracy can no longer be guaranteed.

[0010] However, there are known applications where this minimum distance, the so-called inlet section, cannot be maintained. In such applications, significant measurement errors occur due to the incomplete flow profile. In this case, the customer also lacks information regarding the accuracy and reliability of the measurement, which would allow them to assess and evaluate the quality of the data obtained.

[0011] US20190186967A1 discloses a flow measurement system with an ultrasonic flow meter as the flow meter and transmitter electronics configured to determine exactly one dimensionless quantity PF (“profile factor”) from four locally determined flow velocities and, depending on the PF, to determine a correction quantity MF (“meter factor”) to correct the measured value of the flow velocity of the medium.

[0012] DE19717940A1 discloses a method for determining the vortex intensity of the medium to be monitored for an ultrasonic flow meter. In this method, a ratio between the angular momentum and longitudinal momentum of the medium is used to determine the vortex intensity, which is then used to correct the measured flow rate.

[0013] EP0804717B1 aims to provide an ultrasonic flowmeter with improved measurement accuracy. This is achieved by determining a current Reynolds number, for which an operating flow profile is first recorded as a function of several measured values ​​of the medium's flow velocity, in order to account for the influence of inlet effects. It has been shown that such methods assume that a flow profile is already essentially formed and does not deviate significantly from rotational symmetry.

[0014] DE102013106108A1 discloses a method for determining a compensated flow rate in which, taking into account a distance of the measuring setup to the disturbance, the type of disturbance and optionally the Reynolds number, the correction factor to be applied is determined and used for determining the flow rate.

[0015] A disadvantage of the aforementioned prior art is that, in addition to the determined local measurements of the flow velocity-dependent quantity, further information is always required to identify the flow profile in order to determine a unique correction value suitable for the given situation. The undisclosed DE 10 2024 117 335.1 solves this problem by employing multiple ultrasonic transducers that span at least three different signal paths through the medium channel. This allows for the generation of a large number of local measurement tuples specific to the given flow profile. Based on these, the influence of flow asymmetry can be corrected from the measurement results.

[0016] The invention is based on the objective of providing measuring tubes which meet the requirements necessary for the correction algorithm disclosed in DE 10 2024 117 335.1 (or other correction algorithms).

[0017] The problem is solved by the measuring tube according to claim 1 and the ultrasonic measuring device according to one of claims 16 to 19.

[0018] The measuring tube according to the invention for use in an ultrasonic measuring device comprises:

[0019] - a measuring tube body, wherein the measuring tube body has a measuring section, wherein the measuring tube body in the measuring section has external planar first, second and third surfaces, in particular for attaching transducer elements, wherein the first, second and third surfaces are not parallel to each other.

[0020] Advantageous embodiments of the invention are the subject of the dependent claims.

[0021] One embodiment provides that in a cross-section through the measuring tube body in the measuring section, a first straight line lying in the planar surface, a second straight line lying in the second planar surface and a third straight line lying in the third planar surface span a triangle, in particular an isosceles triangle.

[0022] One embodiment provides that in the cross-section the first straight line and the second straight line span an angle α, with 20° < α < 32°, in particular 22° < α < 28° and preferably α = 26°, wherein the fourth straight line intersects the second straight line perpendicularly.

[0023] One embodiment provides that the measuring tube body has a curvature in cross-section with a radius of curvature R, in particular exactly three curvatures, each with a radius of curvature R, wherein the radius of curvature R is such that 1 < R < 4 millimeters, in particular 2 < R < 3 millimeters and preferably R = 2.1 millimeters.

[0024] One embodiment provides that the measuring tube body has a first, second and third pair of surfaces, wherein the first pair of surfaces comprises the first surface and a fourth surface parallel to it, wherein the second pair of surfaces comprises the second surface and a fifth surface parallel to it, and wherein the third pair of surfaces comprises the third surface and a sixth surface parallel to it.

[0025] One embodiment provides that in the cross-section the first straight line and the second straight line span an angle β, with 130° < β < 142°, in particular 134° < β < 138° and preferably β = 136°.

[0026] One embodiment provides that the measuring tube body has a curvature in cross-section with a radius of curvature R, in particular exactly six curvatures, each with a radius of curvature R, wherein the radius of curvature R is such that 1 < R < 7 millimeters, in particular 2 < R < 4 millimeters and preferably R = 3 millimeters.

[0027] One embodiment provides that the measuring tube body has a fourth pair of surfaces in the measuring section, wherein the fourth pair of surfaces has a planar seventh and eighth surface, wherein the seventh surface runs parallel to the eighth surface, and wherein there is no parallelism between the first, second, third and seventh surface.

[0028] One embodiment provides that the first surface has a first width B1, which is dimensioned such that only a single converter element can be arranged in the cross-section, wherein the second surface, in particular the adjacent one, has a second width B2, which is dimensioned such that more than two converter elements can be arranged offset in the circumferential direction.

[0029] One embodiment provides that the measuring tube body has a fifth pair of surfaces in the measuring section, wherein the fifth pair of surfaces comprises a planar ninth and tenth surface, in particular for attaching at least one transducer element, wherein the ninth and tenth surfaces run parallel to each other, and wherein there is no parallelism between the first, second, third, seventh and ninth surfaces.

[0030] One embodiment provides that the first, second and third surfaces are oriented relative to each other in such a way that their respective perpendicular lines do not intersect in the interior of the measuring tube body in the cross-section, and / or wherein the seventh surface is oriented in such a way that a corresponding perpendicular line of the seventh surface intersects a longitudinal axis, in particular a center point of the interior, in the cross-section, and / or wherein the ninth surface is oriented in such a way that a corresponding perpendicular line of the ninth surface runs off-center through the interior in the cross-section.One embodiment provides that the measuring tube body has a measuring section contour in the measuring section, wherein the measuring tube body has an inlet section and an outlet section, wherein the measuring tube body has a first transition section between the inlet section and the measuring section, and wherein the measuring tube body has a second transition section between the outlet section and the measuring section.

[0031] One embodiment provides that the measuring tube body has an inner first circumference in the inlet section, wherein the measuring tube body has an inner second circumference in the measuring section, wherein the first and second circumferences do not differ from each other by more than 3%, in particular not by more than 1.5%.

[0032] One embodiment provides that the measuring tube body has an outer inlet diameter in the inlet section, wherein the measuring tube body has a first and second outer measuring section diameter in the measuring section, wherein the first and second measuring section diameters intersect a longitudinal axis of the measuring tube, wherein the first measuring section diameter is larger than the inlet diameter, and wherein the second measuring section diameter is smaller than the inlet diameter.

[0033] One embodiment provides that the measuring tube is designed in such a way that it is self-emptying at an inclination of <3° relative to a horizontal.

[0034] The ultrasound measuring device according to the invention for determining a medium property comprises:

[0035] - a measuring tube according to the invention, in particular produced by means of a hydroforming process, wherein the measuring tube is designed to guide a medium;

[0036] - at least one pair of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least one pair of ultrasonic transducers comprises a first pair of ultrasonic transducers arranged in the measuring section, wherein the first pair of ultrasonic transducers has a first and second transducer element, wherein the first transducer element is arranged on the second surface, wherein the second transducer element is arranged on the third surface, wherein the first and second transducer elements form a 2-crossbeam arrangement;

[0037] - measuring electronics which are electrically connected to the at least one pair of ultrasonic transducers, wherein the measuring electronics are configured to determine the medium property as a function of at least one measured value from the at least one pair of ultrasonic transducers; and

[0038] - a housing, wherein the housing surrounds at least one pair of ultrasonic transducers.

[0039] The ultrasound measuring device according to the invention for determining a medium property comprises:

[0040] - a measuring tube according to the invention, in particular produced by means of a hydroforming process, wherein the measuring tube is designed to guide a medium;

[0041] - at least two pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least two pairs of ultrasonic transducers comprise a first and a second pair of ultrasonic transducers arranged in the measuring section, wherein the first pair of ultrasonic transducers has a first and a second transducer element, wherein the first transducer element is arranged on the second (third) surface, wherein the second transducer element is arranged on the sixth (fifth) surface, wherein the first and second transducer elements form a 2-crossbeam arrangement, wherein the second pair of ultrasonic transducers is arranged in the measuring section such that a principal axis of the generating ultrasonic wave is eccentric to the measuring tube body, wherein the second pair of ultrasonic transducers has a first and a second transducer element, wherein the first transducer element is arranged on the first surface,wherein the second converter element is arranged on the fourth surface, wherein the first and second converter elements form a 1- or 2-crossbeam arrangement;

[0042] - measuring electronics which are electrically connected to the at least two pairs of ultrasonic transducers, wherein the measuring electronics are configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and

[0043] - a housing, wherein the housing surrounds the at least two pairs of ultrasonic transducers.

[0044] The ultrasound measuring device according to the invention for determining a medium property comprises:

[0045] - a measuring tube according to the invention, in particular produced by means of a hydroforming process, wherein the measuring tube is designed to guide a medium;

[0046] - at least three pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least two pairs of ultrasonic transducers comprise a first, second and third pair of ultrasonic transducers arranged in the measuring section, wherein the first pair of ultrasonic transducers has a first and second transducer element, wherein the first transducer element is arranged on the first surface, wherein the second transducer element is arranged on the fourth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement, wherein the second pair of ultrasonic transducers is arranged in the measuring section such that a principal axis of the generating ultrasonic wave is eccentric to the measuring tube body, wherein the second pair of ultrasonic transducers has a first and a second transducer element, wherein the first transducer element is arranged on the second surface,wherein the second transducer element is arranged on the fifth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement; wherein the third ultrasonic transducer pair is arranged in the measuring section such that a principal axis of the generating ultrasonic wave is eccentric to the measuring tube body, wherein the third ultrasonic transducer pair has a first and a second transducer element, wherein the first transducer element is arranged on the second surface, wherein the second transducer element is arranged on the fifth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement;

[0047] - measuring electronics which are electrically connected to the at least three pairs of ultrasonic transducers, wherein the measuring electronics are configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and

[0048] - a housing, wherein the housing surrounds the at least three pairs of ultrasonic transducers.

[0049] The ultrasonic measuring device for determining a medium property includes:

[0050] - a measuring tube according to the invention, in particular produced by means of a hydroforming process, wherein the measuring tube is designed to guide a medium;

[0051] - at least five pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least five pairs of ultrasonic transducers comprise a first, second, third, fourth and fifth pair of ultrasonic transducers arranged in the measuring section, wherein the first pair of ultrasonic transducers has a first and second transducer element, wherein the first transducer element is arranged on the first surface, wherein the second transducer element is arranged on the fourth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement, wherein the second pair of ultrasonic transducers has a first and a second transducer element, wherein the first transducer element is arranged on the third surface, wherein the second transducer element is arranged on the sixth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement,wherein the third pair of ultrasonic transducers comprises a first and a second transducer element, wherein the first transducer element is arranged on the seventh surface, wherein the second transducer element is arranged on the eighth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement, wherein the fourth pair of ultrasonic transducers comprises a first and a second transducer element, wherein the first transducer element is arranged on the ninth surface, wherein the second transducer element is arranged on the tenth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement, wherein the fourth pair of ultrasonic transducers is arranged in the measuring section such that a principal axis of the generating ultrasonic wave is eccentric to the measuring tube body, wherein the fifth pair of ultrasonic transducers comprises a first and a second transducer element, wherein the first transducer element is arranged on the second surface.wherein the second transducer element is arranged on the fifth surface, wherein the first and second transducer elements form a 1-crossbeam arrangement, wherein the fifth ultrasonic transducer pair is arranged in the measuring section such that a principal axis of the generating ultrasonic wave intersects the longitudinal axis of the measuring tube,

[0052] - a measuring electronics system which is electrically connected to the at least five pairs of ultrasonic transducers, wherein the measuring electronics system is configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and

[0053] - a housing, wherein the housing surrounds the at least five pairs of ultrasonic transducers.

[0054] The invention is explained in more detail with reference to the following figures. They show:

[0055] Fig. 1 : a partial section of a cross-section through a first embodiment of the measuring tube according to the invention;

[0056] Fig. 2: a cross-section through the first embodiment of the ultrasound measuring device according to the invention;

[0057] Fig. 3: a partial section of a cross-section through a second embodiment of the measuring tube according to the invention;

[0058] Fig. 4: a cross-section through the second embodiment of the ultrasound measuring device according to the invention;

[0059] Fig. 5: a cross-section through the second embodiment of the ultrasound measuring device according to the invention;

[0060] Fig. 6: a cross-section through a third embodiment of the ultrasonic measuring device according to the invention; Fig. 7: a cross-section through a fourth embodiment of the ultrasonic measuring device according to the invention; and

[0061] Fig. 8: a cross-section through a fifth embodiment of the ultrasound measuring device according to the invention.

[0062] Fig. 1 shows a partial section of a cross-section Q through a first embodiment of the measuring tube 1 according to the invention. Fig. 2 shows a cross-section through the first embodiment of the ultrasonic measuring device 10 according to the invention in which the measuring tube 1 from Fig. 1 is inserted.

[0063] The measuring tube 1 for use in an ultrasonic measuring device 10 comprises a measuring tube body 2. The measuring tube body 2 can be made of a metal (e.g., (stainless) steel), a plastic, glass, carbon glass, a ceramic, and / or a glass fiber reinforced or otherwise filled plastic, as well as in multiple parts made of such material combinations. The measuring tube body 2 is preferably metallic. The measuring tube body 2 includes a medium channel through which the medium to be analyzed is guided. The measuring tube body 2 also has an inner surface iMF in contact with the medium and an outer surface äMF that does not come into contact with the medium. The measuring tube body 2 preferably has a measuring tube thickness of 0.5 to 2.5 millimeters and a nominal diameter of less than DN25, in particular less than DN15, and preferably DN8.

[0064] The measuring tube body 2 has a measuring section MA. Measuring section MA is a subsection of the measuring tube body 2 designed to accommodate transducer elements for the ultrasonic measuring device. Measuring section MA is located offset in the flow direction. Within measuring section MA, the measuring tube body 2 exhibits a measuring tube thickness deviation of less than ±3% from a target measuring tube thickness / average measuring tube thickness.

[0065] The measuring tube body 2 has a measuring section contour MK in the measuring section MA, which is constant throughout the entire measuring section MA. The measuring section contour MK can be the outer or inner line of the measuring tube body 2 in the cross-section Q.

[0066] Furthermore, the measuring tube body 2 has an inlet section and an outlet section. The measuring tube body 2 typically has a process connection (e.g., a flange, threaded connection) in both the inlet section EA and the outlet section AA, via which the ultrasonic flow meter 10 can be connected to a process line. The illustrated measuring tube body 2 has a circular inlet section contour EK and outlet section contour AK in both the inlet and outlet sections EA and AA. The inlet section contour EK and outlet section contour AK each have a (circular) basic shape. The two basic shapes can be identical. This can result from the fact that the measuring tube body 2 is formed from a (conventional) cylindrical outlet tube using a hydroforming process. No transducer elements are arranged in the inlet and outlet sections EA and AA.

[0067] The measuring tube body 2 has a first transition section between the inlet section and the measuring section MA. In this first transition section contour, the measuring tube body 2 assumes a flow-direction variable contour that changes from the inlet contour in the flow direction until it assumes the measuring section contour MK. The first transition section contour can take the form of a superellipse. The first transition section ÜA1 has a minimum transition section length, which is chosen such that reflected ultrasonic waves (packets) do not superimpose the evaluation windows. The minimum transition length can be greater than or equal to N / 2 ■ 1.5 • Ida, where N = number of wave trains in the excitation signal and Ida = wavelength of the Lamb wave (e.g., Ida = 1.5 mm and N = 8). The same can apply to further transition sections.

[0068] Furthermore, the measuring tube body 2 has a second transition section between the outlet section and the measuring section MA. In this transition section, the measuring tube body 2 assumes a second transition section contour that changes in the flow direction, starting from the measuring section contour MK and changing in the flow direction until it assumes the outlet contour. The second transition section contour can take the form of a superellipse. The second transition section ÜA2 also has a minimum transition section length, which is chosen such that reflected ultrasonic waves (packets) do not superimpose the evaluation windows. The minimum transition length can be greater than or equal to N / 2 ■ 1.5 • Ida, where N = number of wave trains in the excitation signal and Ida = wavelength of the Lamb wave (e.g., Ida = 1.5 mm and N = 8). The same can apply to further transition sections.

[0069] The measuring tube body 2 can be manufactured using an internal high-pressure forming process (also called hydroforming) that meets the requirements of DIN 8584-7. For this purpose, a conventional hollow cylindrical tube suitable for internal high-pressure forming (=starting tube, e.g., a metal tube) can be formed into the final shape of the measuring tube body 2 by means of tensile-compressive forming. In this process, a liquid (usually a water-oil emulsion) is introduced into the tube under pressure, causing it to deform and assume the predetermined shape of the tool.

[0070] Further cost savings can be achieved if the ultrasonic measuring device requires internal surfaces with very high surface quality, or low roughness, due to its use in hygiene-relevant applications, particularly in the food industry. For this purpose, pre-polished tubes can be used, whose surface quality is only slightly affected by hydrostatic cold forming. This eliminates the need for a final, costly polishing process of the entire measuring tube 1, which is equipped with process connections.

[0071] In measuring section MA, the measuring tube body 2 has an (outer) planar first, second, and third surface PF1, PF2, PF3. The first, second, and third surfaces PF1, PF2, and PF3 each have a width B perpendicular to the longitudinal axis of the measuring tube body 2 and a length L along the longitudinal axis of the measuring tube body 2. The longitudinal extent is greater than the transverse extent. In the first cross-section Q1, a first straight line G1 lying in the first planar surface PF1, a second straight line G2 lying in the second planar surface PF2, and a third straight line G3 lying in the third planar surface PF3 define a triangle, in particular an isosceles triangle. The first cross-section Q1 intersects the first measuring section MA1 through the measuring tube body 2. In the illustrated embodiment, the first, second and third surfaces PF1, PF2, PF3 are the only planar surfaces in the first measuring section MA1.

[0072] The first straight line G1 and the second straight line G2 form an angle α, where 20° < α < 32°, in particular 22° < α < 28°, and preferably 26°. The same applies to the first straight line G1 and the third straight line G3. The second straight line G2 and the third straight line G3 form an angle β, for which a ≥ 180° - 2 • α. By choosing a triangle as the basic shape for the first measuring contour 1, a two-crosshead transducer element arrangement can be realized, in which the ultrasonic waves passing through the medium are reflected once at the inner surface of the measuring tube body 2 before being received at the receiving ultrasonic transducer.

[0073] The width B must be between 2.7 and 3.3 millimeters, preferably B = 3 millimeters. The width B of the planar surfaces PF1, PF2, PF3 is selected such that it provides space for exactly one transducer element in the circumferential direction of the measuring tube body 2. The length L of the planar surfaces PF1, PF2, PF3 is preferably selected such that at least two transducer elements can be arranged offset along the longitudinal direction of the surface. The choice of width B also depends on the wall thickness. If the width is too small, the directivity decreases. If the width B is too large, the near field can become too long. As the wall thickness decreases, the wavelength, and thus the required minimum transducer width—and therefore also the minimum width B—scales downwards proportionally.

[0074] The measuring tube 1 is designed such that the measuring section contour MK, the first transition contour, and the second transition contour are selected such that it is self-draining when the measuring tube 1, in particular the ultrasonic measuring device 10, is inclined at an angle of less than 3° relative to a horizontal. Furthermore, the measuring tube body 2 can have a curvature in cross-section Q with a radius of curvature R, in particular exactly three curvatures, each with a radius of curvature R. For the radius of curvature R, it is the case that 1 < R < 4 millimeters, in particular 2 < R < 3 millimeters, and preferably R = 2.1 millimeters.

[0075] The self-draining capability of an ultrasonic measuring device 10 or a measuring tube 1 in general is an essential requirement, especially in hygienic applications. For example, the ASME BPE hygiene standard requires that radii of curvature maintain a minimum radius of 3 millimeters. However, this is not achievable, particularly with measuring tubes 1 according to the invention, which have small nominal diameters and multiple planar surfaces intended for transducer elements. For instance, the measuring tube body 2, with a nominal diameter of DN8 and an angle α of 26° in the first cross-section Q1, has a radius of curvature of approximately 2.1 millimeters. The angle α of 26° must be maintained to ensure a constant inner circumference (resulting in a constant wall thickness despite hydroforming) along the measuring tube body 2, while simultaneously allowing a transducer element with a width of 3 millimeters to be attached to the planar surfaces.However, by selectively choosing the individual contours, self-emptying can be achieved when the measuring tube 1 or the ultrasonic measuring device 10 is tilted.

[0076] The measuring tube body 2 has an inner first circumference U1 in the measuring section MA, an inner second circumference U2 in the inlet section, and an inner third circumference U3 in the outlet section. The shape of the measuring tube body 2 is chosen such that the first, second, and third circumferences U1, U2, U3 do not deviate from each other by more than 3%, and in particular, not by more than 1.5%. The illustrated design of the measuring tube body 2 has an (inner) circumference that is essentially constant along the entire length of the measuring tube body 2. Essentially constant means that deviations from a mean circumference are no more than 3%, and in particular, not by more than 1.5%. The condition that the first, second, and third circumferences U1, U2, U3 are essentially identical ensures, particularly when using an internal high-pressure forming process, that the wall thickness of the measuring tube body 2 remains unchanged in the measurement-relevant areas of the measuring section MA after forming.This means that during the forming process, the entire length of the measuring section MA is kept as constant as possible and only increased slightly, without locally falling below the required minimum circumferential strain. Thus, especially when using the measuring tube 1 in ultrasound-based measuring devices 10, robust ultrasound signals (e.g., in the form of Lamb waves) can be generated and evaluated.

[0077] The embodiment shown in Figures 1 and 2 comprises at least one pair of ultrasonic transducers, in particular for generating and / or receiving surface acoustic waves, preferably Lamb waves. Each pair of ultrasonic transducers comprises two transducer elements, one of which is configured to generate an ultrasonic wave and the other to receive the generated ultrasonic wave that has passed through the medium or the measuring tube body. Alternatively, both transducer elements forming the pair of ultrasonic transducers can be configured to generate and receive ultrasonic waves, respectively. Furthermore, at least one transducer element of the pair of ultrasonic transducers can be configured to receive the ultrasonic wave from a transducer element not belonging to the pair.

[0078] It is known that measuring tube bodies naturally possess Lamb wave vibration modes, namely vibrations forming mixed pressure and shear waves, in which the tube wall of the measuring tube body performs or can perform Lamb wave-forming vibrations.

[0079] The tube wall is deflected both radially and longitudinally along the measuring tube body 2. Lamb waves can be either symmetrical (SO, S1, S2, ... Sn) or asymmetrical (AO, A1, A2, ... An). The generation and detection of Lamb wave modes is already state of the art, as demonstrated, for example, in patents US6575043B1 and US4735095B.

[0080] The at least one pair of ultrasonic transducers comprises a first pair of ultrasonic transducers – with a first and second transducer element W11, W12 – which is arranged in the measuring section MA. The first transducer element W11 is arranged on the second surface PF2, and the second transducer element W12 is arranged on the third surface PF3. Together, the first and second transducer elements W11, W12 form a two-crossbeam arrangement. This means that the ultrasonic wave generated, for example, by the first transducer element W11 and coupled into the medium or medium channel, is reflected once by the inner surface iMF of the measuring tube body 2 on its way to the second transducer element W21. The first surface PF2 is free of a transducer element. The inner surface PIF1, parallel to the first surface PF1 and also planar, in contact with the medium, is configured as a reflective surface.

[0081] The measuring tube body 1 has a plane of symmetry SE in the first measuring section MA1. A central longitudinal axis of the measuring tube body 2 lies in the plane of symmetry SE. The measuring tube body 1 can also be designed such that the plane of symmetry SE also describes the first and second transition sections in a mirror-symmetric manner.

[0082] The first and second transducer elements W11 and W12 are each configured to generate ultrasonic waves whose principal axes HA1 and HA2 intersect the plane of symmetry SE. In other words, a signal path describing the main propagation of the ultrasonic wave is deflected at the intersection of the inner surface iMF of the measuring tube body 2 and the plane of symmetry SE due to reflection. This also ensures that the main part of the ultrasonic wave propagates off-center to the medium channel.

[0083] The at least one pair of ultrasonic transducers further comprises a second pair of ultrasonic transducers – with a first and second transducer element W21, W22 – which is arranged in the measuring section MA. The first transducer element W21 is arranged on the third surface PF3 and the second transducer element W22 is arranged on the second surface PF2. The third pair of ultrasonic transducers is arranged such that a two-crossbeam configuration is formed.

[0084] Fig. 2 shows a cross-section Q through the first transducer element W11 of the first ultrasonic transducer pair and the first transducer element W21 of the second ultrasonic transducer pair. The cross-section Q does not differ significantly from a cross-section through the second transducer element W12 of the first ultrasonic transducer pair and the second transducer element W22 of the second ultrasonic transducer pair.

[0085] The transducer elements of the individual ultrasonic transducer pairs can be connected directly or indirectly to the measuring tube body 2. For example, so-called coupling elements can be provided, which are arranged between the transducer element and the measuring tube body 2 and are designed and configured such that a driver signal excites a Lamb wave in the measuring tube body 2. The driver signal is provided by a measuring electronics unit 100, which is electrically connected to at least two ultrasonic transducer pairs, and in particular to all ultrasonic transducer pairs. The measuring electronics unit 100 is configured at least to determine the medium property as a function of at least one measured value per ultrasonic transducer pair. Furthermore, the measuring electronics unit 100 is configured to generate the driver signal and provide it to the corresponding transducer elements.The medium property can be the flow rate, the volumetric flow rate, the viscosity, the (acoustic) density, or quantities derived from the aforementioned medium properties (e.g., emulsion, suspension, dispersed bubbles).

[0086] Furthermore, a housing 30 is provided, which surrounds at least one pair of ultrasonic transducers and is designed to protect the transducer elements and, optionally, the measuring electronics 100 from environmental influences. Alternatively, the measuring electronics 100 can be arranged in a so-called transmitter housing (not shown), the interior of which is separate from the interior of the housing 30.

[0087] The ultrasonic measuring device 10 has a measuring device principal axis MHA, which runs perpendicular to a measuring tube longitudinal axis MLA of the measuring tube 1. The measuring device principal axis MHA is the axis that—when the ultrasonic measuring device 10 is horizontally oriented—runs perpendicular to a horizontal and parallel to a direction of gravity. The measuring device principal axis MHA typically passes—if present—through a connector, a transmitter adapter, and / or a transmitter housing (not shown) or parallel to a transmitter housing longitudinal axis. The measuring device principal axis MHA can also, or alternatively, lie in a plane of symmetry of the housing 30.According to the advantageous embodiment, the measuring tube 1 is arranged in the housing 30 such that the plane of symmetry SE of the measuring tube body 2 intersects the main axis MHA of the measuring instrument 10 at an angle 0, where the angle 0 is such that 50° < 0 < 70°, in particular 55° < 0 < 65°, and preferably 0 = 60°. The measuring tube body 2 is therefore tilted circumferentially by the angle β in the housing 30 and fixed in position.

[0088] Fig. 3 shows a partial section of a cross-section through a second embodiment of the measuring tube 1' according to the invention. Figs. 4 and 5 each show a cross-section through the second embodiment of the ultrasonic measuring device 10' according to the invention with the measuring tube 1'.

[0089] Figures 4 and 5 show different configurations for arranging the pairs of ultrasonic transducers on the measuring tube body 2.

[0090] The measuring tube body 2 of the second embodiment has a first, second, and third pair of surfaces. The first pair of surfaces comprises the first surface PF1 and a fourth surface PF4 parallel to it; the second pair of surfaces comprises the second surface PF2 and a fifth surface PF5 parallel to it; and the third pair of surfaces comprises the third surface PF3 and a sixth surface PF6 parallel to it. The illustrated measuring tube 1' can be described as a hexagon with rounded corners.

[0091] The planar second and third surfaces PF2 and PF3 each have a width B1. The planar first surface PF1, however, has a width B2, which differs from the width B1. The illustrated measuring tube body 2 is designed such that the width B1 is smaller than the width B2. In particular, the width B2 is chosen so that two transducer elements identical in construction to the transducer elements of PF2 and PF3, respectively, can be arranged side by side in the circumferential direction.

[0092] The measuring tube body 2 of the second embodiment is designed such that in the cross-section Q, the first straight line G1 and the second straight line G2 form an angle β, with 130° < β < 142°, in particular 134° < β < 138°, and preferably β = 136°. Furthermore, in the cross-section Q, the second straight line G2 and the third straight line G3 form an angle y, and the first straight line G1 and the third straight line G3 form an angle 8. The equation for angle 8 is 8 = 180° - β, and the equation for angle y is y = 180° - 2 - 8.

[0093] Furthermore, the measuring tube body 2 has a curvature in cross-section Q with a radius of curvature R, in particular exactly six curvatures, each with a radius of curvature R, where the radius of curvature R is such that 1 < R < 7 millimeters, in particular 2 < R < 4 millimeters, and preferably R = 3 millimeters. If the radius of curvature R > 3 millimeters is selected, a requirement of the hygiene standard ASME BPE is met, which requires that the radii of curvature be greater than or equal to 3 millimeters to ensure self-emptying of the measuring tube. The second embodiment of the ultrasonic measuring device 10' for determining a medium property comprises the measuring tube 1' shown at least partially in Fig. 3 for guiding the medium. Furthermore, the ultrasonic measuring device 10' comprises at least two pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves.The basic requirement of the second embodiment is that the at least two pairs of ultrasonic transducers comprise a first and a second pair of ultrasonic transducers arranged in the measuring section MA. The first pair of ultrasonic transducers comprises a first and a second transducer element W11, W12, wherein the first transducer element W11 is arranged on the second surface PF2 and the second transducer element W12 is arranged on the sixth surface PF6. The first and second transducer elements W11, W12 are arranged on the measuring tube body 2' such that a two-crossbeam arrangement is formed.

[0094] The first pair of ultrasonic transducers is arranged in the measuring section MA such that a principal axis HA (shown as an arrow) of the generating ultrasonic wave runs off-center to the measuring tube body 2'. The same applies to the second pair of ultrasonic transducers, which has a first and a second transducer element W21, W22. The first transducer element W21 is located on the first surface PF1 and the second transducer element W22 is located on the fourth surface PF4. The first and second transducer elements W21, W22 are arranged offset relative to each other in the longitudinal direction of the measuring tube 1', forming a two-crossbar arrangement.

[0095] The at least two ultrasound transducer pairs further comprise a third, fourth, fifth, sixth, seventh and eighth ultrasound transducer pair, each formed by two transducer elements Wij, where i is a natural number between 3 and 8 and j is either a 1 or a 2.

[0096] The transducer elements of the third ultrasound transducer pair are arranged on the third and sixth surfaces PF3 and PF6.

[0097] The transducer elements of the fourth pair of ultrasonic transducers are arranged on the first and fourth surfaces PF1 and PF4.

[0098] The transducer elements of the fifth ultrasound transducer pair are arranged on the third and sixth surfaces PF3 and PF6.

[0099] The transducer elements of the sixth pair of ultrasonic transducers are arranged on the first and fourth surfaces PF1 and PF4.

[0100] The transducer elements of the seventh ultrasound transducer pair are arranged on the second and fifth surfaces PF2 and PF5. The transducer elements of the eighth ultrasound transducer pair are arranged on the first and fourth surfaces PF1 and PF4.

[0101] The first transducer elements W21, W41, W61, W81 of the second, fourth, sixth, and eighth ultrasonic transducer pairs are arranged on the measuring tube body 2' such that a cross-sectional plane of the measuring tube 1' exists which intersects all four first transducer elements W21, W41, W61, W81. The second transducer elements W22, W42, W62, W82 of the second, fourth, sixth, and eighth ultrasonic transducer pairs are arranged on the measuring tube body 2' such that a cross-sectional plane of the measuring tube 1' exists which intersects all four second transducer elements W22, W42, W62, W82.

[0102] The first transducer elements W11, W31, W51, W71 of the first, third, fifth, and seventh ultrasonic transducer pairs are arranged on the measuring tube body 2' such that a cross-sectional plane of the measuring tube 1' exists which intersects all four first transducer elements W11, W31, W51, W71. The second transducer elements W12, W32, W52, W72 of the first, third, fifth, and seventh ultrasonic transducer pairs are arranged on the measuring tube body 2' such that a cross-sectional plane of the measuring tube 1' exists which intersects all four second transducer elements W12, W32, W52, W72.

[0103] The cross-section shown runs through the first transducer elements of each of the eight ultrasonic transducer pairs. A cross-section through the second transducer elements, which is not shown, would not differ significantly.

[0104] The dashed lines schematically represent the path of the ultrasound waves. The lines do not remain within the depicted cross-section, but extend longitudinally along the measuring tube 2', thus connecting the two longitudinally offset transducer elements of each ultrasound transducer pair. Labeling of all principal axes has been omitted.

[0105] The second design has the advantage of achieving a high coverage of the measuring cross-section by the ultrasonic transducer pairs. This leads to greater robustness of the ultrasonic measuring device despite flow asymmetries caused by inlet-side interference sources (e.g., bends, valves, etc.). Furthermore, the compressed measuring cross-section results in flow acceleration within the measuring section. This also ultimately leads to greater robustness compared to ultrasonic measuring devices with conventional hollow cylindrical measuring tube bodies.

[0106] The four off-center ultrasound waves of the second, fourth, sixth and eighth ultrasound transducer pairs detect the higher velocity components of the flowing medium, while the four off-center ultrasound waves of the first, third, fifth and seventh ultrasound transducer pairs detect the lower velocity component of the flowing medium.

[0107] Fig. 6 shows a cross-section through a third embodiment of the ultrasonic measuring device 10" according to the invention, including an embodiment of the measuring tube 1" according to the invention. The measuring tube body 2" has an additional fourth pair of surfaces in the measuring section, comprising a planar seventh and eighth surface PF7, PF8. The seventh surface PF7 runs parallel to the eighth surface PF8, but there is no parallelism between the first, second, third, and seventh surfaces PF1, PF2, PF3, PF7. The first, second, and third pairs of surfaces are shown in Fig. 6. The shape of the measuring section contour MK can be described by a square base with roughly rounded corners. Alternatively, the measuring section contour can be described by an octagon with rounded corners, in which case the widths of the adjacent surfaces differ.

[0108] The first surface PF1, and in particular the third, fourth, and sixth surfaces PF3, PF4, and PF6, has a first width B1, which is dimensioned such that only a single transducer element identical in construction to the other transducer elements can be arranged in the cross-section Q. The second surface PF2, and in particular the fifth, seventh, and eighth surfaces PF5, PF7, and PF8, has a second width B2, which is dimensioned such that two or more transducer elements can be arranged circumferentially offset in the cross-section Q. The measuring tube body 2" is designed such that the two different widths B1 and B2 alternate circumferentially.

[0109] The illustrated 10" ultrasonic measuring device features six pairs of ultrasonic transducers distributed across eight surfaces PF1 to PF8. The transducer elements of each pair are offset in the flow direction. Furthermore, each pair of ultrasonic transducers forms a 1" crossbeam arrangement. This is particularly advantageous for measuring tubes with large nominal diameters, where the measuring path is longer, as it reduces the attenuation of the received ultrasonic wave caused by the medium.

[0110] The illustrated configuration features two pairs of ultrasonic transducers whose principal axes pass centrally through the medium channel, while four pairs of ultrasonic transducers are positioned such that the respective principal axes of the generated ultrasonic waves pass off-center through the medium channel. As shown, two sets of two ultrasonic transducer pairs are provided, whose ultrasonic waves travel essentially parallel through the medium channel. The ultrasonic waves (or their principal axes) generated by the pairs of ultrasonic transducers arranged on the surfaces with width B1 intersect perpendicularly in the center of the medium channel in an orthogonal projection onto the cross-section Q.The third embodiment can include further pairs of ultrasonic transducers arranged on a common planar surface and configured to perform a reference measurement in conjunction with the measuring electronics, based on which the speed of sound of the ultrasonic waves in the measuring tube body is determined. If the speed of sound is known, it can be used to determine the properties of the medium.

[0111] The off-center ultrasound transducer pairs on the planar surfaces PF2, PF5, PF7, PF8 can exhibit a negative error characteristic, which, however, can be compensated for or corrected by the central measurement paths of the ultrasound transducer pairs on the planar surfaces PF1, PF3, PF4, PF6. This results in natural linearity of the measurement signal.

[0112] The third embodiment of measuring tube 1" features a transition section between the inlet and measuring sections. Due to its shape, this transition length can be reduced to less than 50 millimeters, and in particular less than 40 millimeters, without disrupting the flow profile to such an extent that it adversely affects the measurement performance. Thus, a measuring tube length of less than 400 millimeters can be achieved for a maximum sound velocity of 2100 m / s within the measuring tube body. In comparison, a measuring tube with a rectangular shape and a maximum diameter comparable to that of the measuring tube in the inlet section would require a length of 560 millimeters and a transition length of 100 millimeters in the measuring section.

[0113] The ultrasonic measuring device 10" of the third embodiment comprises at least three pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves. The at least three pairs of ultrasonic transducers comprise a first, second and third pair of ultrasonic transducers, which are arranged in the measuring section.

[0114] The first pair of ultrasonic transducers comprises a first and second transducer element W11, W12, wherein the first transducer element W11 is arranged on the first surface PF1 and the second transducer element W12 on the fourth surface PF4. The first and second transducer elements W11, W12 are arranged relative to each other such that they form a 1-crosshead arrangement. Furthermore, the first pair of ultrasonic transducers is arranged on the measuring tube body 2" such that a large portion of the generated ultrasonic wave propagates through the central longitudinal axis of the measuring tube body.

[0115] The second pair of ultrasonic transducers comprises a first and a second transducer element W21, W22, with the first transducer element W21 located on the second surface PF2 and the second transducer element W22 located on the fifth surface PF5. The first and second transducer elements W21, W22 are arranged relative to each other such that they form a 1-crosshead arrangement. The resulting measurement path of the second pair of ultrasonic transducers runs off-center to the measuring tube body 2". The third pair of ultrasonic transducers comprises a first and a second transducer element W31, W32, with the first transducer element W31 located on the second surface PF2 and the second transducer element W32 located on the fifth surface PF5. The first and second transducer elements W21, W22 form a 1-crosshead arrangement. The resulting measurement path runs off-center to the measuring tube body 2".Furthermore, the measurement path of the third ultrasound transducer pair runs parallel to the measurement path of the second ultrasound transducer pair.

[0116] The fourth pair of ultrasonic transducers comprises a first and a second transducer element W41, W42, with the first transducer element W41 located on the third surface PF3 and the second transducer element W42 on the sixth surface PF6. The arrangement of the first and second transducer elements W41, W42 is a single-crosshead configuration. The resulting measurement path along which the generated ultrasonic wave propagates intersects the medium channel – just like the measurement path of the first pair of ultrasonic transducers – in the center.

[0117] The fifth pair of ultrasonic transducers comprises a first and a second transducer element W51, W52, with the first transducer element W51 being located on the seventh surface PF7 and the second transducer element W52 on the eighth surface PF8. The first and second transducer elements W51, W52 form a 1-crosshead arrangement.

[0118] The sixth pair of ultrasonic transducers comprises a first and a second transducer element W61, W62, with the first transducer element W61 located on the seventh surface PF7 and the second transducer element W62 on the eighth surface PF8. The first and second transducer elements W61, W62 form a 1-crosshead arrangement. The measurement paths of the fifth and sixth pairs of ultrasonic transducers run parallel to each other. Both measurement paths run off-center through the medium channel.

[0119] The arrangements of ultrasound transducer pairs of Figs. 4 and 5 can be implemented individually or in combination in ultrasound measuring devices.

[0120] Figures 7 and 8 each show a cross-section through a fourth embodiment of the ultrasonic measuring device 10'" according to the invention, including an embodiment of the measuring tube 1'" according to the invention. Figures 7 and 8 each show different configurations for arranging the pairs of ultrasonic transducers. The shape of the measuring section contour can be approximately described by a three-leaf clover.

[0121] In addition to the three previously introduced pairs of surfaces PF1, PF2, PF3, the measuring tube body 2'" of the fourth embodiment has at least one further fourth pair of surfaces in the measuring section MA. This fourth pair of surfaces comprises a planar seventh and eighth surface PF7, PF8, with the seventh surface PF7 running parallel to the eighth surface PF8. The first, second, third, and seventh surfaces PF1, PF2, PF3, PF7 must not be parallel.

[0122] Furthermore, the measuring tube body 2'" has a fifth pair of planar ninth and tenth surfaces PF9, PF10 in the measuring section. The ninth and tenth surfaces PF9, PF10 are parallel to each other, whereas there is no parallelism between the first, second, third, seventh and ninth surfaces PF1, PF2, PF3, PF7, PF9.

[0123] A specific feature of the fourth embodiment is that the first, second, and third surfaces PF1, PF2, PF3 are oriented relative to each other in such a way that their respective perpendicular lines do not intersect within the interior of the measuring tube body 2 in the cross-section Q, even though the three surfaces PF1, PF2, PF3 are not parallel to each other. The resulting three measuring paths run through a sub-region of the medium in which, as expected, a negative deviation from the actual flow velocity is measured. However, this negative error characteristic cancels out when the measurement signals of the aforementioned three measuring paths are combined with the measurement signals of the measuring paths running centrally through the medium channel.

[0124] Furthermore, the seventh surface PF7 is oriented such that in the cross-section Q a corresponding perpendicular line of the seventh surface PF7 intersects a central longitudinal axis of the measuring tube body 2'".

[0125] Furthermore, the ninth surface PF9 is oriented such that a corresponding perpendicular line of the ninth surface PF9 runs off-center through the interior of the cross-section Q.

[0126] The measuring tube body 2'" has three longest diameters in cross-section through the measuring section. These intersect in pairs at an angle of 120°.

[0127] The illustrated ultrasonic measuring device 10'“ for determining a medium property has at least five pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves.

[0128] The at least five pairs of ultrasound transducers include a first, second, third, fourth and fifth pair of ultrasound transducers, all of which are arranged in the measuring section.

[0129] The first pair of ultrasonic transducers comprises a first and second transducer element W11, W12, wherein the first transducer element W11 and the second transducer element W12 are also arranged on the first surface PF1. The first and second transducer elements W11, W12 form a two-crossbar arrangement. The second pair of ultrasonic transducers comprises a first and a second transducer element W21, W22, wherein the first transducer element W21 and the second transducer element W22 are also arranged on the third surface PF3. The first and second transducer elements W21, W22 form a two-crossbar arrangement.

[0130] The third pair of ultrasonic transducers comprises a first and a second transducer element W31, W32, with the first transducer element W31 being located on the seventh surface PF7 and the second transducer element W32 on the eighth surface PF8. The first and second transducer elements W31, W32 form a 1-crosshead arrangement. The resulting measurement path runs centrally through the medium channel.

[0131] The fourth pair of ultrasonic transducers comprises a first and a second transducer element W41, with the first transducer element W41 located on the ninth surface PF9 and the second transducer element W42 on the tenth surface PF10. The first and second transducer elements W41 and W42 are oriented relative to each other to form a 1-crosshead arrangement. This results in an off-center path through the measurement channel.

[0132] The fifth pair of ultrasonic transducers comprises a first and a second transducer element W51, W52, wherein the first transducer element W51 is arranged on the second surface PF2 and the second transducer element W52 is also arranged on the second surface PF2. The first and second transducer elements W51, W52 are arranged on the measuring tube body 2'" such that they form a 2-T traverse arrangement.

[0133] It may also be required, as shown, that a sixth, seventh, eighth and ninth pair of ultrasonic transducers are arranged on the measuring tube body 2'".

[0134] The sixth pair of ultrasound transducers forms a 1-crossbeam arrangement (see Fig. 7) and the resulting measurement path runs off-center through the medium channel.

[0135] The seventh pair of ultrasound transducers forms a 1-crosshead arrangement (see Fig. 8) and the resulting measurement path runs centrally through the medium channel.

[0136] The eighth pair of ultrasound transducers forms a 1-crossbeam arrangement (see Fig. 7) and the resulting measurement path runs off-center through the medium channel.

[0137] The ninth pair of ultrasonic transducers forms a 1-crossbeam arrangement (see Fig. 8), and the resulting measurement path runs centrally through the medium channel. Further 2-crossbeams can also be implemented on surfaces PF1, PF2, PF3, PF4, PF5, and PF6, arranged opposite the first, second, and third ultrasonic transducer elements, respectively, so that the measurement paths of the ultrasonic transducer pairs arranged on parallel surfaces intersect twice.

[0138] An advantage of the fourth embodiment is that, with the inventive shape of the measuring tube body, sections can be realized in which 2-crossbeam arrangements can be implemented, even though these would produce excessively damped measurement signals in hollow cylindrical measuring tubes. In combination with the 1-crossbeam arrangements, the negative error characteristics can then be compensated for or corrected.

[0139] In contrast to previous designs, the measuring tube body has, in addition to each first, second and third pair of surfaces, a further pair of surfaces on which transducer elements are arranged and which is formed from surfaces that run parallel to the corresponding surfaces of the assigned first, second and third pair of surfaces.

[0140] The following advantageous features also apply to all previously described configurations.

[0141] The measuring tube bodies each have two different diameters in the measuring section. An (inner) first diameter of the measuring tube body is smaller than the (inner) inlet diameter of the measuring tube body in the inlet section, and an (inner) second diameter is larger than the (inner) inlet diameter.

[0142] Figures 4 to 8 do not show the measuring electronics and the housing, as the shape and design of the housing are not essential to the invention. Similarly, for the sake of clarity, the electrical connection between the measuring electronics and the converter elements is not shown.

[0143] The measuring tube body 2 has an (inner) first circumference U1 in an inlet section. Furthermore, the measuring tube body 2 has an (inner) second circumference U2 in the measuring section. It may be required that the first and second circumferences U1 and U2 do not deviate from each other by more than 3%, in particular not by more than 1.5%. It may also be required that the deviation of all (inner) circumferences of the measuring tube body 2 is less than 3%, in particular less than 1.5%, from a mean value or a target value.

[0144] Furthermore, it may be required that the measuring tube body 2 has an outer inlet diameter DE in the inlet section EA and a first and second outer measuring section diameter D1M, D2M in the measuring section. The first and second measuring section diameters D1M, D2M must intersect a central longitudinal axis of the measuring tube. The measuring tube body is shaped such that the first measuring section diameter D1M is larger than the inlet diameter DE and the second measuring section diameter D2M is smaller than the inlet diameter DE.

[0145] Furthermore, the measuring tube 1, or rather the inlet contour, the transition contours, the measuring section contour and the outlet contour, is designed such that it is self-draining at an inclination of <3°, and in particular at least at an inclination of 3°, relative to a horizontal. For the ultrasonic measuring device to be self-draining, an arrangement of the measuring tube 1 within the housing at an inclination about the longitudinal axis of the measuring tube may also be required.

[0146] This involves at least one surface on which two transducer elements are arranged, their sound paths directed towards each other. The aim is to select the ultrasonic wave generated and measured in this way for determining a reference signal, since the ultrasonic wave does not travel through the medium and is therefore not influenced by it, but moves exclusively within the pipe wall or on the pipe surface. With the reference signals determined in this way (or quantities derived from them, such as amplitude, transit time, or a plate wave property, especially a phase velocity), effects such as temperature or material influence can later be compensated for to a certain extent.

[0147] REFERENCE MARK LIST

[0148] Measuring tube 1

[0149] Measuring tube body 2

[0150] Case 30

[0151] Measuring electronics 100

[0152] Cross section Q1, Q2

[0153] Measuring section MA1, MA2

[0154] Measuring section contour MK1, MK2

[0155] Inlet section EA

[0156] Outlet section AA

[0157] Transition section ÜA1, ÜA2, ÜA3

[0158] Measuring section MA1, MA2 planar surface PF1, PF2, PF3, PF4, PF5

[0159] Straight G1, G2, G3

[0160] Scope U1, U2, U3, U4

[0161] Converter element W11, W12, W21, W22 planar inner surface PIF1, PIF2, PIF3, PIF4, PIF5 inner lateral surface iMF

[0162] Plane of symmetry SE

[0163] Main axis HA1, HA2, HA3, HA4, HA5

[0164] Width B

[0165] MHA

Claims

PATENT CLAIMS 1. Measuring tube (1 , 1', 1“, 1 '“) for use in an ultrasonic measuring device, comprising: - a measuring tube body (2), wherein the measuring tube body (2) has a measuring section (MA), wherein the measuring tube body (2) has in the measuring section (MA) external planar first, second and third surfaces (PF1 , PF2, PF3), in particular for attaching transducer elements, wherein the first, second and third surfaces (PF1 , PF2, PF3) are not parallel to each other.

2. Measuring tube (1 ) according to claim 1 , wherein in a cross-section (Q) through the measuring tube body (2) in the measuring section (MA) a first straight line (G1) lying in the planar surface (PF11), a second straight line (G2) lying in the second planar surface (PF2) and a third straight line (G3) lying in the third planar surface (PF3) span a triangle, in particular an isosceles triangle.

3. Measuring tube (1) according to claim 2, wherein in the cross-section (Q) the first straight line (G1) and the second straight line (G2) span an angle α, with 20° < α < 32°, in particular 22° < α < 28° and preferably α = 26°, wherein the fourth straight line (G4) intersects the second straight line (G2) perpendicularly.

4. Measuring tube (1 ) according to one of the preceding claims, wherein the measuring tube body (2) has in cross-section (Q) a curvature with a radius of curvature R, in particular exactly three curvatures each with a radius of curvature R, wherein for the radius of curvature R it holds that 1 < R < 4 millimeters, in particular 2 < R < 3 millimeters and preferably R = 2.1 millimeters.

5. Measuring tube (1 ', 1“, 1'“) according to claim 1, wherein the measuring tube body (2) has a first, second and third pair of surfaces, wherein the first pair of surfaces comprises the first surface (PF1) and a fourth surface (PF4) parallel thereto, wherein the second pair of surfaces comprises the second surface (PF2) and a fifth surface (PF5) parallel thereto, wherein the third pair of surfaces comprises the third surface (PF3) and a sixth surface (PF6) parallel thereto.

6. Measuring tube (1 ') according to claim 5, wherein in the cross-section (Q) the first straight line (G1) and the second straight line (G2) span an angle β, with 130° < β < 142°, in particular 134° < β < 138° and preferably β = 136°.

7. Measuring tube (1 ') according to claim 5 or 6, wherein the measuring tube body (2) has in cross-section (Q) a curvature with a radius of curvature R, in particular exactly six curvatures each with a radius of curvature R, wherein for the radius of curvature R it is that 1 < R < 7 millimeters, in particular 2 < R < 4 millimeters and preferably R = 3 millimeters.

8. Measuring tube (1 “, 1 “') according to one of claims 5 to 7, wherein the measuring tube body (2) has a fourth pair of surfaces in the measuring section (MA), wherein the fourth pair of surfaces has a planar seventh and eighth surface (PF7, PF8), wherein the seventh surface (PF7) is parallel to the eighth surface (PF8), wherein there is no parallelism between the first, second, third and seventh surfaces (PF1 , PF2, PF3, PF7).

9. Measuring tube (1 “, 1 “') according to one of the preceding claims, wherein the first surface (PF1) has a first width B1 which is dimensioned such that only a single transducer element can be arranged in the cross-section (Q), wherein the, in particular adjacent, second surface (PF2) has a second width B2 which is dimensioned such that two or more transducer elements can be arranged offset in the circumferential direction in a cross-section.

10. Measuring tube (1 “') according to claim 8 or 9, wherein the measuring tube body (2) has a fifth pair of surfaces in the measuring section, wherein the fifth pair of surfaces comprises a planar ninth and tenth surface (PF9, PF10), in particular for attaching at least one transducer element, wherein the ninth and tenth surfaces (PF9, PF10) are parallel to each other, wherein there is no parallelism between the first, second, third, seventh and ninth surfaces (PF1 , PF2, PF3, PF7, PF9).

11. Measuring tube (1"') according to one of the preceding claims, wherein the first, second and third surfaces (PF1 , PF2, PF3) are oriented relative to each other such that their respective perpendicular lines do not intersect in the interior of the measuring tube body (2) in the cross-section (Q), and / or wherein the seventh surface (PF7) is oriented such that a corresponding perpendicular line of the seventh surface (PF7) intersects a longitudinal axis, in particular a center point of the interior, in the cross-section (Q), and / or wherein the ninth surface (PF9) is oriented such that a corresponding perpendicular line of the ninth surface (PF9) passes eccentrically through the interior in the cross-section (Q).

12. Measuring tube (1 , 1 ', 1“, 1“') according to one of the preceding claims, wherein the measuring tube body (2) has a measuring section contour (MK) in the measuring section (MA), wherein the measuring tube body (2) has an inlet section (EA) and an outlet section (AA), wherein the measuring tube body (2) has a first transition section (ÜA1) between inlet section (EA) and measuring section (MA), and wherein the measuring tube body (2) has a second transition section (ÜA2) between outlet section (AA) and measuring section (MA).

13. Measuring tube (1', 1", 1'") according to claim 12, wherein the measuring tube body (2) has an inner first circumference (U1) in the inlet section (EA), wherein the measuring tube body (2) has an inner second circumference (U2) in the measuring section (MA), wherein the first and second circumferences (U1, U2) do not differ from each other by more than 3%, in particular not by more than 1.5%.

14. Measuring tube (1', 1", 1'") according to claim 12, wherein the measuring tube body (2) has an outer inlet diameter (DE) in the inlet section (EA), wherein the measuring tube body (2) has a first and second outer measuring section diameter (D1 M, D2M) in the measuring section (MA), wherein the first and second measuring section diameter (D1 M, D2M) intersect a longitudinal axis of the measuring tube, wherein the first measuring section diameter (D1 M) is larger than the inlet diameter (DE), wherein the second measuring section diameter (D2M) is smaller than the inlet diameter (DE).

15. Measuring tube (1', 1“, 1'“) according to one of the preceding claims, wherein the measuring tube (1) is designed such that it is self-emptying at an inclination of <3°, in particular at least at an inclination of 3°, relative to a horizontal.

16. Ultrasonic measuring device (10) for determining a medium property, comprising: - a measuring tube (1') produced in particular by means of a hydroforming process according to one of claims 1 to 4, wherein the measuring tube (1) is configured to guide a medium; - at least one pair of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least one pair of ultrasonic transducers comprises a first pair of ultrasonic transducers arranged in the measuring section (MA), wherein the first pair of ultrasonic transducers has a first and second transducer element (W11, W12), wherein the first transducer element (W11) is arranged on the second surface (PF2), wherein the second converter element (W12) is arranged on the third surface (PF3), wherein the first and second converter elements (W11 , W12) form a 2-crossbeam arrangement; - measuring electronics which are electrically connected to the at least one pair of ultrasonic transducers, wherein the measuring electronics are configured to determine the medium property as a function of at least one measured value from the at least one pair of ultrasonic transducers; and - a housing (30), wherein the housing (30) surrounds at least one pair of ultrasonic transducers.

17. Ultrasonic measuring device (10') for determining a medium property, comprising: - a measuring tube (1") produced in particular by means of a hydroforming process according to one of claims 5 to 7, wherein the measuring tube (1) is configured to carry a medium; - at least two pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least two pairs of ultrasonic transducers comprise a first and a second pair of ultrasonic transducers arranged in the measuring section (MA), wherein the first pair of ultrasonic transducers comprises a first and a second transducer element (W11, W12), wherein the first transducer element (W11) is arranged on the second (third) surface (PF2), wherein the second transducer element (W12) is arranged on the sixth (fifth) surface (PF6), wherein the first and second transducer elements (W11, W12) form a 2-crossbeam arrangement, wherein the second pair of ultrasonic transducers is arranged in the measuring section (MA) such that a principal axis (HA2) of the generating ultrasonic wave is eccentric to the measuring tube body (2), wherein the second pair of ultrasonic transducers comprises a first and a second transducer element (W21, W22),wherein the first converter element (W21) is arranged on the first surface (PF1), wherein the second converter element (W22) is arranged on the fourth surface (PF4), wherein the first and second converter elements (W21, W22) form a 1- or 2-crossbeam arrangement; - a measuring electronics (100) which is electrically connected to the at least two pairs of ultrasonic transducers, wherein the measuring electronics (100) is configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and - a housing (30) wherein the housing (30) surrounds the at least two pairs of ultrasonic transducers.

18. Ultrasonic measuring device (10") for determining a medium property, comprising: - a measuring tube (1"') according to claim 8 or 9, in particular produced by means of a hydroforming process, wherein the measuring tube (1) is configured to guide a medium; - at least three pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least three pairs of ultrasonic transducers comprise a first, second and third pair of ultrasonic transducers arranged in the measuring section (MA), wherein the first pair of ultrasonic transducers has a first and second transducer element (W11, W12), wherein the first transducer element (W11) is arranged on the first surface (PF1), wherein the second transducer element (W12) is arranged on the fourth surface (PF4), wherein the first and second transducer elements (W11, W12) form a 1-crossbeam arrangement, wherein the second pair of ultrasonic transducers is arranged in the measuring section (MA) such that a principal axis (HA2) of the generating ultrasonic wave is eccentric to the measuring tube body (2), wherein the second pair of ultrasonic transducers has a first and a second transducer element (W21, W22),wherein the first transducer element (W21) is arranged on the second surface (PF2), wherein the second transducer element (W22) is arranged on the fifth surface (PF5), wherein the first and second transducer elements (W21, W22) form a 1-crossbeam arrangement; wherein the third ultrasonic transducer pair is arranged in the measuring section (MA) such that a principal axis (HA3) of the generating ultrasonic wave is eccentric to the measuring tube body (2), wherein the third ultrasonic transducer pair comprises a first and a second transducer element (W31, W32), wherein the first transducer element (W31) is arranged on the second surface (PF2), wherein the second transducer element (W32) is arranged on the fifth surface (PF5), and wherein the first and second transducer elements (W21, W22) form a 1-crossbeam arrangement; - a measuring electronics (100) which is electrically connected to the at least three pairs of ultrasonic transducers, wherein the measuring electronics (100) is configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and - a housing (30) wherein the housing (30) surrounds the at least three pairs of ultrasonic transducers.

19. Ultrasonic measuring device (10'") for determining a medium property, comprising: - a measuring tube (1"') according to one of claims 10 to 15, in particular produced by means of a hydroforming process, wherein the measuring tube (1) is configured to guide a medium; - at least five pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least five pairs of ultrasonic transducers comprise a first, second, third, fourth and fifth pair of ultrasonic transducers arranged in the measuring section (MA), wherein the first pair of ultrasonic transducers comprises a first and second transducer element (W11, W12), wherein the first transducer element (W11) is arranged on the first surface (PF1), wherein the second transducer element (W12) is arranged on the first surface (PF1), wherein the first and second transducer elements (W11, W12) form a 2-crossbeam arrangement, wherein the second pair of ultrasonic transducers comprises a first and a second transducer element (W21, W22), wherein the first transducer element (W21) is arranged on the third surface (PF3), wherein the second transducer element (W22) is arranged on the third surface (PF3), wherein the first and second converter element (W21 ,W22) form a 2-crossbeam arrangement, wherein the third ultrasonic transducer pair comprises a first and a second transducer element (W31, W32), wherein the first transducer element (W31) is arranged on the seventh surface (PF7), wherein the second transducer element (W32) is arranged on the eighth surface (PF8), wherein the first and second transducer elements (W31, W32) form a 1-crossbeam arrangement, and / or wherein the fourth ultrasonic transducer pair comprises a first and a second transducer element (W41, W42), wherein the first transducer element (W41) is arranged on the ninth surface (PF9), wherein the second transducer element (W42) is arranged on the tenth surface (PF10), wherein the first and second transducer elements (W41, W42) form a 1-crossbeam arrangement, wherein the fourth ultrasonic transducer pair is arranged in the measuring section (MA) such that a principal axis (HA4) of the generating ultrasound wave runs off-center to the measuring tube body (2),and / or wherein the fifth ultrasonic transducer pair comprises a first and a second transducer element (W51, W52), wherein the first transducer element (W51) is arranged on the second surface (PF2), wherein the second transducer element (W52) is arranged on the second surface (PF2), wherein the first and second transducer elements (W51, W52) form a 2-crossbeam arrangement, - a measuring electronics (100) which is electrically connected to the at least five pairs of ultrasonic transducers, wherein the measuring electronics (100) is configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and - a housing (30) wherein the housing (30) surrounds the at least five pairs of ultrasonic transducers.

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