Measurement assembly for determining a property of a multiphase flowable medium

Abstract

The invention relates to a measurement assembly (1) for determining a property of a multiphase flowable medium, comprising: - a measuring tube (2) for conveying the medium, wherein the measuring tube (2) has a first antenna receptacle (3), - a first microwave antenna device (5) which is arranged in the first antenna receptacle (3), wherein the first microwave antenna device (5) is designed so as to emit a first microwave signal (A) and a second microwave signal (B), wherein the first microwave signal (A) has a first main radiation direction and the second microwave signal (B) has a second main radiation direction which differs from the first main radiation direction; and - a measurement circuit (9), wherein the measurement circuit (9) is connected to the first microwave antenna device (5), wherein the measurement circuit (9) has a high-frequency generator for supplying the first microwave antenna device (5) with the first microwave signal (A) and the second microwave signal (B), wherein the measurement circuit (9) is configured to determine the property of the medium at least based on the measured first microwave signal (A*), wherein the measurement circuit (9) is configured to detect an inhomogeneity in the measuring tube (2) based on the measured first microwave signal (A*) and the measured second microwave signal (B*).

Description

[0001] MEASURING ARRANGEMENT FOR DETERMINING A PROPERTY OF A MULTI-PHASE, FLOWABLE MEDIUM

[0002] The invention relates to a measuring arrangement for determining a property of a multi-phase, flowable medium by means of a microwave antenna device.

[0003] Microwaves can be used to determine the physical quantities of permittivity and loss factor of a medium in a process line. These two quantities – measured either at one or across many different frequencies – can be used to draw conclusions about application-specific parameters, such as the water content in a mixture of water and other non-polar or slightly polar components, or the solid content in a liquid medium.

[0004] The established transmission-Z-reflection measurement is described in LF Chen, CK Ong, CP Neo, VV Varadan, VK Varadan - “Microwave Electronics, Measurement and Materials Characterization”, John Wiley & Sons Ltd., 2004. For this purpose, the microwave signal is coupled to the medium in a container or measuring tube at two different positions, the scattering parameters (transmission and, if applicable, reflection) between these coupling structures are measured, and the measured scattering parameters are used to calculate the physical properties of the medium.

[0005] WO 2018 / 121927 A1 teaches a measuring arrangement for analyzing the properties of a flowing medium using microwaves. In addition to the microwave antennas, the measuring arrangement comprises an electrically insulating lining layer on the inner surface of the measuring tube. This lining layer forms a dielectric waveguide through which a microwave signal can be transmitted, at least in part, from a first microwave antenna to a second microwave antenna. One application for such a measuring arrangement is the determination of solids content in the liquid medium being conveyed. WO 2021 / 099152 A1 teaches a microwave antenna having a front section in contact with the medium, through which the excitation signal is radiated into the medium.

[0006] Processes in which solids are present in the medium suffer from the deposition of solids on the inner wall of the measuring tube and sedimentation. WO 2016 / 075367 A1 discloses a method for detecting deposits on the microwave antennas used in contact with the medium. In addition to the two conventional opposing microwave antennas, at least one additional microwave antenna is used, which is arranged on the measuring tube in such a way that two measuring paths of different lengths are created. Based on the time between the transmission and reception of the microwave signals (time of flight) for the two measuring paths, the presence of a deposit is determined. A disadvantage of this solution is that at least a third microwave antenna is required.

[0007] The invention is based on the object of providing an alternative. This object is achieved by the measuring arrangement according to claim 1 and the method according to claim 16.

[0008] The measuring arrangement according to the invention for determining a property of a multi-phase, flowable medium, comprising:

[0009] - a measuring tube for guiding the medium, wherein the measuring tube has a first antenna receptacle,

[0010] - a first microwave antenna device arranged in the first antenna receptacle, wherein the first microwave antenna device is configured to emit a first microwave signal and a second microwave signal, wherein the first microwave signal has a first main beam direction and the second microwave signal has a second main beam direction deviating from the first main beam direction; and

[0011] - a measuring circuit, wherein the measuring circuit is connected to the first microwave antenna device, wherein the measuring circuit has a high-frequency generator for feeding the first microwave antenna device with the first microwave signal and the second microwave signal, wherein the measuring circuit is configured to determine the property of the medium at least on the basis of the measured first microwave signal, wherein the measuring circuit is configured to detect an inhomogeneity in the measuring tube on the basis of the measured first microwave signal and the measured second microwave signal.

[0012] In contrast to WO 2016 / 075367 A1, the two measurement paths are realized by two microwave signals with different main beam directions, rather than by two microwave antenna pairs. This can be achieved using just one microwave antenna, which is configured not only to transmit the first microwave signal and the second microwave signal into the measuring tube, but also to receive them again once they have passed through the medium. The advantage of this is that no additional microwave antenna device is required in addition to the number of microwave antenna devices already sufficient for determining the properties of the multiphase medium. Each additional microwave antenna device requires a corresponding antenna mount on the measuring tube, which creates a potential leak point. Furthermore, each microwave antenna device is associated with additional costs.Furthermore, it is also more complex to provide electronics that can process more than two signal paths.

[0013] Advantageous embodiments of the invention are the subject of the subclaims.

[0014] One embodiment provides that the second main beam direction is selected such that a propagation direction of the microwave signal changes between the transmission and the reception of the second microwave signal.

[0015] The second main beam direction with which the second microwave signal is emitted is preferably selected such that the propagation direction changes at least once during the propagation of the second microwave signal through the medium. The change in the propagation direction results from the reflection of the second microwave signal from the inner wall of the measuring tube and / or from a medium boundary.

[0016] One embodiment provides that the first main beam direction points radially into the measuring tube.

[0017] One embodiment provides that the first microwave antenna device is designed to be pivotable, in particular mechanically.

[0018] The generation of the two microwave signals with different main beam directions can be achieved by designing the first microwave antenna so that it can be mechanically pivoted. The first microwave antenna device accordingly comprises a mechanical pivoting device configured to mechanically align the microwave antenna. This allows the two main beam directions to be adjusted. The pivoting device can, for example, comprise at least one electrically controllable piezo element that interacts with the microwave antenna in such a way that the main beam direction of the microwave signal emitted by the microwave antenna can be controlled via the voltage applied to the piezo element. This allows an electromechanical solution for pivoting the microwave antenna device to be implemented.

[0019] The pivoting allows operation in at least two modes. One is the standard mode for optimal determination of the solids content. The other is a diagnostic mode for detecting deposits or partial fillings. One embodiment provides that the first microwave antenna device is designed to electronically pivot the first main beam direction of the second microwave signal.

[0020] The generation of two microwave signals with different main beam directions can be achieved by designing the first microwave antenna device so that it can be electronically pivoted. Microwave antenna devices are known that are suitable for generating microwave signals with different main beam directions.

[0021] An example of this would be the phased array antenna, which is a phased-array antenna with strong directivity. It achieves a focusing of the radiated energy and thus electronic beam steering through the arrangement and interconnection of individual transmitting elements (at least two microwave antennas). The array antenna utilizes the phase shift of the individual transmitting elements arranged in the array to achieve focusing through interference of the individually generated microwave signals. The transmitted energy is amplified in the desired main field direction, while the undesired directions are canceled out by destructive interference.

[0022] One embodiment provides that the two microwave signals are fed into the medium simultaneously, in particular due to an excitation of two modes of the microwave antenna device by means of an excitation signal with at least two different excitation frequencies or by means of at least two excitation signals with different excitation frequencies.

[0023] The waveguide of the microwave antenna can be designed such that not only one mode with exactly one characteristic field pattern propagates within the desired frequency band, but at least two modes form. These modes can be excited by different frequencies, resulting in microwave signals with different main beam directions. Thus, to generate the two microwave signals, it is possible to feed either an excitation signal with at least two different frequencies into the waveguide, or two excitation signals with different frequencies offset in time. Separation of the two measured microwave signals would be possible if the two frequencies were chosen to be sufficiently different.

[0024] One embodiment provides that the measuring arrangement further includes:

[0025] - a second microwave antenna device, which is arranged in a second antenna receptacle of the measuring tube, in particular oriented opposite the first antenna receptacle, wherein the second microwave antenna device is configured to measure the first microwave signal and the second microwave signal. One embodiment provides that the second microwave antenna device is designed to be mechanically pivotable, or wherein the second microwave antenna device is designed to electronically pivot the second main beam direction of the second microwave signal.

[0026] The advantage of limiting the number of microwave antenna devices to exactly two is a more compact, and in particular shorter, design of the measuring arrangement.

[0027] One embodiment provides that the first main beam direction points along a shortest connection between the first microwave antenna device and the second microwave antenna device.

[0028] One embodiment provides that the measuring arrangement comprises a position sensor which is configured to determine a current orientation of the measuring tube and / or the first microwave antenna device relative to the earth, wherein the measuring circuit is configured to take into account the current orientation of the measuring tube when detecting the inhomogeneity, in particular when determining a cause for the inhomogeneity.

[0029] With the help of the position sensor, it is possible to distinguish whether a detected inhomogeneity is due to the formation of deposits or a partial filling of the measuring tube.

[0030] One embodiment provides that the measuring circuit is configured to determine a first measured value for a solid content of the medium from the measured first microwave signal, wherein the measuring circuit is configured to determine a second measured value for the solid content from the measured second microwave signal, wherein the first measured value and the second measured value are included in the detection of the inhomogeneity, in particular in a determination of a cause for the inhomogeneity.

[0031] One embodiment provides that the first microwave antenna device is configured to emit a third microwave signal with a third main beam direction, wherein the third main beam direction of the third microwave signal differs from the first main beam direction and the second main beam direction, wherein the measuring circuit is configured to detect an inhomogeneity in the measuring tube based on the first microwave signal, the second microwave signal and a third microwave signal. One embodiment provides that a measuring tube longitudinal section running through the first microwave antenna device divides the measuring tube into a first measuring tube section and a second measuring tube section, wherein the second main beam direction points into the first measuring tube section and the third main beam direction points into the second measuring tube section.

[0032] One embodiment provides that the inhomogeneity comprises a, in particular asymmetric, deposit formation, a partial filling of the measuring tube and / or a sedimentation formation.

[0033] One embodiment provides that the first main beam direction and the second main beam direction lie in a common measuring tube cross-section of the measuring tube which intersects at least the first microwave antenna device.

[0034] One embodiment provides that the second main beam direction, in particular the second main beam direction and the third main beam direction, has a directional component that points in the longitudinal direction of the measuring tube.

[0035] If the second main beam direction has a directional component that points in the longitudinal direction of the measuring tube, additional information about the properties of the medium outside the measuring cross-section can be determined. With a vertical orientation of the measuring arrangement in the process line and a partial filling of the measuring tube, the partial filling itself can be detected.

[0036] The method according to the invention for determining an inhomogeneity in a measuring tube by means of a measuring arrangement according to one of the preceding claims, comprising the method steps:

[0037] - emitting a first microwave signal having a first main beam direction into the measuring tube by means of a first microwave antenna device;

[0038] - receiving the first microwave signal after transmission, in particular by means of a second microwave antenna device, wherein the received first microwave signal results at least from the transmitted first microwave signal and its interaction with the medium;

[0039] - Emitting a second microwave signal with a second main beam direction into the measuring tube by means of the first microwave antenna device, wherein the first main beam direction differs from the second main beam direction; - Receiving the second microwave signal after emission, in particular by means of a second microwave antenna device, wherein the received second microwave signal results at least from the second microwave transmission signal and its interaction with the medium, wherein the second microwave signal is reflected at least once on an inner surface of the measuring tube, so that the second propagation direction changes spatially at least once between the emission of the second microwave signal and the reception of the second microwave signal;

[0040] - Detecting whether there is an inhomogeneity in the measuring tube depending on the received first microwave signal and the second microwave signal.

[0041] An embodiment of the method according to the invention comprises:

[0042] - emitting a third microwave signal having a third main beam direction into the measuring tube by means of the first microwave antenna device;

[0043] - receiving the third microwave signal after transmission, in particular by means of the second microwave antenna device, wherein the received third microwave signal results at least from the transmitted third microwave signal and its interaction with the medium;

[0044] - Detecting whether there is an inhomogeneity in the measuring tube depending on the received first microwave signal, second microwave signal and third microwave signal.

[0045] The invention is explained in more detail with reference to the following figures. They show:

[0046] Fig. 1: a cross-section through an embodiment of the measuring arrangement according to the invention;

[0047] Fig. 2 : a cross section through a further embodiment of the measuring arrangement according to the invention;

[0048] Fig. 3 : a longitudinal section through a further embodiment of the measuring arrangement according to the invention; and

[0049] Fig. 4 : a cross section through a further embodiment of the measuring arrangement according to the invention.

[0050] Fig. 1 shows a cross-section through an embodiment of the measuring arrangement 1 according to the invention for determining a property of a multiphase, flowable, water-based medium. The measuring arrangement 1 comprises a measuring tube 2 for conveying the essentially aqueous medium with solid components. In the embodiment shown here, the measuring tube 2 is cylindrical and has a metallic inner measuring tube wall. Other measuring tube shapes that are homeomorphic to the cylindrical geometry are also provided according to the invention.

[0051] A first antenna receptacle 3 in the form of a measuring tube opening is incorporated into the measuring tube 2. The measuring tube 2 can be made of metal, and the measuring tube opening can be realized by a bore. A first microwave antenna device 5 is arranged in a medium-tight manner in the first antenna receptacle 3. The first microwave antenna device 5 has at least one microwave antenna. Furthermore, the first microwave antenna device 5 can have a holder for the at least one microwave antenna, which is configured to hold the microwave antenna stationary in the measuring tube opening. The first microwave antenna device 5 is designed to emit a first microwave signal A and a second microwave signal B. The two microwave signals differ essentially in their respective propagation directions.The first microwave signal A has a first main beam direction a with which the microwave signal A is radiated into the medium, and the second microwave signal B has a second main beam direction b, which deviates from the first main beam direction a and with which the second microwave signal B is radiated into the medium. The two microwave signals pass through the measuring tube and interact with the medium flowing through the measuring tube (see first microwave signal A' and second microwave signal B'). The second microwave signal B' is reflected once off the inner wall of the measuring tube. The second main beam direction b is selected such that a propagation direction of the microwave signal changes between the transmission of the second microwave signal B and the reception of the second microwave signal B*.The first main beam direction a and the second main beam direction b lie in a common measuring tube cross-section Y of the measuring tube 2 which intersects at least the first microwave antenna device 5.

[0052] The first microwave antenna device 5 is suitable for beam sweeping. This can be achieved by a mechanical or electromechanical sweeping device, so that the first microwave antenna device 5 is designed to be mechanically sweepable. Alternatively, the first microwave antenna device 5 can be designed to sweep the microwave signal electronically to produce a first main beam direction a and a second main beam direction b. For this purpose, the first microwave antenna device 5 has at least two microwave antennas arranged in an array. The first microwave antenna device 5 is configured to shift the phase position of the microwave antennas such that different main beam directions can be set through interference and focusing.

[0053] The illustrated measuring arrangement 1 further comprises a second microwave antenna device 6, which is arranged in a second antenna receptacle 4 of the measuring tube 2, oriented in particular opposite the first antenna receptacle 3. Thus, the first main beam direction a points along a shortest connection between the first microwave antenna device 5 and the second microwave antenna device 6.

[0054] The second microwave antenna device 6 is configured to receive and measure the first microwave signal A* and the second microwave measurement signal B*. The first microwave signal A' takes the direct path to the second microwave antenna device 6, i.e., it is not reflected. The first microwave signal A' interacts with the medium on the way to the second microwave antenna device 6, so that the measured first microwave signal A* contains information from the medium. The same applies to the second microwave signal B' and the measured second microwave signal B*. The second microwave antenna device 6 can also be designed to be mechanically pivotable. Alternatively, the second microwave antenna device 6 can be designed such that the second main beam direction b of the second microwave signal B can be pivoted electronically.

[0055] The measuring arrangement 1 further comprises a measuring circuit 9, which is connected to the first microwave antenna device 5 and the second microwave antenna device 6. To generate the microwave signals, the measuring circuit 9 comprises a high-frequency generator. The high-frequency generator generates a first microwave signal A, which is fed into the medium or into the interior of the measuring tube via the first microwave antenna device 5. The second microwave signal B is also generated via the high-frequency generator and fed into the medium or the interior of the measuring tube via the first microwave antenna device 5. The measuring circuit 9 is configured to measure the first microwave signal A* and the second microwave signal B*, which have passed through the interior of the measuring tube, at the second microwave antenna device 6. The first microwave signal A and the second microwave signal B propagate through the medium.This results in an interaction between the microwave signals A, B and the medium, which changes the microwave signals A, B.

[0056] The measuring circuit 9 is further configured to determine a first measured value for a solids content of the medium from the measured first microwave signal A* and a second measured value for the solids content from the measured second microwave signal B*. Using an algorithm, the inhomogeneity is then detected based on the first measured value and the second measured value. The inhomogeneities can be a deposit formation, particularly asymmetrical, a partial filling of the measuring tube 2, and / or a sedimentation formation.

[0057] Fig. 2 shows a cross-section through a further embodiment of the measuring arrangement 1 according to the invention. The measuring arrangement shown differs essentially from the embodiment of Fig. 1 in that the measuring arrangement 1 has only one microwave antenna device. This is configured to emit a first microwave signal A with a first main beam direction a, which points, in particular radially, into the measuring tube 2. The generated first microwave signal A propagates along the measuring tube diameter (becoming the first microwave signal A' upon interaction with the medium) and is reflected back on the opposite side of the first microwave antenna device 5. The first microwave signal A* is measured at the first microwave antenna device 5. The resulting measurement path corresponds to twice the inner diameter of the measuring tube 2.The first microwave antenna device 5 is further configured to emit a second microwave signal B having a second main field direction b with which the microwave signal B is emitted, which deviates from the first main field direction a. The second main field direction b is selected such that the second microwave signal B is reflected three times at the inner wall and propagated back to the emitting first microwave antenna device 5, where it is measured. Alternatively, the second main field direction b can be selected such that the microwave signal is reflected only twice at the inner wall before being detected by the first microwave antenna device 5. Alternatively, the second main field direction b can also be selected such that the microwave signal is reflected more than three times at the inner wall before being detected by the first microwave antenna device 5.

[0058] Fig. 3 shows a longitudinal section through a further embodiment of the measuring arrangement 1 according to the invention. The measuring arrangement 1 has a vertical mounting orientation, i.e. the longitudinal axis of the measuring arrangement 1 or of the measuring tube intersects the earth's surface essentially perpendicularly. One potential application is the use of the measuring arrangement 1 in a riser pipe. In such applications, the measuring tube may become partially filled if the medium to be conveyed comes to a standstill and (partial) backflow of the medium occurs. In order to detect the installation position, the measuring arrangement 1 has a position sensor 7 which is designed to determine a current orientation of the measuring tube 2 and / or the first microwave antenna device 5 relative to the earth or gravity. The determined orientation is then included in the detection of the inhomogeneity, in particular in determining a cause for the inhomogeneity.As indicated, the position sensor 7 can be arranged in a common module with the measuring circuit 9. Alternatively, the position sensor 7 can also be arranged in the sensor itself.

[0059] The measuring arrangement 1 has a first microwave antenna device 5 and a second microwave antenna device 6. The first microwave antenna device 5 is designed to radiate a first microwave signal A radially into the measuring tube. The first main beam direction a lies essentially in the cross-sectional plane Y, which intersects the two microwave antenna devices and is oriented perpendicular to the longitudinal axis of the measuring tube. Furthermore, the first microwave antenna device 5 is suitable for emitting a second microwave signal B with a second main beam direction b. The second main beam direction b has a directional component that points in the longitudinal direction of the measuring tube 2. The second main beam direction b thus points out of the cross-sectional plane Y. If the measuring tube is partially filled orthe process line, the second microwave signal B' propagating through the medium is reflected at the medium boundary and measured by the second microwave antenna device 6. The measuring circuit 9 is configured to determine whether the measuring tube is partially filled based on the measured microwave signal B* and the determined orientation.

[0060] Fig. 4 shows a cross-section through a further embodiment of the measuring arrangement 1 according to the invention. The embodiment of Fig. 4 differs from the embodiment of Fig. 1 essentially in that the first microwave antenna device 5 is also designed to emit a third microwave signal C with a third main beam direction c. The third main beam direction c of the third microwave signal C differs from the first main beam direction a and the second main beam direction b. A measuring tube longitudinal section X running through the first microwave antenna device 5 divides the measuring tube 2 into a first measuring tube section I and a second measuring tube section II. In the embodiment shown, the longitudinal axis of the measuring tube also lies in the measuring tube longitudinal section X.What is important for the embodiment shown is that the second main beam direction b points into the first measuring tube section I and the third main beam direction c points into the second measuring tube section II. The measuring circuit 9 is configured to detect an inhomogeneity in the measuring tube 2 based on the first microwave signal A*, the second microwave signal B* and the third microwave signal C* measured at the second microwave antenna device 6. Sedimentation can form in the second measuring tube section II, particularly when the measuring arrangement 1 is installed horizontally. Sedimentation differs from deposit formation in that the solids in the medium are not deposited substantially uniformly over the entire inner circumference of the inner wall, but exclusively in a lower section of the measuring tube. The third microwave signal C' propagates through the medium and also through the sediment.Using the measured third microwave signal C*, it is possible to distinguish whether sedimentation or deposit formation is present. If there is a uniform deposit formation along the circumference of the measuring tube, the measured second microwave signal B* essentially agrees with the measured third microwave signal C*. If sedimentation is present, the two measured microwave signals B* and C* differ more significantly from each other.

[0061] LIST OF REFERENCE SYMBOLS

[0062] Measuring arrangement 1

[0063] Measuring tube 2 first antenna receptacle 3 second antenna receptacle 4 first microwave antenna device 5 second microwave antenna device 6 position sensor 7 measuring circuit 9 first microwave signal A first main beam direction a second microwave signal B second main beam direction b third microwave signal C third main beam direction c measured first microwave signal A* measured second microwave signal B* measured third microwave signal C* first measuring tube section I second measuring tube section II measuring tube longitudinal section X measuring tube cross section Y

Claims

PATENT CLAIMS 1. Measuring arrangement (1) for determining a property of a multi-phase, flowable medium, comprising: - a measuring tube (2) for guiding the medium, wherein the measuring tube (2) has a first antenna receptacle (3), - a first microwave antenna device (5) arranged in the first antenna receptacle (3), wherein the first microwave antenna device (5) is configured to emit a first microwave signal (A) and a second microwave signal (B), wherein the first microwave signal (A) has a first main beam direction (a) and the second microwave signal (B) has a second main beam direction (b) deviating from the first main beam direction (a); and - a measuring circuit (9), wherein the measuring circuit (9) is connected to the first microwave antenna device (5), wherein the measuring circuit (9) has a high-frequency generator for feeding the first microwave antenna device (5) with the first microwave signal (A) and the second microwave signal (B), wherein the measuring circuit (9) is designed to determine the property of the medium at least on the basis of the measured first microwave signal (A*), wherein the measuring circuit (9) is designed to detect an inhomogeneity of a measuring tube content, in particular of the medium in the measuring tube (2), on the basis of the measured first microwave signal (A*) and the measured second microwave signal (B*).

2. Measuring arrangement (1) according to claim 1, wherein the second main beam direction is selected such that a propagation direction of the microwave signal changes between the transmission and the reception of the second microwave signal.

3. Measuring arrangement (1) according to claim 1 or 2, wherein the first main beam direction (a) points radially into the measuring tube (2) and / or in the direction of a longitudinal axis of the first microwave antenna device (5).

4. Measuring arrangement (1) according to at least one of the preceding claims, wherein the first microwave antenna device (5) is designed to be pivotable, in particular mechanically.

5. Measuring arrangement (1) according to one of the preceding claims, wherein the first microwave antenna device (5) is designed to electronically pivot the second main beam direction (b) of the second microwave signal (B).

6. Measuring arrangement (1) according to one of the preceding claims, comprising: - a second microwave antenna device (6) which is arranged in a second antenna receptacle (4) of the measuring tube (2), in particular oriented opposite to the first antenna receptacle (3), wherein the second microwave antenna device (6) is configured to measure the first microwave signal (A*) and the second microwave measurement signal (B*).

7. Measuring arrangement (1) according to claim 6, wherein the second microwave antenna device (6) is designed to be pivotable, in particular mechanically, or wherein the second microwave antenna device (6) is designed to be pivotable electronically. [can be aligned so that the emitted microwave signal can be measured] 8. Measuring arrangement (1) according to claim 6 or 7, wherein the first main beam direction (a) points along a shortest connection between the first microwave antenna device (5) and the second microwave antenna device (6).

9. Measuring arrangement (1) according to one of the preceding claims, wherein the measuring arrangement (1) comprises a position sensor (7) which is designed to determine a current orientation of the measuring tube (2) and / or the first microwave antenna device (5) relative to the earth's gravity, wherein the measuring circuit (9) is designed to take the current orientation of the measuring tube (2) into account when detecting the inhomogeneity, in particular when determining a cause for the inhomogeneity.

10. Measuring arrangement (1) according to one of the preceding claims, wherein the measuring circuit (9) is set up to determine a first measured value for a solid content of the medium from the measured first microwave signal (A*), wherein the measuring circuit (9) is set up to determine a second measured value for the solid content from the measured second microwave signal (B*), and / or wherein the first measured value and the second measured value are included in the detection of the inhomogeneity, in particular in a determination of a cause for the inhomogeneity.

11. Measuring arrangement (1) according to one of the preceding claims, wherein the first microwave antenna device (5) is configured to emit a third microwave signal (C) with a third main beam direction (c), wherein the third main beam direction (c) of the third microwave signal (C) differs from the first main beam direction (a) and the second main beam direction (b), wherein the measuring circuit (9) is configured to detect an inhomogeneity in the measuring tube (2) on the basis of the first microwave signal (A*), the second microwave signal (B*) and a third microwave signal (C*).

12. Measuring arrangement (1) according to claim 11, wherein a measuring tube longitudinal section (X) running through the first microwave antenna device (5) divides the measuring tube (2) into a first measuring tube section (I) and a second measuring tube section (II), wherein the second main beam direction (b) points into the first measuring tube section (I) and the third main beam direction (c) points into the second measuring tube section (II).

13. Measuring arrangement (1) according to at least one of the preceding claims, wherein the inhomogeneity comprises a, in particular asymmetric, deposit formation, a partial filling of the measuring tube (2) and / or a sedimentation formation.

14. Measuring arrangement (1) according to at least one of the preceding claims, wherein the first main beam direction (a) and the second main beam direction (b) lie in a common measuring tube cross-section (Y) of the measuring tube (2) which intersects at least the first microwave antenna device (5).

15. Measuring arrangement (1) according to at least one of claims 1 to 13, wherein the second main beam direction (b), in particular the second main beam direction (b) and the third main beam direction (c), has a directional component which points in the longitudinal direction of the measuring tube (2).

16. Method for determining an inhomogeneity in a measuring tube (2), in particular by means of a measuring arrangement (1) according to one of the preceding claims, comprising the method steps: - emitting a first microwave signal (A) with a first main beam direction (a) by means of a first microwave antenna device (5) into the measuring tube (2); - receiving the first microwave signal (A*) after transmission, in particular by means of a second microwave antenna device (6), wherein the received first microwave signal (A*) results at least from the transmitted first microwave signal (A) and its interaction with the medium; - emitting a second microwave signal (B) with a second main beam direction (b) by means of the first microwave antenna device (5) into the measuring tube (2), wherein the first main beam direction (a) differs from the second main beam direction (b); - receiving the second microwave signal (B*) after emission, in particular by means of a second microwave antenna device (6), wherein the received second microwave signal (B*) results at least from the second microwave signal (B) and its interaction with the medium, wherein the second microwave signal (B) is reflected at least once on an inner circumferential surface of the measuring tube (2), so that the second propagation direction changes spatially at least once between the emission of the second microwave signal (B) and the reception of the second microwave signal (B*); - Detecting whether there is an inhomogeneity in the measuring tube (2) depending on the received first microwave signal (A*) and the second microwave signal (B*).

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