Magnetic-inductive flow meter

Abstract

The invention relates to a magnetic-inductive flow meter (1, 101) for determining a flow-velocity-dependent measurement variable of a flowable medium, said flow meter comprising: - a measuring tube (2) for guiding the medium, - a magnetic-field-generating device (5); - at least one measuring electrode (17), wherein the measuring electrode (17) is arranged in a measuring electrode opening in the measuring tube (2), wherein the measuring electrode (17) has a measuring electrode head (30) which is configured to come into contact with the medium, - a reference electrode (20) for connecting the medium to a reference potential, wherein the reference electrode (20) is arranged in a reference electrode opening in the measuring tube (2), wherein the reference electrode (20) has a reference electrode head (32) which is configured to come into contact with the medium, wherein the reference electrode head (32) has, in a cross-sectional plane A of the measuring tube intersecting the reference electrode and the at least one measuring electrode, a reference electrode diameter D RE , wherein the measuring electrode head (30) has, in the cross-sectional plane A, a measuring electrode diameter D ME , characterised in that the reference electrode diameter D RE is in particular at least 10% and preferably at least 25% smaller than the measuring electrode diameter D ME .

Description

[0001] Magnetic-inductive flowmeter

[0002] The invention relates to a magnetic-inductive flowmeter.

[0003] Magnetic-inductive flow measuring devices are used to determine the flow velocity and volume flow of a flowing medium in a pipeline. Inline magnetic-inductive flow measuring devices are distinguished from magnetic-inductive flow measuring probes, which are inserted into a lateral opening in a pipeline. A magnetic-inductive flow measuring device has a magnetic field-generating device for generating a magnetic field. A main axis of the magnetic field runs essentially perpendicular to the flow direction of the flowing medium. Saddle or cylindrical coils are typically used for this purpose. To create a predominantly homogeneous magnetic field, additional pole pieces are shaped and mounted relative to the flow direction so that the magnetic field lines run across the entire pipe cross-section essentially perpendicular to the transverse axis or parallel to the vertical axis of the measuring tube.In addition, a magnetic-inductive flowmeter has a measuring tube for conveying the medium, on the outer surface of which the magnetic field-generating device is arranged. A pair of measuring electrodes attached to the outer surface of the measuring tube picks up an electrical measuring voltage or current applied perpendicular to the flow direction and the magnetic field.

[0004] The potential difference that occurs when a conductive medium flows in the direction of flow when a magnetic field is applied. Since the measured voltage depends on the velocity of the flowing medium according to Faraday's law of induction, the flow velocity and / or—with the addition of a known pipe cross-section—the volume flow can be determined from the measured induced voltage.

[0005] In contrast to a magnetic-inductive flowmeter, which comprises a measuring tube for conveying the medium with an attached device for generating a magnetic field penetrating the measuring tube and measuring electrodes, magnetic-inductive flow measuring probes with their usually circular-cylindrical housing are inserted into a lateral opening of a pipeline and fixed in a fluid-tight manner. A special measuring tube is no longer necessary. The measuring electrode arrangement and coil arrangement on the outer surface of the measuring tube mentioned above are omitted and replaced by a device for generating a magnetic field arranged inside the housing and in immediate proximity to the measuring electrodes. This device is designed such that an axis of symmetry of the magnetic field lines of the generated magnetic field intersects the front surface or the area between the measuring electrodes perpendicularly.The state of the art already includes a wide variety of different magnetic-inductive flow measuring probes. Magnetic-inductive flow measuring devices are widely used in process and automation technology for fluids with an electrical conductivity of approximately 5 pS / cm and above. The applicant markets corresponding flow measuring devices in a wide variety of designs for various applications, for example, under the names PROMAG or MAGPHANT.

[0006] Magnetic-inductive flowmeters with small nominal diameters (less than 80 millimeters) suffer from the fact that the measurement inaccuracy decreases with a decrease in the conductivity of the medium (less than 10 3 pS / cm) increases.

[0007] The invention is based on the object of remedying the problem.

[0008] The problem is solved by the magnetic-inductive flowmeter according to claims 1 and 5.

[0009] The magnetic-inductive flowmeter according to the invention for determining a flow velocity-dependent measured variable of a flowable medium comprises:

[0010] - a measuring tube for guiding the medium,

[0011] - a magnetic field generating device for generating a magnetic field penetrating the measuring tube;

[0012] - at least one measuring electrode for tapping a measuring voltage induced in the medium, wherein the measuring electrode is arranged in a measuring electrode opening in the measuring tube, wherein the measuring electrode has a measuring electrode head which is designed to come into contact with the medium,

[0013] - a reference electrode for connecting the medium to a reference potential, wherein the reference electrode is arranged in a reference electrode opening in the measuring tube, wherein the reference electrode has a reference electrode head which is designed to come into contact with the medium, wherein the reference electrode head has a reference electrode diameter D in a cross-sectional plane A of the measuring tube intersecting the reference electrode and the at least one measuring electrode Äfi wherein the measuring electrode head in the cross-sectional plane A has a measuring electrode diameter D ME characterized in that the reference electrode diameter D Äfi , in particular at least 10% and preferably at least 25%, smaller than the measuring electrode diameter D ME is.

[0014] The advantage of this solution is that by reducing the reference electrode diameter D REa significant reduction in measurement error for media with low conductivity (ie o < 10 3 fiS / cm) is reached.

[0015] Advantageous embodiments of the invention are the subject of the subclaims.

[0016] One design provides that a ratio D ME / D RE greater than 1.3, in particular greater than 1.6 and preferably greater than 2.

[0017] One embodiment provides that the measuring tube has a measuring tube diameter D MR where for a ratio R = D RE / D MR it applies that 0.05 < R < 0.25, in particular 0.1 < R < 0.2 and preferably 0.13 < R < 0.17.

[0018] One design provides that a minimum distance between the measuring electrode and the reference electrode is greater than 5 millimeters, in particular greater than 7 millimeters and preferably greater than 10 millimeters.

[0019] The task is also solved by the magnetic-inductive flow meter for determining a flow velocity-dependent measured variable of a flowable medium, comprising:

[0020] - a measuring tube for guiding the medium,

[0021] - a magnetic field generating device for generating a magnetic field penetrating the measuring tube;

[0022] - at least one measuring electrode for tapping a measuring voltage induced in the medium, wherein the measuring electrode is arranged in a measuring electrode opening in the measuring tube, wherein the measuring electrode has a measuring electrode head which is designed to come into contact with the medium,

[0023] - a level monitoring electrode is arranged in a level monitoring electrode opening of the measuring tube; wherein the level monitoring electrode has a level monitoring electrode head, wherein the level monitoring electrode head is designed to come into contact with the medium, wherein the level monitoring electrode head has a level monitoring electrode diameter D in a cross-sectional plane A of the measuring tube intersecting the level monitoring electrode and the at least one measuring electrode F ü, wherein the measuring electrode head in the cross-sectional plane A has a measuring electrode diameter D ME characterized in that the level monitoring electrode diameter D FÜ , in particular at least 10% and preferably at least 25%, smaller than the measuring electrode diameter D ME is.

[0024] One embodiment provides that a minimum distance d2 between the measuring electrode and the level monitoring electrode is greater than 5 millimeters, in particular greater than 7 millimeters and preferably greater than 10 millimeters,

[0025] One design provides that a ratio D ME / D Fii greater than 1.3, in particular greater than 1.6 and preferably greater than 2.

[0026] One embodiment provides that the measuring tube has a measuring tube diameter D MR , where the measuring tube diameter D MR larger than the level monitoring electrode diameter Dfü. Where for a ratio r = D F ^ / D MR it applies that 0.05 < R < 0.25, in particular 0.1 < R < 0.2 and preferably 0.13 < R < 0.17.

[0027] One embodiment provides that a longitudinal plane intersecting the reference electrode and / or the level monitoring electrode divides the measuring tube into a first measuring tube section and a second measuring tube section, wherein two measuring electrodes are arranged in the first measuring tube section, wherein the two measuring electrodes span a central angle a of 30 < a < 60°, in particular 40 < a < 50°.

[0028] One embodiment provides that the measuring tube diameter D MR less than 80 millimeters, in particular less than 50 millimeters. One embodiment provides that the measuring electrode and the reference electrode and / or the level monitoring electrode are arranged on the measuring tube in such a way that they are intersected by the common cross-sectional plane A of the measuring tube.

[0029] The invention is explained in more detail with reference to the following figures. They show:

[0030] Fig. 1: a cross section through a first embodiment of the magnetic inductive flow meter according to the invention;

[0031] Fig. 2: a cross section through a second embodiment of the magnetic inductive flowmeter according to the invention; and

[0032] Fig. 3 : Measurement data for a conventional magnetic-inductive flowmeter and a magnetic-inductive flowmeter according to the invention.

[0033] Fig. 1 shows a cross-section through a first embodiment of the magnetic-inductive flowmeter 1 according to the invention. The structure and measuring principle of a magnetic-inductive flowmeter 1 are generally known. A flowable medium having a (minimum) electrical conductivity is passed through a measuring tube 2. The measuring tube 2 comprises a support tube 3, which is typically made of steel, ceramic, plastic, or glass, or at least comprises these materials. An electrically insulating material is applied to the inner surface of the support tube 3.

[0034] A magnetic field generating device 5 for generating a magnetic field is arranged on the support tube 3 such that the magnetic field lines are oriented substantially perpendicular to a longitudinal direction defined by a measuring tube axis of the measuring tube. The magnetic field generating device 5 typically comprises a saddle coil or at least one (cylindrical) coil 6i. A coil core 14i typically extends through a receptacle 15 of the coil 6i. The receptacle 15 is understood to be the volume delimited by the coil wire forming the coil 6i. The receptacle 15 of the coil 6i can thus be formed by a coil holder or by the imaginary enclosed volume. The latter occurs when the coil wire of the coil 6i is wound directly around the coil core 14i. The coil core 14i is formed from a magnetically conductive, in particular soft magnetic, material.The magnetic field-generating device 5 for generating the magnetic field comprises a pole piece 21i arranged at one end of the coil core 14i. The pole piece 21i can be a separate component or monolithically connected to the coil core 14i. In the embodiment shown in Fig. 1, two diametrically arranged coils 6a, 6b each have a coil core 14a, 14b and a pole piece 21a, 21b. The two coil cores 14a, 14b are connected to each other via a field feedback 22. The field feedback 22 connects the opposite sides of the coil cores 14a, 14b to each other. However, magnetic-inductive flowmeters with exactly one coil 6 with exactly one coil core 14 and without field feedback are also known. The coil 6 is connected to an operating circuit 7, which operates the coil 6 with an operating signal.The operating signal can be a voltage with a time-varying profile and is characterized by operating signal parameters, with at least one of the operating signal parameters being adjustable. The magnetic field generated by the magnetic field-generating device 5 is generated by a direct current of alternating polarity, clocked by an operating circuit 7. This ensures a stable zero point and makes the measurement insensitive to the influence of electrochemical interference. The two coils 6a, 6b can be connected separately to the operating circuit 7 or connected in series or parallel to each other.

[0035] When a magnetic field is applied, a flow-dependent potential distribution is created in the measuring tube 2, which can be detected, for example, in the form of an induced measuring voltage. A device 8 for tapping the induced measuring voltage is arranged on the measuring tube 2. In the embodiment shown, the device 8 for tapping the induced measuring voltage is formed by two oppositely arranged measuring electrodes 17a and 17b for forming a galvanic contact with the medium. However, magnetic-inductive flowmeters are known which have measuring electrodes arranged on the outer wall of the support tube 3 that are not in contact with the medium. As a rule, the measuring electrodes 17a, 17b are arranged diametrically and form an electrode axis or are intersected by a transverse axis that runs perpendicular to the magnetic field lines and the longitudinal axis of the measuring tube 2.However, devices 8 for tapping the induced measuring voltage are also known, which have more than two measuring electrodes. The flow velocity-dependent measured variable can be determined based on the measured measuring voltage. The flow velocity-dependent measured variable includes the flow velocity, the volume flow rate, and / or the mass flow rate of the medium. A measuring circuit 23 is configured to detect the induced measuring voltage applied to the measuring electrodes 17a, 17b, the respective electrical potentials present, or a difference between the electrical potentials present, and an evaluation circuit 24 is designed to determine the flow velocity-dependent measured variable. The evaluation circuit 24 can be part of the measuring transducer or the measuring sensor. The measuring electrodes 17a, 17b are usually made of metal.

[0036] The support tube 3 is often made of an electrically conductive material, such as steel. To prevent the measuring voltage applied to the measuring electrodes 17a, 17b from being dissipated via the support tube 3, the inner wall is lined with an insulating material, such as a (plastic) liner 4.

[0037] Commercially available magnetic-inductive flowmeters have, in addition to the measuring electrodes 17a, 17b, two further, usually also metallic, electrodes 19, 20. Firstly, a level monitoring electrode 19, ideally mounted at the highest point in the measuring tube 2, serves to detect partial filling of the measuring tube 1. Furthermore, it is designed to forward this information to the user and / or to take the level into account when determining the volume flow. Furthermore, a reference electrode 20, which is usually mounted diametrically opposite the level monitoring electrode 19 or at the lowest point of the measuring tube cross-section, serves to set a controlled electrical potential in the medium. The reference electrode 20 is generally used to connect the flowing medium to an electrical ground potential.

[0038] The operating circuit 7, controller circuit 10, measuring circuit 23, and evaluation circuit 24 can be part of a single electronic circuit or form separate circuits. The measuring, operating, and / or evaluation circuit 7, 23, 24 is configured to carry out the method according to the invention. For this purpose, the operating circuit is configured to generate the operating signal and provide it to the magnetic field-generating device. Furthermore, the measuring circuit is configured to determine the measured voltage values ​​and forward them to the evaluation circuit. The evaluation circuit is configured to determine the current zero point and to consider it for determining the flow velocity-dependent measured variable.

[0039] The magnetic-inductive flowmeter according to the invention has at least one measuring electrode 17 for tapping a measuring voltage induced in the medium. For this purpose, the measuring electrode 17 is arranged in a measuring electrode opening in the measuring tube 2. The measuring electrode 17 has a measuring electrode head 30 and a measuring electrode shaft. The measuring electrode head 30 is designed to come into contact with the medium. The measuring electrode shaft extends through the measuring electrode opening. The measuring electrode head 30 has a measuring electrode diameter D in the cross-sectional plane A. ME The measuring electrode head 30 does not necessarily have to be circular, but can also be elliptical in shape with its longest extension in the longitudinal direction of the measuring tube.

[0040] The magnetic-inductive flowmeter according to the invention has a reference electrode 20 for connecting the medium to be conveyed to an electrical reference potential. The reference electrode 20 is arranged in a reference electrode opening in the measuring tube 2. It has a reference electrode head 32, which is designed to come into contact with the medium, and a reference electrode shaft. The reference electrode shaft extends through the reference electrode opening. The reference electrode is arranged in the measuring tube 2 such that a reference electrode longitudinal axis runs parallel to the main field axis of the generated magnetic field. In addition, a measuring electrode axis intersecting the measuring electrodes 17a, 17b intersects the reference electrode longitudinal axis perpendicularly. The reference electrode head 32 has a reference electrode diameter D in a cross-sectional plane A of the measuring tube intersecting the reference electrode and the at least one measuring electrode. ÄfiThe measuring electrode head 30 has a measuring electrode diameter D in the same cross-sectional plane A ME To reduce the measurement error, it is essential that the diameters are adjusted. The reference electrode diameter D Äfi is, in particular at least 10% and preferably at least 25%, smaller than the measuring electrode diameter D ME . Accordingly, a ratio DME / DRE is greater than 1.3, in particular greater than 1.6 and preferably greater than 2. Considering the dimensioning of the reference electrode head 32 relative to the measuring tube diameter D MR , then there is a relationship R = D RE / D MR where 0.05 < R < 0.25, in particular 0.1 < R < 0.2 and preferably 0.13 < R < 0.17 applies. Alternatively, a minimum distance d rbetween the measuring electrode 17a or 17b and the reference electrode 20, which is greater than 5 millimeters, in particular greater than 7 millimeters and preferably greater than 10 millimeters.

[0041] The illustrated magnetic-inductive flowmeter 1 also has, in addition to the reference electrode 20, a level monitoring electrode 22, which is arranged in a level monitoring electrode opening of the measuring tube 2. However, magnetic-inductive flowmeters without reference electrodes and magnetic-inductive flowmeters without level monitoring electrodes 22 are also part of the invention. The measuring electrodes 17a, 17b, the reference electrode 20, and the level monitoring electrode 22 are arranged on the measuring tube 2 such that they are intersected by the common cross-sectional plane A of the measuring tube 2. In one embodiment, the cross-sectional plane A is a plane of symmetry for the electrodes arranged on the measuring tube 2.

[0042] The level monitoring electrode 22 has a level monitoring electrode head 34, which is designed to come into contact with the medium when it is guided in the pipe, and a level monitoring electrode shaft that extends into the level monitoring electrode opening. The level monitoring electrode head 34 has a level monitoring electrode diameter D in the cross-sectional plane A of the measuring tube 2. F ü. In order to reduce the measurement error at low conductivities, it is essential that, when a level monitoring electrode is present, the level monitoring electrode diameter Dfü is in particular at least 10% and preferably at least 25% smaller than the measuring electrode diameter D MEAlternatively, it is required that a minimum distance d2 between the measuring electrode 17a, 17b and the level monitoring electrode 22 be greater than 5 millimeters, in particular greater than 7 millimeters, and preferably greater than 10 millimeters. If the advantageous diameters of the reference electrode and the level monitoring electrode are set in relation to the measuring electrode diameter D ME , SO applies to the ratio D ME / D Fi j, that this is greater than 1.3, in particular greater than 1.6 and preferably greater than 2. If the advantageous diameters of the reference electrode and the level monitoring electrode are set in relation to the measuring tube diameter D MR , SO applies to the ratio r = D F ^ / D MRthat 0.05 < R < 0.25, in particular 0.1 < R < 0.2 and preferably 0.13 < R < 0.17. The advantage of the magnetic inductive flowmeter according to the invention is particularly evident in magnetic inductive flowmeters with measuring tube diameters D MR smaller than 80 millimeters, especially smaller than 50 millimeters.

[0043] Fig. 2 shows a cross-section through a second embodiment of the magnetic-inductive flowmeter 101 according to the invention. The magnetic-inductive flowmeter 101 differs from the embodiment of Fig. 1 essentially only in the number of measuring electrodes 107a-d, their positioning in the measuring tube, and the contacting with the measuring circuit 123. A longitudinal plane intersecting the reference electrode 120 and / or the fill level monitoring electrode 22 divides the measuring tube 2 into a first measuring tube section I and an equally sized second measuring tube section II. In the first measuring tube section I, at least two measuring electrodes 107a, 107b, or as shown in the embodiment shown, exactly two measuring electrodes 107a, 107b, are arranged according to the invention. In the second measuring tube section II, likewise according to the invention, at least two measuring electrodes 107c, 107d, orAs shown in the illustrated embodiment, exactly two measuring electrodes 107c, 107d are arranged on the measuring tube. The two measuring electrodes 107a, 107b and also the two measuring electrodes 117c, 117d are arranged on the measuring tube such that their respective measuring electrode longitudinal axes span a central angle α of 30 < α < 60°, in particular 40 < α < 50°. The measuring electrodes of a measuring tube section form a group and are electrically connected or short-circuited to one another. Thus, the measuring circuit 123 is not connected separately to the electrodes, but only to one measuring electrode of each group or to an electrically conductive connecting body connecting the at least two measuring electrodes of a group. In addition to the four measuring electrodes 117a-d shown, two further measuring electrodes can be provided, which—also as shown in Fig. 1—are located on a measuring electrode axis that intersects the main axis of the magnetic field lines perpendicularly.

[0044] Fig. 3 shows measurement results for a conventional magnetic-inductive flowmeter and a magnetic-inductive flowmeter according to the invention. The flow X was recorded with a conventional magnetic-inductive flowmeter in which the two measuring electrodes, the level monitoring electrode and the reference electrode, each have a circular cross-section and an identical diameter. Starting at a conductivity value of 10 3pS / cm, the measurement error increases with decreasing conductivity until it reaches a measurement error value of -3.5% at a conductivity of 10 pS / cm. The curve Y was recorded using an inventive magnetic-inductive flowmeter, in which the diameters of the level monitoring electrode and the reference electrode were chosen to be significantly smaller than the diameters of the measuring electrodes. Thus, the cross-sectional diameter of the measuring electrodes is 8 millimeters, and the diameters of the reference electrode and the level monitoring electrode are 4 millimeters. The measurement series results in a maximum measurement error of approximately -0.8% for curve Y. For conductivities above 10 3 pS / cm, the measured errors of the two magnetic-inductive flowmeters differ only slightly. LIST OF REFERENCE SYMBOLS Magnetic-inductive flowmeter 1 Measuring tube 2

[0045] Support tube 3

[0046] Liner 4 magnetic field generating device 5 operating circuit 7

[0047] Regulator circuit 10

[0048] Coil 13i

[0049] Coil core 14i

[0050] Measuring electrode 17i

[0051] Field feedback body 19 Reference electrode 20

[0052] Pole piece 21 i

[0053] Level monitoring electrode 22 Measuring circuit 23

[0054] Evaluation circuit 24

[0055] Measuring electrode head 30

[0056] Reference electrode head 32

[0057] Level monitoring electrode head 34 magnetic-inductive flowmeter 101 measuring electrode 117i

[0058] Reference electrode 120

[0059] Level monitoring electrode 122 Measuring circuit 123

Claims

PATENT CLAIMS 1. A magnetic-inductive flowmeter (1,101) for determining a flow velocity-dependent measured variable of a flowable medium, comprising: - a measuring tube (2) for guiding the medium, - a magnetic field generating device (5) for generating a magnetic field penetrating the measuring tube (2); - at least one measuring electrode (17) for tapping a measuring voltage induced in the medium, wherein the measuring electrode (17) is arranged in a measuring electrode opening in the measuring tube (2), wherein the measuring electrode (17) has a measuring electrode head (30) which is designed to come into contact with the medium, - a reference electrode (20) for connecting the medium to a reference potential, wherein the reference electrode (20) is arranged in a reference electrode opening in the measuring tube (2), wherein the reference electrode (20) has a reference electrode head (32) which is designed to come into contact with the medium, wherein the reference electrode head (32) has a reference electrode diameter D in a cross-sectional plane A of the measuring tube intersecting the reference electrode and the at least one measuring electrode Äfi wherein the measuring electrode head (30) in the cross-sectional plane A has a measuring electrode diameter D ME characterized in that the reference electrode diameter D Äfi , in particular at least 10% and preferably at least 25%, smaller than the measuring electrode diameter D ME is.

2. Magnetic-inductive flowmeter (1, 101) according to claim 1, wherein a ratio D ME / DRE greater than 1.3, in particular greater than 1.6 and preferably greater than 2.

3. Magnetic-inductive flowmeter (1, 101) according to one of the preceding claims, wherein the measuring tube (2) has a measuring tube diameter D MR where for a ratio R = D RE / D MR it applies that 0.05 < R < 0.25, in particular 0.1 < R < 0.2 and preferably 0.13 < R < 0.

17.

4. Magnetic-inductive flowmeter (1, 101) according to one of the preceding claims, wherein a minimum distance between the measuring electrode (17) and the reference electrode (20) is greater than 5 millimeters, in particular greater than 7 millimeters and preferably greater than 10 millimeters.

5. Magnetic-inductive flowmeter (1,101) for determining a flow velocity-dependent measured variable of a flowable medium, comprising: - a measuring tube (2) for guiding the medium, - a magnetic field generating device (5) for generating a magnetic field penetrating the measuring tube (2); - at least one measuring electrode (17) for tapping a measuring voltage induced in the medium, wherein the measuring electrode (17) is arranged in a measuring electrode opening in the measuring tube (2), wherein the measuring electrode (17) has a measuring electrode head (30) which is designed to come into contact with the medium, - a level monitoring electrode (22), wherein the level monitoring electrode (22) is arranged in a level monitoring electrode opening of the measuring tube (2); wherein the level monitoring electrode (22) has a level monitoring electrode head (34), wherein the level monitoring electrode head (34) is designed to come into contact with the medium, wherein the level monitoring electrode head (34) has a level monitoring electrode diameter D in a cross-sectional plane A of the measuring tube (2) intersecting the level monitoring electrode (22) and the at least one measuring electrode (17) F ü, wherein the measuring electrode head (30) in the cross-sectional plane A has a measuring electrode diameter D ME characterized in that the level monitoring electrode diameter D FÜ , in particular at least 10% and preferably at least 25%, smaller than the measuring electrode diameter D ME is.

6. Magnetic-inductive flowmeter (1, 101) according to claim 5, wherein a minimum distance d2 between the measuring electrode (17) and the level monitoring electrode (22) is greater than 5 millimeters, in particular greater than 7 millimeters and preferably greater than 10 millimeters, 7. Magnetic-inductive flowmeter (1, 101) according to claim 5 or 6, wherein a ratio D ME / D Fii greater than 1.3, in particular greater than 1.6 and preferably greater than 2.

8. Magnetic-inductive flowmeter (1, 101) according to one of claims 5 to 7, wherein the measuring tube (2) has a measuring tube diameter D MR , where the measuring tube diameter D MR larger than the level monitoring electrode diameter Dfü. Where for a ratio r = D F ^ / D MR it applies that 0.05 < R < 0.25, in particular 0.1 < R < 0.2 and preferably 0.13 < R < 0.

17.

9. Magnetic-inductive flowmeter (1, 101) according to one of the preceding claims, wherein a longitudinal plane intersecting the reference electrode (20) and / or the level monitoring electrode (22) divides the measuring tube (2) into a first measuring tube section (I) and a second measuring tube section (II), wherein at least two measuring electrodes (107a, 107b), in particular exactly two measuring electrodes (107a, 107b), are arranged in the first measuring tube section (I), wherein the two measuring electrodes (107a, 107b) span a central angle α of 30 < α < 60°, in particular 40 < α < 50°.

10. Magnetic-inductive flowmeter (1, 101) according to one of the preceding claims Claims, wherein the measuring tube diameter D MR less than 80 millimeters, especially less than 50 millimeters.

11. Magnetic-inductive flowmeter (1, 101) according to one of the preceding claims, wherein the measuring electrode (17) and the reference electrode (20) and / or the level monitoring electrode (22) are arranged on the measuring tube (2) in such a way that they are intersected by the common cross-sectional plane A of the measuring tube (2).

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