Magnetic induction flowmeter

Abstract

The invention relates to a magnetic-inductive flowmeter comprising: a measuring tube for guiding a flowable medium in a longitudinal direction; a measuring electrode arrangement for detecting a measuring voltage which is dependent on the flow velocity and is induced in the medium, the measuring electrode arrangement having two measuring electrode groups which are fastened to the measuring tube opposite each other; and a magnetic field generating device for generating a magnetic field through the measuring tube; the magnetic field generating device having at least two coil core groups, each coil core group having at least two coil cores; a reference plane which divides the measuring tube into a first part and a second part, the reference plane being spanned by the longitudinal axis of the measuring tube and a transverse axis of the measuring tube which intersects the measuring electrodes of the measuring electrode arrangement; the first and second parts of the measuring tube each having at least one coil core group, characterized in that two radii enclose a central angle β which intersect the coil cores of the coil core groups which are located outside the cross section of the measuring tube; and for the central angle β, 80°≤β≤105° holds if each measuring electrode group comprises precisely one measuring electrode, and 60°≤β≤80° holds if each measuring electrode group comprises at least two measuring electrodes.

Description

Technical Field Background Art

[0001] Magnetic-inductive flowmeters are used to determine the flow rate and volume flow of a flowing medium in a pipeline. The magnetic-inductive flowmeter has a magnet system that generates a magnetic field perpendicular to the flow direction of the flowing medium. A single coil is usually used for this purpose. In order to achieve a predominantly uniform magnetic field, pole shoes are additionally formed and attached so that the magnetic field lines extend substantially perpendicularly to the transverse axis of the measuring pipe or parallel to the vertical axis of the measuring pipe over the entire pipe cross section. The measuring electrode pairs attached to the side of the measuring pipe tap an electrical measuring voltage or a potential difference, which is applied perpendicularly to the flow direction and the magnetic field and occurs when the conductive medium flows in the flow direction when the magnetic field is applied. Because according to Faraday's law of induction, the tapped measuring voltage depends on the velocity of the flowing medium, the flow rate u and, with a known pipe cross section, the volume flow rate It can be determined from the induced measurement voltage U.

[0002] Magneto-inductive flowmeters are frequently used in process and automation technology for fluids with a conductivity of approximately 5 μS / cm. Corresponding flowmeters are sold by the applicant in various embodiments for various fields of application—for example, under the name PROMAG.

[0003] DE 10 2014 113 409 A1 discloses a magnetic-inductive flowmeter having a field return and pole pieces that are fastened to the outer wall of the measuring tube and connected to each other via a cylindrical coil core. This arrangement is particularly suitable for magnetic-inductive flowmeters with large nominal diameters. The field return serves to guide the magnetic field lines from the first coil core to the second coil core. However, a disadvantage of this magnetic-inductive flowmeter is that the flow measurement value is sensitive to the flow profile of the medium.

[0004] Conventional magneto-inductive flowmeters are sensitive to the flow profile of the medium. Depending on the pipe system and the instrument, measurement errors of several percent can occur. Therefore, a straight pipe is usually installed on the front of the inlet side, the length of which corresponds to at least five to ten times the nominal diameter of the measuring tube. However, this minimum distance (the so-called inlet section) cannot be maintained in known applications. This is the case, for example, when the pipe system is located in the narrowest spaces. The invention disclosed in DE 10 2014 113 408 A1 provides a solution in which the contraction of the pipe diameter leads to a regulation of the flow rate, thereby minimizing the influence of the flow profile, making it possible to use a 0-DN inlet section. However, a disadvantage of this embodiment is that, although a lower sensitivity to rotationally asymmetric flow profiles can be achieved, pressure losses must be tolerated as a result. Furthermore, this embodiment is limited to pipe systems with DN<350.

[0005] The sensitivity of flow measurement to rotationally asymmetric flow profiles depends on the geometry of the measuring tube and electrodes. Therefore, to correctly describe the velocity-dependent induced voltage, the effects of tube and electrode geometry must be considered. These two effects are mathematically represented by the weighting function GF. The influence of geometry on flow is best described by the following relationship:

[0006]

[0007] Here, to determine the voltage U(x), the flow velocity v(x′) and the weighting function GF(x′, x) are integrated over the volume of the measuring tube. The goal of the optimization method is to optimize the geometry of the structure so that Applicable to the entire flow profile. However, this is not possible for pipes with a single, point-like pair of measuring electrodes. One possible approach involves adapting the electrode shape. However, this is impractical and introduces new difficulties. Another approach involves using multiple pairs of measuring electrodes.

[0008] For example, CN 101294832 A discloses a magnetic-inductive flowmeter having two measuring electrode pairs arranged axially symmetrically in the tube cross section in order to minimize the influence of the flow profile on the volume flow determination. The two electrode axes defined by the respective measuring electrode pairs span an angle of approximately 40° in the cross section of the measuring tube.

[0009] A further embodiment is shown in DE 102015113390 A1, in which the second and third measuring electrode pairs are arranged on defined electrode axes which are arranged at an angle of less than or equal to ±45° relative to a first electrode axis oriented perpendicularly to the magnetic field.

[0010] EP 0878694 A1 also discloses a magnetic-inductive flowmeter that, compared to the prior art, improves measurement accuracy to within a measurement error range of less than 1% by using two additional measuring electrode pairs, the electrode axes of which each extend at an angle of approximately 45° to the measuring tube axis relative to the electrode axes of conventional measuring electrode pairs. This is achieved, in particular, by individually detecting and weighting the potential differences applied to the electrodes.

[0011] However, these embodiments have the disadvantage that, while the measurement accuracy is optimized for small diameters, they do not achieve the desired reduction in measurement errors for commercially available measuring tubes with large nominal widths. A further disadvantage is that a weighting factor must be considered for each measuring electrode pair, and it is not immediately clear how to select this weighting factor depending on the tube system or rotationally asymmetric flow profile. Summary of the Invention

[0012] Starting from the described prior art, it is an object of the present invention to provide a magneto-inductive flow meter which minimizes the influence of rotationally asymmetric flow profiles during the determination of flow measurement values.

[0013] This object is achieved by the magnetic-inductive flow meter according to the invention.

[0014] The magnetic induction flowmeter according to the present invention comprises:

[0015] a measuring tube for guiding the flowable medium in the longitudinal direction;

[0016] a measuring electrode arrangement for detecting a measuring voltage which is dependent on the flow velocity and is induced in the medium,

[0017] wherein the measuring electrode arrangement comprises two measuring electrode groups which are fastened opposite one another on the measuring tube; and

[0018] a magnetic field generating device for generating a magnetic field through the measuring tube,

[0019] The magnetic field generating device has at least two coil core groups, each coil core group has at least two coil cores,

[0020] wherein a reference plane divides the measuring tube into a first part and a second part, the reference plane being spanned by a longitudinal axis of the measuring tube and a transverse axis of the measuring tube intersecting the measuring electrodes of the measuring electrode arrangement,

[0021] The first and second parts of the measuring tube each have at least one coil core group, characterized in that

[0022] two radii spanning a central angle β, which intersect the coil cores of the coil core group located outside the cross section of the measuring tube,

[0023] In which, for the central angle β, if the measuring electrode groups each include precisely one measuring electrode, then 30°≤β≤120°, in particular 60°≤β≤110°, and preferably 80°≤β≤105° is satisfied, and if the measuring electrode groups each include at least two measuring electrodes, then 30°≤β≤120°, in particular 45°≤β≤100°, and preferably 60°≤β≤80° is satisfied.

[0024] Advantageously, at least two coil cores each have at least one coil arranged in the respective section of the measuring tube. This embodiment provides further optimization possibilities for the resulting magnetic field in the measuring tube. These optimization possibilities include the position of the respective coil cores, the number of coils, the diameter of the coil cores, the number of windings, and the winding cross-sections.

[0025] In order to create a flow-profile-independent magneto-inductive flowmeter, the arrangement of the coil cores must be adapted to the number of measuring electrodes. The preferred center angles for both cases are mutually exclusive.

[0026] In other preferred embodiments, the measuring tube is made of metal and is lined with an electrically insulating lining in the fluid contact area. Alternatively, the measuring tube can also be made of ceramic or plastic, with at least two pole pieces and / or at least two return plates being arranged on the outer side of the measuring tube or being embedded in the measuring tube.

[0027] One embodiment provides that two radii span a central angle α, each radius intersecting a measuring electrode of the measuring electrode set that is located outside the cross section of the measuring tube,

[0028] Here, 10°≤α≤60°, in particular 15°≤α≤50°, and preferably 20°≤α≤40° is satisfied.

[0029] Advantageously, the measuring tube includes at least two measuring electrodes instead of a large-area measuring electrode, in order to measure the potential distribution present in the medium at multiple locations or to determine an average value of the potential distribution in the medium over a larger area. The claimed arrangement has proven to be particularly advantageous because the measuring voltage applied to the measuring electrodes is particularly insensitive to asymmetries of the flow profile.

[0030] However, this arrangement is dependent on the arrangement of the coil core. Only by combining these two features can it be insensitive to asymmetries in the flow profile.

[0031] The radius extending through the outer measuring electrode spans a circular cross section in which all measuring electrodes of the measuring electrode set are arranged.

[0032] One embodiment provides that the coil core assembly has at least four (and preferably precisely four) coil cores attached in the cross section of the measuring tube,

[0033] The radii that each intersect the inner coil cores of the coil core group span a central angle γ, which satisfies 1°≤γ≤80°, in particular 2°≤γ≤50°, and preferably 10°≤γ≤40°.

[0034] It is particularly advantageous if, in addition to the two outer coil cores, the coil core assembly also includes at least two further coil cores arranged between the two outer coil cores. This allows the magnetic flux density in the measuring tube to be increased. This also allows for further optimization of the magnetic field control inside the measuring tube.

[0035] As an advantageous embodiment, it has been found that, in addition to increasing the compactness of the components attached to the outer wall of the measuring tube, the above-claimed arrangement of the internal coil cores of the coil core group in combination with the claimed arrangement for the measuring electrodes and the external coil cores also achieves a reduced sensitivity to flow profile asymmetries.

[0036] Preferably, each coil core has a slot through which a clamping band is guided, thereby securing the coil core to the measuring tube. Furthermore, the claimed arrangement is advantageous for securing the coil core and field loop assembly, because, particularly in the claimed arrangement for an inner coil core, the clamping band presses the coil core not only against the outer wall of the measuring tube or against the pole piece and part of the field loop during securing, but also against the end of the field loop. This results in minimizing overshoot or better controlling the overshoot behavior of the magnetic field during changes in direction.

[0037] One embodiment provides that the coil core group has at least three (and preferably exactly three) coil cores,

[0038] The coil core is cut by a transverse axis extending perpendicularly to the reference plane.

[0039] Advantageously, in addition to the two outer coil cores, at least one further coil core is arranged between the outer coil cores.

[0040] Preferably, each coil core group has precisely three coil cores, wherein the centrally attached coil core is spaced equidistantly from the two outer coil cores.

[0041] One embodiment provides that the coil core extends through at least two (and preferably precisely two) coils,

[0042] In this case, the longitudinal axis of the coil core extends parallel to the longitudinal axis of the measuring tube.

[0043] To increase the magnetic flux density in the measuring tube, the number of windings or the coil current must be increased. Increasing the winding diameter and placing additional coils on the measuring tube has been found to be advantageous. This allows for a compact design of the magnetic-inductive flowmeter and enables the realization of magnetic-inductive flowmeters with particularly large nominal diameters from a number of identical components.

[0044] Advantageously, each of the at least four coils has the same geometry, in particular a non-saddle-shaped planar geometry. Advantageously, the use of planar coils reduces the need for copper in terms of cost.

[0045] Furthermore, it is advantageous if each of the at least four coils has the same design. This simplifies design and assembly.

[0046] One embodiment provides that all coils connected in series have a resistance between 2 and 300Ω, in particular between 100 and 280Ω, and preferably between 150 and 260Ω.

[0047] One embodiment provides that the magnetic field generating device has two pole shoes,

[0048] In this case, the pole shoes are fastened relative to one another, in particular against the outer wall of the measuring tube.

[0049] wherein the pole shoes are each formed from at least two (and preferably exactly two or exactly four) pole shoe bodies,

[0050] Therein, the pole shoe body is formed from stacked sheet metal sheets, and in particular electrical steel sheets.

[0051] As a result, a simplified mounting of the pole shoe on the outer wall of the measuring tube can be achieved.

[0052] One embodiment provides that two adjacent pole shoe bodies are spaced apart in the longitudinal direction of the measuring tube by a minimum distance C which is less than 500 mm, in particular less than 50 mm, and preferably between 2 and 5 mm.

[0053] The distance between the two pole shoe bodies forms a guide for guiding the wiring of the measuring electrodes.However, the claimed pole shoe arrangement ensures that the magnetic field lines in the measuring region run essentially perpendicular to the electrode axis and the longitudinal axis of the measuring tube.

[0054] One embodiment provides that at least one field loop component is attached to and in particular abuts an outer wall of the measuring tube,

[0055] Wherein, the field loop assembly includes at least two field loops,

[0056] Therein, the coil core connects the pole shoes to the field circuit.

[0057] In a preferred embodiment, the field loop and the pole shoe have the shape of a rectangular, curved sheet metal piece, with the curvature adapted to the measuring tube. The field loop and pole shoe are fastened so as to abut the outer wall of the measuring tube. In this case, a two-part design of the pole shoe is advantageous because it allows for simple assembly, particularly with measuring tubes having large nominal diameters (≥ DN 1000). The same applies to the field loop.

[0058] Arranging the coils, pole pieces, and field loops directly on the measuring tube significantly reduces the material requirements of these components. Furthermore, fastening them to the measuring tube is particularly simple and stable. While reducing manufacturing costs, high measurement accuracy is achieved because interfering stray fields are minimized. Direct arrangement means that the components are placed directly on the measuring tube. For example, they can be glued directly to the measuring tube.

[0059] Field loop components are typically used to capture magnetic field lines that exit the coil core and do not intersect the measuring tube or only partially intersect the measuring tube, and to guide them from one coil core to the other. Therefore, the field loop typically connects the sides of the coil core facing away from the pole shoe or the respective ends of the coil core that do not contact the pole shoe.

[0060] One embodiment provides that all measuring electrodes of a measuring electrode group are electrically connected to one another and, in particular, short-circuited.

[0061] The short circuit can be produced via conventional cables or by means of specially shaped contact bodies, which simplifies the connection of the measuring electrodes during the manufacture of the magneto-inductive flow meter.

[0062] The technical success of this embodiment of the invention lies in the discovery that, by adding empirically determined weighting factors, the adjustment of angles α and β eliminates the sampling of individual potential differences, and in the event of a fault, the voltages applied to all electrodes deviate by less than 0.5% from the measured values ​​determined using the fully formed flow profile. Therefore, there is no need to weight the individual voltage values, which significantly simplifies the evaluation unit for determining the applied voltage and the resulting flow velocity. It is now sufficient to convert the measured voltage values ​​into flow velocity or volume flow using calibration.

[0063] The electrodes are connected to a measuring circuit that provides information about flow measurements of the medium in the measuring tube based on the voltage induced in the electrodes. The flow measurements include flow velocity, volume flow, and mass flow of the flowing medium.

[0064] One embodiment provides that both parts of the measuring tube each have precisely two coil core groups.

[0065] wherein the first coil core group and the second coil core group are arranged in a first part of the measuring tube,

[0066] wherein the first coil core group is arranged in a first cross section and the second coil core group is arranged in a second cross section,

[0067] The first cross section and the second cross section are spaced apart in the longitudinal direction.

[0068] This results in a symmetrical distribution of the magnetic field in the measuring tube.

[0069] One embodiment provides that the measuring electrode arrangement is arranged in the third cross section,

[0070] Therein, the third cross section is arranged between the first cross section and the second cross section and preferably forms a symmetry plane of the coil core group and preferably forms a symmetry plane of the magnetic field generating device.

[0071] This results in a symmetrical distribution of the magnetic field in the measuring tube, whereby the measuring tube can be operated in both longitudinal directions. This arrangement is particularly suitable for measuring pipes with a nominal diameter ≥ DN 1000.

[0072] The angles α, β and in particular γ are coordinated with one another so that the flowmeter is insensitive to deviations from the rotational symmetry of the flow, so that the measurement error of the flow rate of the magnetic-inductive flowmeter during the test measurement is and / or volume flow measurement errors Less than 1.0%, in particular less than 0.5%, and preferably less than 0.2%, wherein the flow rate u va and / or volume flow It is determined for a flow with a completely formed flow profile, where the flow rate u S and / or volume flow Determined in the case of rotationally asymmetric flows.

[0073] After a disturbance, measurement errors can occur due to an undesirable flow profile, depending on the distance and type of the disturbance. This is because magnetic-inductive flow meters typically exhibit and have been optimized to the effect of a perfectly formed, rotationally symmetrical flow profile. In this context, a flow profile is understood to mean a perfectly formed, rotationally symmetrical flow profile whose flow direction no longer changes. Such a flow profile is achieved, for example, in a measuring tube with an inlet section corresponding to 30 times the nominal width of the measuring tube and a moderate velocity of 2 m / s.

[0074] Test measurements can also be used to adjust the optimum angles α and β, which are then carried out in advance, so that a flow profile-independent magnetic-inductive flow meter is achieved taking into account the angle pair (α-β).

[0075] The test measurement can include many different interference sources, all of which can be installed at any angle. By using enough different interferences, the angles α and β can be optimized so that the measurement error value of a specific interference is less than 0.05%, and the maximum measurement error value of any interference is less than 0.5%.

[0076] It has been found that by using two sufficiently different interference sources, specifically a diaphragm and a 90° elbow, a sufficiently good angle pair (α-β) has been determined for the magnetic-inductive flowmeter, with a maximum measurement error of 0.5% for any of the different types of interference. By incorporating additional interference sources into the test measurements, the optimized parameters and, therefore, the resulting measurement error will only change slightly.

[0077] According to one embodiment, the interference source comprises a diaphragm or a 90° elbow, wherein the diaphragm covers 10% of the cross-section of the measuring tube, wherein the diaphragm has a chord, which delimits the diaphragm toward the tube, wherein the diaphragm has a first diaphragm orientation or a second diaphragm orientation, wherein in the case of the first diaphragm orientation the chord is oriented perpendicular to the magnetic field and in the case of the second diaphragm orientation the chord is oriented parallel to the magnetic field, wherein the 90° elbow presents a first elbow orientation or a second elbow orientation, wherein the first elbow orientation is characterized in that the tube axis extends perpendicular to the magnetic field and to the longitudinal direction of the measuring tube, and the second elbow orientation is characterized in that the tube axis extends parallel to the magnetic field and perpendicular to the longitudinal orientation of the measuring tube.

[0078] Until now, users of magnetic-inductive flowmeters have been provided with a predefined inlet section. This predefined inlet section is necessary to maintain the measurement error specified for the device. The resulting measurement error must be determined once for all, depending on the type of disturbance, distance, installation angle, and possibly the Reynolds number. This can be done through a complex series of measurements, or by simulating flow conditions in the presence of different disturbances and evaluating the calculated flow profiles. This step yields data indicating the measurement error that would result if the magnetic-inductive flowmeter were installed in the corresponding location, as well as the potential measurement error if the design included additional measuring electrodes or magnetic field-generating devices.

[0079] According to other embodiments, the interference is arranged at a distance 0-DN from the entrance-side front face.

[0080] According to a further development, in the case of a Reynolds number of the medium in the measuring tube greater than or equal to 10,000, in particular greater than or equal to 50,000 and preferably greater than or equal to 100,000, there is no sensitivity to rotationally asymmetric flow profiles.

[0081] According to other exemplary embodiments, the measuring electrode set has precisely three measuring electrodes.

[0082] The measuring electrode groups do not necessarily have to be arranged radially. The measuring electrodes are coupled to the measured medium galvanically or capacitively. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] The present invention will be explained in more detail with reference to the following drawings, which are shown below:

[0084] Figure 1 : A first embodiment of a magnetic-inductive flowmeter according to the present invention; and

[0085] Figure 2 : Parallel projections of the first cross section A and the third cross section B through the magnetic-inductive flowmeter of the second embodiment. DETAILED DESCRIPTION

[0086] The construction and measuring principle of magnetic-inductive flowmeters are generally known. Figure 1 A magnetic-inductive flowmeter according to a first embodiment of the present invention is shown. An electrically conductive medium is guided through a measuring tube 1. A magnetic field generating device 4 is arranged on the measuring tube such that the magnetic field lines are oriented substantially perpendicular to the longitudinal direction defined by the measuring tube axis. A saddle coil or pole shoe 5 with an attached coil core 7 and coil 8 is preferably suitable as the magnetic field generating device 4. Figure 1 Two pole shoes 5 are shown, each of which is designed in two parts. The magneto-inductive flowmeter also has a field return assembly 9 consisting of four field return parts 10, of which only two are shown. These are fastened so as to abut against the outer wall 6 of the measuring tube 1. Figure 1 Only six of the eight cylindrical coil cores 7 and coils 8 are shown. The longitudinal axis of the coil core 7 extends essentially parallel to the longitudinal axis 15 of the measuring tube. The coil core 7 connects the pole shoe 5 to the field loop body 10. The coil 8 is arranged between the field loop body 10 and one pole shoe 5. However, according to the present invention, more coils can also be arranged. Each field loop part 10 includes a field loop body 11, which is formed by a plurality of electrical steel sheets punched into bundles. The thickness of the pole shoe body 19 is approximately the same as the thickness of the field loop part 10. The pole shoe body 19 is preferably formed by electrical steel sheets punched into bundles. The field loop parts 10 are each connected to at least two different coil cores 7, thereby achieving magnetic coupling. The various components of the magnet system are fastened to the measuring tube body by means of screws. When a magnetic field is applied, a flow-dependent potential distribution is generated in the measuring tube 1 and is tapped by two opposing measuring electrode groups 16, which are attached to the inner wall of the measuring tube 1. Typically, these measuring electrode groups are arranged radially and form an electrode axis or intersect a transverse axis that extends perpendicularly to the magnetic field lines and the longitudinal axis of the measuring tube. The measuring electrodes 3 are all located in the third cross-section C. In the present embodiment, the measuring electrode group 16 has precisely three measuring electrodes 3. Based on the tapped measuring voltage U and taking into account the magnetic flux density, the flow rate u, and additionally the cross-sectional area of ​​the tube, the volume flow of the medium can be determined. If the medium density is also known, the mass flow can also be monitored To prevent the measuring voltage applied to the measuring electrode set 16 from discharging through the measuring tube 1, the inner wall is lined with an insulating material—for example, a plastic lining. The measuring circuit is configured to detect the measuring voltage applied to the measuring electrode set 16. In this case, the corresponding measuring electrodes 3 of the measuring electrode set 16 are electrically connected to one another. The evaluation circuit is designed to determine the flow rate measurement value of the medium from the detected measuring voltage. The magnetic field generating device 4 is controlled via an operating circuit. In addition to the measuring electrodes 3, commercially available magnetic-inductive flowmeters have two additional electrodes. A level monitoring electrode 12, optimally attached to the highest point in the measuring tube 1, is used to detect partial filling of the measuring tube 1 and is designed to convey this information to the user and / or account for the fill level when determining the volume flow rate. Furthermore, a grounding electrode ensures adequate grounding of the medium. Metal process connections 2 are attached to the ends of the measuring tube. In this case, these are flanges designed to integrate the measuring tube into the pipeline. Furthermore, two collars are attached to the measuring tube between the field loop assembly and the process connection 2, forming the lateral outer walls of the housing. First coil core group 17 . 1 includes coil cores 7 arranged in a first cross-section A. Second coil core group 17 . 2 includes coil cores 7 arranged in a second cross-section B. The positions of the coil cores 7 of each coil core group 17 meet the requirement of 60° ≤ β ≤ 80°. The positions of the individual measuring electrodes 3 meet the requirement of 20° ≤ α ≤ 40°.

[0087] Figure 2A parallel projection of a magnetic-inductive flowmeter according to a second embodiment of the present invention is shown to illustrate the arrangement of the coil cores 7 and measuring electrodes 3. The measuring tube 1 is divided into two sections I and II by means of a reference plane. A first coil core group 17.1 is arranged in the first section I, while a second coil core group 17.2 is arranged in the second section II. Compared to the first embodiment, each coil core group 17 includes two additional coil cores 7, which are arranged between the outer coil cores 7, and their positions are described by a central angle γ. In cross section, two opposing pole shoes 5 are shown, attached to the outer wall of the measuring tube 1. The shape of the two pole shoes 5 can be roughly described as a circular arc. According to this embodiment, four coil cores 7 are arranged on the pole shoes 5, each having at least one coil (not shown) and connecting the field loop to the pole shoes 5. In cross section, the outer coil cores 7 (particularly points located on the longitudinal axis of the respective coil core 7 and the center point 14 of the measuring tube 1) form a circular arc with a central angle β. For the central angle β, 30° ≤ β ≤ 120°, in particular 45° ≤ β ≤ 100°, and preferably 60° ≤ β ≤ 80° are satisfied. The illustrated embodiment has a central angle β of approximately 110°. The external measuring electrodes 3 and the center point 14 of the measuring electrode group 16 form a circular cross-section with a central angle α. For the central angle α, 10° ≤ α ≤ 60°, in particular 15° ≤ α ≤ 50°, and preferably 20° ≤ α ≤ 40° are satisfied. In the depicted embodiment, the central angle α is approximately 30°. The arrangement of the internally mounted coil core can be characterized by the central angle γ. For this variable, 1° ≤ γ ≤ 80°, in particular 2° ≤ γ ≤ 50°, and preferably 10° ≤ γ ≤ 40° are satisfied.

[0088] Reference Signs List

[0089] 1 Measuring tube

[0090] 2 Metal process connections / flanges

[0091] 3 Measuring electrodes

[0092] 4 Magnetic field generating equipment

[0093] 5 pole shoes

[0094] 6 outer wall

[0095] 7 Coil core

[0096] 8 coils

[0097] 9 Field loop components

[0098] 10 Field loop

[0099] 11 Field loop

[0100] 12 Material level monitoring electrode

[0101] 13 Measuring electrode device

[0102] 14 Center Point

[0103] 15 Longitudinal axis of the measuring tube

[0104] 16 Measuring electrode set

[0105] 17 Coil core group

[0106] 17.1 First coil core group

[0107] 17.2 Second coil core group

[0108] 18 Reference Plane

[0109] 19 Pole shoe body

[0110] I. Part 1

[0111] II Part 2

[0112] A First cross section

[0113] B Second cross section

[0114] C Third cross section

Claims

1. A magnetic induction flowmeter, comprising: A measuring tube (1) for guiding a flowable medium in a longitudinal direction; - a measuring electrode arrangement (13) for detecting a measuring voltage which is dependent on the flow velocity and is induced in the medium, wherein the measuring electrode device (13) comprises two measuring electrode groups (16), the two measuring electrode groups being fastened to the measuring tube (1) opposite to each other; and - a magnetic field generating device (4) for generating a magnetic field through the measuring tube (1), The magnetic field generating device (4) has at least two coil core groups (17), each of which has at least two coil cores (7). wherein the coil core (7) extends through at least two coils (8), wherein the longitudinal axis of the coil core extends parallel to the longitudinal axis (15) of the measuring tube (1), wherein a reference plane (18) divides the measuring tube (1) into a first part (I) and a second part (II), the reference plane being spanned by the longitudinal axis (15) of the measuring tube (1) and a transverse axis of the measuring tube (1) intersecting the measuring electrodes (3) of the measuring electrode array (16), The first part (I) and the second part (II) of the measuring tube (1) each have at least one coil core group (17). in, two radii spanning a central angle β, said two radii intersecting a coil core (7) of a coil core group (17) located outside the cross section of the measuring tube (1), It is characterized in that, for the central angle β, if the measuring electrode group (16) includes exactly one measuring electrode (3), then 30°≤β≤120° is satisfied, and if the measuring electrode group (16) includes at least two measuring electrodes (3), then 30°≤β≤120° is satisfied, wherein two radii span a central angle α, each radius intersecting a measuring electrode (3) of a measuring electrode set (16) located outside the cross section of the measuring tube (1), Among them, 10°≤α≤60° is satisfied, wherein all measuring electrodes (3) of the measuring electrode group (16) are electrically connected to one another, wherein the radius intersecting the built-in coil core of the coil core group (17) spans a central angle γ, which satisfies 1°≤γ≤80°, The first part (I) and the second part (II) of the measuring tube (1) each have precisely two coil core groups (17). wherein a first coil core group (17.1) and a second coil core group (17.2) are arranged in the first part (I) of the measuring tube (1), wherein the first coil core group (17.1) is arranged in a first cross section (A), and the second coil core group (17.2) is arranged in a second cross section (B), The first cross section (A) and the second cross section (B) are spaced apart in the longitudinal direction of the measuring tube (1).

2. The flow meter according to claim 1, in, For the central angle β, if each of the measuring electrode groups (16) includes exactly one measuring electrode (3), 60°≤β≤110° is satisfied, and if each of the measuring electrode groups (16) includes at least two measuring electrodes (3), 45°≤β≤100° is satisfied.

3. The flow meter according to claim 2, in, For the central angle β, if the measuring electrode groups (16) each include exactly one measuring electrode (3), then 80°≤β≤105° is satisfied, and if the measuring electrode groups (16) each include at least two measuring electrodes (3), then 60°≤β≤80° is satisfied.

4. The flow meter according to claim 1, in, Satisfying 15°≤α≤50°.

5. The flow meter according to claim 4, in, Satisfying 20°≤α≤40°.

6. The flow meter according to claim 1, in, The coil core group (17) has at least four coil cores (7) attached in the cross section of the measuring tube (1).

7. The flow meter according to claim 6, in, The coil core group (17) has precisely four coil cores (7) attached in the cross section of the measuring tube (1).

8. The flow meter according to claim 1, in, The radii that intersect the built-in coil cores of the coil core group (17) span a central angle γ, which satisfies 2°≤γ≤50°.

9. The flow meter according to claim 8, in, The radii that intersect the built-in coil cores of the coil core group (17) span a central angle γ, which satisfies 10°≤γ≤40°.

10. The flow meter according to claim 1, in, The coil core group (17) has at least three coil cores (7).

11. The flow meter according to claim 10, in, The coil core group (17) has exactly three coil cores (7), One of the three coil cores (7) is intersected by a transverse axis extending perpendicular to the reference plane.

12. Flow meter according to one of claims 1 to 11, in, The coil core (7) extends through precisely two coils (8).

13. The flow meter according to claim 1, in, All coils (8) connected in series have a resistance between 2 and 300Ω.

14. The flow meter according to claim 13, in, All coils (8) connected in series have a resistance between 100 and 280Ω.

15. The flow meter according to claim 14, in, All coils (8) connected in series have a resistance between 150 and 260Ω.

16. Flow meter according to one of claims 1 to 11, in, The magnetic field generating device (4) has two pole shoes (5), wherein the pole shoes (5) are fastened relative to each other against the outer wall of the measuring tube (1), Wherein, the pole shoes (5) are each formed by at least two pole shoe bodies (19), Wherein, the pole shoe body (19) is formed by stacked sheet metal sheets.

17. The flow meter according to claim 16, in, The pole shoes (5) are each formed from precisely two or precisely four pole shoe bodies (19).

18. The flow meter according to claim 16, in, The pole shoe body (19) is formed from electrical steel sheets.

19. The flow meter according to claim 16, in, Two adjacent pole shoe bodies (19) are spaced apart by a minimum distance C in the longitudinal direction of the measuring tube (1), the minimum distance C being less than 500 mm.

20. The flow meter according to claim 19, in, The minimum distance C is less than 50 mm.

21. The flow meter according to claim 20, in, The minimum distance C is between 2 and 5 mm.

22. Flow meter according to one of claims 1 to 11, in, At least one field loop component (9) is attached to the outer wall of the measuring tube (1), The field loop assembly (9) comprises at least two field loops (10), The coil core (7) connects the pole shoe (5) to the field circuit (10).

23. The flow meter according to claim 22, in, At least one field loop component (9) adjoins the outer wall of the measuring tube (1).

24. Flow meter according to one of claims 1 to 11, in, All measuring electrodes (3) of the measuring electrode group (16) are short-circuited.

25. Flow meter according to one of claims 1 to 11, in, The measuring electrode arrangement (13) is arranged in a third cross section (C), The third cross section (C) is arranged between the first cross section (A) and the second cross section (B) and forms a symmetry plane of the coil core group (17) and a symmetry plane of the magnetic field generating device (4).

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