Magnetic-inductive flow meter

Abstract

The invention relates to a magnetic-inductive flow meter for determining a flow-rate-based measurement variable of a medium, comprising: - a measuring tube (10) for guiding the medium; - two measuring electrodes (21, 22); - an electronic measuring circuit (30) which is electrically connected to the two measuring electrodes (21, 22), the measuring circuit (30) being designed to determine a measurement voltage induced at the two measuring electrodes (21, 22), and the measuring circuit (30) being designed to determine a measurement value of the flow-rate-based measurement variable on the basis of the determined voltage value of the measurement voltage; - a coil assembly (41) for generating a magnetic field which at least partly passes through the measuring tube (10), the coil assembly (41) comprising a coil (45), and the coil (45) having a coil opening (49); and - a magnetic field guide (40), the magnetic field guide (40) comprising a coil core (47) which is situated in the coil opening (49). The magnetic-inductive flow meter is characterized in that the coil core (47) has two coil core parts (47a, 47b), between which is a separation (80).

Description

[0001] Magnetic-inductive flow meter

[0002] The invention relates to a magnetic-inductive flow meter for determining a flow velocity-dependent measured quantity of a medium.

[0003] Magnetic-inductive flowmeters are used to determine the flow velocity and / or volumetric flow rate of a free-flowing, electrically conductive medium in a pipeline. A magnetic-inductive flowmeter always includes a magnetic field-generating device designed to produce a magnetic field perpendicular to the horizontal axis of the measuring tube. This is typically achieved using a coil arrangement with a single coil or with several opposing coils. To ensure a largely homogeneous magnetic field, pole pieces can be shaped and attached so that the magnetic field lines run essentially perpendicular to the transverse axis across the entire cross-section of the pipe.A pair of measuring electrodes attached to the outer surface of the measuring tube detects an inductively generated electrical voltage. This voltage arises when a conductive medium flows along the longitudinal axis of the measuring tube under an applied magnetic field. Since the detected voltage depends on the velocity of the flowing medium according to Faraday's law of induction, the flow velocity and, with the addition of a known cross-sectional area of ​​the measuring tube, the volumetric flow rate of the medium can be determined from the voltage.

[0004] DE 10 2010 001 393 A1 discloses a magnetic-inductive flowmeter with a coil arrangement comprising two opposing coils, each with a coil former containing exactly one coil core made of stacked electrical steel sheets. The coil core has a widened end that serves as a pole piece. The coil core is fastened to the coil former by means of a sheet-metal fastening element, which has a groove that engages with a bung of the coil core in such a way as to achieve a positive-locking connection between the fastening element and the coil core.

[0005] A magnetic-inductive flowmeter is known from DE 10 2011 079 352, comprising a magnetic system of two opposing assemblies. Each assembly includes a pole shoe, a cylindrical coil with a coil core, and a field feedback plate. The two field feedback plates overlap in an electrode area. The two assemblies are fixed to the measuring tube by means of a mounting clip, which serves as a spring clamping element, and a screw. A disadvantage of this solution is the fixing of the two field feedback plates in the electrode area, since there is no bearing surface for the two field feedback plates in this area, and they must therefore be connected to each other while suspended in mid-air.DE 10 2016 133 461 A1 teaches a magnetic-inductive flowmeter with a magnetic system consisting of two cylindrical coils, two coil cores and two field feedback plates, which field feedback plates are arranged on the measuring tube in such a way that the respective end areas of the field feedback plates in the coil areas rest on the respective coil bodies and overlap there.

[0006] The magnetic systems of the aforementioned prior art are not suitable for applications requiring very rapid measurements. Such a requirement exists when solids are present in the medium, the medium has very low conductivity, and / or rapid flow rate changes are expected (e.g., in a filling process). Therefore, it is necessary to find a solution.

[0007] The problem is solved by the magnetic-inductive flowmeter according to claim 1.

[0008] The magnetic-inductive flow meter according to the invention for determining a flow velocity-dependent measured quantity of a medium, comprising:

[0009] - a measuring tube for guiding the medium;

[0010] - two measuring electrodes;

[0011] - an electronic measuring circuit which is electrically connected to the two measuring electrodes, wherein the measuring circuit is configured to determine a measuring voltage induced at the two measuring electrodes, wherein the measuring circuit is configured to determine a measured value of the flow velocity-dependent measured quantity as a function of a determined voltage value of the measuring voltage;

[0012] - a coil arrangement for generating a magnetic field penetrating the measuring tube at least partially, wherein the coil arrangement comprises a coil, the coil having a coil opening,

[0013] - a magnetic field guide, wherein the magnetic field guide comprises a coil core which is arranged in the coil opening, characterized in that the coil core has two coil core parts, wherein there is a separation, in particular a complete separation, between the two coil core parts, wherein the two coil core parts are spaced apart by the separation in a transverse direction to a longitudinal axis of the measuring tube.

[0014] It has been found that by providing a spatial separation between the two coil core sections, or by separating a typically single-piece coil core into two sections, a significantly higher sampling rate can be achieved than with conventional magnetic-inductive flowmeters that have seamless and usually single-piece coil cores. The separation must be greater than the typical coating thicknesses (e.g., enamel coating) found on electrical steel sheets, which are only a few micrometers thick.

[0015] Investigations have shown that separating the two coil core sections transversely relative to the flow direction of the medium significantly reduces the interference signal in the form of voltage spikes at the measuring electrodes. These results are comparable to those obtained with active compensation of the measurement signal using shield voltages. The interference signal consists of voltage spikes that occur at the measuring electrodes when the magnetic field switches.

[0016] Advantageous embodiments of the invention are the subject of the dependent claims.

[0017] One embodiment provides that a non-magnetic spacer is arranged at least partially between the two coil core parts, which effects the separation.

[0018] The spacer can be an electrically insulating separator plate (e.g., a conventional printed circuit board). Alternatively, the spacer can also be electrically conductive. The spacer has a first contact surface that makes contact with the first of the two coil core sections and a second contact surface that makes contact with the second of the two coil core sections. Furthermore, the spacer can completely fill the space between the two coil core sections. However, this is not mandatory.

[0019] However, a large number of spacers can also be provided, which, for example, are spaced apart from each other between the two coil core parts in such a way that an air-filled free space is formed between the two coil core parts.

[0020] Plastic with a specific electrical conductivity of less than 1 • IO is particularly suitable as a material. -13 S / m. The spacers must be designed in such a way that eddy currents propagating in the respective coil core parts are electrically decoupled.

[0021] One embodiment provides that the magnetic field guide comprises a pole shoe, wherein the pole shoe has two pole shoe parts. These two pole shoe parts are separated from each other transversely to the longitudinal axis of the measuring tube and a principal axis of the magnetic field or the coil of the measuring tube, and the two pole shoe parts are separated from the coil core. The separation of the two pole shoe parts can also be achieved by a spacer provided or arranged between the two pole shoe parts. The separation between the two pole shoe parts and the coil core can also be achieved without a spacer. In this case, the separation between the two pole shoe parts and the coil core is simply an air gap. According to this embodiment, it is only required that the pole shoe and the coil core are not a single component. In this case, the coil core can rest on the pole shoe, so that preferably no gap (e.g.,an air gap forms in between.

[0022] One embodiment provides that the coil core is designed at its end as a pole shoe, wherein the pole shoe has two pole shoe parts which are, in particular completely, separated from each other.

[0023] The pole shoe is the section of the coil core located outside the coil opening and between the coil and the measuring tube. The separation between the two pole shoe parts can also be achieved by a spacer positioned between them.

[0024] One embodiment provides that the separation of the coil core, in particular between the two coil core parts, has a minimum width bmin, where bmin is such that 0.1 mm < bmin < 10 mm, in particular 0.5 mm < b'min < 7 mm.

[0025] One embodiment provides that the separation of the pole shoe, in particular between the two pole shoe parts, has a minimum width b'min, where b'min is such that 0.1 mm < b'min < 10 mm, in particular 0.5 mm < b'min < 7 mm.

[0026] One embodiment provides that the magnetic field guidance includes a field feedback arrangement, which field feedback arrangement is designed to guide a magnetic field generated by the coil arrangement outside the measuring tube, wherein the field feedback arrangement includes two field feedback bodies, wherein the two field feedback bodies are arranged opposite each other on the measuring tube in such a way that at least one gap is formed between the two, which separates the two field feedback bodies from each other.

[0027] The gap between the two field feedback elements can be a pure air gap, meaning that the volume forming the gap is filled exclusively with air. Alternatively, the spacer of the coil core can extend section by section between the two field feedback elements, thus forming the gap. In this case, at least section by section, a material, particularly a non-magnetic material, is present in the gap. Therefore, it is not a pure air gap. However, if the spacer fills only a relatively small portion of the gap volume, it is still an air gap as defined by the invention. Alternatively or additionally to the spacer of the coil core, a separate spacer for the field feedback arrangement can be provided, configured to form the gap between the two field feedback elements. For example, the spacer can be part of the coil core.The spacer is preferably non-magnetic or non-magnetizable. The spacer can completely fill the gap, thereby creating a gap as defined in the invention, although not an air gap.

[0028] One design provides for the gap and the separation to be positioned one above the other.

[0029] One embodiment provides that the two field feedback bodies and the coil core are symmetrical with respect to an imaginary plane of symmetry, wherein the longitudinal axis of the measuring tube lies in the plane of symmetry, and a measuring electrode axis intersecting the two measuring electrodes perpendicularly intersects the plane of symmetry.

[0030] One embodiment provides that the coil comprises a first coil longitudinal axis, wherein the coil longitudinal axis passes through the separation, and the coil longitudinal axis intersects the gap.

[0031] One embodiment provides that the coil arrangement comprises a first and a second coil, wherein the first coil and the second coil are arranged opposite each other on the measuring tube, wherein the first coil and the second coil are connected to each other via the field feedback arrangement in such a way that magnetic field lines generated via the first coil are guided to the second coil (and vice versa) via the field feedback arrangement, in particular the two field feedback elements.

[0032] One embodiment provides that the magnetic field guidance in a cross-section through the magnetic-inductive flowmeter is completely separated by the plane of symmetry.

[0033] This achieves a complete separation of the magnetic circuit into two independent magnetic circuits.

[0034] One embodiment provides that the two coil core parts comprise a first coil core part and a second coil core part, wherein the coil core further comprises at least a third coil core part, wherein the third coil core part is arranged offset in the longitudinal direction of the measuring tube to the first coil core part, wherein there is a further separation between the third coil core part and the first coil core part, wherein the first coil core part and the third coil core part are spaced apart in the direction of the longitudinal axis of the measuring tube by the further separation.

[0035] One embodiment provides that a non-magnetic and / or electrically insulating spacer is arranged between the first and third coil core parts, which causes further separation.

[0036] One embodiment provides that the spacer and the further spacer are monolithic.

[0037] The invention is explained in more detail with reference to the following figures. They show:

[0038] Fig. 1 : a first embodiment of a coil core according to the invention;

[0039] Fig. 2: a top view of a magnetic field guide according to the invention;

[0040] Fig. 3: a cross-section through a first embodiment of the magnetic-inductive flowmeter according to the invention;

[0041] Fig. 4: a cross-section through a second embodiment of the magnetic-inductive flowmeter according to the invention;

[0042] Fig. 5: a longitudinal section through a third embodiment of the magnetic-inductive flowmeter according to the invention; and

[0043] Fig. 6: a second embodiment of the coil core according to the invention.

[0044] Fig. 1 shows an embodiment of a coil core 47 according to the invention for arrangement in a coil opening of a coil and for amplifying the magnetic field strength of the magnetic field generated by the coil. The coil core 47 shown is composed of several individual parts. In this specific case, the coil core 47 comprises two coil core parts 47a, 47b, which are spaced apart from each other by a complete separation 80. This means that the two coil core parts 47a, 47b are neither in contact nor form a single component, as is taught, for example, in DE 10 2018 125 865 A1. The two coil core parts 47a, 47b can be identical parts. Furthermore, the two coil core parts 47a, 47b can each consist of electrical steel sheets stacked and stamped perpendicular to their own longitudinal axis. Both coil core parts 47a, 47b are shaped at their ends in such a way that the magnetic field lines exit over as large an exit area as possible.For this purpose, the effective thickness of the respective coil core sections 47a, 47b increases towards their ends. Furthermore, the coil core sections 47a, 47b are curved in the end section EA, with the curvature assuming a radius of curvature equal to that of the outer surface of the measuring tube. The aforementioned end section EA of the coil core 47 functions as a pole shoe 71. The respective end sections EA of the two coil core sections 47a, 47b function as pole shoe sections 71a, 71b. According to the illustrated embodiment, the pole shoe sections 71a, 71b are each monolithically connected to the coil core sections 47a, 47b. The pole shoe sections 71a, 71b are completely separated from each other and do not touch.

[0045] The separation 80 of the coil core 47 has a minimum width bmin. For bmin, 0.5 mm < bmin < 10 mm. In the illustrated embodiment, the separation 80 extends along the entire length of the coil core 47, i.e., the separation 80 separates the coil core parts 47a, 47b, as well as the pole shoe parts 71a, 71b. The width of the separation 80 is constant along its entire longitudinal axis and is between 1 and 2 millimeters. The width of the separation 80 can be between 0.5 and 10 millimeters.

[0046] In the illustrated embodiment, the separation 80 of the two coil core parts 47a, 47b is achieved by a non-magnetic and / or electrically insulating spacer 81, which is arranged between the two coil core parts 47a, 47b. The spacer 81 can, for example, be made of a plastic, particularly a fiber-reinforced plastic. The illustrated spacer 81 has a rectangular cross-section. However, the spacer 81 can also have a different shape. Furthermore, the spacer 81 is bonded to the two coil core parts 47a, 47b (e.g., by adhesive bonding). The spacer 81 can also be bonded to the two pole shoe parts 71a, 71b.

[0047] One embodiment provides that a separation 82 of the pole shoe 71, in particular between the two pole shoe parts 71 a, 71 b, has a minimum width b'min, for which 0.5mm < b'min < 10mm (see also Fig. 4).

[0048] Fig. 2 shows a top view of an embodiment of the magnetic field guide 40 according to the invention (see Fig. 3). A coil former 70 of the coil 45 has (exactly) one coil opening in which the coil core of Fig. 1 is fixedly arranged. A field feedback arrangement 42 is configured to guide a magnetic field generated by the coil arrangement 41 outside the measuring tube. For this purpose, the field feedback arrangement 42 comprises two field feedback elements 43, 44, which are in contact with the coil core at their respective end regions. A gap 50, in particular an air gap, is located between the two field feedback elements 43, 44, so that the field feedback elements 43, 44 do not touch each other at any point. An air gap within the meaning of the invention means that the gap 50 is neither filled by a magnetizable material nor bridged by a magnetizable component which rests on an outer surface of the field feedback body 43, 44 facing away from the measuring tube 10.The gap 50 has a longitudinal axis which lies within an imaginary plane of symmetry of the coil core passing through the separation 80. The plane of symmetry of the separation 80 does not touch the two coil core parts.

[0049] The field feedback elements 43, 44 can be two identical parts, each formed from a multitude of electrical steel sheets stacked, particularly in the flow direction of the medium. The field feedback elements 43, 44 are U-shaped and together encircle the measuring tube.

[0050] The field feedback arrangement 42 is arranged relative to the coil core in such a way that the gap 50 and the separation 80 are superimposed.

[0051] The separation 80 can have a guide for at least one signal cable. The at least one signal cable connects one of the measuring electrodes to the measuring electronics. Alternatively, the signal cable can also be routed along the outer surface of the coil core or at least between the coil former and the coil core.

[0052] Fig. 3 shows a cross-section through a first embodiment of the magnetic-inductive flowmeter according to the invention for determining a flow velocity-dependent measured quantity. The flow velocity-dependent measured quantity is typically the current flow velocity of the flowable and electrically conductive medium to be monitored. Alternatively, the flow velocity-dependent measured quantity can be a volumetric flow rate or – if the medium density is known – a mass flow rate.

[0053] To guide the medium, the magnetic-inductive flowmeter typically has a measuring tube 10. The measuring tube 10 comprises a support tube. This support tube can be made of metal or of an electrically insulating plastic. If the support tube is metallic, its inner surface is usually lined with an electrically insulating material. The measuring tube typically has a hollow cylindrical shape, at least in some sections; however, magnetic-inductive flowmeters with a rectangular measuring tube cross-section, at least in some sections, are also known. The measuring tube 10 can be [unclear - possibly referring to a specific type of measuring tube] in the measuring section.

[0054] To determine the measured values ​​of the flow velocity-dependent quantity, the magnetic-inductive flowmeter typically has at least two measuring electrodes 21, 22 arranged in the measuring section of the measuring tube 10. The two measuring electrodes 21, 22 are arranged opposite each other and are intersected by an imaginary measuring electrode axis MEA. The measuring electrode axis MEA runs perpendicular to a longitudinal axis ML of the measuring tube and to a principal axis of the generated magnetic field or to a symmetry axis SE. Magnetic-inductive flowmeters with more than two measuring electrodes are also known. The two measuring electrodes 21, 22 shown are in contact with the medium; that is, when a medium flows through the measuring tube, the measuring electrodes are in contact with the medium.However, capacitive measuring electrodes are also known that measure through the wall of the support tube and / or the liner and thus do not need to be in direct contact with the medium. Furthermore, magnetic-inductive flowmeters are also known that have two, three, or more measuring electrodes on each side. The two measuring electrodes shown in Fig. 3 are electrically connected to an electronic measuring circuit 30. This circuit is configured to determine a measuring voltage induced at the (at least) two measuring electrodes 21, 22. Based on the determined voltage value, a measured value of the flow velocity-dependent quantity can be determined by the measuring circuit 30. The measuring circuit 30 includes electronic components such as amplifiers, converters, microcontrollers, and / or microprocessors for this purpose.If the magnetic-inductive flowmeter has more than two measuring electrodes, the measuring electrodes located on each side of the measuring tube can be electrically short-circuited before being connected to the measuring circuit 30. Alternatively, each measuring electrode can be connected separately to the measuring circuit 30.

[0055] To generate the magnetic field, the magnetic-inductive flowmeter has a coil arrangement 41. The coil arrangement 41 can comprise one coil 45 or several coils 45, 46. In the prior art shown, the coil arrangement 41 comprises two opposing coils 45, 46. The coils 45, 46 can each comprise a coil former, usually made of plastic, around which a coil wire is wound. The coil former itself has a coil opening for a coil core 47, 48. The coil cores 47, 48 are part of a magnetic field guide 40, which is designed to guide the magnetic field lines outside the measuring tube and partially inside the coil 45, 46. Pole shoes 71, 72 can also be provided, each magnetically coupled to one of the two coil cores 47, 48 and arranged between the coil core 47, 48 and the measuring tube. The pole shoes 71, 72 are also part of the magnetic field guide 40.The coil assembly 41 is designed to generate the magnetic field. For this purpose, the coil assembly is electrically connected to an electronic operating circuit that provides an operating voltage to the coil assembly. The operating voltage can be configured such that the generated magnetic field alternates periodically between different field states.

[0056] Both coil cores 47, 48 are variants of the coil core shown in Fig. 1. The reference numerals from Fig. 1 have been adopted. The field feedback arrangement 42 is designed to guide a magnetic field generated by the coil arrangement 41 outside the measuring tube 10. For this purpose, the field feedback arrangement 42 has at least two field feedback elements 43, 44. Fig. 3 shows exactly two field feedback elements 43, 44 in the form of field feedback plates, which are arranged opposite each other on the measuring tube 10. The field feedback elements 43, 44 are magnetically coupled directly to a coil core 47, 48. Furthermore, the two field feedback bodies 43, 44 are arranged opposite each other on the measuring tube 10 such that a gap 50 forms between them, separating them from one another. This gap 50 can be implemented as an air gap, i.e.,that the gap is free of material other than air, and ensures a minimum distance n between the two field feedback bodies 43, 44. As already taught in DE 10 2019 112 742 A1, separating the field feedback bodies by a gap leads to a faster adjustment of the electrical voltage induced by the magnetic field in the medium when transitioning from a first field state to a second field state.

[0057] Furthermore, the two field feedback bodies 43, 44, or rather their basic form, are symmetrical with respect to a plane of symmetry SE. For clarity, the plane of symmetry SE is shown in Fig. 3 slightly offset from a coil longitudinal axis SL1 of coil 45 and a coil longitudinal axis SL2 of coil 46. The measuring tube longitudinal axis ML of the measuring tube 10 lies in the plane of symmetry SE or, together with one of the two coil longitudinal axes SL1, SL2, or a main field axis of the generated magnetic field, spans the plane of symmetry SE. In addition, a measuring electrode axis MEA, which intersects the two measuring electrodes 21, 22, intersects the plane of symmetry SE perpendicularly. Symmetrical can mean mirror symmetry. Alternatively or additionally, the two field feedback bodies 43, 44 can also be point-symmetrical with respect to a center of symmetry that lies on the measuring tube longitudinal axis ML.Alternatively or additionally, the two field feedback bodies 43, 44 can have axial symmetry in a cross-section through the measuring tube 10 and the two field feedback bodies 43, 44.

[0058] The illustrated coil arrangement 41 has a coil 45 with a coil longitudinal axis SL1. The gap 50 is located radially behind the coil core 47 and / or the coil 45, extending from the measuring tube. According to Fig. 3, the coil longitudinal axis SL1 intersects the gap 50. Furthermore, the imaginary coil longitudinal axis SL1 runs within the separation 80 of the coil core 47.

[0059] A further gap 51 may also be provided, located in an area around the coil 46 and likewise formed by the two field feedback elements 43, 44. The imaginary longitudinal axis of the coil SL2 runs within the separation of the coil core 48 and intersects the gap 51. Fig. 4 shows a cross-section through a second embodiment of the magnetic-inductive flowmeter according to the invention. The second embodiment differs from the first embodiment essentially in that the pole shoe 71 and the coil core 47, or the pole shoe 72 and the coil core 48, are not formed as a single piece. The coil core 47 shown is composed of several individual parts. In this specific case, the coil core 47 comprises two coil core parts 47a, 47b, which are spaced apart from each other by a separation 80. The separation 80 can be implemented by a spacer, as shown in Fig. 1.The two coil core parts 47a, 47b are identical. Separate pole shoes 71, 72 are provided. These each comprise two pole shoe parts 71a, 71b, which are themselves separated from each other by a separator 82. The separator 82 can be implemented by a spacer.

[0060] Furthermore, the magnetic system 40, as shown, can have a magnetic or magnetizable coupling element 60 that bridges the gap 50 between the two field feedback elements 43, 44, so that these two are magnetically coupled to each other via the coupling element 60. The coupling element 60 is arranged, at least partially, directly or indirectly on the respective outer surface of the two field feedback elements 43, 44, thus achieving magnetic coupling. "Magnetic" in the sense of the invention means that it is a component with soft magnetic or hard magnetic properties. It has been experimentally demonstrated that with such an arrangement, a better matching of the induced electronic voltage in the medium can be achieved than with magnetic-inductive flow meters with two overlapping field feedback elements.

[0061] According to the embodiment shown in Fig. 4, a further coupling element 61 can be provided, which bridges the gap 51 formed by the two field feedback elements 43, 44 in the area of ​​the coil 46. The further coupling element 61 can also be arranged, like the coupling element 60, either directly or indirectly resting on the outer surfaces of the two field feedback elements 43, 44. The two coupling elements 60, 61 can be identical components.

[0062] Alternatively, the two coupling bodies 60, 61 can overlap the respective columns 50, 51 of the two field feedback bodies 43, 44 in the electrode area.

[0063] As shown, two coil core coupling bodies 90, 91 can be provided, each arranged between the coil core 47, 48 and the gap 50, 51, and providing magnetic coupling between the coil core 47, 48 and the field feedback bodies 43, 44. Alternatively, the magnetic-inductive flowmeter can also be free of a coil core coupling body 90, 91, and the magnetic coupling between the coil core 47, 48 and the two field feedback bodies 43, 44 is achieved via direct contact, as shown in Fig. 3. Fig. 5 shows a longitudinal section through a third embodiment of the magnetic-inductive flowmeter according to the invention. The measuring tube 2 shown has a constricted cross-section (i.e., a cross-sectional narrowing in the measuring section).In addition to a first coil core section 47a and a second coil core section (not shown) spaced transversely from the first coil core section 47a relative to the longitudinal axis ML of the measuring tube, the coil core 47 further comprises at least a third coil core section 47c. Figure 5 shows that the third coil core section 47c is arranged offset from the first coil core section 47a in the longitudinal direction of the measuring tube 2. Furthermore, there is a further complete separation 110 between the third coil core section 47c and the first coil core section 47a. This further separation 110 spaced the first coil core section 47a and the third coil core section 47c apart in the direction of the longitudinal axis ML of the measuring tube. The separation 110 can be a pure air gap, a partially filled air gap, or a completely filled gap.

[0064] The coil core 47 can also include a fourth coil core (not shown), which is arranged transversely to the third coil core along the longitudinal axis ML of the measuring tube. A separation can also be provided between the third coil core section 47c and the fourth coil core section. Furthermore, the fourth coil core can be positioned offset from the second coil core section (not shown) in the longitudinal direction of the measuring tube 2, so that a separation is also achieved between the second and fourth coil core sections.

[0065] The complete separation 110 can be achieved by a further non-magnetic and / or electrically insulating spacer 111 arranged between the first and third coil core sections 47a, 47c. This further spacer 111 can be a separate component positioned between the first and third coil core sections 47a, 47c. Alternatively, the spacer 81 and the further spacer 111 can be monolithic. For example, the monolithic spacer component can have a cross-sectional contour resembling a Swiss cross.

[0066] Fig. 6 shows a second embodiment of the coil core 47 according to the invention. The second embodiment differs from the first embodiment of Fig. 1 essentially in that the separation 80 is implemented as a pure air gap and no spacer is provided. Likewise, the separation 82 of the pole shoe 71 is designed as a pure air gap.

Claims

PATENT CLAIMS 1. Magnetic-inductive flow meter for determining a flow velocity-dependent measured quantity of a medium, comprising: - a measuring tube (10) for guiding the medium; - two measuring electrodes (21 , 22); - an electronic measuring circuit (30) which is electrically connected to the two measuring electrodes (21 , 22), wherein the measuring circuit (30) is configured to determine a measuring voltage induced at the two measuring electrodes (21 , 22), wherein the measuring circuit (30) is configured to determine a measured value of the flow velocity-dependent measured quantity as a function of a determined voltage value of the measuring voltage; - a coil arrangement (41) for generating a magnetic field penetrating the measuring tube (10) at least partially, wherein the coil arrangement (41) comprises a coil (45), the coil (45) having a coil opening (49), - a magnetic field guide (40), wherein the magnetic field guide (40) comprises a coil core (47) which is arranged in the coil opening (49), characterized in that the coil core (47) has two coil core parts (47a, 47b), wherein there is a complete separation (80) between the two coil core parts (47a, 47b), wherein the two coil core parts (47a, 47b) are spaced apart by the separation (80) in a transverse direction to a longitudinal axis (ML) of the measuring tube (10).

2. Magnetic-inductive flow meter according to claim 1, wherein a non-magnetic and / or electrically insulating spacer (81) is arranged between the two coil core parts (47a, 47b), which effects the separation (80).

3. Magnetic-inductive flow meter according to claim 1 or 2, wherein the magnetic field guide (40) comprises a pole shoe (71), wherein the pole shoe (71) has two pole shoe parts (71a, 71b) which are completely separate from each other.

4. Magnetic-inductive flowmeter according to claim 1 or 2, wherein the coil core (47) is designed at its end as a pole shoe (71), wherein the pole shoe (71) has two pole shoe parts (71a, 71b) which are separated from each other, wherein the two pole shoe parts (71a, 71b) are separated from the coil core (47).

5. Magnetic-inductive flowmeter according to one of the preceding claims, wherein the separation (80) has a minimum width bmin, wherein bmin is such that 0.5mm < bmin < 10mm.

6. Magnetic-inductive flowmeter according to one of the preceding claims, wherein the magnetic field guide (40) comprises a field feedback arrangement (42) which field feedback arrangement (42) is configured to guide a magnetic field generated by means of the coil arrangement (41) outside the measuring tube (10), wherein the field feedback arrangement (42) comprises two field feedback bodies (43, 44), wherein the two field feedback bodies (43, 44) are arranged opposite each other on the measuring tube (10) such that at least one gap (50) is formed between the two, which separates the two field feedback bodies (43, 44) from each other.

7. Magnetic-inductive flow meter according to claim 6, wherein the gap (50) and the separation (80) are located one above the other.

8. Magnetic-inductive flowmeter according to one of claims 6 to 7, wherein the two field feedback bodies (43, 44) and the coil core (47) are symmetrical with respect to a plane of symmetry (SE), wherein the longitudinal axis (ML) of the measuring tube (10) lies in the plane of symmetry (SE), and wherein a measuring electrode axis (MEA) intersecting the two measuring electrodes (21, 22) intersects the plane of symmetry (SE) perpendicularly.

9. Magnetic-inductive flowmeter according to one of claims 6 to 8, wherein the coil (45) comprises a first coil longitudinal axis (SL1), wherein the coil longitudinal axis (SL1) passes through the separation (80), wherein the coil longitudinal axis (SL1) intersects the gap (50).

10. Magnetic-inductive flowmeter according to claims 6 to 9, wherein the coil arrangement (41) comprises a first and second coil (45, 46), wherein the first coil (45) and the second coil (46) are arranged opposite each other on the measuring tube (10), wherein the first coil (45) and the second coil (46) are connected to each other via the field feedback arrangement (42) in such a way that magnetic field lines generated via the first coil (45) are guided via the field feedback arrangement (42), in particular the two field feedback elements (43, 44), to the second coil (46) (and vice versa).

11. Magnetic-inductive flowmeter according to one of the preceding claims, wherein the magnetic field guide (40) in a cross-section through the magnetic-inductive flowmeter is completely separated by the plane of symmetry (SE).

12. Magnetic-inductive flowmeter according to one of the preceding claims, wherein an electronic operating circuit (100) is configured to provide an operating voltage to the coil arrangement (41), wherein the operating voltage is configured such that the generated magnetic field alternates periodically between different field states, wherein a frequency of a change of the field states is greater than 5 Hz and in particular greater than 12 Hz and preferably greater than 20 Hz.

13. Magnetic-inductive flowmeter according to one of the preceding claims, wherein the two coil core parts (47a, 47b) comprise a first coil core part (47a) and a second coil core part (47b), wherein the coil core (47) further comprises at least a third coil core part (47c), wherein the third coil core part (47c) is arranged offset in the longitudinal direction of the measuring tube (2) relative to the first coil core part (47a), wherein there is a further complete separation (110) between the third coil core part (47c) and the first coil core part (47a), wherein the first coil core part (47a) and the third coil core part (47c) are spaced apart by the further separation (110) in the direction of the longitudinal axis (ML) of the measuring tube.

14. Magnetic-inductive flow meter according to claim 13, wherein a non-magnetic and / or electrically insulating further spacer (111) is arranged between the first and third coil core part (47a, 47c), which effects the further separation (110).

15. Magnetic-inductive flow meter according to claim 14, wherein the spacer (81) and the further spacer (111) are monolithic.

Images