Magnetic-inductive flow meter
The magnetic-inductive flowmeter addresses the issue of suboptimal magnetic field distribution by using spaced coil cores and a field return mechanism with spacers, enhancing sensitivity and reducing assembly time, leading to improved flow measurements.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ENDRESS HAUSER FLOWTEC AG
- Filing Date
- 2025-12-02
- Publication Date
- 2026-06-25
Smart Images
Figure EP2025085036_25062026_PF_FP_ABST
Abstract
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 2019 123 409 A1 discloses a magnetic-inductive flowmeter with a magnetic system comprising at least one two-part pole shoe, in which the two pole shoe parts are separated by a gap transverse to the longitudinal direction of the measuring tube, and magnetic field guide plates resting directly on the outer surface of the measuring tube. Coil cores are arranged on the magnetic field guide plates, magnetically coupling the magnetic field guide plates and the pole shoe. The coil cores extend through coil formers whose longitudinal axis is parallel to the longitudinal axis of the measuring tube. A disadvantage of the magnetic system of DE 10 2019 123 409 A1 is the increased CALF (calculated magnetic field strength) or lower sensitivity resulting from the magnetic field distribution.
[0005] The invention is based on the objective of providing a remedy for this problem.
[0006] The problem is solved by the magnetic-inductive flowmeter according to claim 1.
[0007] The magnetic-inductive flow meter according to the invention for determining a flow velocity-dependent measured quantity of a medium comprises:
[0008] - a measuring tube for guiding the medium;
[0009] - two measuring electrodes; - an electronic measuring circuit which is electrically connected to the two measuring electrodes;
[0010] - a coil arrangement for generating a magnetic field penetrating at least section by section of the measuring tube, wherein the coil arrangement comprises a first coil with a first coil core receptacle and a second coil with a second coil core receptacle; and
[0011] - a magnetic field guide, wherein the magnetic field guide comprises a first coil core and a second coil core, wherein the first coil core is arranged in the first coil core receptacle, wherein the second coil core is arranged in the second coil core receptacle, wherein the magnetic field guide comprises a field return which connects the first coil core to the second coil core, wherein the field return is spaced apart from the measuring tube by means of at least one, in particular arc-shaped, spacer.
[0012] By protruding a spaced-apart field feedback element, preferably arranged in the same cross-sectional plane as the first and / or second coil core, it can be ensured that the magnetic field lines of the generated magnetic field do not have to extend along the longitudinal axis of the measuring tube in the direction of the field feedback element, but remain essentially in the cross-sectional plane. The field feedback element preferably comprises at least one non-grain-oriented electrical steel sheet.
[0013] Furthermore, the use of spacers simplifies the assembly of the magnetic system and significantly reduces the assembly time.
[0014] Advantageous embodiments of the invention are the subject of the dependent claims.
[0015] One embodiment provides that the first and second coil cores are fixed to the measuring tube via a band, with at least one spacer bridging the band.
[0016] One embodiment provides that the magnetic-inductive flowmeter is cut by an imaginary longitudinal plane which divides the measuring tube into a first and second side, wherein at least two measuring electrodes are attached to the first side, wherein the at least two measuring electrodes of the first side are short-circuited to each other via a first connecting element, wherein the at least one spacer bridges the connecting element.
[0017] One embodiment provides that the at least one spacer has a cable guide, in particular in the form of two hooks, for a grounding, signal and / or coil cable. Another embodiment provides that the at least one spacer is dimensioned such that a minimum distance Dmin is maintained between the outer surface of the measuring tube and the first magnetic field guide plate, wherein the minimum distance Dmin is such that 10 < Dmin < 100 millimeters, in particular
[0018] 15 < Dmin < 75 millimeters and preferably Dmin < 60 millimeters.
[0019] One embodiment provides that the maximum distance Dmax is dimensioned such that an outer diameter of a housing enclosing the magnetic field guide and the coil arrangement is smaller than an outer diameter of a connection element (e.g. flange).
[0020] One embodiment provides that the field feedback comprises a first magnetic field guide plate and a second magnetic field guide plate, wherein the first magnetic field guide plate and / or the second magnetic field guide plate connects the first coil core to the second coil core.
[0021] One embodiment provides that the at least one spacer has a bearing surface on which the first magnetic field guide plate rests, wherein the at least one spacer is connected to the first magnetic field guide plate by material, form and / or force-fit.
[0022] One embodiment provides that at least one spacer is made of a non-magnetic material, in particular a plastic.
[0023] One embodiment provides that at least one spacer comprises a bent sheet metal part.
[0024] The invention is explained in more detail with reference to the following figures. They show:
[0025] Fig. 1 : a partial section of a cross-section through an embodiment of the magnetic-inductive flowmeter according to the invention;
[0026] Fig. 2: a further partial section of a cross-section through the design of the magnetic-inductive flowmeter of Fig. 1;
[0027] Fig. 3: a perspective view of the design of the magnetic-inductive flowmeter according to the invention of Fig. 1;
[0028] Fig. 4: an exploded view of a further embodiment of the magnetic-inductive flowmeter according to the invention; Fig. 5: a perspective view of a partial section of an embodiment of the magnetic-inductive flowmeter according to the invention; and
[0029] Fig. 6: an embodiment of a spacer.
[0030] Fig. 1 shows an upper partial section of a cross-section through an embodiment of the magnetic-inductive flowmeter 1a according to the invention. Fig. 2 shows a further partial section of a cross-section through the embodiment of the magnetic-inductive flowmeter 1a according to the invention. Fig. 3 shows a perspective view of the embodiment of the magnetic-inductive flowmeter 1a according to the invention. The magnetic-inductive flowmeter 1a is configured to determine a flow velocity-dependent measured quantity of a medium. 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.
[0031] The magnetic-inductive flowmeter 1a comprises a measuring tube 10 for guiding the medium, which is particularly conductive and flowable. The measuring tube 10 includes a support tube 102. This support tube can be metallic or made of an electrically insulating plastic. If the support tube 102 is metallic, its inner surface is usually provided with an electrically insulating material, also referred to as a liner 101. The measuring tube 10 typically has a hollow cylindrical shape, at least in some sections; however, magnetic-inductive flowmeters with a rectangular cross-section are also known. The measuring tube 10 has an inner surface that is in contact with the medium during operation and an outer surface MF that faces away from the medium.The measuring tube 10 itself has a characteristic nominal diameter DN, which is usually between 10 and 3000 millimeters for magnetic-inductive flow meters.
[0032] To determine the measured values of the flow velocity-dependent quantity, the magnetic-inductive flowmeter typically has at least two measuring electrodes 21, 22 (see Fig. 3). 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 LA of the measuring tube and to a principal axis MFA of the generated magnetic field, or to an axis of symmetry of the magnetic field. The measuring electrode axis MEA does not necessarily have to pass through the center point of the measuring tube 2, but can also intersect the measuring tube 10 off-center. The at least two measuring electrodes 21, 22 shown are in contact with the medium; that is, when a medium flows through the measuring tube 10, the at least two measuring electrodes 21, 22 are in direct contact with the medium. For this purpose, at least two measuring electrodes 21, 22 are each inserted into a designated measuring electrode opening (e.g.The measuring electrodes are arranged (e.g., in the form of a through-opening) of the measuring tube 10. However, capacitive measuring electrodes (not shown) are also known which measure through the wall of the support tube 102 and / or the liner 101 and thus do not need to be in direct contact with the medium. The at least two measuring electrodes 21, 22 are electrically connected to an electronic measuring circuit 30 (shown schematically in Fig. 3). The measuring circuit 30 is configured to determine a measuring voltage induced at the two measuring electrodes and to determine the flow velocity-dependent measured quantity as a function of the induced measuring voltage. The measuring circuit 30 can be part of the sensor or part of a transmitter (not shown), as shown.
[0033] Furthermore, magnetic-inductive flowmeters are also known which have two, three, or more measuring electrodes on each side of the measuring tube. A longitudinal plane perpendicular to the measuring tube axis MEA divides the measuring tube into a first and second measuring tube side. The illustrated embodiment of the magnetic-inductive flowmeter 1a has a total of six measuring electrodes 21, 22, 24, 25, 26, 27. Three measuring electrodes are provided per measuring tube side. The three measuring electrodes 21, 24, 25 of the first measuring tube side and / or the three measuring electrodes 22, 26, 27 of the second measuring tube side can be electrically connected (i.e., short-circuited) to each other via an electrically conductive connecting element (cable or sheet metal part).
[0034] To generate a magnetic field that penetrates at least part of the measuring tube 10, the magnetic-inductive flowmeter 1a has a coil arrangement 41. The coil arrangement 41 comprises at least one coil arranged on the outer surface MF of the measuring tube 10. The at least one coil can be a cylindrical coil. Typically, at least two opposing coils are used.
[0035] The illustrated coil arrangement 41 has a first coil 45a, which itself comprises a first coil former 46a, in particular a monolithic one, around which a coil wire 48 is wound. The first coil former 46a can be made of a non-magnetic plastic. According to the invention, the first coil former 46a is configured such that it has a first coil core receptacle SKA1. The first coil core receptacle SKA1 can, for example, be configured as a through-chamber.
[0036] The illustrated coil arrangement 41 has a second coil 45b, which itself comprises a second coil former 46b, in particular a monolithic one, around which a coil wire is wound. The second coil former 46a can be made of a non-magnetic plastic. According to the invention, the second coil former 46b is configured such that it has a second coil core receptacle SKA2. The second coil core receptacle SKA2 can, for example, be configured as a through-hole.
[0037] The first coil former 46a can have a third coil core receptacle SKA3. The first coil core receptacle SKA1 can be completely spatially separated from the third coil core receptacle SKA3, particularly perpendicular to an imaginary principal axis SHA of the first coil former 46a. This ensures that the coil cores arranged in the respective coil core receptacles are completely magnetically decoupled from one another. The imaginary principal axis SHA of the first coil former 46a runs parallel to the imaginary principal axis MFA of the generated magnetic field and perpendicular to a longitudinal axis LA of the measuring tube. The first coil former 46a and / or the second coil former 46b can be a plastic part manufactured by an injection molding process.
[0038] The first coil former 46a can have at least one partition 44a, as shown, which separates the first coil core receptacle SKA1 from the third coil core receptacle SKA3. The partition 44a can extend in the direction of the longitudinal axis LA, with its longitudinal extent being greater than its transverse extent to the longitudinal direction of the measuring tube 10. The partition 44a at least partially delimits the first coil core receptacle SKA1.
[0039] Furthermore, the first coil body 46a can have a feedthrough chamber DK through which at least one signal cable 100, at least partially a level monitoring electrode 20, at least partially a reference electrode 23, and / or a fixing bolt 71 extend. The signal cable 10 is configured to connect the measuring electrodes of one side of the measuring tube, or the measuring electrode of one side of the measuring tube, to the measuring circuit 30. The level monitoring electrode 20 is electrically connected to the measuring circuit 30. This circuit is configured to determine a level in the measuring tube 10, for example, by measuring the impedance at the level monitoring electrode 20. The reference electrode 23 is electrically connected to a reference potential. The fixing bolt is configured to fix the first coil 46a in a fixed position on the measuring tube 10.The feedthrough chamber DK can be located between the first coil core receptacle SKA1 and the third coil core receptacle SKA3 and can be separated from the first coil core receptacle SKA1 by at least one partition wall 44a. The feedthrough chamber DK is free of magnetic or magnetizable materials. For example, the feedthrough chamber DK can be predominantly filled with air or a potting compound (e.g., silicone).
[0040] The first coil former 46a can have a further partition 44b, which at least partially delimits the third coil core receptacle SKA3 and ensures that the first coil core receptacle SKA1 is separated from the third coil core receptacle SKA3. The further partition 44b also separates the third coil core receptacle SKA3 from the feedthrough chamber DK.
[0041] The first and / or second coil core holder SKA1, SKA2 can each have a non-circular contour in a longitudinal section, i.e., for example, an angular, in particular a rectangular, contour. The first and / or second coil core holder SKA1, SKA2 can each have planar surfaces that are adapted to a shape or surface of the coil core to be held.
[0042] The second coil former 46b, with the second and fourth coil core receptacles SKA2 and SKA4, may have partitions 44c and 44d designed to separate the second coil core receptacle SKA2 from the fourth coil core receptacle SKA4. The first and second coil formers 46a and 46b may be identical components. A feedthrough chamber may be provided between the second and fourth coil core receptacles, in which at least a reference electrode and / or a fixing pin is located.
[0043] Furthermore, the magnetic-inductive flowmeter 1a according to the invention has a magnetic field guide 40. The magnetic field guide 40 comprises magnetizable components that are suitable and configured to guide the magnetic field generated by the coil arrangement outside the measuring tube 10. The illustrated magnetic field guide 40 comprises, for example, a first and second coil core 47a, 47b, which are configured to increase the magnetic flux density in the first coil 45a. The first coil core 47a is arranged in the first coil core receptacle SKA1 and the second coil core 47b is arranged in the second coil core receptacle SKA2.
[0044] The first coil core 47a can, as shown, comprise a plurality N of coil core laminations 147a, ... , 147n stacked circumferentially around the measuring tube 10. In contrast to what is taught in DE 10 2015 109 747 A1 and DE 10 2010 001 393 A1, the coil core laminations 147a, ... , 147n are stacked transversely to the longitudinal axis LA and not along the longitudinal axis LA of the measuring tube. This has the advantage that the respective end sections of the coil core laminations 147a, ... , 147n do not need to have a shape adapted to the radius of the measuring tube in order to achieve ideal contact between the first coil core 47a and the outer surface of the measuring tube 10. Thus, coil core laminations adapted to the respective nominal diameter of the measuring tube 10 are no longer necessary. At least two adjacent coil core laminations 147i, 147i+1 of the plurality of coil core laminations 147a, ... , 147n each have a coil core lamination main axis SKHA1 , SKHA2 (see Fig.5) which runs parallel to an imaginary principal axis SHA of the first coil body 46a. The at least two adjacent coil core laminations 147i, 147i+1 can be positioned offset from each other in the direction of their respective coil core lamination principal axis SKHA1, SKHA2. Additionally, it may be required that all coil core laminations 147a, ... , 147n are arranged offset from each other in the direction of the imaginary principal axis SHA of the first coil body 46a. The first coil core receptacle SKA1 is designed such that, after the coil core laminations 147a, ... , 147n have been attached, their displacement in the circumferential direction and in the longitudinal direction of the measuring tube 10 is limited. However, displacement in the mounting direction remains possible. Only then is it possible to adapt the contact surface of the first coil core 47a to the outer surface MF of the measuring tube or to a first pole shoe 80a resting on the outer surface MF.Only the first fixing element 50a prevents the individual coil core laminations 147a, ... , 147n from shifting in the assembly direction or against the assembly direction.
[0045] The first coil core 47a can have a surface that can be described by a first curvature R1. The outer surface MF of the measuring tube 10, facing away from the medium, can be described by a second curvature R2. The first curvature R1 does not deviate from the second curvature R2 by more than 50%, in particular not by more than 25%, and preferably not by more than 10%. Preferably, the first curvature R1 is identical to the second curvature R2.
[0046] The first coil former 46a can have a first collar 72a for the first coil core receptacle SKA1, which is designed such that it prevents the first coil core 47a, in particular the coil core laminations 147a, ... , 147n, from fanning out. The first collar 72a can form part of the boundary of the first coil core receptacle SKA1. Furthermore, the first collar 72a can be described as enclosing the end regions of the coil core laminations 147a, ... , 147n.
[0047] The first coil former 46a can further have a second collar 72b for the third coil core receptacle SKA3, which is designed such that it prevents the third coil core 47c, and in particular the coil core laminations forming the third coil core 47c, from fanning out. The second collar 72b can form part of the boundary of the third coil core receptacle SKA3.
[0048] The first coil core 47a and / or the second coil core 47b can be arranged at least in a form-fitting manner, in particular exclusively in a form-fitting manner, in the first coil core receptacle SKA1 or the first and second coil core receptacles SKA1, SKA2.
[0049] Furthermore, the magnetic field guide 40 can include a first pole shoe 80a, in particular a curved one, which rests on the outer surface MF of the measuring tube. The first pole shoe is designed to distribute the magnetic field lines emanating from the first coil. The first coil core 47a and / or the third coil core 47c can rest, at least partially and directly, on the first pole shoe 80a. Furthermore, the magnetic field guide 40 can include a second pole shoe 80b, in particular a curved one, which rests on the outer surface MF of the measuring tube 10. The second pole shoe 80b is designed to distribute the magnetic field lines emanating from the second coil 45a. The second coil core 47b and / or the fourth coil core 47d can rest, at least partially and directly, on the second pole shoe 80b.
[0050] The first pole shoe 80a can comprise two pole shoe parts 80a', 80a" which are spaced apart from each other offset in the direction of the longitudinal axis LA of the measuring tube 10. A gap 81 for guiding a signal cable can thus be present between the two pole shoe parts 80a', 80a". The signal cable serves to connect one of the at least two measuring electrodes to the measuring circuit 30.
[0051] The first coil core 47a and / or the third coil core 47c can be arranged such that it bridges the two pole shoe parts 80a', 80a". The two pole shoe parts 80a', 80a" can each be a strip-shaped sheet made of stacked electrical steel sheets.
[0052] It is advantageous if there is a distance S between the first and third coil core 47a, 47c, for which S < 100 millimeters, in particular S < 60 millimeters, and S > 1 millimeter, in particular S > 30 millimeters.
[0053] The coil core laminations 147a, ... , 147n can be individual, electrically insulated electrical steel sheets. An electrical steel sheet is typically a cold-rolled strip of iron-silicon alloy. Electrical steel sheets used in magnetic systems are subject to standards EN 10106 and EN 10107. According to the design, the electrical steel sheets are loosely stacked. This means that there is no material bond between the individual coil core laminations 147a, ... , 147n. They can therefore be moved relative to each other in their stacked but not yet fully assembled state. This ensures that the contact surface of the coil core adapts to the outer surface MF of the measuring tube 10 during assembly, thus preventing an air gap.
[0054] The individual coil core laminations 147a, ... , 147n, designed as identical parts, can assume a polygonal (e.g., rectangular) contour. A longitudinal section through the coil core (or the stacked coil core laminations 147a, ..., 147n) extending to the main axis SKHA1, SKHA2 of the individual coil core laminations 147a, ... , 147n can also result in a polygonal (e.g., rectangular) contour. Furthermore, at least one coil core lamination 147a, 147n, or all of them, can
[0055] Coil core laminations 147a, ... , 147n each have a recess 140 for guiding a signal cable. The recess 140 can be located above the gap 81.
[0056] The magnetic field guide 40 can further comprise a field return 42. The field return 42 is configured to guide the magnetic field lines from the rear of the first and / or third coil core 47a, 47c to the rear of the second and / or fourth coil core 47b, 47d. The illustrated field return 42 comprises a first and second magnetic field guide plate 43a, 43b, which is configured to guide the magnetic field lines outside the measuring tube from the first coil 46a to the second coil 46b. For this purpose, the first magnetic field guide plate 43a, which connects the first coil core 47a to the third coil core 47c, and the second magnetic field guide plate 43b, which connects the second coil core 47b to the fourth coil core 47d, can be in direct contact with each other. Thus, the end regions of the first and second magnetic field guide plates 43a, 43b can overlap at the level of the measuring electrodes 21, 27.Alternatively, the first and second magnetic field guide plates 43a, 43b can also be arranged butt-jointed. Furthermore, the first and second magnetic field guide plates 43a, 43b rest on the surfaces of the corresponding coil cores 47a-d facing away from the measuring tube 10. The magnetic field guide plates positioned above the coil cores offer corresponding magnetic advantages for the measurement performance. The magnetic field remains more concentrated on the axis of the measuring tube, resulting in a lower CALF (Circular Acuity Fault). This allows the width of the magnetic system to be reduced, enabling a slimmer design. The field feedback 42, in particular the first and second magnetic field guide plates, is / are fixed above the measuring tube 10 by means of spacers 60 made of injection-molded plastic parts. The spacers 60 are also designed to be suitable for all nominal diameters and vary only in quantity.Cable guides are directly attached to these spacers 60, allowing the grounding cable, signal cable, and / or coil power cable to be routed across the entire length of the measuring tube 10 to the other side. The ends of the magnetic field guide plates 43a and 43b are placed one on top of the other on the spacer 60 above the signal electrode and fixed there. The magnetic field guide plates 43a and 43b are fastened to the spacer 60 by screws or rivets.
[0057] The magnetic-inductive flowmeter 1a can further comprise a first fixing element 50a. This element is designed to fix the first and second magnetic field guide plates 43a, 43b in a fixed position. For this purpose, it is curved and preferably non-magnetic. The first fixing element 50a is arranged such that it presses the first magnetic field guide plate 43a, 43b directly against the first coil core 47a or the first coil core 47a and the third coil core 473. Furthermore, the first fixing element 50a can be arranged such that it presses the second magnetic field guide plate 43b directly against the third coil core 47b. The first fixing body 50a can be overbent in the assembled state, so that a bending radius of the first fixing body 50a does not deviate by more than 10%, in particular 5% and preferably 1%, from a bending radius of a surface of the first and / or second coil core 47a, 47b facing the first fixing body 50a.The first fixing element 50a can be made of a non-magnetic and also non-magnetizable material. Stainless steel (e.g. 1.4301) is therefore preferably suitable as a material.
[0058] A second fixing body 50b can also be provided, which is arranged opposite the first fixing body 50a and is designed to press the second magnetic field guide plate 43b onto the second and fourth coil cores 47b, 47d or the first magnetic field guide plate 43b onto the second coil core 47b and the second magnetic field guide plate 43b onto the fourth coil core 47d.
[0059] The magnetic-inductive flowmeter 1a can further comprise a housing 200, which is designed to protect the measuring electrodes, measuring circuit, coil arrangement, and magnetic field guide. Magnetic-inductive flowmeters are also known in which the measuring circuit 30 is arranged outside the housing 200 in a separate transmitter housing (not shown).
[0060] The spacer 60 is dimensioned such that a maximum distance Dmax between the outer surface MF of the measuring tube and the back of the field feedback is selected such that the outer diameter of a housing 200 enclosing the magnetic field guide 40 and the coil assembly 41 is smaller than the outer diameter of a connection element (e.g., flange). A typical outer diameter of a connection element is between 55 and 60 millimeters. The housing 200 is preferably designed to have a pressure rating of PN6.
[0061] The illustrated embodiment of the magnetic-inductive flowmeter 1a is intersected by an imaginary longitudinal plane that divides the measuring tube 10 into a first and second side I, II. At least two measuring electrodes 21, 24, and in particular exactly three measuring electrodes 21, 24, 25, are attached to the first side I. The at least two measuring electrodes 21, 24 of the first side I are short-circuited to each other via a first connecting element 120. The connecting element 120 can be an electrically conductive cable or an electrically conductive sheet metal part that creates an electrical connection between the at least two measuring electrodes. The at least one spacer 60 is arranged and designed to bridge the connecting element 120. For this purpose, the spacer 60 has an arc.Furthermore, one of the at least one spacer 60 can also bridge a fastening device for fixing the measuring electrode shaft of the measuring electrodes. The fastening device can comprise a fastening sleeve, a leaf spring and / or a nut. The distance between the field feedback and the outer surface is also dimensioned such that it does not fall below the height of the coil former.
[0062] The at least one spacer 60 is connected to the measuring tube 10 by bolts. The bolts are connected to the measuring tube 10 by a weld. The first pole shoe 80a, in particular the pole shoe parts 80a', 80a", are also attached to the measuring tube 10 by the same bolts. A locking washer secures the pole shoe part 80a', 80a" to the measuring tube 10 in a first assembly step. Subsequently, the at least one spacer 60 is connected to the bolts, e.g., by means of nuts. The at least one spacer 60 has a recess for the locking washer (e.g., a quick-lock) on its lower side. The longest extension of the spacer, in particular the arc in the form of a beam bridging the pole shoe parts 80a', 80a", the connecting element 120, the mounting device of the measuring electrode 21, and / or the cable, points in the longitudinal direction of the measuring tube 10.
[0063] The at least one spacer 60 has a planar contact surface AF on which the first magnetic field guide plate 43a rests. A material-fit, form-fit, and / or force-fit connection can exist between the at least one spacer 60 and the first magnetic field guide plate 43a.
[0064] Fig. 4 shows an exploded view of a further embodiment of the magnetic-inductive flowmeter 1b according to the invention. Fig. 4 shows the first coil 45a with the coil former 46a and the first and third coil cores 47a, 47c arranged in the first and third coil core receptacles SKA1, SKA2. Fig. 4 also shows the first fixing element 50a. The following description also applies to the second coil (not shown) and the area around the second coil. The embodiment shown differs essentially from the embodiment of Fig.1 to 3 by the fact that the first and second magnetic field guide plates 43a, 43b are separated from each other by an (air) gap 130, such that the first magnetic field guide plate 43a is in contact exclusively with the first coil core 47a and second coil core 47b of the magnetic field guide 40, and the second magnetic field guide plate 43b is in contact exclusively with the third and fourth coil cores 47c, 47d of the magnetic field guide 40. There is no direct contact between the two magnetic field guide plates 43a, 43b.
[0065] The magnetic field guide 40 has a first and second magnetic field guide plate 43a, 43b, each configured to guide the magnetic field lines outside the measuring tube 10 from the first coil 46a to the second coil 46b and from the second coil 46b to the first coil 46a, respectively. The two magnetic field guide plates 43a, 43b are arranged such that the first magnetic field guide plate 43a, in particular exclusively, connects the first coil core 47a to the second coil core 47b, and the second magnetic field guide plate 43b, in particular exclusively, connects the third coil core 47c to the fourth coil core 47d.
[0066] The first fixing element 50a can, as shown, at least partially cover the gap 130. The first fixing element 50a is preferably made of a non-magnetic and non-magnetizable material. Alternatively, the first fixing element 50a can also be designed and arranged such that the gap 130 is completely exposed, thus forming an air gap that is uncovered in the radial direction.
[0067] Fig. 5 shows a perspective view of a partial section of an embodiment of the magnetic-inductive flowmeter according to the invention. The first coil 45a is shown with a first coil former 46a around which a coil wire is wound. The coil former 46a accommodates a first and a third coil core 47a, 47c. The first coil former 46a is held on the measuring tube 10 by two bolts, each with an end-mounted collar nut. The first coil core 47a has two openings 160a, 160b through which a band 150a, 150b extends, which is designed to clamp the first and third coil cores 47a, 47c to the measuring tube 10. The two bands 150a, 150b can be made of stainless steel. The two bands 150a, 150b extend along the entire circumference of the measuring tube 10.
[0068] A field feedback loop 42 connects the first and third coil cores 47a, 47c to further coil cores arranged on the opposite side of the measuring tube 10 (not shown, see Fig. 2). The field feedback loop 42 shown comprises at least one first magnetic field guide plate 43a. It may also include a second magnetic field guide plate (not shown). The first magnetic field guide plate 43a may comprise a plurality of stacked electrical steel sheets.
[0069] The field feedback 42, in particular the first magnetic field guide plate 43a, is spaced from the outer surface of the measuring tube 10 and / or the first pole shoe 80a by at least one spacer 60. The at least one spacer 60 can be connected to the first magnetic field guide plate 43a by material, form and / or force fit.
[0070] The at least one spacer 60 is shaped and attached to the measuring tube 10 in such a way that it bridges the band 150a and also the band 150b.
[0071] The illustrated spacer 60 has a cable guide 61 designed to secure the cable to be routed (e.g., a grounding, signal, and / or coil cable). Additional strain relief ensures that any force acting on the (coil) cable is absorbed by the cable guide 61. The illustrated cable guide 61 comprises two identical hooks rotated 180° relative to each other. The cable guide 61 prevents the cable from moving longitudinally along the measuring tube 10 in the area of the cable guide 61. This significantly reduces the need for temporary adhesive tape fixing of the cables to the measuring tube 10. As a result, material savings, reduced assembly time, and simplified assembly steps are achieved.
[0072] Fig. 6 shows an embodiment of a spacer 60, which is also depicted in Figures 3 to 5. The at least one spacer 60 is preferably made of a non-magnetic material, in particular a plastic in the form of an injection-molded part. The spacer 60 comprises two feet 62a, 62b, by which it rests on the measuring tube or on the pole shoe of the magnetic-inductive flowmeter when mounted. The feet 62a, 62b each have a through-opening 64a, 64b, through which a bolt, sleeve, or screw attached to the measuring tube can be passed. Thus, the spacer 60 can be fixedly attached to a measuring tube. The two feet 62a, 62b are connected by a sectionally straight arc 63 in the form of a beam. The arc 63 has two sleeves 64a, 64b, via which a form-fit and / or force-fit attachment of the field return to the spacer 60 can be effected.The two sleeves 64a, 64b can each have a thread for a screw connection. Furthermore, the two sleeves 64a, 64b can be pressed into the arc or cast in place. The field return can also be attached to the spacer 60 by riveting.
[0073] REFERENCE MARK LIST
[0074] Magnetic-inductive flow meter 1a, 1b
[0075] Measuring tube 10
[0076] Level monitoring electrode 20
[0077] Measuring electrode 21, 22, 24, 26, 27
[0078] Reference electrode 23
[0079] Measuring circuit 30
[0080] Magnetic field guidance 40
[0081] Coil arrangement 41
[0082] Field return 42
[0083] Magnetic field guide plate 43a, 43b
[0084] Partition wall 44a, 44b
[0085] Coil 45a, 45b
[0086] Coil bodies 46a, 46b
[0087] Coil core 47a, 47b, 47c, 47d
[0088] Coil wire 48
[0089] Fixer bodies 50a, 50b
[0090] Spacers 60
[0091] Fixing bolt 71
[0092] Collar 72a, 72b
[0093] Polschuh 80a, 80b
[0094] Pole shoe part 80a', 80a"
[0095] Gap 81
[0096] Signal cable 100
[0097] Liner 101
[0098] Carrier tube 102
[0099] Gap 130
[0100] Coil core sheet 147a, ... , 147i, 147i+1, ..., 147n
[0101] Case 200
[0102] Coil core holder SKA1, SKA2, SKA3, SKA4
[0103] Implementing Chamber DK
[0104] Main axis SHA
[0105] Coil core sheet main axis SKHA1, SKHA2
[0106] Outer surface area MF
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); - a coil arrangement (41) for generating a magnetic field penetrating at least section by section the measuring tube (10), wherein the coil arrangement (41) comprises a first coil (45a) with a first coil core receptacle (SKA1) and a second coil (45b) with a second coil core receptacle (SKA2); and - a magnetic field guide (40), wherein the magnetic field guide (40) comprises a first coil core (47a) and a second coil core (47b), wherein the first coil core (47a) is arranged in the first coil core receptacle (SKA1), wherein the second coil core (47b) is arranged in the second coil core receptacle (SKA2), wherein the magnetic field guide (40) comprises a field return (42) which connects the first coil core (47a) to the second coil core (47b), wherein the field return (42) is spaced apart from the measuring tube (10) by means of at least one, in particular arc-shaped, spacer (60).
2. Magnetic-inductive flowmeter according to claim 1, wherein the first and second coil cores (47a, 47b) are fixedly attached to the measuring tube (10) via a band (150a), wherein the at least one spacer (60) bridges the band (150a).
3. Magnetic-inductive flowmeter according to one of claims 1 or 2, wherein the magnetic-inductive flowmeter (1) is cut by an imaginary longitudinal plane which divides the measuring tube (10) into a first and second side (I, II), wherein at least two measuring electrodes (21 , 24) are attached to the first side (I), wherein the at least two measuring electrodes (21 , 24) of the first side (I) are short-circuited to each other via a first connecting element (120), wherein the at least one spacer (60) bridges the connecting element (120).
4. Magnetic-inductive flow meter according to one of the preceding claims, wherein the at least one spacer (60) has a cable guide (61), in particular in the form of two hooks, for a grounding, signal and / or coil cable.
5. Magnetic-inductive flowmeter according to one of the preceding claims, wherein the at least one spacer (60) is dimensioned such that a minimum distance dmin is maintained between the outer surface of the measuring tube (10) and the first magnetic field guide plate (43a), wherein the minimum distance Dmin is such that 10 < Dmin < 100 millimeters, in particular 15 < Dmin < 75 millimeters and preferably Dmin < 60 millimeters.
6. Magnetic-inductive flowmeter according to one of the preceding claims, wherein the maximum distance Dmax is dimensioned such that an outer diameter of a housing enclosing the magnetic field guide (40) and the coil arrangement (41) is smaller than an outer diameter of a connection element (e.g. flange).
7. Magnetic-inductive flowmeter according to one of the preceding claims, wherein the field feedback (42) comprises a first magnetic field guide plate (43a) and a second magnetic field guide plate (43b), wherein the first magnetic field guide plate (43a) and / or the second magnetic field guide plate (43b) connects the first coil core (47a) to the second coil core (47b).
8. Magnetic-inductive flow meter according to claim 7, wherein the at least one spacer (60) has a bearing surface (AF) on which the first magnetic field guide plate (43a) rests, wherein the at least one spacer (60) is connected to the first magnetic field guide plate (43a) by material, form and / or force connection.
9. Magnetic-inductive flow meter according to one of the preceding claims, wherein the at least one spacer (60) is formed from a non-magnetic material, in particular from a plastic in the form of an injection-molded part.
10. Magnetic-inductive flow meter according to any one of the preceding claims 1 to 9, wherein the at least one spacer (60) comprises a bent sheet metal part.