Magnetic induction flow meter

Abstract

The invention relates to a magnetic-inductive flowmeter (1) for determining a flow-rate-dependent measurement variable, comprising:-a measuring tube (2) for conducting a flowable medium, the measuring tube (2) having an electrically conductive carrier tube (3) with a first electrode opening (40); -magnetic field generating means (5) for generating a magnetic field penetrating the measuring tube (2), the magnetic field generating means (5) being arranged on an outer lateral surface of the measuring tube (2); -a first electrode arrangement (42), which is arranged in the first electrode opening (40); and-a first electrode cap (44), which is arranged on the first electrode arrangement (42) in a snap-fit manner and / or in a press-fit manner and is designed to prevent the formation of a moisture bridge between the first electrode arrangement (42) and the carrier tube (3).

Description

Technical Field

[0001] The invention relates to a magnetic induction flowmeter. Background Art

[0002] The magnetic induction flowmeter is used to determine the flow rate and volume flow of the flowing medium in the pipeline. The magnetic induction flowmeter has a magnetic field generating device, which generates a magnetic field perpendicular to the flow direction of the flowing medium. Typically, multiple single coils are used for this purpose. In order to achieve a mainly uniform magnetic field, a pole shoe is additionally formed, and the pole shoe is attached so that the magnetic field line extends substantially perpendicular to the transverse axis of the measuring tube or parallel to the vertical axis of the measuring tube over the entire pipeline cross section. In addition, the magnetic induction flowmeter has a measuring tube, and the magnetic field generating device is arranged on the measuring tube. The measuring electrode pair is attached to the lateral surface of the measuring tube or is arranged in the electrode opening in the measuring tube, which taps out an electrical measuring voltage or potential difference perpendicular to the flow direction and perpendicular to the magnetic field, which occurs when the conductive medium flows through the applied magnetic field in the flow direction. Due to the Faraday induction law, the tapped measurement voltage depends on the velocity and flow rate of the flowing medium, and in the case of a known pipe cross section, the volume flow rate can be determined according to the measured induced measurement voltage.

[0003] Magneto-inductive flow meters are commonly used in process and automation engineering for fluids and start from a conductivity of about 5 μS / cm. Corresponding flow meters are sold by the applicant in a number of specific devices for use in various fields of application, for example under the name PROMAG.

[0004] At present, the installation of measuring electrodes in the openings in the tube wall of the measuring tube of a magnetic-inductive flowmeter is a relatively time-consuming and therefore costly process. The installation time is about one hour. One reason for this is that the measuring electrodes need to be carefully sealed to prevent the formation of moisture bridges. The known installation method has the following steps: inserting the measuring electrode into the bore, sealing the measuring electrode against the measuring tube, and properly fixing the measuring electrode in the bore. For the purpose of sealing and insulation, the potting mold is temporarily attached to the outer surface of the measuring tube in the area of ​​the measuring electrode. After the curing process of the potting compound, the potting mold is removed. In order to achieve a sufficient seal, a release agent, such as grease, is applied between the contact surface of the curing mold and the outer surface of the measuring tube. The dimensions of the potting mold are adjusted according to the specific application. The liquid potting compound is poured into the potting mold. The curing process is accelerated by supplying heat. For this purpose, a heating sleeve is wound around the potting mold. Once the potting compound has cured, the potting mold is removed, the measuring tube is rotated 180°, and the previously mentioned method steps are repeated to install the second measuring electrode.

[0005] DE 10 2007 009 050 A1 discloses an alternative method for mounting a measuring electrode in a magnetic-inductive flow meter. To this end, the measuring electrode is positioned in a measuring electrode opening, a potting mold is arranged on the outer surface of the measuring tube and around the electrode axis of the measuring electrode, and a potting compound is introduced into the potting mold. After the potting compound has cured, the potting mold is removed. The disadvantage of the disclosed solution is that it is still very expensive and time-consuming. Summary of the invention

[0006] The object of the present invention is to remedy this problem.

[0007] This object is achieved by a magnetic-inductive flow meter according to claim 1 .

[0008] According to the invention, the magnetic-inductive flowmeter for determining a flow rate-related measured variable comprises: - a measuring tube for conducting the flowable medium, The measuring tube has an electrically conductive support tube. wherein the supporting tube has a first electrode opening; - a magnetic field generating device for generating a magnetic field penetrating the measuring tube, wherein the magnetic field generating device is arranged on an outer lateral surface of the measuring tube; - a first electrode arrangement, wherein the first electrode arrangement is arranged in the first electrode opening; and - A first electrode cap which is arranged on the first electrode arrangement in a snap-fit ​​manner and / or in a force-fit manner and is designed to prevent the formation of moisture bridges between the first electrode arrangement and the carrier tube.

[0009] In such magnetic-inductive flow meters, moisture can form on any component surfaces due to pressure and temperature differences if they are not water-resistant. In order to prevent moisture bridges from forming between the metal carrier tube and the electrode arrangement for tapping off the induced measurement voltage and thus interfering with the determination of the flow rate-dependent measured variable, such moisture bridges must be eliminated.

[0010] Typically, the conventional process for partially potting the electrode arrangement requires 2 hours of processing time for each magnetic-inductive flowmeter. The reusable potting mold must be laboriously cleaned after each process. The solution to this problem is to position the electrode cap on the electrode arrangement, thereby acting as a protective cap. The use of the cap eliminates the labor-intensive potting process and thereby shortens the manufacturing time of the magnetic-inductive flowmeter.

[0011] Advantageous embodiments of the invention are subject matter of the dependent claims.

[0012] One embodiment provides that the first electrode arrangement comprises an electrode body, The electrode body has an electrode head. The electrode body comprises an electrode shaft, in particular an electrode shaft provided with a thread, The first electrode cap is connected to the electrode shaft in a snap-fit ​​manner and / or in a press-fit manner.

[0013] The advantage of this embodiment is that the electrode cap is easier to install. A press-fit and / or snap-fit ​​connection with a carrier tube (e.g., as disclosed in DE 10 2007 009 050 A1 for a potting mold) or even an integral connection with a carrier tube is very laborious to assemble. In contrast, the snap-fit ​​and / or press-fit connection of the first electrode cap can be carried out intuitively by the installer without requiring additional preparation work.

[0014] One embodiment provides that the first electrode cap comprises an electrode shaft receiving portion, into which the electrode shaft extends, and in particular, the electrode shaft receiving portion is designed as a blind hole.

[0015] One embodiment provides that the diameter of the electrode shaft holder is undersized relative to the diameter of the electrode shaft.

[0016] This offers the advantage that the electrode cap can be pressed into the thread of the electrode shaft, thereby further increasing the fastening of the first electrode cap.

[0017] One embodiment provides that the first electrode cap delimits an inner volume for accommodating air and the electrode shaft.

[0018] According to the invention, the first electrode cap should not be interpreted as a potting mold. According to the invention, no potting material is provided around a section of the first electrode arrangement which protects the first electrode arrangement from moisture and prevents the formation of moisture bridges. The first electrode cap replaces conventional potting material.

[0019] One embodiment provides that the first electrode arrangement comprises an insulating body, wherein at least one section of the insulating body is designed to be hydrophobic in order to prevent the formation of moisture bridges between the first electrode arrangement and the carrier tube, The insulating body at least partially encloses the electrode shaft.

[0020] One embodiment provides that the first electrode cap is connected to the insulating body in a snap-fit ​​manner and / or in a force-fit manner.

[0021] This results in an improved fixing of the first electrode cap to the first electrode arrangement.

[0022] One embodiment provides that the magnetic induction flow meter comprises: - a measuring circuit for determining the flow rate-dependent measured variable based on the measurement signal tapped off by means of the first electrode arrangement, wherein the first electrode arrangement is electrically connected to the measuring circuit via a signal cable, The first electrode cap has a signal cable opening, and the signal cable extends through the signal cable opening.

[0023] The signal cable opening is dimensioned such that, preferably, no moisture enters into the inner volume of the first electrode cap.

[0024] One embodiment provides that the first electrode arrangement comprises an electrode body, wherein the first electrode arrangement comprises a sleeve for centering the electrode body in the first electrode opening, At least one section of the sleeve is designed to be hydrophilic.

[0025] Due to the hydrophilic design of the sleeve, moisture will be preferentially accumulated at the sleeve. Since the first electrode cap radially encloses the sleeve, the formation of moisture bridges can be reduced.

[0026] One embodiment provides that the magnetic induction flow meter comprises: - a second electrode arrangement, The supporting tube has a second electrode opening, wherein the second electrode arrangement is positioned in the second electrode opening, The first electrode arrangement and the second electrode arrangement are electrically connected via an electrode bridge, - a first electrode cap, which is arranged on the second electrode arrangement in a snap-fit ​​manner and / or in a force-fit manner and is designed to prevent the formation of moisture bridges between the second electrode arrangement and the carrier tube, The first electrode cap and the second electrode cap each have an electrode bridge opening, and the electrode bridge extends through the electrode bridge opening.

[0027] Positioning the electrical connection of the electrode arrangement on one side of the measuring tube has the advantage that the measurement of the flow rate-related measured variable is less sensitive to asymmetries in the flow profile. Such asymmetries are usually caused by disturbances on the inlet side. In the context of the present patent application, reference is made to the entire content of DE 10 2018 108 197 A1, in which the basic principle of electrically short-circuited measuring electrodes or electrode arrangements is explained.

[0028] One embodiment provides that the electrode bridge comprises a flat connector lug and a flat plug, wherein the flat plug is electrically connected to the electrode body of the first electrode arrangement via the flat connector tab, The electrode bridge opening of the first electrode arrangement is designed such that the flat connector lug can pass through the electrode bridge opening.

[0029] This embodiment has the effect of significantly simplifying the installation and connection of the electrode arrangement, thereby reducing the time required for installation.

[0030] One embodiment provides that the signal cable opening, in particular the diameter of the signal cable opening, is small relative to the diameter of the signal cable, and / or the electrode bridge opening, in particular the diameter of the electrode bridge opening, is small relative to the electrode bridge, in particular relative to the diameter of the electrode bridge.

[0031] This results in an improved fastening of the first electrode cap and / or the second electrode cap and ensures that moisture cannot penetrate at all, or only in non-critical amounts.

[0032] One embodiment provides that the inner diameter of the first electrode cap is undersized relative to the outer diameter of the insulating body.

[0033] This results in an improved fastening of the first electrode cap to the first electrode arrangement or to the insulating body.

[0034] One embodiment provides that the first electrode cap and / or the second electrode cap at least partially exhibits a ductility of at least 100%, in particular at least 250% and preferably 500%.

[0035] This has the advantage that signal cables and / or electrode bridges can be passed more easily through corresponding openings.

[0036] One embodiment provides that the first electrode cap and / or the second electrode cap is formed from an injection-moldable sealing material suitable for preventing moisture ingress, the sealing material in particular comprising an elastomer.

[0037] The selection of a suitable material for the first electrode cap and / or the second electrode cap can further increase the effect of preventing the formation of moisture bridges. This is particularly advantageous if liquid has already entered the housing.

[0038] One embodiment provides that the first electrode cap is at least partially formed of at least one of the following materials: - Silicone, - synthetic rubber, - Closed cell foam, - latex, - Thermoplastic polyurethane, - Thermoplastic polyethylene, - Rubber.

[0039] One embodiment provides that the nominal diameter of the measuring tube is DN 350 or more.

[0040] In particular, for magnetic-inductive flow meters with measuring tubes with nominal diameters greater than DN 350, the housing is not fully potted. However, this means that the electrodes are no longer protected from moisture bridging to the carrier tube and instead must be potted individually, which is labor-intensive. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be explained in more detail with reference to the following drawings.

[0042] In the attached picture:

[0043] Figure 1 shows a cross section through a magnetic-inductive flow meter;

[0044] Figure 2 A partial cross-sectional view of one embodiment of a first electrode cap is shown;

[0045] Figure 3 shows a cross section through a first electrode arrangement and a first electrode cap;

[0046] Figure 4 A partial cross-sectional view of one embodiment of a second electrode cap is shown;

[0047] Figure 5 shows a cross section through a second electrode arrangement and a second electrode cap;

[0048] Figure 6 shows a cross section through another embodiment of a magnetic-inductive flow meter; and

[0049] Figure 7 A cross section through another embodiment of a magnetic-inductive flow meter is shown. DETAILED DESCRIPTION

[0050] Figure 1 A cross section through a magnetic-inductive flowmeter 1 is shown. In principle, the construction and measuring principle of a magnetic-inductive flowmeter 1 are known. A flowable medium with a sufficiently high electrical conductivity is guided through a measuring tube 2. The measuring tube 2 comprises a support tube 3, which is usually made of or at least comprises steel, ceramic, plastic or glass. In particular, when a metal support tube 3 is used, moisture bridges may form between the measuring electrodes 18, 19 and the support tube 3, resulting in undesirable short circuits. In order to prevent the measurement voltage induced in the medium from being dissipated via the support tube 3, the inner wall is lined with an insulating material, such as a (plastic) lining 4 or a ceramic tile.

[0051] The magnetic field generating device 5 is arranged on the carrier tube 3 in such a way that the magnetic field lines are oriented substantially perpendicularly to the longitudinal direction defined by the axis of the measuring tube. The magnetic field generating device 5 generally comprises at least one saddle coil or comprises at least one coil 13 with a coil core 14. The magnetic field generating device 5 also comprises at least one pole shoe 21, which is arranged at one end of the coil core 14. The pole shoe 21 can be a separate component or can be connected to the coil core 14 in an integral manner. Figure 1 In the embodiment shown, the magnetic-inductive flowmeter 1 has two coils 13 arranged in the diametric direction, each coil 13 having a coil core 14 and a pole shoe 21. The two coil cores 14 are connected to each other, in particular magnetically, via a magnetic field return 22. The magnetic field return 22 connects the opposite sides of the coil core 14 to each other. However, magnetic-inductive flowmeters 1 with exactly one coil 13 are also known, wherein the at least one coil 13 has exactly one coil core 14 and has no magnetic field return 22. In addition, magnetic-inductive flowmeters 1 with saddle coils are also known, in which no coil core is arranged. The coil 13 is connected to an operating circuit 7, which drives the coil 13 with an operating signal. The operating signal can be a voltage with a time-varying curve and is characterized by operating signal parameters, wherein at least one of the operating signal parameters is controllable. The magnetic field generated by the device 5 for generating a magnetic field is generated using a pulsed direct current with alternating polarity provided by the operating circuit 7. This ensures a stable zero point and makes the measurement insensitive to influences due to electrochemical interference. The two coils 13 may be individually connected to the operating circuit 7 , or may be connected in series or in parallel with each other.

[0052] When a magnetic field is applied, a flow rate-dependent potential distribution is generated in the measuring tube 2, which potential distribution can be detected, for example, in the form of an induced measuring voltage. A device for tapping off the induced measuring voltage is arranged on the measuring tube 2. In the embodiment shown, the device for tapping off the induced measuring voltage is formed by two oppositely arranged measuring electrodes 17, 18, which establish galvanic contact with the medium and are each arranged in a corresponding electrode opening. However, magnetic-inductive flowmeters 1 are also known, which include measuring electrodes 17, 18 arranged on the outer wall of the carrier tube 3, which measuring electrodes 17, 18 are not in contact with the medium. The measuring electrodes 17, 18 are usually arranged in the diametrical direction and form an electrode axis, or intersect a transverse axis that is perpendicular to the magnetic field lines and the longitudinal axis of the measuring tube 2. However, devices for tapping off the induced measuring voltage and having more than two measuring electrodes are also known (see Figure 6 and Figure 7 ). The flow rate-related measured variable can be determined based on the measured voltage of the measured quantity. The flow rate-related measured variable includes the flow rate, volume flow rate and / or mass flow rate of the medium. The measuring circuit 7 is configured to detect the induced measurement voltage applied to the measuring electrodes 17, 18. The evaluation circuit 24 is configured to determine the flow rate-related measured variable based on the measured measurement voltage. The measuring electrodes 17, 18 shown are shown only in a simplified form. Typically, the measuring electrodes 17, 18 are composed of an electrode arrangement structure 42, which includes an electrode body 46 (the electrode body 46 has an electrode head 47 and an electrode shaft 48), an insulating body in the form of an insulating sleeve 51, a (snap-on) sleeve for centering the electrode body 46, and at least one fastening device for fixing the electrode body 46 in the electrode opening. The electrode body 46 is conductive. Typically, an electrode body 46 made of steel, tantalum or titanium is used. The first electrode arrangement structure 42 is electrically connected to the measuring circuit 23 via a signal cable 52. The signal cable 52 can be, for example, a coaxial cable. In this example, the first electrode cap 44 has a signal cable opening ( Figure 1 Not shown, but depicted in Figure 2 ), the signal cable 52 extends through the signal cable opening.

[0053] Commercially available magnetic-inductive flow meters have two further electrodes in addition to the measuring electrodes 17, 18. In the first case, a fill level monitoring electrode 19, which is optimally attached at the highest point in the measuring tube 2, serves to detect partial filling of the measuring tube 2 and is configured to convey this information to the user and / or to take this fill level into account when determining the volume flow. Furthermore, a reference electrode 33, which is usually attached diametrically to the fill level monitoring electrode 19 or to the lowest point of the measuring tube cross section, serves to establish a controlled potential in the medium. Typically, the reference electrode 33 serves to connect the flowing medium to ground potential.

[0054] The operating circuit 7 , the measuring circuit 23 and the evaluation circuit 24 may be parts of a single electronic circuit or may form separate circuits.

[0055] According to the invention, the magnetic-inductive flow meter comprises a first electrode cap 44 for each measuring electrode 17, 18 or first electrode arrangement 42 on one side of the measuring tube. The first electrode cap 44 is arranged on the first electrode arrangement 42 in a snap-fit ​​manner or in a force-fit manner and is designed to prevent the formation of moisture bridges between the first electrode arrangement 42 and the carrier tube 3. The details of the first electrode cap 44 and its arrangement on the measuring tube 2 are as follows: Figure 2 and Figure 3 shown.

[0056] Figure 2 FIG. 4 shows a partial cross-sectional view of an embodiment of a first electrode cap 44. The substantially hollow cylindrical first electrode cap 44 can be arranged on the first electrode arrangement in a snap-fit ​​manner and / or a press-fit manner and is designed to prevent the formation of moisture bridges between the first electrode arrangement and the conductive carrier tube. The first electrode cap 44 has an electrode shaft receiving portion 49 (which is located at the bottom of the electrode shaft receiving portion 49). Figure 2 The first electrode cap 44 is designed as a blind hole in the middle), after the first electrode cap 44 is attached to the first electrode arrangement, the electrode shaft of the first electrode arrangement extends into the electrode shaft receiving portion 49. The diameter of the electrode shaft receiving portion 49 is undersized relative to the diameter of the electrode shaft so as to achieve improved fastening of the first electrode cap 44 to the first electrode arrangement. The first electrode cap 44 can also be connected to the insulating body (not shown) of the first electrode arrangement 42 in a snap-fit ​​manner and / or a press-fit manner. For this purpose, in the fastening area with the insulating body, the inner diameter of the first electrode cap 44 is undersized relative to the outer diameter of the insulating body.

[0057] Furthermore, the first electrode cap 44 shown has exactly one signal cable opening 53 through which a signal cable 52 for connecting the first electrode arrangement 42 to the measuring circuit can pass. The signal cable opening 53 is designed to allow a cable lug attached to the signal cable 52 to pass through. The signal cable opening 53 is positioned in the lateral surface of the first electrode cap 44. The longitudinal axis B of the signal cable opening is located in the cross section of the first electrode cap or intersects the longitudinal axis A of the first electrode cap perpendicularly.

[0058] In addition, the first electrode cap 44 has at least one electrode bridge opening 56, through which an electrode bridge (such as a cable or wire) can pass, so as to electrically connect the two electrode arrangements. In the embodiment shown, the first electrode cap 44 has exactly two electrode bridge openings 56, through which an electrode bridge can pass. In addition, the electrode bridge opening 56 is designed to also allow the flat connector tab of the electrode bridge to pass therethrough. To this end, the first electrode cap 44 at least partially exhibits a ductility of at least 100%, in particular at least 250%, preferably 500%. The first electrode cap 44 is formed by an injection moldable sealing material suitable for preventing moisture intrusion, which sealing material in particular includes an elastomer. The electrode bridge opening 56 is positioned in the front surface of the first electrode cap 44. The longitudinal axis C of the electrode bridge opening extends parallel to the longitudinal axis A of the electrode cap. Opposite the front surface, an electrode cap opening 59 for receiving the first electrode arrangement is provided to allow the first electrode arrangement to pass through it. Arranged downstream of the electrode bridge opening 56 is an electrode bridge guide 60 , along which the electrode bridge can be guided to the electrode arrangement.

[0059] Silicone, synthetic rubber, closed cell foam, thermoplastic polyurethane, thermoplastic polyethylene, rubber and / or latex have proven to be suitable materials.

[0060] In the same or modified form, the first electrode cap 44 shown is also suitable as a second electrode cap. The main difference between the first electrode cap 44 and the second electrode cap is that the second electrode cap does not have a signal cable opening. In one embodiment, the second electrode cap also has exactly one electrode bridge opening, while the number of electrode bridge openings of the first electrode cap 44 corresponds to the number of other second electrode arrangements arranged on the same side of the carrier tube. The second electrode cap can be arranged on the second electrode arrangement in a snap-fit ​​manner or in a press-fit manner and is designed to prevent the formation of a moisture bridge between the second electrode arrangement and the carrier tube. In particular, it has an electrode bridge opening through which the electrode bridge can pass.

[0061] Figure 3 Shows penetration Figure 24 and a cross section of a first electrode arrangement structure 42 and a first electrode cap 44 arranged in the embodiment of the present invention. The first electrode arrangement structure 42 is arranged in the first electrode opening 40. In addition, the first electrode arrangement structure 42 includes an electrode body 46, which has an electrode head 47 and an electrode shaft 48, and the electrode shaft 48 is particularly provided with a thread. When a medium is present in the measuring tube, the electrode head 47 contacts the medium. The first electrode cap 44 is connected to the electrode shaft 48 in a tight and / or press-fit manner because the electrode shaft 48 extends into the electrode shaft receiving portion 49. In this example, the diameter of the electrode shaft retaining portion 49 is small in size relative to the diameter of the electrode shaft 48.

[0062] The first electrode cap 44 and the outer support tube wall define an inner volume 50 containing air and at least the electrode shaft 48. According to the invention, the inner volume 50 is designed to be potting-free.

[0063] The first electrode arrangement 42 comprises an insulating body 51, at least one section of which is designed to be partially hydrophobic. The insulating body 51 is used to prevent moisture bridging between the first electrode arrangement 42 and the supporting tube 3. The insulating body 51 is designed as a cylindrical sleeve and at least partially encloses the electrode shaft 48. To ensure sufficient fastening of the first electrode cap 44 to the first electrode arrangement 42, the first electrode cap 44 is connected to the insulating body 51 in a snap-fit ​​manner and / or a press-fit manner.

[0064] Furthermore, the first electrode arrangement 42 comprises a (snap-on) sleeve 54 for centering the electrode body 46 in the first electrode opening 40. The sleeve 54 comprises a coil spring 61 designed to relax or tighten in response to mechanical movement of the liner caused by temperature changes. At least one section of the sleeve 54 is designed to be hydrophilic. Therefore, there is a risk that moisture will accumulate on the sleeve 54 and form a water film. The purpose of the first electrode cap 44 is to prevent this.

[0065] The electrode bridge 55 shown has a flat plug 58 and a flat connector lug 57, and the flat plug 58 is electrically connected to the electrode body 46, in particular the electrode body 46 of the first electrode arrangement 42, via the flat connector lug 57. The electrode bridge opening 56 is designed so that the flat plug 58 can pass through the electrode bridge opening 56. If the flat connector lug 57 cannot be connected to the flat plug 58 alone, the electrode bridge opening 56 is designed so that the flat connector lug 57 can pass through the electrode bridge opening 56.

[0066] Figure 4A partial cross-sectional view of an embodiment of a second electrode cap 45 is shown. The substantially hollow cylindrical second electrode cap 45 can be attached to the second electrode arrangement in a snap-fit ​​manner and / or a press-fit manner and is designed to prevent the formation of moisture bridges between the second electrode arrangement and the conductive carrier tube. The second electrode cap 45 has an electrode shaft receiving portion 49 (which is located at Figure 2 The second electrode cap 45 is designed as a blind hole in the middle), after the second electrode cap 45 is attached to the second electrode arrangement, the electrode shaft of the second electrode arrangement extends into the electrode shaft receiving portion 49. The diameter of the electrode shaft receiving portion 49 is undersized relative to the diameter of the electrode shaft so as to achieve improved fastening of the second electrode cap 45 to the second electrode arrangement. The second electrode cap 45 can also be connected to the insulating body (not shown) of the second electrode arrangement in a snap-fit ​​manner and / or a press-fit manner. For this purpose, in the fastening area where the second electrode cap 45 contacts the insulating body, the inner diameter of the second electrode cap 44 is undersized relative to the outer diameter of the insulating body.

[0067] In addition, unlike the first electrode cap, the second electrode cap 45 shown has no signal cable opening. The second electrode cap 45 has at least one electrode bridge opening 56, through which an electrode bridge (such as a cable, wiring or sheet metal component) can pass, so as to electrically connect the two electrode arrangements. An example of a sheet metal component is described in DE 10 2018 116 400 A1. In the embodiment shown, the second electrode cap 45 has exactly one electrode bridge opening 56, through which at least one, in particular exactly one, electrode bridge can pass. In addition, the electrode bridge opening 56 is designed to also allow the flat connector tab of the electrode bridge to pass therethrough. For this reason, the second electrode cap 45 at least partially exhibits a ductility of at least 100%, in particular at least 250% and preferably 500%. The second electrode cap 45 is formed by an injection moldable sealing material suitable for preventing moisture intrusion, the sealing material in particular comprising an elastomer. The electrode bridge opening 56 is arranged in the lateral surface of the second electrode cap 45. The longitudinal axis E of the electrode bridge opening is located in the cross section of the electrode cap and intersects, in particular perpendicularly intersects, the longitudinal axis D of the electrode cap. The second electrode cap 45 has an electrode cap opening 59 for receiving the second electrode arrangement structure to allow the second electrode arrangement structure to pass therethrough.

[0068] Silicone, synthetic rubber, closed cell foam, thermoplastic polyurethane, thermoplastic polyethylene, rubber and / or latex have proven to be suitable materials.

[0069] Figure 5 Shows penetration Figure 4The cross section of the second electrode arrangement structure and the second electrode cap. The second electrode arrangement structure 43 is arranged in the second electrode opening 41. In addition, the second electrode arrangement structure 43 includes an electrode body 46, which has an electrode head 47 and an electrode shaft 48, and the electrode shaft 48 is particularly provided with a thread. When a medium is present in the measuring tube, the electrode head 47 contacts the medium. The second electrode cap 45 is connected to the electrode shaft 48 in a tight and / or press-fit manner because the electrode shaft 48 extends into the electrode shaft receiving portion 49. In the present example, the diameter of the electrode shaft retaining portion 49 is small in size relative to the diameter of the electrode shaft 48.

[0070] The second electrode arrangement 43 also has an insulating body 51, at least one section of which is designed to be partially hydrophobic. The insulating body 51 is used to prevent the formation of moisture bridges between the second electrode arrangement 43 and the support tube 3. The insulating body 51 is designed as a cylindrical sleeve and at least partially encloses the electrode shaft 48. To ensure sufficient fastening of the second electrode cap 45 to the second electrode arrangement 43, the second electrode cap 45 is connected to the insulating body 51 in a snap-fit ​​manner and / or a press-fit manner.

[0071] Furthermore, the second electrode arrangement 43 comprises a (snap-on) sleeve 54 for centering the electrode body 46 in the second electrode opening 41. The sleeve 54 comprises a coil spring 61 designed to relax or tighten in response to mechanical movement of the liner caused by temperature changes. At least one section of the sleeve 54 is designed to be hydrophilic. Therefore, there is a risk that moisture will accumulate on the sleeve 54 and form a water film. The purpose of the second electrode cap 45 is to prevent this.

[0072] The electrode bridge 55 shown has a flat plug 58 and a flat connector lug 57, and the flat plug 58 is electrically connected to the electrode body 46, in particular the electrode body 46 of the second electrode arrangement 43, via the flat connector lug 57. The electrode bridge opening 56 is designed so that the flat plug 58 can pass through the electrode bridge opening 56. If the flat connector lug 57 cannot be connected to the flat plug 58 alone, the electrode bridge opening 56 is designed so that the flat connector lug 57 can pass through the electrode bridge opening 56.

[0073] Figure 6 A cross section through another embodiment of a magnetic-inductive flow meter 1 is shown, which has a Figure 2 The first electrode arrangement structure 42 combined with the first electrode cap 44 and according to Figure 4The first electrode cap 44 and the second electrode cap 45 each have an electrode bridge opening, through which the electrode bridge 55 extends, and the first electrode arrangement 42 and the second electrode arrangement 43 are electrically connected via the electrode bridge opening. The arrangements of the first electrode arrangement 42 and the second electrode arrangement 43 are mirrored on opposite sides of the measuring tube, in particular substantially mirrored on the longitudinal plane F. The first two electrode arrangements 42 are each connected to the measuring circuit 23 via a signal cable 52. For this purpose, the first electrode cap 44 each has a signal cable opening 53.

[0074] Figure 7 A cross section through another embodiment of a magnetic-inductive flow meter 1 is shown, which has a Figure 2 The first electrode arrangement structure 42 combined with the first electrode cap 44 and the two electrodes are respectively Figure 4 The first electrode cap 44 has two electrode bridge openings. The two second electrode caps 45 each have an electrode bridge opening, through which the electrode bridge 55 extends, and the first electrode arrangement 42 is electrically connected to the corresponding second electrode arrangement 43 via the electrode bridge opening. The arrangements of the first electrode arrangement 42 and the second electrode arrangement 43 are mirrored on opposite sides of the measuring tube, in particular substantially mirrored on the longitudinal plane F. The first two electrode arrangements 42 are each connected to the measuring circuit 23 via a signal cable 52. For this purpose, the first two electrode caps 44 each have a signal cable opening 53.

[0075] Alternatively, one of the two second electrode caps 45 may have two electrode bridge openings, an electrode bridge 55 is arranged in each of the two electrode bridge openings, and the two electrode bridge openings are electrically connected to the first electrode arrangement structure 42 and the second electrode arrangement structure 43 via the electrode bridge 55, respectively.

[0076] Alternatively, more than two or three electrode arrangements can also be provided on one side of the measuring tube. Figure 6 and / or Figure 7 Each of these electrode arrangements is configured according to the electrode arrangement shown in .

[0077] Reference numerals list

[0078] Magnetic induction flowmeter 1

[0079] Measuring tube 2

[0080] Loading tube 3

[0081] Lining 4

[0082] Magnetic field generating device 5

[0083] Operation circuit 7

[0084] Control circuit 10

[0085] Coil 13

[0086] Coil core 14

[0087] Measuring electrodes 17, 18

[0088] Fill level monitoring electrode 19

[0089] Pole shoe 21

[0090] Magnetic field return part 22

[0091] Measurement circuit 23

[0092] Evaluation circuit 24

[0093] Reference electrode 33

[0094] First electrode opening 40

[0095] Second electrode opening 41

[0096] First electrode arrangement 42

[0097] Second electrode arrangement 43

[0098] First electrode cap 44

[0099] Second electrode cap 45

[0100] Electrode body 46

[0101] Electrode head 47

[0102] Electrode shaft 48

[0103] Electrode shaft holding portion 49

[0104] Internal volume 50

[0105] Insulation body 51

[0106] Signal cable 52

[0107] Signal cable opening 53

[0108] Casing 54

[0109] Electrode bridge portion 55

[0110] Electrode bridge opening 56

[0111] Flat connector lug 57

[0112] Flat plug 58

[0113] Electrode cap opening 59

[0114] Electrode bridge guide 60

[0115] Coil spring 61

[0116] Thread 62

Claims

1. A magnetic inductive flow meter (1) for determining a flow rate-related measurement variable, comprising: - a measuring tube (2) for conducting a flowable medium, The measuring tube (2) has an electrically conductive support tube (3). The supporting tube (3) has a first electrode opening (40); - a magnetic field generating device (5), the magnetic field generating device (5) being used to generate a magnetic field penetrating the measuring tube (2), wherein the magnetic field generating device (5) is arranged on the outer lateral surface of the measuring tube (2); - a first electrode arrangement (42), wherein the first electrode arrangement structure (42) is arranged in the first electrode opening (40); and - a first electrode cap (44), which is arranged on the first electrode arrangement (42) in a snap-fit ​​manner and / or in a force-fit manner and is designed to prevent the formation of moisture bridges between the first electrode arrangement (42) and the carrier tube (3).

2. The magnetic induction flowmeter (1) according to claim 1, The first electrode arrangement structure (42) comprises an electrode body (46), The electrode body (46) has an electrode head (47). The electrode body (46) has an electrode shaft (48), in particular an electrode shaft provided with a thread (62). The first electrode cap (44) is connected to the electrode shaft (48) in a snap-fit ​​manner and / or in a press-fit manner.

3. The magnetic induction flowmeter (1) according to claim 2, The first electrode cap (44) has an electrode shaft receiving portion (49), and the electrode shaft (48) extends into the electrode shaft receiving portion (49). In particular, the electrode shaft receiving portion (49) is designed as a blind hole.

4. The magnetic induction flowmeter (1) according to claim 3, The diameter of the electrode shaft receiving portion (49) is smaller than the diameter of the electrode shaft (48).

5. The magnetic-inductive flow meter (1) according to at least one of claims 2 to 4, The first electrode cap (44) defines an internal volume (50) for accommodating air and the electrode shaft (48).

6. The magnetic-inductive flow meter (1) according to at least one of the preceding claims, The first electrode arrangement structure (42) has an insulating body (51), wherein at least one section of the insulating body (51) is designed to be hydrophobic so as to prevent the formation of a moisture bridge between the first electrode arrangement (42) and the supporting tube (3), The insulating body (51) at least partially encloses the electrode shaft (48).

7. The magnetic induction flowmeter (1) according to claim 6, The first electrode cap (44) is connected to the insulating body (51) in a fastening manner and / or a press-fit manner.

8. The magnetic-inductive flow meter (1) according to at least one of the preceding claims, comprising: - a measuring circuit (23) for determining the flow rate-related measured variable based on the measurement signal tapped off by means of the first electrode arrangement (42), wherein the first electrode arrangement (42) is electrically connected to the measuring circuit (23) via a signal cable (52), The first electrode cap (44) has a signal cable opening (53), and the signal cable (52) extends through the signal cable opening (53).

9. The magnetic-inductive flow meter (1) according to at least one of the preceding claims, The first electrode arrangement structure (42) comprises an electrode body (46), wherein the first electrode arrangement (42) comprises a sleeve (54) for centering the electrode body (46) in the first electrode opening (40), At least a section of the sleeve (54) is designed to be hydrophilic.

10. The magnetic-inductive flow meter (1) according to at least one of claims 6 to 9, The inner diameter of the first electrode cap (44) is smaller than the outer diameter of the insulating body (51).

11. The magnetic-inductive flow meter (1) according to at least one of the preceding claims, comprising: - a second electrode arrangement (43), The supporting tube (3) has a second electrode opening (41). wherein the second electrode arrangement structure (43) is arranged in the second electrode opening (41), The first electrode arrangement structure (42) and the second electrode arrangement structure (43) are electrically connected via an electrode bridge portion (55), - a second electrode cap (45), which is arranged on the second electrode arrangement (43) in a snap-fit ​​manner and / or in a force-fit manner and which is designed to prevent the formation of moisture bridges between the second electrode arrangement (43) and the carrier tube (3), The first electrode cap (44) and the second electrode cap (45) each have an electrode bridge opening (56), and the electrode bridge (55) extends through the electrode bridge opening (56).

12. The magnetic induction flow meter (1) according to claim 11, The electrode bridge portion (55) includes a flat connector lug (57) and a flat plug (58). wherein the flat plug (58) is electrically connected to the electrode body (46) of the first electrode arrangement (42) via the flat connector lug (57), The electrode bridge opening (56) of the first electrode arrangement (42) is designed such that the flat plug (57) can pass through the electrode bridge opening (56).

13. The magnetic induction flow meter (1) according to claim 11 or 12, The diameter of the signal cable opening (53), in particular the signal cable opening (53), is smaller than the diameter of the signal cable (52), in particular the diameter of the signal cable (52), and / or the diameter of the electrode bridging portion opening (56), in particular the electrode bridging portion opening (56), is smaller than the diameter of the electrode bridging portion (55), in particular the diameter of the electrode bridging portion (55).

14. Magnetic-inductive flow meter (1) according to at least one of the preceding claims, The first electrode cap (44) and / or the second electrode cap (45) at least partially exhibits a ductility of at least 100%, in particular at least 250% and preferably 500%.

15. The magnetic-inductive flow meter (1) according to at least one of the preceding claims, The first electrode cap (44) and / or the second electrode cap (45) are formed of an injection-moldable sealing material suitable for preventing moisture intrusion, and the sealing material particularly comprises an elastomer.

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