DE102020121155A1 - Electromagnetic flow meter - Google Patents

Abstract

The invention relates to a magnetic-inductive flow meter (1), comprising: - a measuring tube (2) for guiding a flowable medium; - an electrical connector (25); - a device (5) for generating a magnetic field penetrating the measuring tube, comprising a Coil arrangement (6) with at least two coils (13.1, 13.2), in particular diametrically oriented and preferably electrically connected to one another, each with at least one coil core (14.1, 14.2) and a field return arrangement (18) which connects the coil cores (14.1, 14.2) with two field return bodies (19.1, 19.2) with each other, slots (28.1, 28.2) in the field return body (19.1, 19.2) each starting from a field return body edge (20) inwardly of the respective field return body (19.1, 19.2); and a method for producing the magnetic-inductive flowmeter according to the invention.

Description

The invention relates to a magneto-inductive flow meter and a method for producing the magneto-inductive flow meter.

Electromagnetic flowmeters are used to determine the flow rate and volume flow of a flowing medium in a pipeline. A magneto-inductive flowmeter has a magnet system that generates a magnetic field perpendicular to the flow direction of the flowing medium. Individual coils are usually used for this. In order to achieve a predominantly homogeneous magnetic field, additional pole shoes are formed and attached in such a way that the magnetic field lines run essentially perpendicular to the transverse axis or parallel to the vertical axis of the measuring tube over the entire tube cross-section. A pair of measuring electrodes attached to the lateral surface of the measuring tube picks up an electrical measuring voltage or potential difference perpendicular to the direction of flow and to the magnetic field, which arises when a conductive medium flows in the direction of flow with an applied magnetic field. Since the measured voltage depends on the speed of the flowing medium according to Faraday's law of induction, the flow rate u and, with the addition of a known pipe cross-section, the volume flow V̇ can be determined from the induced measuring voltage U.

Electromagnetic flowmeters are widely used in process and automation technology for fluids with an electrical conductivity of around 5 µS/cm. Corresponding flow measuring devices are sold by the applicant in a wide variety of embodiments for different areas of application, for example under the name PROMAG.

The object of the invention is to provide an assembly-friendly magnetic-inductive flowmeter.

In addition, the invention is based on the object of providing an assembly-friendly method for producing a magneto-inductive flow measuring device.

The object is achieved by the magnetic-inductive flow meter according to claim 1 and the manufacturing method according to claim 5.

• - ein Messrohr zum Führen eines fließfähigen Mediums;
• - einen elektrischen Steckverbinder;
• - eine Vorrichtung zum Erzeugen eines das Messrohr durchdringenden Magnetfeldes,

wobei die Vorrichtung eine am Messrohr angeordnete Spulenanordnung umfasst,
wobei die Spulenanordnung mindestens zwei, insbesondere diametral orientierte und bevorzugt elektrisch miteinander verbundene Spulen mit jeweils mindestens einem Spulenkern umfasst,
wobei die Vorrichtung eine Feldrückführungsanordnung aufweist, welche die Spulenkerne miteinander verbindet,
wobei die Feldrückführungsanordnung zwei Feldrückführungskörper umfasst,
wobei die Spulenanordnung über einen ersten elektrischen Leiter und einen zweiten elektrischen Leiter mit dem Steckverbinder verbunden ist,
wobei die zwei Feldrückführungskörper jeweils einen Schlitz aufweisen,
wobei die zwei Schlitze jeweils entlang eines Verlaufes eine Feldrückführungsöffnung aufweisen,
wobei sich die Schlitze jeweils ausgehend von einem Feldrückführungskörperrand des jeweiligen Feldführungskörpers einwärts erstrecken,
wobei zumindest einer der Spulenkerne eine Spulenkernöffnung aufweist;

• - eine Vorrichtung zum Erfassen einer im Medium induzierten Messspannung,

wobei die Vorrichtung über einen dritten elektrischen Leiter und einen vierten elektrischen Leiter mit dem Steckverbinder verbunden sind,
wobei sich der dritte Leiter und der vierte Leiter durch die Feldrückführungsöffnungen erstreckt,
wobei sich der dritte Leiter und der vierte Leiter durch die Spulenkernöffnung erstrecken,
wobei sich der dritte Leiter und der vierte Leiter zumindest teilweise zwischen einer der mindestens zwei Spulen und dem Messrohr erstreckt; und

• - einen Messumformer zum Ermitteln einer strömungsgeschwindigkeitsabhängigen Messgröße in Abhängigkeit von der induzierten Messspannung und zum Betreiben der Vorrichtung zum Erzeugen des Magnetfeldes,

wobei der Messumformer über den Steckverbinder mit der Vorrichtung zum Erfassen der induzierten Messspannung und der Vorrichtung zum Erzeugen des Magnetfeldes elektrisch verbunden ist.The magnetic-inductive flowmeter according to the invention includes:

• - A measuring tube for guiding a flowable medium;
• - an electrical connector;
• - a device for generating a magnetic field penetrating the measuring tube,

wherein the device comprises a coil arrangement arranged on the measuring tube,
wherein the coil arrangement comprises at least two coils, in particular diametrically oriented and preferably electrically connected to one another, each with at least one coil core,
the device having a field feedback arrangement connecting the coil cores together,
wherein the field feedback arrangement comprises two field feedback bodies,
wherein the coil arrangement is connected to the plug connector via a first electrical conductor and a second electrical conductor,
the two field return bodies each having a slot,
the two slots each having a field return opening along one run,
wherein the slots each extend inwards starting from a field return body edge of the respective field guide body,
wherein at least one of the coil cores has a coil core opening;

• - a device for detecting a measurement voltage induced in the medium,

wherein the device is connected to the connector via a third electrical conductor and a fourth electrical conductor,
the third conductor and the fourth conductor extending through the field return openings,
wherein the third conductor and the fourth conductor extend through the coil core opening,
wherein the third conductor and the fourth conductor extend at least partially between one of the at least two coils and the measuring tube; and

• - a measuring transducer for determining a flow rate-dependent measured variable as a function of the induced measuring voltage and for operating the device for generating the magnetic field,

the measuring transducer being electrically connected via the plug connector to the device for detecting the induced measurement voltage and the device for generating the magnetic field.

The provision of two slots in the field guide bodies has the advantage that it is no longer necessary to laboriously guide the electrical conductors through the field return opening. Instead, the electrical conductors can be Attaching the field guide body to the measuring tube along the course of the slot to the field return opening.

Advantageous configurations of the invention are the subject matter of the dependent claims.

One embodiment provides for the slits to each extend transversely to the longitudinal direction of the measuring tube, starting from the edge of the field return body.

One embodiment provides that the at least two coils are arranged diametrically,
wherein the device for tapping the measurement voltage comprises at least two diametrically arranged measurement electrodes,
wherein a coil axis runs through the at least two coils,
wherein a measuring electrode axis runs through the at least two measuring electrodes,
where the coil axis is perpendicular to the measuring electrode axis,
wherein the slots of each field guide body are covered at least in one direction of the coil axis by the respective other field guide body.

This configuration has the advantage that the magnetic field is optimally guided between the at least two coils.

One embodiment provides that the slots each have a slot width b,
where the slot width b is 0.5≦b≦3.8 millimeters.

• - Bereitstellen einer ersten Baugruppe an ein Messrohr,

wobei die erste Baugruppe einen Steckverbinder, einen ersten Leiter, einen zweiten Leiter, einen dritten Leiter, einen vierten Leiter und eine Spulenanordnung, umfassend mindestens zwei insbesondere miteinander elektrisch verbundene Spulen mit jeweils mindestens einem Spulenkern, aufweist,
wobei die Spulenanordnung über den ersten Leiter und den zweiten Leiter mit dem Steckverbinder verbunden ist,
wobei sich der dritte Leiter und der vierte Leiter durch eine Spulenkernöffnung eines Spulenkerns erstrecken;

• - Verbinden des dritten Leiters und des vierten Leiters mit einer am Messrohr angeordneten Vorrichtung zum Erfassen einer induzierten Messspannung,

wobei sich der dritte Leiter und der vierte Leiter zumindest teilweise zwischen einer der mindestens zwei Spulen und dem Messrohr erstreckt;

• - Anordnen der Spulenanordnung an das Messrohr,
• - Bereitstellen einer zweiten Baugruppe,

wobei die zweite Baugruppe zwei Feldrückführungskörper umfasst, wobei die zwei Feldrückführungskörper jeweils einen insbesondere durchgehenden Schlitz aufweisen,
wobei sich die Schlitze jeweils ausgehend von einem Feldrückführungskörperrand einwärts erstrecken,
wobei die Schlitze jeweils entlang eines Verlaufes eine Feldrückführungsöffnung aufweisen, durch welche sich nach dem Anordnen der zweiten Baugruppe der dritte Leiter und der vierte Leiter erstrecken,

• - Anordnen der zweiten Baugruppe,

wobei beim Anordnen der zweiten Baugruppe der dritte Leiter und der vierte Leiter durch die Schlitze zu den jeweiligen Feldrückführungsöffnungen geführt werden.The method according to the invention for producing a magneto-inductive flow meter comprises the method steps:

• - Providing a first assembly to a measuring tube,

wherein the first subassembly has a plug connector, a first conductor, a second conductor, a third conductor, a fourth conductor and a coil arrangement, comprising at least two coils that are in particular electrically connected to one another and each have at least one coil core,
wherein the coil assembly is connected to the connector via the first conductor and the second conductor,
wherein the third conductor and the fourth conductor extend through a coil core opening of a coil core;

• - connecting the third conductor and the fourth conductor to a device arranged on the measuring tube for detecting an induced measuring voltage,

wherein the third conductor and the fourth conductor extend at least partially between one of the at least two coils and the measuring tube;

• - arranging the coil assembly on the measuring tube,
• - Provision of a second assembly,

wherein the second subassembly comprises two field return bodies, wherein the two field return bodies each have an in particular continuous slot,
the slots each extending inwardly from a field return body edge,
the slots each having a field return opening along one run through which the third conductor and the fourth conductor extend after placement of the second assembly,

• - arranging the second assembly,

wherein in assembling the second assembly the third conductor and the fourth conductor are routed through the slots to the respective field return openings.

Dividing the components to be assembled into a first subassembly with at least partially preassembled individual components and a second subassembly with the field feedback bodies has the advantage that the susceptibility to errors during assembly and the assembly time are significantly reduced.

Furthermore, the method for producing the magneto-inductive flowmeter can include further method steps. For example, if a housing is provided, the measuring tube can be arranged with the previously arranged first subassembly and the second subassembly in a housing or the housing can be arranged on the measuring tube. Depending on the application, the housing can also be potted with a potting compound.

Advantageous configurations of the invention are the subject matter of the dependent claims.

One embodiment provides that the slots each extend transversely to the longitudinal direction of the measuring tube, starting from the field return edge.

One embodiment provides that the at least two coils are arranged diametrically,
wherein the device for tapping the measurement voltage comprises at least two diametrically arranged measurement electrodes,
wherein a coil axis runs through the at least two coils,
wherein a measuring electrode axis runs through the at least two measuring electrodes,
where the coil axis is perpendicular to the measuring electrode axis,
wherein the slots are each covered at least in one direction of the coil axis by one of the two field guide bodies.

One embodiment provides that the slits each have a slit width b, with the slit width b being 0.5≦b≦3.8 millimeters.

One embodiment provides that the first assembly includes exactly one plug connector, the coil arrangement consisting of two coils, each with exactly one coil core.

• 1: eine Explosionsdarstellung einer Ausgestaltung des erfindungsgemäßen magnetisch-induktiven Durchflussmessgerätes; und
• 2: eine Draufsicht auf eine Ausgestaltung des Feldführungskörpers.

The invention is explained in more detail with reference to the following figures. It shows:

• 1 : an exploded view of an embodiment of the magnetic-inductive flowmeter according to the invention; and
• 2 1: a plan view of an embodiment of the field guide body.

the 1 shows an exploded view of an embodiment of the magneto-inductive flow meter 1 according to the invention. The magneto-inductive flow meter 1 comprises a measuring tube 2 for guiding a flowable medium. The measuring tube 2 has a cylindrical support tube made of an electrically insulating material. However, magnetic-inductive flowmeters 1 with metal support tubes are also known, which have an electrically insulating liner on an inner surface of the support tube. Furthermore, support tubes with tapers, ie cross-sectional constrictions, are known which have a round cross-sectional area or an oval cross-sectional area or a cross-sectional area deviating from a circular shape in the tapered support tube section. A device 5 for generating the magnetic field is arranged on the support tube and is set up to generate a magnetic field that varies over time. The device 5 for generating the magnetic field comprises a coil arrangement 6, which is already arranged on the support tube in the illustration shown. The coil arrangement 6 comprises two diametrically arranged coils 13.1, 13.2, the coil 13.1 shown being covered by an electrical insulating body. The coils 13.1, 13.2 are so-called saddle coils. These are electrically connected to one another in series and connected to a plug connector 25 via the electrical conductors 26.1., 26.2. Furthermore, the coils 13.1, 13.2 each have a receptacle for one of the two coil cores 14.1, 14.2, the receptacle being limited by the wound coil wire. The coil cores 14.1, 14.2 are each additionally arranged with an electrical insulating body in the receptacle. The electrical insulating body is used to electrically insulate the coil wire of the coils 13.1, 13.2 from the respective coil cores 14.1, 14.2 that are in direct contact. The coil core 14.1 has a coil core opening 15. This is designed as a through opening and set up to guide the electrical conductors 26.1, 26.2. A field feedback arrangement 18 is provided for guiding the magnetic field generated by the coil arrangement 6 between the two coils 13.1, 13.2 of the coil arrangement 6 in such a way that the stray magnetic field outside the support tube is as small as possible. For this purpose, the field feedback arrangement 18 comprises two field feedback bodies 19.1, 19.2 which, according to the configuration shown, are each designed as bent sheet metal parts and are suitable for conducting the magnetic field. These connect the rear sides of the coil cores 14.1, 14.2 facing away from the support tube to one another. Both field return bodies 19.1, 19.2 each have at least one slot 28.1, 28.2 with a field return opening 27.1. 27.2, through which the electrical conductors 26 extend in the final assembled state. The field return body 19.1, 19.2 are designed as bent sheet metal parts.

In addition, the magnetic-inductive flowmeter 1 has a device 8 for detecting the induced measurement voltage in the flowing medium. The device 8 for detecting the induced measuring voltage comprises two diametrically arranged measuring electrodes 17.1, 17.2, which are suitable for being in contact with the medium and which are set up for tapping off a voltage induced in the flowing medium. Electromagnetic flowmeters 1 with more than two measuring electrodes 17.1, 17.2 and/or with non-diametrically arranged measuring electrodes 17.1, 17.2 are also known. The measuring electrodes 17.1, 17.2 are connected to a plug connector 25 via the electrical conductors 26.3, 26.4. The support tube has a depression 30 along which the conductors 26.3, 26.4 extend and thus run underneath the coil 13.1. Furthermore, the conductors 26.3, 26.4 run through the coil core opening 15 up to the connector 25 and are electrically connected to it. A mechanically separable, electrical connection to a measuring transducer 29 is realized via the plug connector 25 . The measuring transducer 29 includes an operating circuit with which an operating signal is impressed on the coil arrangement 6 . As a result, a time-varying magnetic field is generated via the coil arrangement 6 . In addition, the measuring transducer 29 includes a measuring circuit, with which one is connected to the device 8 for detecting the induced measuring voltage low induced measuring voltage or a variable dependent on it is measured. An evaluation circuit is set up to determine a process variable that is dependent on the flow rate of the flowable medium as a function of the measured voltage or measured variable.

The slots 28.1, 28.2 have a field return opening 27.1, 27.2 along their respective course. The slots 28.1, 28.2 each extend inward, starting from the field return body edge 20, transversely to the longitudinal direction of the measuring tube 2. Such a configuration of the field return bodies 19.1, 19.2 means that the conductors 26 no longer have to be laboriously passed through the field return openings 27.1, 27.2. Instead, the conductors 26 are routed along the slot 28.1, 28.2 until they are located in the field return opening 27.1, 27.2 provided. This has the advantage that the field return bodies 19.1, 19.2 can be attached to the side of the measuring tube 2 after the coil arrangement 6 and the coil cores 14.1, 14.2 have already been arranged and after the device 8 for detecting the induced measuring voltage has already been connected via the conductors 26.3, 26.4 are connected to the connector 25. In addition, in the assembled state of the magneto-inductive flowmeter, the slots 28.1, 28.2 of each field guide body 19.1, 19.2 are at least partially covered at least in one direction of a coil axis of the coil arrangement 6 by the respective other field guide body 19.1, 19.2, in particular slot sections of the slots 28.1, 28.2, which are located between the respective field guide body edge 20 and field guide opening 27.1, 27.2.

In the illustrated embodiment, the first assembly has exactly one connector 25 and the coil arrangement 6 consists of exactly two coils 13.1, 13.2, each with exactly one coil core 14.1, 14.2.

• - Bereitstellen einer ersten Baugruppe und eines Messrohres 2.

The method for producing the magnetic-inductive flowmeter 1 according to the invention is explained below with reference to the exploded view. The process comprises the process steps:

• - Provision of a first assembly and a measuring tube 2.

• - Verbinden des dritten Leiters 26.3 und des vierten Leiters 26.4 mit einer am Messrohr 2 angeordneten Vorrichtung 8 zum Erfassen einer induzierten Messspannung.

The first assembly is to be understood as a single unit and includes or in the illustrated case consists of a connector 25, a first conductor 26.1, a second conductor 26.2, a third conductor 26.3, a fourth conductor 26.4 and a coil arrangement 6, which at least has two electrically connected coils 13.1, 13.2, each with at least one coil core 14.1, 14.2. The coil arrangement 6 is connected to the plug connector 25 via the first conductor 26.1 and the second conductor 26.2. Only the third conductor 26.3 and the fourth conductor 26.4 extend through a coil core opening 15 of a coil core 14.1.

• - Connecting the third conductor 26.3 and the fourth conductor 26.4 to a device 8 arranged on the measuring tube 2 for detecting an induced measuring voltage.

• - Anordnen der Spulenanordnung 6 an das Messrohr 2 derart, dass die mindestens zwei Spulen 13.1, 13.2 diametral angeordnet sind und eine Spulenachse bilden.

When connecting, it is ensured that the third conductor 26.3 and the fourth conductor 26.4 extend at least partially between one of the at least two coils 13.1 and the measuring tube 2. A recess can be provided in the support tube for this purpose. The third conductor 26.3 and the fourth conductor 26.4 are connected to the at least two measuring electrodes 17.1, 17.2, which are in particular arranged diametrically and form a measuring electrode axis.

• - Arranging the coil arrangement 6 on the measuring tube 2 in such a way that the at least two coils 13.1, 13.2 are arranged diametrically and form a coil axis.

• - Bereitstellen einer zweiten Baugruppe,

After the first assembly has been mounted on the measuring device, the process steps follow:

• - Provision of a second assembly,

• - Anordnen der zweiten Baugruppe.

The second assembly consists of two magnetically conductive field return bodies 19.1, 19.2, each with a field return opening 27.1, 27.2, through which at least the third conductor 26.3 and the fourth conductor 26.4 extend after the second assembly is arranged on the measuring tube. In order to simplify the assembly of the two field return bodies 19.1, 19.2, both have a slot 28.1, 28.2, which is in particular continuous, which extends inward starting from the edge 20.1, 20.2 of the field return body. In addition, the slots 28.1, 28.2 each have a slot width b, for which it applies that 0.5≦b≦3.8 millimeters.

• - Arranging the second assembly.

In assembling the second assembly, the third conductor 26.3 and the fourth conductor 26.4 are fed through the slots 28.1, 28.2 to the designated field return openings 27.1, 27.2. If the coil axis runs perpendicular to the measuring electrode axis, the slots 28.1, 28.2 are each covered at least in one direction of the coil axis and at least partially by one of the two field guide bodies 19.1, 19.2.

the 2 shows a plan view of an embodiment of the field guide body 19, which is designed as a stamped sheet metal part. The field feedback Body 19 has a slot 28 which has a field return opening 27 along its length through which the electrical conductors pass when the magneto-inductive flowmeter is assembled. The slot 28 extends inwards starting from the edge 20 of the field return body, in particular in the direction of a longitudinal axis 32 of the field return body. The panel return opening 27 and slots 28 can be formed using a stamping process or a laser cutting process. The slits 28 each have a slit width b, at least in one slit section, for which 0.5≦b≦3.8 millimeters applies. In the illustrated embodiment, an opening width of the field guiding opening 27 is larger than the slit width b of the slit 28 in the slit portion, the slit portion being between the field returning opening 27 and the field returning body edge 20 . Furthermore, the slot 28 has a fastener opening 31 along its length, through which a fastener extends in the assembled state. The fastener opening 31 is machined between the panel guide opening 27 and the panel return body edge 20 .

reference list

1

electromagnetic flow meter

2

measuring tube

5

Device for generating the magnetic field

6

coil arrangement

8th

Device for detecting the induced measuring voltage

13

Kitchen sink

14

coil core

16

coil core opening

17

measuring electrode

18

field feedback arrangement

19

field return body

20

field return body edge

25

connector

26

ladder

27

field return port

28

slot

29

transmitter

30

deepening

31

fastener opening

32

Field return body longitudinal axis

Claims (9)

Electromagnetic flow meter (1), comprising: - a measuring tube (2) for guiding a flowable medium; - an electrical connector (25); - a device (5) for generating a magnetic field penetrating the measuring tube, the device (5) comprising a coil arrangement (6) arranged on the measuring tube (2), the coil arrangement (6) having at least two, in particular diametrically oriented and preferably electrically connected to one another Coils (13.1, 13.2) each having at least one coil core (14.1, 14.2), the device (5) having a field feedback arrangement (18) which connects the coil cores (14.1, 14.2) to one another, the field feedback arrangement (18) having two field feedback bodies (19.1, 19.2), the coil arrangement (6) being connected to the plug connector (25) via a first electrical conductor (26.1) and a second electrical conductor (26.2), the two field return bodies (19.1, 19.2) each having a slot (28.1, 28.2), the two slots (19.1, 19.2) each having a field return opening (27.1, 27.2) along a path, d the slots (28.1, 28.2) each extend inwards starting from a field return body edge (20) of the respective field guide body (19.1, 19.2), wherein at least one of the coil cores (14.1) has a coil core opening (15); - A device (8) for detecting a measurement voltage induced in the medium, the device (8) being connected to the connector (25) via a third electrical conductor (26.3) and a fourth electrical conductor (26.4), the third conductor (26.3) and the fourth conductor (26.4) extending through the field return openings (27.1, 27.2), the third conductor (26.3) and the fourth conductor (26.4) extending through the coil core opening (15), the third conductor (26.3 ) and the fourth conductor (26.4) extends at least partially between one of the at least two coils (13.1, 13.2) and the measuring tube (2); and - a measuring transducer (29) for determining a flow velocity-dependent measured variable as a function of the induced measuring voltage and for operating the device (5) for generating the magnetic field, the measuring transducer (29) being electrically connected via the plug connector (25) to the device (5) for detecting the induced measurement voltage and the device (8) for generating the magnetic field. Electromagnetic flowmeter according to claim 1 , wherein the slits (28.1, 28.2) each extend starting from the field return body edge (20) transversely to the longitudinal direction of the measuring tube (2). Electromagnetic flowmeter according to claim 1 and/or 2, wherein the at least two coils (13.1, 13.2) are arranged diametrically, wherein the device (8) for tapping the measurement voltage comprises at least two diametrically arranged measuring electrodes (17.1, 17.2), wherein a coil axis passes through the at least two coils ( 13.1, 13.2), with a measuring electrode axis running through the at least two measuring electrodes (17.1, 17.2), with the coil axis running perpendicular to the measuring electrode axis, with the slots (28.1, 28.2) of a field guide body (19.1, 19.2) at least in one direction the coil axis and are at least partially covered by the respective other field guide body (19.1, 19.2). Electromagnetic flow meter according to at least one of Claims 1 until 3 , wherein the slits (28.1, 28.2) each have a slit width b, with the slit width b being 0.5≦b≦3.8 millimeters. Method for producing a magnetic-inductive flowmeter (1), comprising the method steps: - Providing a first assembly and a measuring tube (2), wherein the first assembly comprises a connector (25), a first conductor (26.1), a second conductor (26.2), a third conductor (26.3), a fourth conductor (26.4) and a coil arrangement (6), comprising at least two, in particular electrically connected to one another connected coils (13.1, 13.2), each with at least one coil core (14.1, 14.2), wherein the coil arrangement (6) is connected to the plug connector (25) via the first conductor (26.1) and the second conductor (26.2), the third conductor (26.3) and the fourth conductor (26.4) extending through a coil core opening (15) of a coil core (14.1); - connecting the third conductor (26.3) and the fourth conductor (26.4) to a device (8) arranged on the measuring tube (2) for detecting an induced measuring voltage, the third conductor (26.3) and the fourth conductor (26.4) extending at least partially between one of the at least two coils (13.1) and the measuring tube (2); - arranging the coil arrangement (6) on the measuring tube (2), - Provision of a second assembly, wherein the second assembly comprises two field return bodies (19.1, 19.2), the two field return bodies (19.1, 19.2) each having an in particular continuous slot (28.1, 28.2), the slots (28.1, 28.2) each extending inwards starting from a field return body edge (20.1, 20.2), wherein the slots (28.1, 28.2) each have a field return opening (27.1, 27.2) along one course, through which the third conductor (26.3) and the fourth conductor (26.4) extend after the arrangement of the second assembly, - arranging the second assembly, wherein when locating the second assembly, the third conductor (26.3) and the fourth conductor (26.4) are passed through the slots (28.1, 28.2) to the respective field return openings (27.1, 27.2). procedure after claim 5 , wherein the slits (28.1, 28.2) each extend transversely to the longitudinal direction of the measuring tube (2), starting from the field return edge. procedure after claim 5 and/or 6, wherein the at least two coils (13.1, 13.2) are arranged diametrically, wherein the device (8) for tapping the measurement voltage comprises at least two measuring electrodes (17.1, 17.2), in particular arranged diametrically, with a coil axis passing through the at least two coils (13.1, 13.2), with a measuring electrode axis running through the at least two measuring electrodes (17.1, 17.2), with the coil axis running perpendicular to the measuring electrode axis, with the slots (28.1, 28.2) each extending at least in one direction of the coil axis and at least partially through one of the two field guide bodies (19.1, 19.2) are covered. Process according to at least one of Claims 5 until 7 , wherein the slits (28.1, 28.2) each have a slit width b, with the slit width b being 0.5≦b≦3.8 millimeters. Process according to at least one of Claims 5 until 8th , where the first module has exactly one connector binder (25), wherein the coil arrangement (6) consists of two coils (13.1, 13.2), each with exactly one coil core (14.1, 14.2).

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