DE102020121681A1 - Coriolis flow meter - Google Patents

Abstract

The invention relates to a Coriolis flowmeter, comprising: - a measuring tube arrangement (4), the measuring tube arrangement (4) comprising at least one measuring tube (3) through which a medium can flow; - at least one vibration exciter (7), which is set up for the at least excite a measuring tube (3) to vibrate;- at least one vibration sensor (8) which is set up to detect the vibrations of the at least one measuring tube (3), comprising at least two vibration sensor components, the at least two vibration sensor components having at least one sensor magnet (38) and at least one sensor coil (39), wherein the at least one sensor magnet (38) has a magnet cross-sectional area AM perpendicular to a main magnet field axis (54), the sensor coil (39) having a coil cross-sectional area AS perpendicular to a main coil field axis (55), where AM> AS holds, having a coil front surface (58) and a magnet front surface (59). andet are, - a carrier device (16), comprising a receiving device (23) with a receptacle (29) and a vibration sensor component of the at least two vibration sensor components, wherein the measuring tube arrangement (4) can be arranged at least partially in the receptacle (23) and can be mechanically detachable with the carrier device (16) can be connected.

Description

The invention relates to a Coriolis flow meter, in particular for preferably pharmaceutical bioprocess applications.

Field devices in process measurement technology with a vibration-type sensor and, in particular, Coriolis flowmeters have been known for many years. The basic structure of such a measuring device is, for example, in EP 1 807 681 A1 described, with reference being made in full to the structure of a generic field device within the scope of the present invention to this publication.

Coriolis flowmeters typically have at least one or more oscillatable measuring tubes, which can be made to oscillate by means of an oscillating exciter. These vibrations are transmitted over the length of the pipe and are varied by the type of medium in the measuring pipe and its flow rate. A vibration sensor or, in particular, two vibration sensors spaced apart from one another can record the varied vibrations in the form of a measurement signal or a plurality of measurement signals at another point on the measuring tube. An evaluation unit can then determine the mass flow rate, the viscosity and/or the density of the medium from the measurement signal or signals.

Coriolis flowmeters with interchangeable disposable measuring tube assemblies are known. For example, in the WO 2011/099989 A1 teaches a method for producing a monolithic measuring tube arrangement of a Coriolis flowmeter with curved measuring tubes, wherein the measuring tube body of the respective measuring tubes is first formed solidly from a polymer and the channel for guiding the flowable medium is then worked in under tension. the WO 2011/099989 A1 teaches - just like them US 10,209,113 B2 - a connecting body which is set up to receive and support an exchangeable measuring tube arrangement comprising thin-walled plastic tubes. The measuring tube arrangement is fastened in a carrier device equipped with the necessary exciters and sensors via the connecting body.

gilt, mit der in einer Sensorspule induzierten Spannung U_ind, der Schwingfrequenz ƒ und der mechanischen Amplitude A des Messrohres.A particular challenge in Coriolis flowmeters with interchangeable disposable measuring tube assemblies is the reproducibility of the positioning of the disposable measuring tube assembly - in particular the vibration sensor components arranged on the disposable measuring tube assembly - relative to the corresponding vibration sensor components usually arranged on the carrier device. Furthermore, manufacturing tolerances of the replaceable disposable measuring tube, but also of the carrier device, mean that the sensor constant K _S previously determined in an adjustment process can only be reproduced with great uncertainty, with the sensor constant $$K_s=\raisebox{1ex}{$u_{in\mathrm{i.e}}$}\!\left/ \!\raisebox{-1ex}{$2\pi ƒ\cdot A$}\right.$$

applies, with the voltage U _ind induced in a sensor coil, the oscillation frequency ƒ and the mechanical amplitude A of the measuring tube.

The object of the invention is to provide a Coriolis flowmeter which has a lower measurement error caused by installation and/or manufacturing tolerances.

The object is achieved by the Coriolis flow meter according to claim 1.

• - eine Messrohranordnung, wobei die Messrohranordnung mindestens ein, von einem Medium durchströmbares Messrohr umfasst;
• - mindestens einen Schwingungserreger, welcher dazu eingerichtet ist, die Messrohranordnung, insbesondere das mindestens eine Messrohr zu Schwingungen anzuregen;
• - mindestens einen Schwingungssensor, welcher dazu eingerichtet ist, die Schwingungen des mindestens einen Messrohres zu erfassen, umfassend mindestens zwei Schwingungssensorkomponenten, wobei die mindestens zwei Schwingungssensorkomponenten mindestens einen Sensormagneten und mindestens eine Sensorspule umfassen, wobei zumindest eine Schwingungssensorkomponente der mindestens zwei Schwingungssensorkomponenten an der Messrohranordnung, insbesondere an dem mindestens einen Messrohr angeordnet ist, wobei der mindestens eine Sensormagnet eine Magnetquerschnittsfläche A_M senkrecht zu einer Magnethauptfeldachse aufweist, wobei die Sensorspule eine Spulenquerschnittsfläche A_S senkrecht zu einer Spulenhauptfeldachse aufweist, wobei A_M > A_S gilt, wobei die Sensorspule eine Spulenstirnseite und der Sensormagnet eine Magnetstirnseite aufweist, wobei die Spulenstirnseite und die Magnetstirnseite einander zugewandt sind, wobei die Spulenstirnseite eine Spulenfrontfläche und die Magnetstirnseite eine Magnetfrontfläche aufweist, wobei die Spulenfrontfläche und die Magnetfrontfläche beabstandet sind,
• - eine Trägervorrichtung, umfassend eine Aufnahmevorrichtung mit einer Aufnahme und eine Schwingungssensorkomponente der mindestens zwei Schwingungssensorkomponenten, wobei die Messrohranordnung zumindest teilweise in die Aufnahme anordenbar ist und mechanisch lösbar mit der Trägervorrichtung verbindbar ist.

The Coriolis flow meter according to the invention comprises:

• - a measuring tube arrangement, wherein the measuring tube arrangement comprises at least one measuring tube through which a medium can flow;
• - at least one vibration exciter, which is set up to excite the measuring tube arrangement, in particular the at least one measuring tube, to oscillate;
• - at least one vibration sensor, which is set up to detect the vibrations of the at least one measuring tube, comprising at least two vibration sensor components, wherein the at least two vibration sensor components comprise at least one sensor magnet and at least one sensor coil, wherein at least one vibration sensor component of the at least two vibration sensor components on the measuring tube arrangement, is arranged in particular on the at least one measuring tube, the at least one sensor magnet having a magnetic cross-sectional area A _M perpendicular to a main magnet field axis, the sensor coil having a coil cross-sectional area A _S perpendicular to a main coil field axis, wherein A _M > A _S applies, the sensor coil having a coil end face and the sensor magnet has a magnet face, wherein the coil face and the magnet face face each other, wherein the coil face has a coil face and the magnet face has a magnet face, the coil face and the magnet face being spaced apart,
• - A carrier device, comprising a receiving device with a receptacle and a vibration sensor component of the at least two vibration sensor components, wherein the measuring tube arrangement can be arranged at least partially in the receptacle and can be mechanically detachably connected to the carrier device.

In a conventional vibration sensor with a plunger coil, the sensor magnet is at least partially arranged within the exchange coil, in particular within a volume delimited by a plunger coil winding, and thus has a magnet cross-sectional area that is significantly smaller than the coil cross-sectional area of the exchange coil. The area where the magnetic field changes significantly is inside the voice coil. Coriolis flowmeters with interchangeable measuring tube arrangements have vibration exciters or vibration sensors in which the corresponding exciter magnet or sensor magnet does not extend into the exciter coil or sensor coil. Instead, a gap is provided between the two respective components. However, simply arranging the sensor and/or excitation magnets just outside the sensor and/or excitation coil leads to inferior measurement performance. The reason for this is that the speed-dependent measurement signal changes as a function of the distance between the sensor magnet and the sensor coil itself in the range of tenths of a millimeter and less.

By designing the sensor magnet in such a way that the magnet cross-sectional area is larger than the coil cross-sectional area, the vibration sensor achieves good linearity and positioning tolerance. The generated field lines of the magnetic field of the at least one sensor magnet in the area of the sensor coil have an approximately constant magnetic field gradient. As a result, the magnetic field decreases relatively slowly and approximately linearly in the direction of the main magnetic field axis. The result of this is that the sensor constant hardly changes when shifted in the direction of the main magnet field axis or in the direction of oscillation and thus a high positioning tolerance in the direction of the main magnet field axis or direction of oscillation is achieved. This proves to be particularly advantageous when the signals from two electromagnetic sensors are added by a series circuit, since in this case particularly low tolerances for the amplitudes of the voltage signals from the electromagnetic vibration sensors must be met.

The positioning tolerance in the direction perpendicular to the main magnet field axis is even better since the magnetic field through the sensor coil hardly changes in the direction perpendicular to the main magnet field axis.

The measuring tube arrangement forms the part of the Coriolis flow meter that can be replaced depending on the changing application and is to be understood as a disposable item. The measuring tube arrangement is therefore designed and set up in such a way that it can be connected to the carrier device in a mechanically separable manner. For this purpose, the carrier device has a receiving device with a receptacle into which the measuring tube arrangement can be inserted. The receiving device can have a fixing device for fastening the measuring tube arrangement to the carrier device.

Conventional vibration exciters used in Coriolis flowmeters include at least one exciter magnet and one exciter coil. An operating circuit is set up to generate an operating signal and apply it to the exciter coil so that it generates a magnetic field that varies over time. Conventional vibration sensors used in Coriolis flowmeters include at least one sensor magnet and one sensor coil. A measurement circuit is set up to detect a measurement voltage induced at the sensor coil.

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

One embodiment provides that the coil front surface and the magnet front surface are spaced apart by a distance x,
where x ≤ 2.5 mm and preferably x ≤ 2 mm,
where x ≥ 0.25 mm and preferably x ≥ 0.5 mm.

The coil front surface and the magnet front surface face each other and are also spaced apart by a distance x. The claimed value range for the distance x has turned out to be particularly advantageous for the alignment of the sensor coil relative to the sensor magnet, so that the sensor constant determined in the adjustment process can be reproduced more accurately in use compared to arrangements in which larger or smaller distances x exist. The sensor constant of a vibration sensor that satisfies the requirements specified here generally has a relatively flat maximum in the claimed distance range, ie the change in the sensor constant as a function of the distance is minimal. To achieve the maximum positioning tote The distance should be chosen so that a maximum value of the sensor constant is reached.

1,5 und bevorzugt $3\le \sqrt{A_M}/h_M\le 12$

gilt.One embodiment provides that an extension of the sensor magnet in the direction of the main magnet field axis has a magnet thickness h _M
whereby $\sqrt{A_M}/H_M\ge 1.5$

1.5 and preferred $3\le \sqrt{A_M}/H_M\le 12$

is applicable.

gilt.One embodiment provides that an extension of the sensor coil has a thickness h _S in the direction of the main coil field axis,
whereby $H_S<\sqrt{A_S}$

is applicable.

A further embodiment provides that h _S ≦10 mm, in particular h _S ≦5 mm and preferably h _S ≦2 mm.

One embodiment provides that A _M ≧1.77*A _S , preferably A _M ≧4*A _S and in particular A _M ≧16*A _S .

Such a configuration has the advantage that the inhomogeneous magnetic field generated by the sensor magnet in the edge area does not run through the sensor coil. As a result, a deviation from an ideal position of the sensor coil relative to the sensor magnet has only a slight influence on the sensor constant determined in the adjustment process. In this case, the ideal position describes the positioning of the sensor coil relative to the sensor magnet, which was present during the operational adjustment process.

One embodiment provides that the sensor coil has a number of turns N
where 250≦N≦2500 and preferably 500≦N≦2000.

One embodiment provides that the sensor coil includes a sensor coil wire,
wherein the sensor coil wire has a sensor coil wire diameter D _SD ,
where D _SD ≦150 μm, in particular D _SD ≦100 μm and preferably D _SD ≦20 μm.

To compensate for the small dimensions of the sensor coil and to compensate for the reduced magnetic field strength in the area of the coil due to the distance and dimensions of the magnet, it has proven advantageous to design the number of turns of the sensor coil to be higher than is usual with conventional vibration sensors. In addition, the thinnest possible winding wire must be used so that the sensor coil meets the advantageous geometric requirements and at the same time is designed to detect a sufficiently large measurement signal.

One embodiment provides that the measuring tube arrangement comprises two measuring tubes, namely a first measuring tube and a second measuring tube.
wherein the Coriolis flow meter comprises four vibration sensors, each with a sensor coil and a sensor magnet,
wherein a first vibration sensor comprises a first sensor coil and a first sensor magnet,
wherein a second vibration sensor comprises a second sensor coil and a second sensor magnet,
wherein a third vibration sensor comprises a third sensor coil and a third sensor magnet,
wherein a fourth vibration sensor comprises a fourth sensor coil and a fourth sensor magnet,
wherein the first sensor magnet and the second sensor magnet are arranged on the first measuring tube,
wherein the third sensor magnet and the fourth sensor magnet are arranged on the second measuring tube,
wherein the first sensor coil and the third sensor coil and/or the second sensor coil and the fourth sensor coil are each electrically connected in series.
wherein the first sensor coil and the third sensor coil are on the upstream side and the second sensor coil and the fourth sensor coil are on the downstream side.

According to the embodiment, the measurement voltage determined during operation by means of the measurement circuit always has the contribution of both sensor coils. Therefore, it is particularly necessary that the individual vibration sensors have the highest possible positioning tolerance in all three spatial directions, so that the amplitude signals of the individual vibration sensors are robust against variations in the distances between the coils and the magnets and thus no additional when adding the signals through the series connection phase error is generated. Only then can a simplified evaluation of the measurement signals be carried out with the aid of such an interconnection of the individual sensor coils.

One embodiment provides that the magnet front surface has a centroid and the coil front surface has a centroid,
where the two centroids are separated by a maximum distance amax,
where a max ≦20 mm, in particular a max ≦10 mm and preferably a max ≦3 mm, applies.

One embodiment provides that an evaluation circuit is set up for this purpose, at least as a function of a measured variable determined by means of the at least one vibration sensor and of the at least one vibration sensor to determine a variable dependent on the mass flow of the medium from the assigned sensor constant K _S,x dependent on the distance x,
where at an optimal working point the sensor constant K _S,x assumes a value of an optimal sensor constant K _S,opt ,
wherein the sensor magnet and the sensor coil are designed and oriented to one another in such a way that a deviation of the sensor constant K _S,x from the sensor constant K _S,opt in a distance range around the optimum operating point is always less than 0.3%, in particular less than 0.25% and is preferably less than 0.2%,
the distance range having two limits which are 0.01 mm, in particular 0.05 mm and preferably 0.1 mm apart from the optimum working point.

• 1: ein für pharmazeutische Bioprozessanwendungen geeignetes Coriolis-Durchflussmessgerät;
• 2: eine Schnittansicht durch einen Schwingungssensor;
• 3: eine mittels Finite-Elemente-Simulation erstellte Simulation des Magnetfelds in der Schnittansicht (wie 2) des Schwingungssensors; und
• 4: die mittels Finite-Elemente-Simulation berechnete Abhängigkeit der Sensorkonstante eines Schwingungssensors von dem Abstand eines Sensormagneten zur Sensorspule für die Konfiguration in 2 und 3.

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

• 1 : a Coriolis flow meter suitable for pharmaceutical bioprocess applications;
• 2 : a sectional view through a vibration sensor;
• 3 : a finite element simulation of the magnetic field in the section view (like 2 ) of the vibration sensor; and
• 4 : the dependence of the sensor constant of a vibration sensor on the distance between a sensor magnet and the sensor coil for the configuration in calculated using finite element simulation 2 and 3 .

the 1 shows a Coriolis flow meter suitable for pharmaceutical bioprocess applications, on which the principle of a Coriolis flow meter used in pharmaceutical bioprocess applications is explained below. The measuring tube arrangement 4 is suitable for being used in a Coriolis flow meter, in particular in a carrier device 16 of the Coriolis flow meter, in an exchangeable and mechanically detachable manner. For this purpose, individual components of the vibration exciter and the vibration sensors—in the case shown, the respective magnet arrangements 9.1, 9.2—are attached to the measuring tube arrangement 4. The other components are arranged in the carrier device 16, in particular in the receptacle 29 of the carrier device 16, which is suitable and designed for receiving the measuring tube arrangement 4. The respective components are each attached in such a way that it is possible to insert and remove the measuring tube arrangement 4 from the receiving device 23 without the corresponding components sterically impeding one another. The measuring tube arrangement 4 comprises two curved measuring tubes 3.1, 3.2 running parallel to one another, which are connected to one another via a coupler arrangement 1, in this case consisting of four coupling elements 6, and via a connecting body 5. The shape and the number of the measuring tubes 3.1, 3.2 are not essential to the invention. Measuring tube arrangements 4 with at least one straight measuring tube 3 are also known. Two coupling elements 6.1 are integrally attached in an inlet and two coupling elements 6.2 are attached in the outlet of the respective measuring tubes 3.1, 3.2. The measuring tubes 3.1, 3.2 shown are shaped in such a way that the direction of flow in the inlet is oriented opposite to the direction of flow in an outlet. A flow divider (not shown) can be arranged in the inlet and in the outlet, which has a process connection for connecting the measuring tube arrangement to a hose and/or plastic tube system. According to one embodiment, exactly one flow divider body can be provided instead of two separate flow dividers, which is pushed onto the inlet and outlet and contributes to mechanically decoupling the measuring tube arrangement 4 from the environment after installation in the carrier device. The individual coupling elements 6 are plate-shaped and in one or two parts. The coupling elements can in each case completely or only partially encompass the measuring tubes. The measuring tubes 3.1, 3.2 are U-shaped, ie they each have two legs which run essentially parallel to one another and are connected via a curved section. A magnet arrangement 9.1, 9.2 is arranged on each measuring tube 3.1, 3.2. A magnet 10.1 of the magnet arrangement 9.1, which forms a vibration exciter component of the vibration exciter, is arranged in the curved section of the respective measuring tubes 3.1, 3.2. A magnet 10.2, which forms part of the vibration exciter, is fitted in the respective legs of the measuring tubes 3.1, 3.2. The magnets 10 are attached to attachment surfaces. In the embodiment, the attachment surfaces are located on the respective measuring tubes 3.1, 3.2. The respective vibration exciter is arranged in the direction of flow between the two vibration sensors.

The measuring tube arrangement 4 is partially inserted into a receiving device 23 with a receiving device 29 of a carrier device 16 . An arrow indicates the direction of insertion. In the embodiment, this runs perpendicularly to a longitudinal direction of the receptacle 29 and the measuring tube arrangement 4. The receptacle 29 can also be designed in such a way that the measuring tube arrangement 4 can be inserted in the longitudinal direction of the receptacle 29 (not shown). The carrier device 16 has a measuring and/or operating circuit 29 which is connected to the vibration exciters and vibration sensors, in particular are specially connected to the respective coil systems and set up to generate and/or detect a magnetic field that changes over time. An evaluation circuit 53 is set up to determine at least one mass flow as a function of the measurement signal measured by the vibration sensors, in particular as a function of a phase difference. Furthermore, the evaluation circuit can be set up to determine a viscosity and/or a density of the medium to be conveyed. The carrier device 16 has a carrier device body 22 in which the receptacle 29 is located. The connecting body 5 of the measuring tube arrangement 4 has mounting surfaces 26 which are used to arrange the measuring tube arrangement 4 in a predetermined position in the carrier device 16 . According to the illustrated embodiment, the perpendicular of the mounting surface 26 points perpendicular to the longitudinal direction of the measuring tube arrangement 4. According to a further advantageous embodiment, the perpendicular of the mounting surface 26 points in the direction of the longitudinal direction of the measuring tube arrangement 4. The surface of the carrier device body that is in contact with the mounting surface 26 of the connecting body 5 22 is the bearing surface 27.

The carrier device 16 has two side surfaces which are oriented parallel to one another and delimit the receptacle 29 transversely to the longitudinal direction of the receptacle 29 . The coil devices of the vibration sensors 8.1, 8.2 and the coil device of the vibration exciter 7 are arranged in the side surfaces. The coil devices of the vibration sensors 8.1, 8.2 are arranged in the longitudinal direction of the receptacle 29 for the coil device of the vibration exciter 7. All three coil devices are in one coil plane. Furthermore, the three coil devices are designed as plate coils and sunk into the side surface. On the side surface, three coil devices are arranged substantially opposite the three coil devices. A guide is worked into each of the two side surfaces, which guide extends perpendicularly to the longitudinal direction of the receptacle 29 and parallel to the plane of the coil. According to the embodiment shown, the receptacle 29 extends over two end faces of the receptacle 29. This enables the measuring tube arrangement 4 to be inserted perpendicularly to the longitudinal direction of the measuring tube arrangement 4. According to a further embodiment, the receptacle 29 extends exclusively over one end face. In this case, the measuring tube arrangement 4 is to be introduced into the supporting device 16 in the longitudinal direction of the measuring tube arrangement 4 - or the supporting device 16 .

The vibration sensors shown have sensor magnets with a magnet cross-sectional area and sensor coils with a coil cross-sectional area, in the case shown the magnet cross-sectional area being smaller than the coil cross-sectional area. Thus, the design differs 1 of the solution according to the invention, which in 2 is pictured.

The measuring tube arrangement 4 comprises two measuring tubes 3, namely a first measuring tube 3.1 and a second measuring tube 3.2. Four vibration sensors 8 each with a sensor coil and a sensor magnet are arranged on the measuring tube arrangement 4 . The sensor coils shown can be designed as LTCC coils (Low Temperature Cofired Ceramics), for example in the DE 102018119330 B3 are taught as multilayer PCB coils made of conventional materials such as FR4, or as conventional wound coils made of enameled copper wire. The sensor magnets are at least partially cylindrical. A first vibration sensor 8.1 includes a first sensor coil 39.1 and a first sensor magnet 38.1, a second vibration sensor 8.2 includes a second sensor coil 39.2 and a second sensor magnet 38.2, a third vibration sensor 8.3 includes a third sensor coil 39.3 and a third sensor magnet 38.3 and a fourth vibration sensor 8.4 fourth sensor coil 39.4 and a fourth sensor magnet 38.4. The first sensor magnet 38.1 and the second sensor magnet 38.2 are arranged on the first measuring tube 3.1 and the third sensor magnet 38.3 and the fourth sensor magnet 38.4 are arranged on the second measuring tube 3.2. The first sensor coil 39.1 and the third sensor coil 39.3 and/or the second sensor coil 39.2 and the fourth sensor coil 39.4 are each electrically connected in series. The carrier device 16 includes a receiving device 23 with a receptacle 29 and a vibration sensor component of the at least two vibration sensor components, which form a vibration sensor. The measuring tube arrangement 4 can be arranged at least partially in the receptacle 23 and can be connected to the carrier device 16 in a mechanically detachable manner.

the 2 shows a sectional view through a vibration sensor, which is used in a Coriolis flowmeter according to the invention, and the magnetic field calculated using finite element simulation - represented by arrows - of the sensor magnet 38 is also shown in 3 shown. The vibration sensor 8 shown, which is set up to detect the vibrations of the at least one measuring tube 3, comprises at least two vibration sensor components, the at least two vibration sensor components comprising at least one sensor magnet 38 and at least one sensor coil 39, which are held together by a sensor magnet holder 40 and a sensor coil holder 41 can be attached 2 is to be understood as axially symmetrical. Without limiting the claims, in 2 So a cylindrical coil and a cylindrical magnet are shown as an example. At least one vibration sensor component of the at least two vibration sensor components is arranged on the measuring tube arrangement, in particular on the at least one measuring tube 3 . The sensor coil 39 has a coil face 56 and the sensor magnet 38 has a magnet face 57, the coil face 56 and the magnet face 57 facing each other. The coil face 56 has a coil face 58 and the magnet face 57 has a magnet face 59 . In contrast to conventional approaches, in which the coil magnet is inserted into the plunger coil, the sensor coil 39 and the sensor magnet 38 are spaced apart in such a way that they do not sterically impede one another when moving perpendicularly to the main field axis. This is realized, for example, in that the coil front surface 58 and the magnet front surface 59 are spaced apart. The at least one sensor magnet 38 has a magnet cross-sectional area A _M perpendicular to a main magnet field axis 54 . The sensor coil 39 has a coil cross-sectional area A _S perpendicular to a main coil field axis 55 . It applies to the two cross-sectional areas that A _M > A _S .

und bevorzugt $3\le \sqrt{A_M}/h_M\le 12$

auf. Eine Ausdehnung der Sensorspule 39 in Richtung der Spulenhauptfeldachse 55 weist eine Dicke h_S auf mit $h_S<\sqrt{A_S}.$

Außerdem gilt für die die Dicke h_S, dass h_S ≤ 10 mm, insbesondere h_S ≤ 5 mm und bevorzugt h_S ≤ 2 mm ist. Es ist zudem äußerst vorteilhaft, wenn wie in 2 schematisch angedeutet die Magnetquerschnittsfläche A_M ≥ 1,77 • A_S, bevorzugt A_M ≥ 4 • A_S und insbesondere A_M ≥ 16 • A_S ist. Die Sensorspule 39 weist eine Windungszahl N auf für die 250 ≤ N ≤ 2500 und bevorzugt 500 ≤ N ≤ 2000 gilt. Zudem umfasst die Sensorspule 39 einen Sensorspulendraht, der einen Sensorspulendrahtdurchmesser D_SD aufweist mit D_SD ≤ 150 µm, insbesondere D_SD ≤ 100 µm und bevorzugt D_SD ≤ 20 µm. Die Magnetfrontfläche 59 und die Spulenfrontfläche 58 weisen jeweils einen Flächenschwerpunkt auf, die mit einem Maximalabstand amax beabstandet sind. Dabei gilt vorzugsweise amax ≤ 20 mm, insbesondere amax ≤ 10 mm und bevorzugt amax ≤ 3 mm. Somit kann sichergestellt werden, dass der Abstand der Sensorspule relativ zum Randbereich des Sensormagneten möglichst maximal ist. Der im Randbereich des Sensormagneten erzeugte Magnetfeld ist stark inhomogen, d.h. dass im Randbereich die Richtung der einzelnen Magnetlinien streut und dass die Magnetstärke stark von dem Abstand zum Magneten abhängt. Dies wird durch die Größe der Pfeile dargestellt.The coil front surface 58 and the magnet front surface 59 are separated by a distance x, where the distance x≦2.5 mm and preferably x≦2 mm applies and at the same time x≧0.25 mm and preferably x>0.5 mm applies. An expansion of the sensor magnet 38 in the direction of the main magnet field axis 54 has a magnet thickness h _M $\sqrt{A_M}/H_M\ge 1.5$

and preferred $3\le \sqrt{A_M}/H_M\le 12$

on. An extension of the sensor coil 39 in the direction of the main coil field axis 55 has a thickness h _S with $H_S<\sqrt{A_S}.$

In addition, it applies to the thickness h _S that h _S ≦10 mm, in particular h _S ≦5 mm and preferably h _S ≦2 mm. It is also extremely advantageous if, as in 2 indicated schematically, the magnet cross-sectional area is A _M ≧1.77 • A _S , preferably A _M ≧4 • A _S and in particular A _M ≧16 • A _S . The sensor coil 39 has a number of turns N for which 250≦N≦2500 and preferably 500≦N≦2000. In addition, the sensor coil 39 includes a sensor coil wire which has a sensor coil wire diameter D _SD with D _SD ≦150 μm, in particular D _SD ≦100 μm and preferably D _SD ≦20 μm. The magnet front surface 59 and the coil front surface 58 each have a centroid which is spaced apart by a maximum distance amax. In this case, a max ≦20 mm preferably applies, in particular a max ≦10 mm and preferably a max ≦3 mm. It can thus be ensured that the distance between the sensor coil and the edge area of the sensor magnet is as maximum as possible. The magnetic field generated in the edge area of the sensor magnet is highly inhomogeneous, ie the direction of the individual magnetic lines scatters in the edge area and the magnet strength depends heavily on the distance to the magnet. This is represented by the size of the arrows.

An evaluation circuit is set up to determine a variable dependent on the mass flow rate of the medium, at least as a function of a measured variable determined by means of the at least one vibration sensor 8 and a sensor constant K _S,x assigned to the at least one vibration sensor 8 and dependent on the distance x. At an optimal working point, the sensor constant K _S,x assumes a value of an optimal sensor constant K _S,opt . The sensor magnet 38 and the sensor coil 39 are designed and oriented to one another in such a way that a deviation of the sensor constant K _S,x from the sensor constant K _S,opt in a distance range around the optimum operating point is always less than 0.3%, in particular less than 0.25%. and is preferably less than 0.2%. The distance range has two limits, which are 0.01 mm, in particular 0.05 mm and preferably 0.1 mm apart from the optimal operating point.

the 4 Fig. 12 is a graph showing the relationship between the sensor constant (Y-axis) of a vibration sensor and the distance between the magnet face and the coil face of the vibration sensor (X-axis). A filled-in circle represents the optimum working distance. This distance is preferably set when adjusting the measuring tube arrangement, and it must be reproduced within a certain tolerance when the disposable measuring tube arrangement is used or replaced by the customer. An area delimited by two bars represents the distance range in which the sensor constant does not deviate from the optimal sensor constant by more than 0.2%. Such an insensitivity to a deviation from the optimal working distance results from observing the geometric features of the sensor coil and the sensor magnet required in the configurations.

reference list

1

coupler arrangement

2

gauge

3

measuring tube

4

measuring tube arrangement

5

fixing body

6

coupler element

7

vibration exciter

8th

vibration sensor

9

magnet assembly

10

magnet

11

leg

12

side

13

measuring tube body

15

Measuring and/or operating circuit

16

carrier device

22

carrier unit body

23

recording device

24

side face

25

coil device

26

mounting surface

27

side face

29

admission

38

sensor magnet

39

sensor coil

53

evaluation circuit

54

main magnetic field axis

55

coil main field axis

56

coil face

57

magnet face

58

coil face

59

magnet face

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 1807681 A1 [0002]
• WO 2011/099989 A1 [0004]
• US10209113B2 [0004]
• DE 102018119330 B3 [0034]

Claims (11)

Coriolis flow meter, comprising: - a measuring tube arrangement (4), wherein the measuring tube arrangement (4) comprises at least one measuring tube (3) through which a medium can flow; - at least one vibration exciter (7), which is set up to excite the measuring tube arrangement (4), in particular the at least one measuring tube (3), to oscillate; - at least one vibration sensor (8), which is set up to detect the vibrations of the at least one measuring tube (3), comprising at least two vibration sensor components, wherein the at least two vibration sensor components comprise at least one sensor magnet (38) and at least one sensor coil (39), wherein at least one vibration sensor component of the at least two vibration sensor components is arranged on the measuring tube arrangement (9), in particular on the at least one measuring tube (3), wherein the at least one sensor magnet (38) has a magnet cross-sectional area A _M perpendicular to a main magnet field axis (54), the Sensor coil (39) has a coil cross-sectional area A _S perpendicular to a coil main field axis (55), where A _M > A _S applies, the sensor coil (39) having a coil end face (56) and the sensor magnet (38) having a magnet end face (57), wherein the coil face (56) and the magnet face (57) face each other d, wherein the coil end face (56) has a coil front face (58) and the magnet face (57) has a magnet front face (59), the coil front face (58) and the magnet front face (59) being spaced apart, - a carrier device (16), comprising a Recording device (23) with a recording (29) and a vibration sensor component of the at least two vibration sensor components, wherein the measuring tube arrangement (4) can be arranged at least partially in the recording (23) and can be mechanically detachably connected to the carrier device (16). Coriolis flow meter according to claim 1 , wherein the coil front surface (58) and the magnet front surface (59) are spaced apart by a distance x, where x≦2.5 mm and preferably x≦2 mm, where x≧0.25 mm and preferably x≧0.5 mm is applicable. Coriolis flow meter according to claim 2 , wherein an extension of the sensor magnet (38) in the direction of the main magnet field axis (54) has a magnet thickness h _M , where $\sqrt{A_M}/H_M\ge 1.5$

1.5 and preferred $3\le \sqrt{A_M}/H_M\le 12$

is applicable. Coriolis flowmeter according to at least one of the preceding claims, wherein an extension of the sensor coil (39) in the direction of the coil main field axis (55) has a thickness h _S , where $H_S<\sqrt{A_S}$

is applicable. Coriolis flow meter according to claim 4 , where h _S ≦10 mm, in particular h _S ≦5 mm and preferably h _S ≦2 mm. Coriolis flowmeter according to at least one of the preceding claims, wherein A _M ≥ 1.77 · A _S , preferably A _M ≥ 4 · A _S and in particular A _M ≥ 16 · A _S applies. Coriolis flow meter according to at least one of the preceding claims, wherein the sensor coil (39) has a number of turns N, where 250≦N≦2500 and preferably 500≦N≦2000. Coriolis flowmeter according to at least one of the preceding claims, wherein the sensor coil (39) comprises a sensor coil wire, the sensor coil wire having a sensor coil wire diameter D _SD , where D _SD ≤ 150 µm, in particular D _SD ≤ 100 µm and preferably D _SD ≤ 20 µm . Coriolis flowmeter according to at least one of the preceding claims, wherein the measuring tube arrangement (4) comprises two measuring tubes (3), namely a first measuring tube (3.1) and a second measuring tube (3.2), the Coriolis flowmeter having four vibration sensors (8), each with a sensor coil (39) and a sensor magnet (38), with a first vibration sensor (8.1) comprising a first sensor coil (39.1) and a first sensor magnet (38.1), with a second vibration sensor (8.2) comprising a second sensor coil (39.2) and a second sensor magnet (38.2), wherein a third vibration sensor (8.3) comprises a third sensor coil (39.3) and a third sensor magnet (38.3), wherein a fourth vibration sensor (8.4) comprises a fourth sensor coil (39.4) and a fourth sensor magnet (38.4), wherein the first sensor magnet (38.1) and the second sensor magnet (38.2) are arranged on the first measuring tube (3.1), the third sensor magnet (38.3) and the fourth sensor magnet (38.4) are arranged on the second measuring tube (3.2), the first sensor coil (39.1) and the third sensor coil (39.3) and/or the second sensor coil (39.2) and the fourth sensor coil (39.4) are each electrically connected in series. Coriolis flow meter according to at least one of the preceding claims, wherein the magnet front surface (59) has a centroid and the coil front surface (58) has a centroid, where the centroids are spaced by a maximum distance amax, where a max ≦20 mm, in particular a max ≦10 mm and preferably a max ≦3 mm, applies. Coriolis flowmeter according to at least one of the preceding claims, wherein an evaluation circuit (53) is set up to, at least as a function of a measured variable determined by means of the at least one vibration sensor (8) and one of the at least one vibration sensor (8) assigned and dependent on the distance x Sensor constant K _S,x to determine a variable dependent on the mass flow rate of the medium, with the sensor constant K _S,x assuming a value of an optimal sensor constant K _S,opt at an optimum operating point, with the sensor magnet (38) and the sensor coil (39) are designed and oriented to each other in such a way that a deviation of the sensor constant K _S,x from the sensor constant K _S,opt in a distance range around the optimal operating point is always less than 0.3%, in particular less than 0.25% and preferably less than 0.2% is, wherein the distance range has two limits, which are 0.01 mm, in particular 0.05 mm and preferably 0.1 mm from the optimal Arbe its point are spaced.

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