DE102017121918A1 - Measuring tube for guiding a fluid and measuring device comprising such a measuring tube - Google Patents

Abstract

Measuring tube (1) for guiding a fluid (F), comprising at least a portion (2) of a pipe (3) for guiding the fluid, and a within the portion (2) of the pipe (3) outgoing pipe socket (4) for fluidic Connecting a device for determining a physical size of the fluid (50), wherein the pipeline (3), within the subsection (2) on a pipe wall (6) of the pipeline (3), at least one, preferably opposite the outgoing pipe socket (4) arranged, bluff body (7) which projects into the pipe (3), so that by the bluff body (7) results in an increased exchange of the fluid (F) in the pipe socket (4).

Description

The invention relates to a measuring tube for guiding a fluid and a measuring device, which comprises such a measuring tube.

Measuring tubes are used in conjunction with a plurality of measuring devices or field devices for determining at least one physical variable or a process variable. The physical variable or process variable to be determined and / or monitored can be, for example, the density of a fluid flowing through the measuring tube. It can also be given by pressure, flow, viscosity, conductivity, temperature or pH. Also optical sensors, such as turbidity or absorption sensors are known.

In order to measure a physical size of the fluid, such measuring devices or field devices must be brought into fluidic contact with the fluid. Usually, for this purpose, the measuring devices and / or field devices are at least partially introduced into a pipeline via a pipe socket of a T-piece.

The disadvantage here is that the pipe socket of the T-piece is closed by the introduction of the meter and / or field device and thus forms a fluid dead end, which in turn causes the fluid resistance in the pipe socket compared to the fluidic resistance of the pipeline clearly increases, so that the fluid exchange in the pipe socket is essentially purely diffusion-driven. For the meter and / or field device, this means that rapid changes in the physical size of the fluid are relatively slow to measure, since the exchange mechanism between the "new" and "old" fluid in the spigot is dominated by the relatively slow diffusion process.

It is therefore an object of the invention to propose a measuring tube in which a measuring device and / or field device introduced into the pipe socket detects a change in the physical quantity of the fluid carried in the measuring pipe as quickly as possible.

The object is achieved by the measuring tube according to claim 1 and a measuring device according to claim 11.

The measuring tube for guiding a fluid according to the invention comprises at least a portion of a pipeline for guiding the fluid, and a pipe socket outgoing from the pipeline within the partial section for fluidically connecting a device for determining a physical quantity of the fluid, the pipeline, within the partial section at a Pipe wall of the pipe, at least one, preferably arranged opposite the outgoing pipe socket, bluff body which projects into the pipe, so that there is an increased exchange of the fluid in the pipe socket by the bluff body.

According to the invention it is proposed to introduce a Störköper in such a way in the pipeline, that a faster mixing of the fluid takes place in the pipe socket. The disruptive body disturbs the fluid flow through the pipeline and induces convection in the outgoing from the pipeline pipe socket in which the meter and / or field device is at least partially introduced.

As a pipe socket is referred to in the sense of the invention, the end portion of any pipe. The pipeline of the pipe socket is preferably rigid but at least partially flexible. Furthermore, it may be formed from one or more layers of any materials, such as, for example, plastic and / or metal, but in particular of a metal. The pipe and / or the pipe socket may, for example, be a round pipe, a square pipe, a rectangular pipe or a pipe bend. The same applies to the section of the pipeline.

The invention offers the advantage that a faster mixing takes place with the fluid "accumulated" in the pipe socket, so that a shorter response time for the determination of the physical quantity results for the measuring device and / or field device.

An advantageous embodiment of the measuring tube according to the invention provides that the disruptive body is arranged in a central region, preferably substantially in a center, of the partial section of the pipeline.

An alternative embodiment of the measuring tube according to the invention provides that the disruptive body is arranged in an edge region, preferably substantially at an edge of the subsection of the pipeline.

A further advantageous embodiment of the measuring tube according to the invention provides that the disruptive body is formed substantially plate-shaped. In particular, the embodiment may provide that the perturbation body is formed such that a is flowed through the fluid area A _sturgeon the bluff body up to 80%, preferably up to 60%, particularly preferably up to 55%, most preferably up to 50%, with respect to a cross-sectional area A _{pipe of} the pipeline occupies.

An alternative embodiment of the measuring tube according to the invention provides that the disruptive body is formed substantially helically. In particular, the embodiment can provide that the bluff body is designed such that the bluff body up to a height of 80%, preferably up to a height of 60%, more preferably up to a height of 55%, most preferably up to a height of 50%, with respect to a diameter of the pipe in the section projecting into the pipeline.

A further advantageous embodiment of the measuring tube according to the invention provides that at least the partial section of the pipeline and the bluff body are made of one piece, preferably by means of a generative or machining process.

In the following, a generative or additive manufacturing process is to be understood as meaning such a process in which plastic parts are produced in a primary molding process. Such generative manufacturing processes, which in principle represent an industrialized and mass-capable further development of so-called rapid prototyping, have been increasingly used in industrial production for some years. An overview of the various principles and most common methods is accordingly known from a variety of publications.

All generative manufacturing methods have in common that the desired three-dimensional workpiece is first designed and digitized, for example by computer, by means of a model, or also by means of CAD (computer-aided design). Subsequently, the workpiece is constructed according to the digital data, in particular in layers, from one or more liquid or solid, in particular pulverulent, raw materials under the expiration of physical or chemical hardening or melting processes. Typical raw materials are plastics, synthetic resins, ceramics and metals, whereby depending on the used material another functional principle comes into play.

In this case, a machining process refers to a process in which a given geometric shape is given to a workpiece as a starting product by separating excess material in the form of chips by mechanical means. This includes, in particular, turning, drilling, grinding and milling, which in the present case is particularly preferred for the cutting process.

A further advantageous embodiment of the measuring tube according to the invention provides that the measuring tube is designed in the form of a T-piece.

A further advantageous embodiment of the measuring tube according to the invention provides that the measuring tube metal, preferably stainless steel, particularly preferably stainless steel has. Particularly suitable here are the stainless steels 316L and 17-4PH proved.

The invention further relates to a measuring device comprising a measuring tube according to at least one of the embodiments described above and at least one device for determining a physical size of the fluid, which is introduced into the pipe socket in such a way that the device is in fluidic contact with the sensor element in at least the end with a sensor element Measuring tube guided fluid is.

An advantageous embodiment of the measuring device according to the invention provides that the at least one device is further introduced into the pipe socket in such a way that the sensor element projects at least partially into the pipe.

An alternative embodiment of the measuring device according to the invention provides that the at least one device is further introduced into the pipe socket in such a way that the sensor element does not protrude into the pipe.

An advantageous embodiment of the measuring device according to the invention provides that the device further comprises a arranged in a device housing glass feedthrough and a printed circuit board having a first region and a second region, wherein the sensor element is arranged in the first region, wherein the device housing and the pipe socket in such a manner are matched, that the device housing is detachably connectable to the pipe socket and in the connected state, the first region of the circuit board from the second region through the glass bushing is hermetically separated, so that only the sensor element is in fluidic contact with the guided in the measuring tube fluid.

A further advantageous embodiment of the measuring device according to the invention provides that the sensor element comprises a quartz oscillator, comprising a quartz crystal, preferably in the form of a quartz watch, for generating an electrical oscillation with a specific frequency, preferably with a frequency of about 32.768 kHz, a housing in which is introduced the quartz crystal and a quartz crystal electronics, which is adapted to control the quartz oscillator for generating the electrical oscillation and to provide a dependent on the frequency output signal (Sout) has, wherein in the housing of the quartz oscillator at least one Is introduced so that the fluid whose physical size, in particular a density is to be determined, come into contact with the quartz crystal and the frequency of the quartz crystal as a function of physical size, in particular the density change, so that from the output signal, which represents the frequency dependent on the physical quantity, the physical quantity can be determined.

• 1: eine erste Ausgestaltung des erfindungsgemäßen Messrohrs,
• 2: eine zweite Ausgestaltung des erfindungsgemäßen Messrohrs,
• 3: eine Ausgestaltung des erfindungsgemäßen Messgerätes,
• 4: exemplarisch eine Vorrichtung zum Bestimmen einer physikalischen Größe, die über den Rohrstutzen des Messrohrs in fluidischen Kontakt mit dem Fluid gebracht werden kann,
• 5: einen schematischen Ablauf eines Verfahrens zur Herstellung einer Vorrichtung zum Bestimmen der Fluiddichte, insbesondere Gasdichte, welche bspw. über den Rohrstutzen zumindest mit dem Sensorelement in fluidischen Kontakt zu dem in der Rohrleitung geführten Fluid gebracht werden kann, und
• 6: ein Sensorelement in Form eines Quarzoszillators, dessen Gehäuse derartig punktiert ist, dass die Öffnungen einen Partikelfilter ausbilden.

The invention will be explained in more detail with reference to the following drawings. It shows:

• 1 a first embodiment of the measuring tube according to the invention,
• 2 a second embodiment of the measuring tube according to the invention,
• 3 : an embodiment of the measuring device according to the invention,
• 4 by way of example a device for determining a physical quantity which can be brought into fluidic contact with the fluid via the pipe socket of the measuring tube,
• 5 : a schematic sequence of a method for producing a device for determining the fluid density, in particular gas density, which can be brought, for example. Via the pipe socket at least with the sensor element in fluidic contact with the guided in the pipeline fluid, and
• 6 a sensor element in the form of a quartz oscillator whose housing is dotted in such a way that the openings form a particle filter.

1 shows a first embodiment of the measuring tube according to the invention 1 which is a subsection 2 a pipeline 3 for guiding a fluid F , For example, in the form of a gaseous or liquid medium, and a pipe socket 4 includes. The pipe socket 4 goes from the pipeline 3 preferably at right angles, so that the measuring tube 1 has a substantially T-shaped configuration. It should be noted, however, that the pipe socket 4 can also depart in any other angle α in the range of 0 ° <α <180 ° between a wall of the pipe and its longitudinal axis. The area in which the pipe socket 4 doing so from the pipeline 3 go defines a subsection 2 the pipeline 3 and in the 1-3 is indicated by two dashed lines. The pipeline 3 can only affect the area in which the pipe socket 4 going off, so the subsection 2 self, restrict (not in 1 shown) or over the area in which the pipe socket 4 go out, extend (in 1-3 shown). Through the pipeline 3 becomes a fluid F , for example, a gas, led.

The pipe socket 4 serves to provide a device for determining at least one physical quantity 50 , For example, a fluid density, in particular a gas density, fluidly to the pipeline 3 connect, ie in contact with the in the pipeline 3 guided fluid F bring. The device 50 is preferably configured such that a device housing 517 the pipe socket 4 closes, leaving the pipe socket 4 represents a fluidic dead end. This can be done, for example, by the fact that the device housing 517 with an external thread in the Rohrstutzte 4 is screwed in with a corresponding inside thread. The integration can of course also via any other conventional mounting option, eg, welding, etc., take place. The device 50 can be so deep in the pipe socket 4 be incorporated that a sensor element 53 the device 50 exclusively in the pipe socket 4 is located so that it is not directly from that in the pipeline 3 guided fluid F is streamed ( 1 ) or alternatively that the sensor element 53 at least partially into the pipeline 3 dips, leaving it in the pipeline 3 at least in parts ( 2 ).

According to the invention, the measuring tube 1 Furthermore, a bluff body 7 on, in a flow direction of the fluid F as an obstacle to the fluid F is introduced. In the figures, the flow direction of the fluid F represented by an arrow and is thus directed from left to right. The disruptive body 7 is formed such that it is in the subsection 2 the pipeline 3 So in the area of the outgoing pipe socket 4 is set in the pipeline 3 protrudes.

The disruptive body 7 For example, it may be substantially plate-shaped, ie in the form of a planar component, which is arranged with its plane preferably orthogonal to the flow direction. The plate-shaped disruptive body 7 can be formed, for example, in the form of a rectangle or a square. Alternatively, the bluff body 7 also be formed substantially helically, ie the bluff body 7 Essentially, this is similar to a screw in the pipeline 3 protrudes.

The disruptive body 7 may also be somewhere in the subsection 2 the pipeline 3 be arranged. Especially effective in increasing the exchange rate of the fluid F in the pipe socket 4 However, it has proved, the Störkörper 7 in a middle area 2a , which in about one third of the entire subarea 2 corresponds to arrange. Within the center area 2a It has proved most effective when the bluff body is substantially centrally, ie in the middle of the sub-area, arranged.

In addition to this, it has proved to be particularly effective when in the middle area 2a of the subsection 2 arranged bluff body 7 is configured such that it in the case that it is plate-shaped, a surface A _sturgeon of up to 60%, preferably up to 55%, more preferably up to 50% with respect to a cross-sectional area of the pipeline A _pipe in the subsection 2 occupies.

In the case that the bluff body 7 helical, it has proved to be particularly effective when the bluff body 7 up to a height H from 80%, preferably up to a height of 60%, more preferably up to a height of 55%, most preferably up to a height of 50%, in relation to a diameter D the pipeline 3 in the section 2 into the pipeline 3 protrudes.

Alternatively to the arrangement in the middle area 2a can the bluff body, as in 2 shown, even in a border area 2 B , which in about one third of the entire subarea 2 corresponds to be arranged. Here, the bluff body 7 both in the border area 2 B be located downstream or in the edge region upstream. In addition, it has proven to be particularly effective when in the edge area 2 B of the subsection 2 arranged bluff body 7 is designed such that it has a height of up to 85%, preferably up to 80% with respect to a diameter D the pipeline 3 in the subsection 2 having.

In a preferred variant, the subsection 2 the pipeline 3 and the bluff body integrally formed, ie, made of one piece, for example. In the form of a tee. This can be done, for example, by a machining process, such as milling, or a generative process. The measuring tube is preferably made of a metal, for example a stainless steel, such as 316L or 17-4PH.

3 shows a measuring device according to the invention, in particular a measuring device of automation technology, comprising an inventively ausgestaltetes measuring tube for guiding the fluid 1 and a device for determining a physical quantity of the fluid 50 , The device 50 is doing so in the pipe socket 4 of the measuring tube 1 introduced that the sensor element 53 the device completely in the pipe socket 4 located. In the illustrated embodiment, the bluff body 7 in the middle of the section 2 arranged and has a height of about 50% based on the diameter D the pipeline 3 on. Alternatively, the bluff body 7 , as in 3 shown in gray, also in one of the two border areas 2 B be arranged and a height of up to about 80% based on the diameter of the pipeline 3 exhibit.

In the apparatus for determining a physical quantity 50 it may, for example, be a device for determining a fluid density, in particular a gas density. Exemplary is in 4 such a device is shown, which is a quartz oscillator 53 as a sensor element, a printed circuit board 58 on the one hand the quartz oscillator 53 and second, an evaluation unit 57 , For example, in the form of an ASIC or a microprocessor sits and a device housing 517 into which the circuit board 58 is introduced has. The quartz oscillator is according to the in 5 prepared and described below for determining the gas density prepared accordingly, in particular punctured. Further, the quartz oscillator 53 in a at a first end of the circuit board 58 located first area 512 and the evaluation unit 57 in a second area located at a second end of the circuit board opposite the first end 513 arranged. The electrical connection is here via printed conductors of the printed circuit board 58 realized.

It has proved to be advantageous if in the middle section 514 that is between the first and second area 512 . 513 lies a glass passage 515 is arranged, via which the electrical connection or the output signal Sout of the quartz oscillator 53 between the two areas 512 and 513 realized or managed. In 4 this is indicated by a dashed line. The circuit board 58 , the glass passage 515 and the device housing 517 are in such a way to each other and coordinated that after inserting the circuit board 58 with the glass passage 515 into the device housing 517 the first area 512 from the second area 513 hermetically separated. In this way, the device with the first end of the circuit board 58 be exposed to the fluid without the medium can get into the second area.

The circuit board 58 may also have a notch in the region of the middle section 514 exhibit. Through the notch, the front part or first area 512 get separated easier. In this way, the circuit board for both the variant with glass feedthrough 515 as well as the variant without glass passage 515 be prepared in the same way.

The notch is also in the variant with glass passage 515 the width of the device is not changed substantially.

5 shows a schematic sequence of a method for producing the device for determining the fluid density, in particular gas density, which over the pipe socket at least with the Sensor element is brought into fluidic contact with the guided in the pipeline fluid.

In a first process step S100 becomes a quartz oscillator 53 provided as the actual sensor element in the form of a stationary component. The quartz oscillator 53 in this case comprises a quartz crystal 54 , a quartz crystal electronics 56 and a housing 5 , The quartz crystal 4 and the quartz crystal electronics 56 are in the case 55 introduced and hermetically encapsulated to the environment. Furthermore, the housing 55 during production of the quartz oscillator 53 at least in some areas have been vacuumized, so that at least the quartz crystal 54 in the case 55 stored in a vacuum. About the quartz crystal electronics 56 becomes the quartz crystal 54 controlled such that it oscillates electrically with a predetermined frequency or resonance frequency, preferably in the form of a sinusoidal oscillation. Furthermore, the quartz crystal electronics 56 adapted to convert the generated oscillation into square wave signals of the same frequency and as an output signal Sout at an exit pin 516 of the quartz oscillator 53 provide. Such quartz oscillators 53 are, as previously mentioned, commercially available as separately designed components in a variety of variants. It is advantageous if as a quartz oscillator 53 a conventional quartz watch is provided because it is due to the high quantities in which it is produced, economically obtainable. Watch quartz has a crystal oscillating with a frequency of 32.768 kHz or an integer multiple or an integral fraction thereof.

In a second process step S200 becomes the quartz oscillator 53 on a circuit board 58 applied. The application can be carried out, for example, by a soldering step in which the quartz oscillator 53 on the circuit board 58 is soldered.

The circuit board 58 has at least one evaluation unit 57 and is formed such that the soldered quartz oscillator 53 via conductor tracks electrically to the evaluation unit 57 connected, so that of the quartz crystal electronics 56 generated output signal of the quartz oscillator Sout the evaluation unit 57 is supplied.

In a third process step S300 becomes the case 55 of the quartz oscillator 53 dotted in such a way that the housing 5 at least one inlet opening 59 for the medium 52 having. The generation of the inlet opening 59 can be done in principle by any suitable mechanical tool or a laser. As a mechanical tool, the use of a punching punch has proven to be particularly advantageous. When using a laser, it has proved to be advantageous to use a pulsed laser, for example a picosecond or also a femtosecond laser, since during its use the housing material is abruptly evaporated and thus no material parts are drawn into the vacuum-sealed housing prior to puncturing as is the case when using a non-pulsed laser. However, a disadvantage of using a pulsed laser is that the machining of the housing is relatively expensive. Because of this, as an alternative to using the pulsed laser, the use of a combination of a mechanical tool and a non-pulsed laser has been used to puncture the housing 5 exposed. Here, first, the inlet opening 9 as an initial opening in the housing 59 by a mechanical tool, for example. A punching iron, introduced and then become more openings 510 in the case 59 introduced by a non-pulsed laser insofar as further openings in the housing are desired.

In the third method step may further be provided that the housing 55 of the quartz oscillator 53 is punctured such that more openings 510 in the case 55 be introduced. The other openings 10 and if necessary the inlet opening serve as a particle filter 511 To avoid particles with a certain diameter in the housing 55 to arrive and thus the quartz crystal 54 to protect.

Accordingly, at least the other openings 510 in this case carried out such that no particles with a geometric equivalent diameter smaller than 35 microns, preferably less than 30 microns, more preferably less than 25 microns into the housing 55 can penetrate when the case 55 the medium 52 is exposed. In the simplest case, the other openings 510 as substantially circular openings introduced into the housing, which have a diameter of less than 35 microns, preferably less than 30 microns, more preferably less than 25 microns. Conceivable, however, are other geometric designs than the circular openings. For example. the openings may also be designed in the form of a slot, wherein the slot or ggfl. the slots are then designed so that no particles with a geometric equivalent diameter smaller than 35 microns, preferably less than 30 microns, more preferably less than 25 microns can penetrate into the housing. In the event that the combination of mechanical tool and the non-pulsed laser is used for puncturing the housing, it is necessary that the inlet opening, which was introduced as an initial opening by the mechanical tool in the housing, after the introduction of the other openings the non-pulsed laser, is closed again, since the inlet opening is significantly larger than the other openings. Closing the inlet opening 59 can be done, for example, by means of an adhesive or a soldering point.

A device made according to the method described above can be used to determine the density of a fluid F , In particular, a gas used. For this purpose, the dotted quartz oscillator 3 be exposed to the fluid, so that the fluid F in the case 55 penetrate and depending on its density can dampen the electrical oscillation. On the basis of the damped electrical oscillation can thus on the density of the fluid F be inferred. For example, this can be an evaluation unit 57 serve, which is adapted to, based on the output signal Sout of the quartz oscillator 53 one for the present fluid F determine the corresponding density. In first approximation, is in the evaluation unit 57 a linear relationship between the frequency of the electrical oscillation of the quartz crystal 54 and the density of the fluid F deposited.

6 shows a quartz oscillator 53 whose case 55 is punctured in such a way that the openings have a particle filter 511 form. For this purpose is in the housing 55 an inlet opening 59 introduced as an initial opening by a punching punch and after the introduction of the other openings 510 closed again by a non-pulsed laser. The particle filter 511 is in 6 formed in the form of a 5 × 10 matrix and limited to a portion of one side of the surface of the housing. In principle, however, the particle filter can have any m × n matrix. However, it has proven to be advantageous if an m × n matrix greater than 5 × 10 is used. Furthermore, it has also been found to be advantageous if the formation of the matrix on at least one side of the housing 55 is distributed substantially completely.

LIST OF REFERENCE NUMBERS

1

measuring tube

2

part Of

2a

mid-range

2 B

border area

3

pipeline

4

pipe socket

6

pipe wall

7

disturbing body

50

Device for determining a physical size of the fluid

53

sensor element

54

quartz crystal

55

Housing of the quartz oscillator

56

Quartz crystal electronics

57

evaluation

58

circuit board

59

Opening or initial opening

510

more openings

511

particulate Filter

512

First area of the circuit board

513

Second area of the circuit board

514

mid section

515

Glass bushing

516

output pin

517

device housing

A _pipe

Cross-sectional area of the pipeline in the section in which the Störköper is arranged

A _sturgeon

Surface of the bluff body streamed by the fluid

F

Fluid, in particular gaseous fluid

H

Height of the obstruction body

D

Diameter of the pipeline in the section

Sout

Output signal of the sensor element

S100

Providing a quartz oscillator in the form of a standard component

S200

Soldering the quartz oscillator on a PCB or PCB

S300

Dotting of a housing of the quartz oscillator

S300A

Dotting an initial opening in the housing by means of a mechanical tool

S300b

Dotting an initial opening in the housing by means of a pulsed laser

S301

Dotting further openings in the housing by means of a laser

S400

Closing the initial opening

Claims (15)

Measuring tube (1) for guiding a fluid (F), comprising at least a portion (2) of a pipe (3) for guiding the fluid, and a within the portion (2) of the pipe (3) outgoing pipe socket (4) for fluidic Connecting a device for determining a physical size of the fluid (50), wherein the pipeline (3), within the subsection (2) on a pipe wall (6) of the pipeline (3), at least one, preferably opposite the outgoing pipe socket (4) arranged, bluff body (7) which projects into the pipe (3), so that by the bluff body (7) results in an increased exchange of the fluid (F) in the pipe socket (4). Measuring tube according to the preceding claim, wherein the disruptive body (7) in a central region (2a), preferably substantially in a center, of the subsection (2) of the pipeline (3) is arranged. Measuring tube after Claim 1 , wherein the bluff body (7) in an edge region (2b), preferably substantially at an edge of the subsection (2) of the pipeline (3) is arranged. Measuring tube according to at least one of the preceding claims, wherein the bluff body (7) is formed substantially plate-shaped. Measuring tube according to at least the preceding claim, wherein the disruptive body (7) is designed in such a way that an area (A _sturgeon ) of the obstructing body (7) that is flowed through by the fluid is up to 80%, preferably up to 60%, particularly preferably up to 55%. , most preferably up to 50%, with respect to a cross-sectional area (A _pipe ) of the pipeline (3) occupies. Measuring tube after at least one of Claims 1 - 4 , wherein the bluff body (7) is formed substantially helically. Measuring tube according to at least the preceding claim, wherein the disruptive body (7) is designed such that the disruptive body (7) up to a height (H) of 80%, preferably up to a height of 60%, particularly preferably up to a height of 55%, most preferably up to a height of 50%, with respect to a diameter (D) of the pipe (3) in the section (2), projects into the pipe (3). Measuring tube according to at least one of the preceding claims, wherein at least the partial section (2) of the pipeline (3) and the bluff body (7) are made in one piece, preferably by means of a generative or machining process. Measuring tube according to at least one of the preceding claims, wherein the measuring tube (1) is designed in the form of a T-piece. Measuring tube according to at least one of the preceding claims, wherein the measuring tube (1) metal, preferably stainless steel, particularly preferably stainless steel. Measuring device comprising a measuring tube (1) according to at least one of the preceding claims and at least one device for determining a physical quantity of the fluid (50), which is introduced into the pipe socket (4) in such a way that the device (50) is at least end with a sensor element (53) is in fluidic contact with the fluid (F) guided in the measuring tube (1). Measuring device according to the preceding claim, wherein the at least one device (50) is further introduced into the pipe socket (4) such that the sensor element (53) projects at least partially into the pipe (3). Meter after Claim 11 , wherein the at least one device (50) is further introduced into the pipe socket (4) such that the sensor element (53) does not protrude into the pipe (3). Measuring device according to at least one of Claims 11 - 13 wherein the apparatus (50) further comprises a glass duct (515) disposed in a device housing (517) and a circuit board (58) having a first area (512) and a second area (513), the sensor element (53) being in the first housing (512) is arranged, wherein the device housing (517) and the pipe socket (4) are coordinated such that the device housing (517) is releasably connectable to the pipe socket (4) and in the connected state, the first region (512) the printed circuit board (58) is hermetically separated from the second region (513) by the glass feedthrough (515) so that only the sensor element (53) is in fluidic contact with the fluid (F) guided in the measuring tube (1). Measuring device according to at least one of Claims 11 - 14 in which the sensor element comprises a quartz oscillator (53) comprising a quartz oscillator (54), preferably in the form of a quartz watch, for generating an electrical oscillation having a specific frequency, preferably a frequency of approximately 32.768 kHz, a housing (55) wherein the quartz oscillator (54) is incorporated and a quartz oscillator electronics (56) adapted to drive the oscillator quartz (54) to produce the electrical oscillation and to provide a frequency dependent output signal (Sout), wherein the housing (55) of the quartz oscillator (53) at least one opening (59) is introduced so that the fluid (F) whose physical size, in particular a density is to be determined, come into contact with the quartz crystal and the frequency of the quartz oscillator in dependence physical size, in particular density, can change, so based of the output signal representing the physical quantity dependent frequency, the physical quantity is determinable.

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