WO2014053325A2

WO2014053325A2 - Temperature sensor and a flow-meter

Info

Publication number: WO2014053325A2
Application number: PCT/EP2013/069441
Authority: WO
Inventors: Frank Voigt; Werner Wohlgemuth; Günther Bähr
Original assignee: Endress+Hauser Flowtec Ag
Priority date: 2012-10-01
Filing date: 2013-09-19
Publication date: 2014-04-10
Also published as: WO2014053325A3; DE102012109312A1

Abstract

The invention relates to a temperature sensor (4, 24, 51) for arranging in a pipe, comprising a housing body (14, 34, 54) and a housing top (15, 35, 55) in which a temperature probe, particularly a resistance thermometer or a thermal element (5, 25), is arranged, and which is particularly designed to be rotationally symmetrical, said housing top (15, 35, 55) comprising an end face (12, 32, 52) with a central point (M), the progression of the end face (12, 32, 52) to the central point (M) in the radial direction reaching a point (P) from which an increase follows a positive gradient, and the distance (t) of point (P) to the central point (M) in the longitudinal axial direction being greater than the wall thickness (u) of the housing top (15, 35, 55) along the longitudinal axis (A) at the central point (M) of said temperature sensor (4, 24, 51). The invention also relates to a flow-meter which comprises the temperature sensor described.

Description

Temperature sensor and flowmeter

The present invention relates to a temperature sensor according to the preamble of claim 1 and a flow meter according to the preamble of claim 9.

There are known temperature sensors, which are used in a flowmeter. Already known are DE 10 2009 0046 653 A1, EP 1 387 148 A2 and DE 10 2007 005 670 A1, in which temperature sensors are used and used in measuring electrodes of an EMF. However, these sensors have comparatively slow response times when the temperature of the medium changes, that is, the actual time of the

Temperature change downstream time until detection and display of the actual temperature. Therefore, for example, in critical applications, for example, in the temperature measurement in pipes in a synthesis plant in which too late detection of a rapidly growing exothermic reaction leads to cooling measures can not be effectively initiated, such temperature sensors can not be used

As an example, the problem of temperature measurement in the flow measuring range is described in EP 2 203 027 B1. This document discloses a method for monitoring the hazard potential with respect to microbial contamination at a flow meter. It is u.a. the operation of a corresponding temperature sensor discussed in more detail. The temperature sensor should be given time to determine the actual temperature of the ultimately tapped water. EP 2 203 027 B1 proposes to solve this problem to wait a few seconds with the registration of the medium temperature during a medium change. This so-called dead time should, however, be reduced as far as possible during temperature detection during a flow measurement.

Based on this prior art, it is an object of the present invention to provide a temperature sensor for arrangement in a tube, which has an improved temperature response.

The invention achieves this object by a temperature sensor having the features of claim 1 and a flow meter having the features of claim 9.

According to the invention, a temperature sensor for determining the temperature of a medium has a sensor housing in which a temperature sensor, in particular a resistance thermometer or a thermocouple, is arranged and wherein the sensor housing has a housing head with an end face with a center, wherein the profile of the end face in radial

Direction to the center reaches a point, from which an increase of one in the medium direction positive slope occurs and wherein the distance of the point to the center in the longitudinal axial direction is greater than the wall thickness of the housing head along the longitudinal axis at the center of the housing. Medium direction means in this context that if the temperature sensor vertically in a tube with a tube axis or another cylindrical container with a

Longitudinal axis is arranged, that the medium direction is orthogonal to this longitudinal axis in the direction of the pipe or container interior. The medium direction thus runs towards the medium. Due to the protrusion of an area of the end face arranged around the center point beyond the edge area in combination with a small wall thickness in precisely this area, the housing has a shape which allows a particularly preferred temperature response in the case of a passing medium.

According to the invention, a temperature sensor for determining a temperature of a medium with a housing body and a housing head in which a temperature sensor, in particular a resistance thermometer or a thermocouple, is arranged and which is in particular rotationally symmetrical, has a center, the course of the end face in the radial direction to Center first describes a convex course in the medium direction and then a concave profile, wherein the concave curve has a vertex and wherein the distance of the point to the center in the longitudinal axial direction is greater than the wall thickness of the housing head along the longitudinal axis at the midpoint of the

Temperature sensor.

Advantageous embodiments of the invention are the subject of the dependent claims. It is advantageous if the end face has at least one first edge region radially spaced from the midpoint, wherein at least the first edge region defines a first arch curved in the medium direction or a parabolic arched in the medium direction and wherein the housing head is rotationally symmetrical. The arrangement of the center above the arc defined by the edge region is an improved

Flow behavior of the medium reaches the temperature-sensitive area of the temperature sensor.

It is advantageous if the edge region extends over a radially extending to the center portion of at least 2%, preferably at least 4%, in particular at least 10%, of the diameter of the housing head to ensure a secure fit It is also advantageous if the housing has a cylindrical housing body and the housing head has a protrusion of material, which extends in the radial direction over the

Outside diameter of the housing body extends beyond. This material projection serves to seal the temperature sensor on the medium side when it is arranged in a wall.

A particularly high sealing effect to the wall is achieved, provided that the material projection extends at least 10%, preferably at least 20%, of the width of the housing body beyond the outer diameter of the housing body. It is advantageous if the housing head has a groove on the side facing away from the front side. This groove serves to engage in a wall material and allows a further sealing of the temperature sensor in a wall hole.

It is advantageous if the end face has a cylindrical shape, with a

Cylinder wall, which in the longitudinal axial direction at least four times, preferably six times, in particular eight times longer than the minimum wall thickness of the cylindrical shape in this area. Due to the cylindrical shape, a well-defined inflow region is ensured on all sides. Possibly. The cylindrical shape in the transition between a cylinder base surface and a cylinder wall, a rounded transition region. However, this does not change the basic form of the shape as a cylinder.

According to the invention, a flow meter has a measuring tube and a device for determining the flow rate and / or the volume flow rate of a medium in the measuring tube, wherein the flow measuring device has a temperature sensor according to claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

In this case, the temperature sensor can be designed as at least one measuring electrode and / or as an electrode of a filling level monitoring system. This ensures a compact design of the flowmeter. On additional holes in the measuring tube can be dispensed with integration of the temperature sensor in an electrode, wherein the electrode also forms the housing of the temperature sensor.

It is possible by combination of a level monitoring and temperature measurement, not only to indicate a drop below the level with relevance to the flow measurement, but in particular to detect that the temperature electrode is no longer in contact with the Medium is. If this is the case, a larger measurement deviation can occur, which can be passed on to the user in the form of a warning message. Thus, the benefits

Temperature measuring function, from level monitoring.

In particular, this flow meter may be designed as a magnetic-inductive flow meter, wherein, in addition to the measuring electrodes arranged in the measuring tube, at least one electrode belonging to the filling level monitoring system is preferably arranged. Each of these electrodes can be designed as a temperature sensor according to the invention.

Hereinafter, the invention with reference to some preferred embodiments below

With the help of the following figures described in more detail. Show it:

1 arrangement of a first temperature sensor according to the invention in the form of a

Electrode in the measuring tube of a magnetic-inductive flowmeter;

A detail view of the first temperature sensor according to the invention in the form of

Electrode in installed condition;

3 detail view of the first temperature sensor according to the invention in the form of

Electrode in disassembled state;

4 arrangement of a second temperature sensor according to the invention in the form of a second electrode in the measuring tube of a magnetic-inductive flowmeter; 5 detail view of the second temperature sensor according to the invention in the installed

Status;

Fig.6 Detail view of the second temperature sensor according to the invention in dismantled

Status;

Fig.7 partial view of a temperature sensor according to the prior art;

8 partial view of a fourth temperature sensor according to the invention in the form of a

Electrode; and

9 shows a schematic representation of several further variants of inventive

Temperature sensors and a diagram of the temperature response of these variants over the variant of the prior art.

The temperature sensors shown in FIGS. 1-9 are designed as electrodes and arranged in a measuring tube. In this case, the preferably metallic main body of the electrode also forms the housing of the temperature sensor. The following terms electrode body and electrode head are therefore synonymous in the context of this invention for the terms housing body and housing head. The measuring principle of a magnetic-inductive flow measuring device 1, as shown in Fig. 1, is basically known. According to Faraday's law of induction, a voltage is induced in a conductor moving in a magnetic field. Magnetic-inductive

Measuring principle corresponds to the flowing medium to the moving conductor. A magnetic field is generated by two field coils not shown on both sides of a measuring tube 2. Perpendicular to this are located on the tube inner wall of the measuring tube, two measuring electrodes 3 which tap the voltage generated when flowing through the medium. The induced voltage is proportional to the flow velocity and thus to the volume flow. The magnetic field built up by the field coils is generated by a clocked DC alternating polarity. This ensures a stable zero point and makes the measurement more insensitive to influences by multiphase substances, inhomogeneity in the liquid or low conductivity. Magnetic-inductive flowmeters with coil arrangements with more than two field coils and other geometrical arrangements are known. In the following, the embodiments illustrated in FIGS. 1-9 will first be described in more detail.

1 shows a measuring tube 2 with a measurement tube inner wall of a flow measuring device 1 according to the invention which is rotationally symmetrical about a horizontal measuring tube axis S and which in the specific embodiment is designed as a magnetic-inductive flowmeter. The measuring tube 2 has two flanges 2 a, 2 b, which connect to a

Enable process connection. Within the measuring tube is a plastic lining - a so-called liner 2d - applied. The outer wall of the measuring tube has a magnet system 2e above and below the measuring tube axis. During operation of the magneto-inductive flowmeter, this coil arrangement generates a magnetic field perpendicular to the measuring tube axis S. At the same height as the measuring tube axis S, two measuring electrodes 3 are arranged which are diametrically opposed and pick up a voltage generated by the measuring medium during operation. If the volume flow is to be measured, it is particularly important that the filling of the measuring tube 2 is as complete as possible. Therefore, an electrode 4 of a level monitoring system is arranged on the measuring tube axis in horizontal installation at one of the highest points of the inner diameter of the measuring tube 2. This extends through the liner 2d, as well as the metallic measuring tube wall and is fastened to the side of the outer wall of the measuring tube 2 facing away from the medium. Temperature sensor Temperature sensor

2 shows an exemplary mounting variant of the temperature sensor 4 in the

Tube wall of the measuring tube 2. FIG. 2 shows a fastening device 81 for fastening the temperature sensor 4. This fastening device 81 has a multipart, in particular rotationally symmetrical housing 82 with a housing longitudinal axis, which is seated on the wall of the measuring tube and fixed thereto.

The electrode 4 itself has a rotationally symmetrical electrode body 14 and a rotationally symmetrical electrode head 15 with a center M and a longitudinal axis A. On the electrode body 14, a thread is arranged, in which the union nut 20 can attack. The electrode also has at the electrode head a preferably radially encircling sealing strip or a material protrusion or a Auskrempung, which in the radial direction from

Center M extends beyond the diameter of the electrode body 14 addition.

The metallic electrode body of the temperature sensor serves as the housing of the

Temperature sensor, in particular the resistance thermometer or the thermocouple. The following terms electrode body and electrode head are therefore synonymous in the context of this invention for the terms housing body and housing head.

When tightening the union nut 20 a longitudinal axial tensile force is exerted on the electrode 4, which leads away radially from the measuring tube axis S. The electrode 4 follows this movement until the supernatant 16 is supported on the inner wall of the measuring tube 2 and builds up a force which is directed in the same direction. In this case, the material protrusion 16 engages on the side facing away from the end face of the electrode head 15 in the liner layer, so that when tightening the

Union nut 20 a sealing effect of the electrode 4 is achieved.

In the case shown in Fig. 2, the fastening device has a one-piece

rotationally symmetrical housing 82. This fastening device has a compact construction.

FIG. 3 shows a detailed view of a first embodiment of an electrode, as it was shown as MSÜ electrode in FIGS. 1, 2.

Fig. 4 shows a second preferred embodiment variant of an inventive

Flow meter, which is designed as a magnetic-inductive flow meter 21, with an electrode which can be used in a level monitoring system of a pipe. This electrode, which is shown in detail in FIG. 6, can be used in particular for

Flow meters are used with measuring tubes with small diameters, which are preferably DN <25. The magnetically inductive flow measuring device 21 shown in FIG. 4 in this case has a measuring tube 22 with a rotationally symmetrical inner tube wall and a horizontal measuring tube axis S. The measuring tube 22 shown in FIG. 4 has asymmetrically formed terminal tube flanges 22a and 22b. The measuring tube 22, like the measuring tube shown in FIG. 1, has a

Measuring tube wall, which consists of metal, preferably made of stainless steel. The inner wall of the measuring tube also has a so-called liner layer 22d, which extends in Fig. 2 by a perpendicular to the measuring tube axis S extending bore 22 f to the outer wall of the measuring tube 22. The measuring tube also has two diametrically perpendicular to the measuring tube axis S.

Magnetic systems 22e, with which a perpendicular to the measuring tube axis S magnetic field is generated. On a plane with the measuring tube axis in each case two measuring electrodes 23 are arranged diametrically opposite on both sides of the measuring tube 22. In the hole 22f in

Measuring tube 22 is an EPD electrode 24 with an integrated in the electrode body

Temperature sensor, in particular a resistance thermometer or a thermocouple, 25 arranged. FIG. 5 shows a detailed representation of the positioning of the electrode 24 in the measuring tube 22. The electrode 24 is of rotationally symmetrical construction with a longitudinal axis A and has an electrode body 34 and an electrode head 35. The electrode body 34 has on the edge barbs 40, which lead away from the longitudinal axis A. These barbs engage in the liner material, which is arranged in the bore 22f of the measuring tube 22 and ensure a permanent positioning of the electrode 24 in the measuring tube 22. In the electrode body is a temperature sensor, in particular a resistance thermometer or a thermocouple, 25 arranged with a sensor body 31 This sensor base body 31 is arranged on the inside of the electrode 24 along an inner wall section of the electrode whose outer wall is bounded by the end face 12 of the electrode head 15.

In the following, the special embodiment of the electrode 4, as shown in Fig. 3, explained in more detail with the specially designed electrode head 15.

The electrode shape or housing shape of the temperature sensor shown particularly in FIG. 3 has a better temperature response compared to the prior art For example, according to FIG. 7 and can be adapted and optimized both for the EPD electrode or the reference electrode and for the measuring electrodes.

The electrode 4 shown in FIG. 3 has the pin-shaped or cylindrical electrode body 14 and the electrode head 15. In this case, the electrode 4 is constructed in particular rotationally symmetrical and has the longitudinal axis A. The electrode 4 also has an inner

rotationally symmetrical cylinder cavity 16, which extends into the electrode head 15. Endständig in this cylinder cavity 16 is a sensor body 1 1 of the

Temperature sensor 5, in particular of the resistance thermometer or the thermocouple, arranged so that the temperature at which a medium on an end face 12 of the

Electrode head 15 meets over the material wall of the end face 12 as large as possible and over the shortest possible distance to the temperature sensor, in particular a resistance thermometer or a thermocouple, 5, respectively, the sensor body 1 1, passed. In Fig. 3, the electrode 4 is shown with a preferred face geometry, respectively geometry of an electrode head. The end face has a first peripheral preferably peripheral edge portion R, whose course a first arc K or a

Parabolic arch defined. However, the course of the end face of the electrode head does not follow the shape of the arc defined by the edge portion R. This first arc K is determined by radial course of the edge portion R to the center M of the end face 12, in particular by their initial rise, the center M of the end face 12 in

Longitudinal direction of the electrode 4 is arranged above this first circular arc K. In other words, the center M of the end face 12 protrudes from the arc K. The angle α of the circular arc K is preferably less than 170 °, preferably equal to or less than 160 °. The course of the end face 12 in the radial direction to the center M thereby reaches a point P from which there is an increase of the positive slope, wherein the distance t of the point P to the center M in the longitudinal axial direction is greater than the wall thickness u of the electrode head 15 along the longitudinal axis A at the center M of the electrode 4 or the end face 12. The edge region or edge section R preferably extends over a section running radially to the center M of at least 2%, preferably at least 4%,

in particular at least 10% of the diameter di _{5 of} the electrode head 15. Preferably, the edge portion R is between 2-70%, in particular between 10-60% of the diameter d _{15 of} the electrode head 15th For the sake of clarity, the radial course of the end face will be described in greater detail on the basis of the substantially identical variant E of FIG. 9. Approximately on one third of the distance between the outermost edge point of the end face and the center M of the end face deviates from the face of the shape of the first arc K, such that a second portion Z of the end face in the longitudinal axial direction below the circular arc K. , In this second section, the end face up to a point P has a negative slope or a negative gradient running to the center point. At point P, the second portion of the end face merges into a third portion Y with a positive slope and finally into a fourth portion X whose course is subsequently defined to the midpoint of a flat surface.

The end face shape of the electrode of the variant E of FIG. 9 and FIG. 3 thus has a peripheral portion R in the form of a shoulder, followed by an annular groove Z and finally in the center of a cylindrical shape which limits in cross section through Y and X. becomes. The electrode shape of the variant E shown in FIG. 9, which corresponds to the embodiment of FIG. 3, is distinguished from the other variants shown in FIG. 9 for

Electrode shapes by a particularly good performance, especially in terms of Temperaturansprechverhaltes and the achievable accuracy of the temperature measurement in equilibrium.

The end face 12 of the electrode head 4 is preferably at least 1.2 times wider than the diameter _{dM of} the electrode body 14, preferably at least 1.5 times wider, more preferably at least 1.7 times wider. The electrode head has an annular sealing strip or a material overhang or a

Auskrempung, which extends in the radial direction over the wall of the pin-shaped

cylindrical electrode body 14 also extends. The top of the annular

Material supernatant 16 forms part of the end face 12 of the electrode. The underside of the annular material projection has a groove 17. The fillet 17 permits a partial material absorption of the liner material arranged on the measuring tube inner wall of the magnetically inductive flowmeter, whereby a sealing effect is achieved and penetration of the medium to be measured into the region between the

Electrode body 14 and the measuring tube 2 is prevented. The opening width, ie the maximum distance between the two edges of the groove, at the edges of the groove 17 is preferably between 2-20% of the diameter di _{4 of} the electrode body, more preferably 5-10% of the diameter d _{14 of} the electrode body. The front side has an annular groove 18. This means that the end face has a partial area which is below the circular arc K defined by the first edge section

Electrode body 14 is arranged towards. Through the annular groove 18, a flow control is achieved, which additionally improves the temperature response of the disposed in the electrode body resistance thermometer 5. The annular groove 18 may preferably be more than 1%, more preferably more than 3% of the diameter d _{14 of} the electrode body 14.

In the center of the electrode head, the electrode head 15 has a cylindrical formation 19, wherein the cylinder jacket extends parallel to the longitudinal axis of the electrode body. A

inner base surface of the cylindrical formation is preferably at least partially flat and extends perpendicular to the longitudinal axis of the electrode body. This has proven to be particularly favorable in order to achieve the highest possible connection between the temperature sensor or the sensor base body and the wall in the region of the cylindrical formation 19. This base surface is preferably arranged in the medium direction above the first circular arc K, which is defined by the edge regions R of the end face 12 of the electrode head 14. The sensor base body 11 within the temperature sensor or the electrode can have different shapes. So he can, for example, a cylindrical shape, a in

Cross-section square shape or have a conical shape. The wall thickness u of the

Electrode head in the region of the cylindrical shape is preferably less than the inner diameter of the cylindrical shape, preferably less than 50% of

Inner diameter of the cylindrical shape, in particular between 10 to 40% of

Inner diameter of the cylindrical shape. The wall thickness u is preferably substantially equal in size both within the area of the cylinder jacket and in the area of the terminal circular area of the cylindrical formation 19 within a tolerance range of 15% of the wall thickness, so that a favorable heat transfer is also provided in the region of the cylinder jacket. Due to these low wall thicknesses, an improved heat transfer to the

Resistance thermometer possible, the wall thickness at the same time a sufficient

provides mechanical protection of the resistance thermometer.

In this case, the inner diameter of the cylindrical formation 19 is preferably smaller than the inner diameter of the electrode body 14, particularly preferably at least 1, 2 times smaller, in particular at least 1, 5 times smaller than the inner diameter of the

Electrode body 14. At the electrode head 15, the cylindrical electrode body 14 connects. This has a cylinder wall, with a wall thickness which is preferably less in regions than the inner diameter of the electrode body dn, particularly preferably less than 50% of the

Inner diameter electrode body.

The electrode body 14 has a front region, which opens directly into the electrode head and a rear region, which preferably protrudes from the measuring tube 2. In this rear region, in particular, the outer wall of the electrode body 14 has a connection point, not shown, for discharging a signal. This may be, for example, a solder pad, which allows a connection of a cable, which is connected to an evaluation unit not shown and evaluates the received or applied voltage or current and outputs a status signal on the filling state of the measuring tube. This takes place in cooperation with, in particular, a second electrode or, for example, with an electrically conductive process connection. The contacting of both electrodes takes place with sufficient filling state via the medium.

The electrode material of the aforementioned embodiments is preferably made of steel.

Inside the electrode 15, the sensor body 1 1 is arranged in the region of the electrode head. This can preferably be done by a temperature-resistant electrically conductive adhesive. Alternatively or additionally, the sensor base 1 1 can also be arranged by a thermal paste on the inner wall of the cylindrical shape. This thermal compound reduces in particular the insulating air volume between the base body 11 and the inner wall of the cylindrical formation 19 of the electrode head 14.

Alternatively, the sensor body can also be arranged and held by press fit against the inner wall of the cylindrical formation 19 in the center of the electrode head 14. As shown in FIG. 3, an electrical lead and an electrical lead in the form of cables depart from the probe body. These are discharged in the longitudinal direction through the interior of the electrode body to the outside and are electrically insulated from each other.

At the end of the electrode body, a cable guide is arranged for positioning and protecting the cables. The electrode 4 shown in FIG. 3, which is used as a medium for measuring medium (EPD electrode), thus simultaneously enables the determination of the temperature of the medium, wherein the electrode body of the electrode 4 at the same time the sensor housing of the temperature sensor,

in particular a resistance thermometer or a thermocouple 5 forms. EPD electrodes are usually used to detect an unfavorable partial filling of a measuring tube. Such a partial filling of a measuring tube occurs, for example, in the case of outgassing measuring substances or applications, in particular in the case of fluctuating process pressure, in the event of leaks or in the case of deliberate emptying of the line. In the flowmeter according to the invention of FIGS. 1 and 4 in a MSÜ electrode 4, 24 with an electrode body 14, 34 and an electrode head 15, 35, a temperature sensor, in particular a resistance thermometer or a thermocouple, 5, 25 in the form of a

Resistance thermometer arranged. The sensor body 1 1 can also be in the form of a

Thin-film element may be formed. Suitable material for a metal wire in the

Resistance thermometer is u.a. Nickel or platinum. In principle, the resistance value of the temperature sensor used, in particular the resistance thermometer or the thermocouple, depending on the measuring tube diameter and possibly also wall thickness of the EPD electrode can be selected. Commercially available resistance thermometers, which can preferably be used, have, for example, resistance values of 100, 500 or 1000 ohms.

Although not shown in Figs. 7-9, the terminal area of the cylinder cavities in the electrodes shown here, respectively the electrode body, also serves the arrangement of Fühlergrundkörpern of temperature sensors, in particular of a resistance thermometer or a thermocouple, which is identical to the temperature sensor, the Fig. 3 are formed. Variants 9 A-C have terminal conical areas in the cavities. These are less preferred than flat end regions, as shown in variant D and E, due to poorer heat transfer. This can be partially offset by a higher amount of thermal grease. Overall, the cavities with terminal conical end regions are to be understood as a cylindrical shape in the context of the application.

In the following, the preferred embodiment of an electrode 24, as shown in Fig. 6, described in more detail.

The electrode shown in Fig. 6 has an electrode body 34 and an electrode head 35 and is rotationally symmetrical with a longitudinal axis A. In Fig. 6, the electrode 24 is shown with a preferred face geometry, respectively, a geometry of an electrode head. The end face has a first edge-side preferably peripheral edge portion R, whose course defines a first arc K or a parabola. However, the course of the end face of these differently shaped electrode heads does not follow the shape of the arc defined by the edge portions K. This first arc K is determined by radial course of the edge portions R to the center M of the end face 32, in particular by their initial rise, the Center M of the end face 32 is arranged in the longitudinal direction of the electrode 24 above this first circular arc K. The angle α of the circular arc K defined in this way is preferably less than 170 °, preferably equal to or less than 160 °, in order to achieve a favorable inflow behavior of the medium. The course of the end face 32 in the radial direction to the center M thereby reaches a point P from which an increase of the positive slope takes place, wherein the distance t of the point P to the center M in the longitudinal axial direction is greater than the wall thickness u of the electrode head 35 along the longitudinal axis A at the midpoint M of the electrode 24 and the end face 32nd

The edge region or edge section R preferably extends over a section running radially to the center M of at least 2%, preferably at least 4%,

in particular at least 10%, of the diameter d _{35 of} the electrode head 35. Preferably, the edge portion R between 2-70%, in particular between 10-60%, of the diameter d ₃ 5 of the electrode head 35th

Approximately on one third of the distance between the outermost edge point of the end face 32 and the center M of the end face 32, the end face 32 deviates from the shape of the first arc K, such that the course merges into a second section with a positive steeper slope and finally, in a third section whose course is subsequently defined to the midpoint of a flat surface.

The end face shape of the electrode of FIG. 6 thus has a peripheral portion R in the form of a shoulder, followed by a cylindrical shape in the center.

The end face 32 of the electrode head 24 is preferably at least 1.2 times wider than the diameter d _{34 of} the electrode body 34, preferably at least 1.5 times wider, more preferably at least 1.7 times wider. In the present case, the diameter of the electrode body corresponds to the diameter of the electrode head. The electrode head has an annular sealing strip or a material projection or a Auskrempung, which extends in the radial direction over the wall of the pin-shaped

cylindrical electrode body 34 also extends. The top of the annular

Material supernatant 36 forms part of the end face 32 of the electrode.

In the center of the electrode head, the electrode head 32 has a cylindrical formation 39, wherein the cylinder jacket runs parallel to the longitudinal axis of the electrode body 34. A

Base surface of the cylindrical formation 39 extends perpendicular to the longitudinal axis of the

Electrode body. This base surface is preferably arranged in the medium direction above the first circular arc K, which is defined by the edge regions R of the end face 32 of the electrode head 34. Since the sensor body 31 is disposed within the cylindrical formation 39, a particularly favorable temperature transfer takes place via the end face 32 on the resistance thermometer 25. The wall thickness u of the electrode head in the region of the cylindrical formation is preferably less than the inner diameter of the

cylindrical shape, preferably less than 50% of the inner diameter of the cylindrical shape, in particular between 10 to 40% of the inner diameter of the cylindrical

Formation. Due to these low wall thicknesses, an improved temperature transition to the resistance thermometer is possible, with the wall thickness at the same time offering sufficient mechanical protection of the resistance thermometer.

In this case, the inner diameter of the cylindrical formation 39 is preferably smaller than the inner diameter of the electrode body 34, more preferably at least 1, 2 times smaller, in particular at least 1, 5 times smaller than the inner diameter of the

Electrode body 34.

In addition, a terminal wall portion 34 a of the electrode body 34 a

Contact surface, particularly preferably a gold contact on. At this contact surface or

Gold contact may be attached to a non-illustrated cable, which is a

Establishes signal connection with an evaluation unit.

At the electrode head 35, the cylindrical electrode body 34 connects. This has a cylinder wall in regions with a wall thickness which is preferably less than the inner diameter of the electrode body d ^, more preferably less than 50% of

Inner diameter electrode body. The electrode body 34 has a front region which opens directly into the electrode head and a rear region, which preferably protrudes from the measuring tube 22. In this rear region, in particular, the outer wall of the electrode body 34, a connection point, not shown, for discharging a signal. This may be, for example, a solder pad, which allows a connection of a cable which is connected to an evaluation unit, not shown, and evaluates the received voltage or current and outputs as a result a status signal on the filling state of the measuring tube. This is done in cooperation with a second electrode. The contacting of both electrodes takes place with sufficient filling state via the medium.

The electrode material of the aforementioned embodiments is preferably made of steel

Further less preferred variants of an electrode form are shown in FIGS. 7-9. The advantageous effect and the advantageous use of the invention

Level monitoring system can in principle be carried out in all medium-carrying pipes in which a medium flows with at least low conductivity. In the following, further special advantages are to be described when used in flowmeters, in particular in magnetic-inductive flowmeters.

There are various ways to monitor the medium, also called "empty pipe detection" (EPD), so far, among other things, it has been possible to measure the electrical resistance between the EPD electrode and a reference electrode or the process connection In this case, the electrical resistance, for example in the measurement of mineral water, increases very sharply when the measuring tube changes from fully filled to partially filled, in which case there would be a difference between the reference electrode or the process connection and the MCR Instead of the conductivity of water, the conductivity of air would enter the resistance of the electrode instead of water, and the corresponding change in impedance at the EPD electrode is detected by the evaluation unit and output by an output unit Degree of the measuring tube output.

Based on this MSÜ technology, which is already known per se, essentially an approach of the present invention via the EPD electrode is also a temperature determination

enable. In a first embodiment, as shown in FIGS. 1 and 4, the

Temperature detection thereby allows the EPD electrode to perform a resistance measurement in combination with a reference electrode and / or the process connection as a function of the conductivity of the medium. The filling state of the measuring tube can be determined by an evaluation unit, not shown, and to a not shown here

Output unit to be passed. In the MSÜ electrode, or in the electrode body, a resistance thermometer is introduced, which has a related to the medium temperature property, which of the evaluation unit for determining the

Medium temperature can be used. The temperature information can in turn be forwarded to the output unit. To a smaller error of the

To obtain medium temperature, it has proven to be advantageous that the end face protrudes by a few μιη or mm in the measuring tube 2, 22 and is washed by the medium. The MSÜ electrode is cylindrical and has a terminal end face, which projects into the measuring tube.

Within the EPD electrode, a temperature sensor, in particular a resistance thermometer or a thermocouple, 5, wherein the MSÜ electrode with the temperature sensor disposed within the electrode 5, in particular a resistance thermometer or a

Thermocouple, at the same time a temperature sensor in the sense of the application is.

The protrusion of the EPD electrode 4, 24 into the medium, however, has a later response of the EPC to the sequence or a response at a lower degree of filling when mounted horizontally and as intended in the uppermost region in the interior of the measuring tube MSÜ electrode. This can be advantageously counteracted by the end face 12, 32 of the electrode head 15, 35 is coated in sections electrically insulating, while the heat conductivity of the coating 13, 33 should be as high as possible. Due to the partial isolation of the end face 12, 32, in particular in the region of the center of the

rotationally symmetrical electrode head 15, 35 there is the medium contacting the electrically conductive regions of the EPD electrode, which are located almost on a plane with the wall of the measuring tube.

In a second embodiment of the invention, the EPD function or the onset of partial filling can be detected by a jump in the measured temperature. The condition for this is that the actual medium temperature is known as a reference. This can be detected by a device arranged in the second temperature sensor, in particular a resistance thermometer or a thermocouple. In this case, the electrically insulating coating from the previous section could be dispensed with. One condition, however, would be sufficient large temperature difference between the medium temperature and the free space prevailing in the partially filled measuring tube prevailing temperature.

In the embodiments illustrated in FIGS. 1, 3 and 4, the temperature sensor, in particular a resistance thermometer or a thermocouple, 5, 25 integrated into the EPD electrode 4, 24, wherein the electrode body 14, 34 and the electrode head 15, 35 at the same time Housing for the temperature sensor, in particular a resistance thermometer or a thermocouple, acts.

As an alternative to the arrangement in an EPD electrode, in a third embodiment, the reference electrode may have an integrated temperature sensor, in particular a resistance thermometer or a thermocouple, wherein said reference electrode is secondarily to the

Medium monitoring is used and sends out a signal that is received by the EPD electrode. This reference electrode can also determine the medium temperature.

Condition for an MTÜ monitoring is in aforementioned embodiments, that at least one of the electrodes, the EPD electrode or the reference electrode, at the top of the

Inner wall of the measuring tube is arranged so that an incomplete filling is detected immediately.

In a preferred embodiment of the aforementioned embodiments, the EPD electrode is arranged on the opposite side of the reference electrode of the measuring tube perpendicular or obliquely to the measuring tube axis on or in the inner wall of the measuring tube.

In a fourth embodiment of the invention, both the reference electrode and the EPD electrode may have an integrated resistance thermometer. It is both the

Reference electrode and the EPD electrode arranged at the uppermost point of the tube cross-section offset in the flow direction. By such an arrangement is for example a

Covering detection under the condition of a temperature variance between the

Medium temperature and the ambient temperature possible. If there is a change in the resistance between the two electrodes due to an insufficient degree of filling of the measuring tube, the temperatures of the temperature sensors, in particular a resistance thermometer or a thermocouple, of the EPD electrode and of the reference electrode should, in the ideal state, be equalized to the ambient temperature in a time interval. However, if a determined temperature requires a much longer time to adjust to the ambient temperature, so there may be a coating at this point. Independently of this, the temperature measurement by means of both the EPD electrode and the reference electrode makes it possible to compare the measured data and to determine a technical disturbance with non-uniform values. In a fifth embodiment of the invention, in addition to the MSÜ electrode and the reference electrode, the two measuring electrodes of the magneto-inductive

Flowmeter be equipped with a resistance thermometer.

The four aforementioned electrodes are arranged in a preferred embodiment of the fifth embodiment to an adjacent electrode at an angle of 90 ° on the circumference of the tube cross-section perpendicular to the pipe axis in the region of the magnet system, wherein the two measuring electrodes are diametrically opposed and the connecting line between the Meßelektorden perpendicular to the main direction of the applied magnetic field. In the sectioned tube side view, the measuring electrodes may be arranged in the flow direction behind or, more preferably, in front of the EPD electrode and the reference electrode or in the same position along the tube axis as the EPD electrode and the reference electrode.

The advantageous embodiment of this arrangement makes it possible to draw conclusions about the compensation of the flow profile over the pipe cross-section. Usually, a magnetic-inductive flowmeter is designed for a rotationally symmetrical flow profile. The arrangement of electrodes described above, each with at least one integrated temperature sensor, in particular a resistance thermometer or a thermocouple, allows in certain applications to register deviations from the rotational symmetry during the measurement and to reduce their influence on the measurement results.

The aforementioned arrangement of the electrodes would allow to take into account the rotational symmetry of the flow when changing rapidly to a medium with a different temperature. This can be done either by issuing a warning to the presence of a non-rotationally symmetric flow or by a measured value correction. For the latter, however, is an empirical predetermination of temperature distribution dependent

Correction values e.g. necessary in a calibration procedure that can be used at commissioning. The aforementioned arrangement is of course only one possible embodiment. It is understood that a departure from the

Rotation symmetry is already at least detectable via a three-point determination, for example by the EPD electrode and the two measuring electrodes. Generally, that applies with As the number of measuring points along the circumference of the pipe increases, an increasingly better determination of rotational symmetry becomes possible. However, since the aforementioned four electrodes are already provided in measuring devices in this arrangement, there is no need for further structural adaptation of the measuring tube and the electrode symmetry but it can be used on existing proven arrangements.

Usually, the volume flow of a medium is determined in an electromagnetic flowmeter. In a sixth embodiment of the invention, it is possible to derive an indication of the average density from the temperature measurement, for example between the reference electrode and the EPD electrode or between the reference electrode, the EPD electrode and the two measuring electrodes by measuring the temperature at a known density of the medium , which allows conclusions about a mass flow of the medium.

In this case, a connection between the temperature distribution of the flow in the region of the measuring tube wall and the density distribution of the medium can be determined by numerical simulation and corresponding correction functions can be derived.

For the aforementioned embodiments, the electrode shape of both the EPD electrode, the reference electrode and / or the measuring electrodes can be adapted and optimized. Various preferred embodiments of the electrodes are described in more detail below with reference to FIGS. 7-9.

The electrodes shown in detail in FIGS. 7-9 are of rotationally symmetrical construction with an electrode body 44, 54 and the electrode head 45, 55 with an end face 12, 32. The electrodes have an inner cylinder cavity 46, 56. Terminal in this cylinder cavity 46, 56, the temperature sensor, in particular a resistance thermometer or a thermocouple, arranged so that the temperature on the end face on the temperature sensor, in particular a resistance thermometer or a thermocouple, 5, 25 can be detected.

FIG. 7 shows a first preferred electrode shape of an EPD electrode 41 or reference electrode, which has hitherto already been used in magnetic-inductive flowmeters. This electrode has an arcuate end face 42. The radian measure α of the circular arc is preferably less than 170 °, preferably less than 160 ° in order to achieve a favorable temperature response for an end face 42 in a circular arc shape. This temperature response is shown in FIG. 9. It can be seen that the circular arc shape of the end face compared to other advanced forms less advantageous Temperature response has. The advantage of this type of electrode, however, is that this electrode has a very low flow resistance.

In Fig. 8 and 9 are further particularly preferred embodiments of a

End face geometry of an electrode, respectively an electrode head shown. The embodiments shown in these figures have end faces, each with a first edge-side preferably peripheral edge portion whose course defines a first arc A or a parabola. In contrast to FIG. 7, however, the course of the end face of these differently shaped electrode heads does not follow the shape of the through which

Edge sections of defined circular arc A.

This first circular arc is determined by radial course of the edge portions to the center of the end face, in particular by the initial increase, wherein the center of the end face is arranged in the longitudinal direction of the electrode above this first arc.

In other words, the center of the end face protrudes from the circular arc.

The course of the end face in the radial direction to the center M thereby reaches a point P from which an increase of the positive slope takes place, wherein the distance t of the point P to the center M in the longitudinal axial direction is greater than the wall thickness u of the respective

Electrode head along the longitudinal axis A at the midpoint M of the electrode

FIG. 8 shows a second preferred electrode shape of an EPD electrode or reference electrode, as a further development of the aforementioned variant. The end face of the electrode has a center. Starting from the points of the end face which are furthest apart from the center of the end face, the course of the end face initially describes a first circular arc shape with a first center point angle. This course preferably extends over an edge portion radially spaced from the center of the end face of at least 10% of the end face,

preferably at least 20% of the end face, in particular between 25-60% of the end face. The center of the end face protrudes from the first circular arc shape in the longitudinal direction of the pin-shaped electrode.

The illustrated in Fig. 8 specific embodiment of the course of the end face describes a second circular arc shape with a second center angle. The second midpoint angle is smaller than the first midpoint angle. The electrode in Fig. 7 has the front side in the form of a circular arc with a certain radius and angle. In Fig. 8, there are two

Curvature change. The area around point P could also be considered as a circular arc with a smaller radius and angle range, the center of this circle outside the Electrode would be (concave). Following this, another change of curvature takes place. The upper end face is, for example, in turn formed as a circular arc with the center inside the electrode (convex). The radius is significantly smaller than the radius of the first arc. On the other hand, the angle can be even greater than that of the first arc. Of course, other contours than circular arcs are conceivable. The aim of the optimization is to achieve a good coupling of the temperature sensor to the medium, which speaks for a thin wall thickness and a wide intrusion into the medium. The averaged over the solid angle distance to the medium should therefore be as low as possible. Boundary conditions can be derived from considerations of mechanical strength, manufacturability and influence on the flow profile. A corresponding change in curvature from convex to concave can also be found in the

Observe embodiments of FIGS. 1-6 and 9.

FIG. 9 shows further preferred electrode forms of an EPD electrode or reference electrode (variant B-E). As can be seen from the time course of the temperature response, these electrode shapes are preferred over the variant shown in FIG. Also in these embodiments describes the radially spaced from the center of the end face

Edge portion of a first circular arc shape with a first center angle. In variants B and C, the region of the midpoint M of the end face assumes a second circular arc shape with a second center point angle, which second center point angle is preferably less than a quarter, more preferably less than one eighth of the first center point angle of the first circular arc shape.

FIG. 9 also shows two further preferred electrode forms with respect to variants A-C with a cylindrical region of the end face. In this case, the course directed to the center of a first edge-side section R defines the electrode, as for example in the case of FIG

Embodiment of Figure 3, a first arc. Approximately halfway between the outermost edge point of the end face and the center of the end face, the end face deviates from the shape of the first arc, such that a second portion Z of the end face is arranged below the arc in the longitudinal direction of the electrode. In this second section, the end face preferably has a negative rise to the center. This second portion of the end face merges into a third portion Y with a positive slope, and finally enters a fourth portion X over its course in FIG

Connection to the midpoint defines a flat surface. The end face of the electrode forms of the variants BE of FIG. 9 thus have a peripheral portion R in the form of a shoulder, followed by an annular groove Z in variants D and E and finally a cylindrical shape Y and X in the center. The electrode shape of the variant E shown in FIG. 9, which corresponds to the exemplary embodiment of FIG. 3, is distinguished from the other variants shown in FIG

Electrode shapes by a particularly good performance, especially in terms of Temperaturansprechverhaltes and the measurable temperature range. Therefore, this electrode shape is particularly preferred.

The electrodes of the aforementioned exemplary embodiments can have an insulating coating 13 in a region arranged around the center, in particular in FIGS. 3 and 9, the end face of the cylindrical formation 19 and possibly also its cylinder jacket. Technically advantageous could be provided a polycrystalline diamond coating, which combines a very high thermal conductivity with electrical insulation and is chemically, thermally and mechanically highly resilient.

Basically, all the aforementioned embodiments are in measuring tubes of a

Flowmeter attachable, which is completely made of plastic, e.g. Polyethylene, or entirely of metal, e.g. Stainless steel. In the case of the latter, however, sufficient thermal insulation of the temperature electrode to the measuring tube must be ensured, depending on the design of the device. However, particularly preferred are measuring tubes made of metal with an inner lining made of plastic, preferably a plastic inner tube and / or a so-called. Liner. This inner lining allows a thermal insulation between the measuring medium and the metallic tube, whereby a thermal decoupling of the temperature electrode is achieved by the measuring tube. It is important that the electrodes e.g. is isolated by the lining of the "colder" measuring tube, otherwise it leads to larger measuring deviations.

In addition, a two-electrode arrangement of the fill level monitoring system allows an additional determination of the microbial state of the electrodes in process water. In this case, the evaluation unit is designed so that both the determination of the medium temperature and the coating condition of the electrode as well as the determination of the filling state of the Tube is made possible. A separate evaluation unit is therefore not necessary, resulting in a reduction in the space requirement of the level monitoring system.

In particular, it is very advantageously possible to detect, by evaluating the signal of the EPD electrode, whether the temperature sensor integrated in the EPD electrode is still in direct contact with the medium. Direct contact here means that the electrode in which the temperature sensor is integrated with direct contact to the electrode is free of coating and the electrically conductive areas of the electrode outside of the lining are in contact with the medium. By an electrically insulating and thermally conductive coating of a part of the electrode, it is possible that the MSÜ already responds as soon as the intended in contact with the medium

Electrode surface to less than 20%, advantageously less than 50%, in particular less than 90% in contact with the medium. Should the electrode to a lesser extent or in particular no longer be in direct contact with the medium, this can lead to a higher

Measurement deviation of the temperature lead, which by evaluating the level and

Trace detection function can be detected. Upon detection of this case, it is possible to provide appropriate measures in the common evaluation unit, in particular to issue a warning message regarding the accuracy of the temperature measurement.

The fill level monitoring system has an evaluation unit which is designed to monitor the degree of filling of the tube and which evaluation unit emits a warning signal if the degree of filling falls below a limit value, preferably a degree of filling of 55% of the inner tube diameter. For all filling levels below 55%, a warning signal is always output. Particularly preferably, a warning signal can already be emitted if the degree of filling drops below 75%, preferably 95%, in particular 98% of the inner tube diameter. However, this requires a positioning of an EPD electrode or a reference electrode in the upper region of the tube. Preferably, the selection of a suitable limit value of the degree of filling may depend on the different pipe diameter.

With smaller pipe diameters, due to its geometry, the EPD electrode protrudes into the measuring tube by more than one percent of the pipe diameter in relation to the degree of filling than in the case of large pipe diameters. Therefore, a preferred gradual distinction can be made.

With a nominal pipe diameter DN between 2 and 8, the limit value of the degree of filling is preferably selected from a range between 55 to 99%. With a nominal pipe diameter DN between 8 and 200, the limit value of the degree of filling is preferably selected from a range of more than 75%.

With a nominal pipe diameter DN between 200 and 1000, the limit value of the degree of filling is preferably selected from a range of more than 95%. With a nominal pipe diameter DN between 1000 and 2000, the limit value of the degree of filling is preferably selected from a range of over 99%.

With a nominal pipe diameter DN over 2000, the limit value of the degree of filling is preferably selected from a range of over 99.6%.

reference numeral

1, 21 flow meter;

2, 22 measuring tube;

2a, 22a side part / flange;

2b, 22b flange

2d, 22d liner

2e, 22e magnet system

22f hole

3, 23 measuring electrodes

4, 24, 41, 51, electrode

5, 25 temperature sensors

6, body

7, metal wire

8, 28 power supply

9, 29 Electricity drainage

10, protective layer

1 1, 31 sensor round body

12, 32, 42, 52 end face or end face

13, 33 coating

14, 34, 44, 54 electrode body

15, 35, 45, 55 electrode head

16, 36 cylinder cavity

17 throat

18 ring groove

19, 39 cylindrical shape

20, 40 fasteners

81 Fastening device

82 housing

S measuring axis

A longitudinal axis (electrode)

M midpoint (face)

K circular arc

R edge section

P point (positive slope change)

Z section Y section

X section

u wall thickness

t longitudinal axial distance (P-M) α arc angle

du, d ₃₄ diameter (electrode body) d ₁₅ , diameter (electrode head)

Claims

claims

A temperature sensor (4, 24, 51,) for determining a temperature of a medium with a housing body (14, 34, 54) and a housing head (15, 35, 55) in which a

Temperature sensor (5, 25), in particular a resistance thermometer or a

Thermoelement, is arranged and which is in particular rotationally symmetrical, wherein the housing head (15, 35, 55) has an end face (12, 32, 52) with a center (M), wherein the course of the end face (12, 32, 52) in the radial direction to

Center point (M) reaches a point (P), from which an increase in a positive direction in the medium gradient and the distance (t) of the point (P) to the center (M) in the longitudinal axial direction is greater than the wall thickness (u) of the Housing head (15, 35, 55) along the longitudinal axis (A) at the midpoint (M) of the temperature sensor (4, 24, 51).

Second temperature sensor (4, 24, 51,) for determining a temperature of a medium with a housing body (14, 34, 54) and a housing head (15, 35, 55) in which a

Temperature sensor, in particular a resistance thermometer or a thermocouple, (5, 25) is arranged and which is in particular rotationally symmetrical, wherein the housing head (15, 35, 55) has an end face (12, 32, 52) with a center (M), wherein the course of the end face (12, 32, 52) in the radial direction to the midpoint (M) in the medium direction initially describes a convex course and thereto

Subsequently, a concave profile, wherein the concave curve has a vertex (P) and wherein the distance (t) of the point (P) to the center (M) in the longitudinal axial direction is greater than the wall thickness (u) of the housing head (15, 35, 55) along the longitudinal axis (A) at the midpoint (M) of the temperature sensor (4, 24, 51).

3. Temperature sensor according to claim 1 or 2, characterized in that the end face (12, 32, 52) at least a first to the midpoint (M) radially spaced edge region (R), wherein at least the first edge region (R) has a first in the medium direction arcuate arc (K) or a curved in the medium direction parabola or any other convex surface contour defined, wherein the housing head (15, 35, 55)

is formed rotationally symmetrical with a longitudinal axis (A) of the temperature sensor.

4. Temperature sensor according to one of the preceding claims, characterized

characterized in that

Temperature sensor (4, 24, 51) is designed as an electrode.

5. Temperature sensor according to one of the preceding claims, characterized in that the edge region (R) extending over a radially to the midpoint (M) extending portion of at least 2%, preferably at least 4%, in particular at least 10%, of the diameter of the housing head (15 , 35, 55).

6. Temperature sensor according to one of the preceding claims, characterized in that the housing head (15, 35, 55) has a material projection, which extends in the radial direction over the outer diameter of the preferably rotationally symmetrical

Housing body (14, 34, 54) extends out.

7. Temperature sensor according to claim 6, characterized in that the material projection at least 10%, preferably at least 20% of the outer diameter of the

Housing body (14, 34, 54) is.

8. Temperature sensor according to claim 6, characterized in that the housing head (15, 35, 55) on the front side facing away from a groove (17).

9. Temperature sensor according to one of the preceding claims, characterized in that the end face has a cylindrical shape (19, 39), with a

Cylinder wall, which in the longitudinal axial direction at least four times, preferably six times, in particular eight times longer than the minimum wall thickness (u) of

cylindrical shape (19, 39) in this area.

10. Flowmeter (1, 21) with a measuring tube (2, 22) and a device for determining the flow rate and / or the volume flow rate of a medium in the measuring tube (2, 22), characterized in that the flowmeter (1, 21) a temperature sensor (4, 24, 51) according to claim 1-9.

1 1. A flowmeter according to claim 10, characterized in that the

Flowmeter (1, 21) is designed as a magnetic-inductive flowmeter and that the temperature sensor (4, 24, 51) as at least one measuring electrode and / or as an electrode of a level monitoring system and / or as an electrode for tapping the electric potential of Medium is designed as a reference for the transmitter.