THERMOMETER

Description

[0001] The invention relates to a thermometer for determining and / or monitoring the temperature of a medium in automation technology, as well as a method for producing a device according to the invention.

[0002] Thermometers have become known in a wide variety of designs from the state of the art. There are thermometers that use the expansion of a liquid, gas, or solid with a known coefficient of expansion to measure temperature, and there are also those that relate the electrical conductivity of a material or a derived value to temperature, such as electrical resistance when using resistance elements or the thermoelectric effect in the case of thermocouples. In contrast, radiation thermometers, especially pyrometers, utilize the thermal radiation of a substance to determine its temperature. The underlying measurement principles have been described in numerous publications.

[0003] Temperature sensors in the form of resistance elements include thin-film and thick-film sensors, as well as NTC thermistors. A thin-film sensor, particularly a resistance temperature detector (RTD), uses a sensor element provided with connecting wires and applied to a carrier substrate. The back of the carrier substrate is usually coated with metal. Sensor elements used are so-called resistance elements, which are formed, for example, by platinum elements. These are also commercially available under the designations PT10, PT100, and PT1000, among others.

[0004] With temperature sensors in the form of thermocouples, the temperature is determined by a thermoelectric voltage that arises between the thermocouple wires made of different materials that are connected at one end. Thermocouples according to DIN standard IEC584, e.g., thermocouples of type K, J, N, S, R, B, T, or E, are typically used as temperature sensors for temperature measurement. However, other material pairs, particularly those with a measurable Seebeck effect, are also possible. The temperature sensors are often part of a measuring insert, which is inserted, for example, into an immersion body immersed in the medium or a protective tube. In this regard, reference is made to CH 647 867 A5. Similar thermometer designs have also become known for non-invasive temperature measurement.In this case, the respective temperature sensor comes into contact with the medium via the wall of the respective container in which the medium is located and is suitably attached to the wall of the container.

[0005] For reliable temperature determination, it is important that the respective temperature sensor and the medium are essentially in thermal equilibrium for at least the time required to record the temperature. The time it takes for a thermometer to react to a temperature change is also referred to as the thermometer's response time.

[0006] The measuring accuracy of a thermometer depends sensitively on the respective thermal contacts and the prevailing heat conduction. In particular, the heat flows between the medium, the container in which the medium is located, the thermometer components and the process environment play a crucial role here. In the case of invasive temperature measurement using an immersion body, heat dissipation to the environment plays an increasing role as the length of the immersion body decreases. The heat from the process reaches not only the temperature sensor via the protective tube, but also the environment. In non-invasive temperature measurement, the influence of this unwanted heat dissipation to the environment is even greater, since the temperature sensor is not directly surrounded by the medium.

[0007] Therefore, the object of the invention is to improve the measuring accuracy of thermometers.

[0008] This object is achieved by the device according to claim 1. The device according to the invention for determining and / or monitoring the temperature of a medium in a container, in particular a tank or a pipeline, comprises a measuring insert with a temperature sensor for detecting the temperature and a protective tube in which the temperature sensor is arranged. Furthermore, the device comprises a thermally conductive molded piece, which is arranged in the protective tube and surrounds the measuring insert at least in sections, in particular also in a region of the temperature sensor facing away from the medium.

[0009] The molded part serves to conduct heat from the process to the temperature sensor or to distribute heat within the thermometer. In particular, the molded part serves to ensure a substantially homogeneous temperature distribution in a predefined volume surrounding the temperature sensor. This advantageously results in a significantly reduced temperature gradient in the area of ​​the temperature sensor due to heat dissipation to the environment. Rather, the area surrounding the temperature sensor is heated substantially uniformly. Compared to a thermally conductive paste, the molded part according to the invention advantageously ensures reproducible, substantially constant thermal contact over time.

[0010] Depending on the design of the thermometer, the fitting is designed to at least partially surround the temperature sensor and is in thermal contact with at least one other component of the thermometer, in particular the protective tube. In this case, an area around the temperature sensor facing away from the process is particularly relevant for reducing heat dissipation.

[0011] Advantageously, the fitting according to the invention can also be used to retrofit existing thermometers

[0012] In an advantageous embodiment, the shaped piece is made of copper, silver, graphite, boron nitride, a steel, in particular stainless steel, or an alloy comprising at least one of these materials.

[0013] According to the invention, the fitting is tubular, in particular cylindrical, at least in some sections. In the tubular region, the fitting is then arranged around the measuring insert in the protective tube, i.e., it is located between the measuring insert and the protective tube.

[0014] A further preferred embodiment involves the shaped piece being cup-shaped. The shaped piece thus has a tubular section and a bottom surface. Such a design is suitable, for example, for a non-invasive thermometer. Here, the measuring insert is inserted into the cup-shaped shaped piece.

[0015] In another design with a cup-shaped fitting, the bottom surface of the fitting has a bore through which the measuring insert can be inserted. This design is suitable, for example, for invasive temperature measurement. The bottom surface is located on the side of the temperature sensor facing away from the medium. The bottom surface thus essentially serves as a lid and separates the volume surrounding the temperature sensor from the environment. However, this design can equally be implemented in conjunction with a non-invasive thermometer.

[0016] In a particularly preferred embodiment of the invention, the shaped piece has, at least in sections, a geometry corresponding to a geometry of the protective tube and / or the measuring insert. In particular, the geometry of the shaped piece is adapted, at least in sections, to the geometry of the protective tube in the area in which the shaped piece can be inserted into the protective tube, to that of the protective tube, or, in the area in which the shaped piece surrounds the measuring insert, to that of the measuring insert. This measure allows the shaped piece to be inserted into the protective tube with a precise fit, at least in sections. This improves the respective thermal contact between the shaped piece and the protective tube or the measuring insert.

[0017] In another embodiment, the molded part has an end piece whose outer diameter is larger than an outer diameter of the molded part in a central region of the molded part. Such a configuration is particularly advantageous for protective tubes with a variable inner diameter, in particular for protective tubes in which the inner diameter of the protective tube is smaller in a first region, in which the temperature sensor can be arranged, than in a second region facing away from the process. In this case, the end piece is arranged in particular in the second region and at least partially closes off the first region from the environment.

[0018] In this respect, it is advantageous if the end piece is disc-shaped. Depending on the design of the thermometer, it is also advantageous if the end piece has a hole through which the measuring insert can be inserted.

[0019] It is also advantageous if the geometry of the end piece is configured to at least partially correspond to the geometry of the protective tube in a region into which the fitting can be inserted. For a protective tube with a first and second region with different diameters, the geometry of the fitting is particularly adapted to the geometry of the protective tube in a transition region between the first and second regions.

[0020] According to the invention, the device further comprises fastening means for releasably securing the fitting in the protective tube and to the measuring insert. The fastening means serves to improve the thermal contact between the fitting and the protective tube and / or the fitting and the measuring insert.

[0021] It is advantageous if the fastening means are designed and arranged in such a way that a contact pressure, in particular a predeterminable one, can be exerted on the molded part by means of the fastening means. To exert the contact pressure or to exert a predeterminable contact pressure on the molded part, the fastening means can, for example, be designed in such a way that a spring force of the measuring insert itself is utilized.

[0022] In other embodiments, the fastening means may comprise, for example, a spring, a screw cap, or a bayonet closure. With regard to the fastening means, in principle, all methods known to those skilled in the art for suitable fastening of the fitting in the protective tube and / or to the measuring insert are conceivable and fall within the scope of the present invention.

[0023] According to the invention, the fastening means comprise at least one, in particular cylindrical, base body arranged around the fitting in the protective tube. The base body can serve, for example, to transmit a predeterminable contact force to the fitting.

[0024] Furthermore, in one embodiment of the invention, the base body can be made of a heat-insulating material. In this case, the base body also provides insulation from the environment. While the molded piece ensures homogeneous heat distribution in the area surrounding the temperature sensor, the base body then serves as additional thermal insulation from the environment.

[0025] It is therefore advantageous if the base body is made of a plastic, especially PEEK, PEK, or PPS.

[0026] In another embodiment, the base body can also be made of a thermally conductive material. In this case, for example, a thin wall thickness or a clever geometry can be chosen for the base body to ensure that the molded part is shielded from the environment.

[0027] A further embodiment includes the fastening means comprising at least one spring, which can transmit the predeterminable contact force via the base body. The spring surrounds at least one section of the base body. The base body is suitably designed for force transmission. For example, the base body has a shoulder in an outer region on which the spring can be arranged.

[0028] Finally, a further embodiment of the invention includes that the temperature sensor comprises at least one resistance element or a thermocouple.

[0029] The invention is explained in more detail with reference to the following figures. They show: Fig. 1 : a thermometer for invasive temperature measurement with a protective tube according to the state of the art; Fig. 2 : a thermometer for non-invasive temperature measurement according to the state of the art; Fig. 3 : a first embodiment of a thermometer according to the invention for non-invasive temperature determination with a shaped piece according to the invention; Fig. 4 : exemplary embodiments of a molded part according to the invention; Fig. 5 : a second embodiment of a thermometer according to the invention for invasive temperature determination with a shaped piece according to the invention; and Fig. 6 : a shaped part according to the invention with a possible design for the fastening means.

[0030] In the figures, identical elements are each provided with the same reference numeral.

[0031] In Fig.1 is a schematic illustration of a thermometer 1 according to the prior art for measuring the temperature T of a pipeline 2 through which a medium M flows. The thermometer 1 is inserted into the pipeline 2 by means of a protective tube 3. The temperature sensor 5 is part of a measuring insert 4, which can be detachably inserted into the protective tube 3. With such an arrangement, the achievable measuring accuracy depends, among other things, on the respective heat dissipation W to the process environment. The undesired heat dissipation increases with decreasing immersion depth of the protective tube 3 into the pipeline 2, so that an increased measuring error is to be expected, especially for pipelines 2 with a small diameter.

[0032] A similar problem also arises in the case of non-invasive temperature determination, as in Fig. 2 illustrated. Here, the thermometer 1 does not protrude into the pipe 2, but is rather placed from the outside on a wall 2a of the pipe 2. Here, too, the measuring insert 3 comprises a temperature sensor 5. For the thermometer 1 made of Fig. 2 Furthermore, connecting cables 6a, 6b are shown, by means of which the temperature sensor 5 can be connected to an electronics unit 7. While the thermometer 1 shown is designed in a compact construction with integrated electronics 7, in other thermometers 1 the electronics 7 can also be arranged separately from the measuring insert 3. The temperature sensor 5 can, for example, comprise a resistance element or a thermocouple, and depending on the design of the temperature sensor 5, the number of connecting cables 6 used can vary. In this case, too, undesirable heat dissipation W to the environment occurs, which impairs the measuring accuracy of the thermometer 1.

[0033] To reduce the negative influence of heat dissipation, a thermometer according to the invention comprises a shaped piece 8, which is arranged in the protective tube 3 and at least partially surrounds the measuring insert 4. The shaped piece 8 is thus arranged at least partially between the measuring insert 4 and the protective tube 3.

[0034] A first embodiment of a device 1 according to the invention with a shaped piece according to the invention is the subject of Fig. 3 The device is a non-invasive thermometer 1 similar to the thermometer 1 of Fig. 2 The shaped piece 8 is cup-shaped for this embodiment. In a section, which for the embodiment shown here is located in the region of a bottom surface B of the shaped piece 8, the shaped piece 8 is arranged between the measuring insert 4 and a bottom surface of the protective tube 3 or the wall 2a of the container. The shaped piece 3 serves to preferably uniformly heat a volume V surrounding the temperature sensor 5 and to prevent undesirable temperature gradients in the region of the temperature sensor 5 due to heat dissipation to the environment.

[0035] In Fig. 4 Three possible, preferred embodiments for a molded part 8 according to the invention are illustrated, all of which, just like the one in Fig. 3 The fitting shown can be used for both an invasive and a non-invasive thermometer. The fitting 8 made of Fig. 4a is designed in a tube shape. In the variant shown, it has a circular cross-sectional area, but other cross-sectional areas are also possible and fall under the scope of the present invention. The shaped piece 8 can be made in a further, not separate, but similar to the one shown in Fig. 3 shown embodiment, further have a bottom surface B. In this bottom surface B, a bore can also be arranged, through which bore the measuring insert can be guided. The bore then has a diameter, in particular adapted to the diameter of the measuring insert 4, which is smaller than an outer diameter of the shaped piece 8. The outer diameter of the shaped piece 8 is in turn adapted, for example, at least in the tubular section, to an inner diameter of the protective tube 3. In an end region E, the geometry of the shaped piece 8 can further be adapted to the geometry of the measuring insert 4 and / or the protective tube 3.

[0036] A further possible embodiment for a shaped piece 8 according to the invention is shown in Fig. 4b shown. Here, the shaped piece 8 also has a cylindrical section. In addition, the shaped piece 8 comprises an end piece 9, whose outer diameter d 9 is larger than an outer diameter d 8 in a central region of the shaped piece 8. The end piece 9 is disk-shaped for the embodiment shown. Here, the end piece 9 also has an optional bore through which the measuring insert 3 can be guided. Fig. 4c The fitting 9 shown has a tubular section and an end piece 9. The end piece 9 is, in contrast to Fig. 4b However, it is adapted to the geometry of the protective tube 3 or designed to correspond to it.

[0037] Another exemplary embodiment of a device 1 according to the invention is shown in Fig. 5 This is a thermometer 1 for invasive temperature determination, similar to the thermometer 1 from Fig. 1 . The thermometer 1 comprises a shaped piece 8, which is analogous to the shaped piece 8 of Fig. 4c is constructed. The shaped piece 8 is arranged in the protective tube 3 and partially surrounds the measuring insert 4. The protective tube 3 has a variable inner diameter. In a first region B 1 it has a smaller inner diameter than in a second region B 2 . The end piece 9 of the shaped piece 8 is arranged in a transition region between the first region B1 and second region B2 of the protective tube 3 and is arranged in the transition region corresponding to the geometry of the protective tube. The end piece 9 thus has the function of a cover which seals off the volume V surrounding the temperature sensor 5 from the environment. The shaped piece 8 serves to conduct heat which flows through the protective tube 3 to the environment to the temperature sensor 5. In this way, a homogeneous temperature distribution around the temperature sensor 5 can be ensured and undesired heat dissipation W to the process environment can be avoided.

[0038] In order to ensure the best possible thermal contact between the fitting 9 and the protective tube 3 or measuring insert 4, the device 1 comprises Fig. 5 additionally optional fastening means 10. It should be noted that all embodiments shown here for thermometers 1 according to the invention can optionally have suitable fastening means 10 and that all fastening means 10 well known to the person skilled in the art are conceivable within the scope of the present invention.

[0039] The fasteners made of Fig. 5 comprise a cylindrical base body 11, which is arranged at least partially around the shaped piece 8 in the protective tube 3, and a spring 12 for exerting a predeterminable contact pressure on the shaped piece. To transmit the contact pressure by means of the spring 12, the base body 11 has a shoulder 13 on which the spring 12 is arranged.

[0040] A more detailed description of this arrangement is given in Fig. 6 to see. For those here and in Fig. 5 As shown, the base body 11 also serves to thermally insulate the molded part 8 from the environment. For this purpose, the base body 11 for the embodiment shown is made, for example, of a heat-insulating material and is arranged such that it surrounds the cylindrical section of the molded part. Bezugszeichenliste

[0041] 1Device 2Container; 2a Wall of the container 3Protective tube 4Measuring insert 5Temperature sensor 6Connecting wires 7Electronics 8Fitting 9End piece 10Fastening means 11Base body 12Spring 13Step in the base body MMedium TTemperature WWeasure dissipation dDiameter B 1 , B 2 Areas VVolume surrounding the temperature sensor BBottom area of ​​the fitting

Claims

1. A device (1) for determining and / or monitoring a temperature (T) of a medium (M) in a container (2), comprising: A measuring insert (4) with a temperature sensor (5) for detecting the temperature (T), a protective tube (3), in which the temperature sensor (5) is arranged, a thermally conductive shaped piece (8), which is arranged in the protective tube (3) and surrounds the measuring insert (4) at least in sections, including in an area of the temperature sensor that is facing away from the medium (M), wherein the shaped piece (8) has the shape of a tube at least in sections and the shaped piece (8) is arranged around the measuring insert (4) in the protective tube (3) in the tube-shaped section of the shaped piece (8) and is located between the measuring insert (4) and the protective tube (3), and mounting materials (10) for mounting the shaped piece (8) in the protective tube (3) and on the measuring insert (4) such that it can be removed again, wherein the mounting materials (10) have at least one basic body (11) made from a heat-insulating material, said basic body (11) being arranged around the shaped piece (10) in the protective tube (3).

2. The device (1) as claimed in claim 1, wherein the shaped piece (8) is made from copper, silver, graphite, boron nitride, a steel, in particular stainless steel, or an alloy containing at least one of these materials.

3. The device (1) as claimed in claim 1 or 2, wherein the shaped piece (8) has a cylindrical-shaped design at least in sections.

4. The device (1) as claimed in at least one of the preceding claims, wherein the shaped piece (8) has a cup-shaped design.

5. The device (1) as claimed in claim 4, wherein a base area (B) of the shaped piece (8) has a hole through which the measuring insert (4) can be guided.

6. The device as claimed in claim 5, wherein the base area is arranged on a side of the temperature sensor that is facing away from the medium (M).

7. The device (1) as claimed in at least one of the preceding claims, wherein the shaped piece (8) has a geometry corresponding at least in sections to a geometry of the protective tube (3) and / or the measuring insert (4).

8. The device (1) as claimed in at least one of the preceding claims, wherein the shaped piece (8) has an end piece (9) with an external diameter (d9) which is larger than an external diameter (d8) of the shaped piece (8) in a central area of the shaped piece (8).

9. The device (1) as claimed in claim 8, wherein the end piece (9) is has a disk-shaped design.

10. The device (1) as claimed in claim 8 or 9, wherein a geometry of the end piece (9) is designed so that it at least partly corresponds to a geometry of the protective tube (3) in an area into which the shaped piece (8) can be inserted.

11. The device (1) as claimed in at least one of the preceding claims, wherein the mounting materials (10) are configured and arranged in such a way that the mounting materials (10) can be used to exert a contact force, in particular one that is specifiable, onto the shaped piece (8) .

12. The device (1) as claimed in at least one of the preceding claims, wherein the basic body is cylindrical.

13. The device (1) as claimed in at least one of the preceding claims, wherein the basic body (11) is made from a plastic, in particular PEEK, PEK, or PPS.

14. The device (1) as claimed in at least one of the preceding claims, wherein the mounting materials (10) at least have a spring (12), said spring (12) being capable of exerting the specifiable contact force by means of the basic body (11).

15. The device (1) as claimed in at least one of the preceding claims, wherein the temperature sensor (5) comprises at least a resistor element or a thermocouple.