Non-invasive thermometer

Abstract

The invention relates to a device (1) for determining and / or monitoring a process variable, in particular the temperature (T) or the flow of a medium (M) in a containment (2), comprising a temperature sensor (5) to record the temperature (T) and a flexible, thermally insulating support element (7), which can be arranged on the outer surface of a wall (W) of the containment (2), and wherein the temperature sensor (5) is fixed to the support element (7).

Description

TECHNICAL FIELD

[0001] The present application relates to a device for determining and / or monitoring the temperature of a medium in a containment. The containment is, for example, a container or a pipe. BACKGROUND

[0002] In various embodiments of the prior art, thermometers are known. Thus, there are thermometers for measuring temperature which use the expansion of a liquid, gas or solid, etc. with a known thermal expansion coefficient, associate the electrical conductivity of a material or a variable derived therefrom, for example the electrical resistance in the case of a resistance element or the thermoelectric effect in the case of a thermocouple, with the temperature. Conversely, in the case of radiation thermometers, in particular pyrometers, the thermal radiation of a substance is utilized in order to determine the temperature thereof. The measurement principles of these measuring devices are described in a large number of publications.

[0003] In the case of temperature sensors in the form of resistance elements, so-called thin-film and thick-film sensors and so-called NTC thermistors, etc. are known. In the case of thin-film sensors, in particular resistance temperature detectors (RTD), sensor elements are used, for example sensor elements which are equipped with connecting wires and applied on a substrate, wherein the rear of the support substrate is usually provided with a metal coating. As sensor elements, so-called resistance elements are used, which are based, for example, on platinum elements and are also commercially available under the names PT10, PT100 and PT1000, etc.

[0004] In the case of temperature sensors in the form of thermocouples, the temperature is again determined from the thermoelectric voltage, which occurs between the single-sided connected thermocouple wires of different materials. For temperature measurement, thermocouples according to DIN standard IEC 584 are usually employed as temperature detectors, for example: K, J, N, S, R, B, T or E type thermocouples. However, other material pairs, in particular material pairs with a measurable Seebeck effect, are also possible.

[0005] The accuracy of the temperature measurement depends sensitively on the thermal contact and in particular on the prevailing thermal conduction. In this case, the heat flow between the medium, the containment in which the medium is located, the thermometer and the process environment plays a decisive role. In order to determine the temperature reliably, it is important that the temperature sensor and the medium are in thermal equilibrium, at least for a certain time which is required for recording the temperature. The response time of the thermometer to a temperature change is also referred to as the response time of the thermometer.

[0006] A high accuracy of the measurement can be achieved, in particular, when the temperature sensor is immersed in the medium. Thus, a large number of thermometers are known, in the case of which the temperature sensor is in more or less direct contact with the medium. This allows a good coupling between the medium and the temperature sensor.

[0007] However, for different processes and many recipients, especially small vessels or pipes, a non-invasive determination of the temperature is advantageous. Thus, likewise, the following thermometers are known, which can be fixed externally / internally to the recipient in which the medium is located. Such devices, also called surface thermometers or contactless sensors, are known, for example, from the documents DE 102 014 118 206 A1 or DE 102 015 113 237 A1. In the case of such measuring devices, the temperature sensor does not come into direct contact with the process. This requires that, in order to ensure a good thermal coupling, various additional aspects have to be taken into account. Thus, for example, the mechanical contact and with it the thermal contact between the vessel and the thermometer is decisive for the achievable measurement accuracy. In the case of insufficient contact, an accurate temperature determination is not possible.

[0008] The measuring insert used as a surface thermometer or skin point thermometer usually has a temperature sensor in the form of a thermocouple, which is directly welded to the outer surface or skin of the pipe or vessel. In this case, the replacement of the thermocouple can be both time-consuming and expensive, especially since the replacement can require a temporary shutdown of the process and / or the application. In order to overcome these disadvantages, embodiments of thermometers are known in each case, which enable a simple replacement of the temperature sensor, for example by means of US 5382093 and the European patent application No. 18198608.4, which was not published as of the earliest filing date of the present application.

[0009] In addition, many different embodiments of thermometers for non-invasive temperature measurement are known, such as described in the documents US 2016 / 0047697 A1, DE 102 005 040 699 B3, EP 3230704 B1 or EP 2038625 B1.

[0010] In the case of a non-invasive temperature determination, the core problem is to drain the heat from the process to the environment. This leads to a significantly greater measurement error compared to the case where the temperature sensor is introduced directly into the process. SUMMARY

[0011] It is therefore an object of the present application to provide a thermometer for non-invasive temperature measurement, which is characterized by a high accuracy of the measurement.

[0012] This object is achieved by a device for determining and / or monitoring a process variable, in particular the temperature or the flow of a medium in a recipient, in particular a vessel or a pipe, according to the present application. The device of the present application comprises a temperature sensor to record the temperature and a flexible, thermally insulating support element, which can be arranged on the outer surface of the recipient, wherein the temperature sensor is fixed to the support element.

[0013] The support element is in particular embodied such that it can be fitted to the contour of the containing body or to the contour of the outer surface of the wall of the containing body. The support element can for example be arranged at least partially around the wall of the containing body. In the case of a containing body in the form of a tube, it is particularly preferred to be arranged along the peripheral line of a cross section perpendicular to the longitudinal axis of the containing body.

[0014] The temperature sensor is preferably fixed to the support element in a state arranged thereon in a region of the support element facing the containing body. The device is in thermal contact with the containing body from an outer region of the containing body. The temperature of the medium is thus determined indirectly via the wall of the containing body. In this case, the emission of heat to the environment is reduced or prevented by the thermally insulating support element. In this way, in the immediate vicinity of the temperature sensor, at least at times, a substantial thermal equilibrium with the process is established. The temperature sensor is thus substantially exposed to the process temperature, even though it is located outside the containing body. This in turn leads to an increased measurement accuracy of the device.

[0015] The device can optionally further have an electronic device. Alternatively, the electronic device can also be a separate component which can be connected to the device. Furthermore, advantageously associated with the temperature sensor is at least one connection line for electrical contacting.

[0016] An embodiment comprises a temperature sensor which is a resistance element or a thermocouple.

[0017] The device can further comprise more than one temperature sensor, wherein all temperature sensors are fixed to the support element.

[0018] A further embodiment comprises a device for in situ calibration and / or verification of at least the temperature sensor comprising at least one reference element which is fixed to the support element and at least partially composed of at least one material which has at least one phase transition in the temperature range relevant for calibrating the first temperature sensor at at least one predetermined phase transition temperature, at which phase transition the material remains in the solid state. In this regard, reference is made in general to EP 0 261 212 B1 in the context of the present invention. Advantageously, the support element prevents an undesired emission of heat of the temperature sensor and the reference element, independent of the exact arrangement of the temperature sensor and the reference element relative to each other on the support element. Preferably, the temperature sensor and the reference element are always substantially in thermal equilibrium.

[0019] In an embodiment, the device comprises a heating element which is fixed to the support element. By means of the heating element, the device can additionally be heated to a predetermined temperature. Again, the thermally insulating support element provides for a reduction or prevention of an undesired emission of heat.

[0020] Furthermore, by means of the heating element, a determination of the flow rate can be carried out according to the measurement principle of heat flow measurement as per se known in the prior art.

[0021] Accordingly, the flow rate can be determined in two different ways. Within the scope of the present application, the term "flow rate" includes both the volumetric flow rate as well as the mass flow rate of the medium. Likewise, the flow velocity or flow rate of the medium can be determined.

[0022] In the first measurement principle, the sensor element is exposed to the medium flowing through the pipe and is heated such that its temperature remains essentially constant. In the case of known and at least sometimes constant properties of the medium, such as the temperature thereof, its density or composition, the mass flow rate of the medium flowing through the pipe can be determined on the basis of the heating power required to maintain the temperature at a constant value. In this case, the temperature of the medium is the temperature which the medium has without additional heating input by the heating element. In contrast, in the case of the second measurement principle, the heating element is operated with a constant heating power, and the temperature of the medium is measured downstream of the heating element. In this case, the measured temperature of the medium provides information about the mass flow rate.

[0023] For example, the heating element can be an electrical resistance heater. For example, so-called resistance elements are used, for example, RTD resistance elements (resistance temperature detectors), in particular platinum elements, such as are commercially available under the names PT10, PT100 and PT1000, etc. The resistance elements are heated via the electrical power supplied to them, for example, as a result of an increased current supply.

[0024] In a further embodiment of the device, the temperature sensor comprises a temperature- sensitive sensor element, which is electrically connected via at least a first and a second connecting line, wherein the first connecting line is divided into a first and a second section, wherein the first section, close to the sensor element, consists of a first material, and wherein the second section, remote from the sensor element, consists of a second material different from the first material, wherein the second connecting line consists of the second material, and wherein the first section of the first connecting line and at least one subregion of the second connecting line form a first temperature difference sensor in the form of a thermocouple. In this regard, reference is made in the context of the present application in its entirety to the German patent application No. 102018116309.6, which was not published as of the earliest filing date of the present application. With this embodiment of the temperature sensor, the thermal discharge in the region of the temperature sensor can be recorded. An exact knowledge of the thermal discharge further improves the accuracy of the measurement of the device. In the case of the determination of the flow rate, with a reduction in the thermal discharge, a higher flow rate of the medium in the containment body can be detected, i.e. the measurement range of the device can be expanded.

[0025] Preferably, the at least one temperature sensor, and in the given case also the reference element and / or the heating element, are together fixed to the support element in the region thereof facing the containment body, in the state arranged thereon. In this case, all conceivable, in particular geometric, arrangements of the aforementioned components of the device on the support element are possible and fall within the scope of the present application.

[0026] A preferred embodiment of the device according to the application is that at least partially on the support element a unit is arranged which at least partially comprises a material having an anisotropic thermal conductivity. In this regard, reference is made in the context of the present application in its entirety to German patent application No. DE 102017100267 Al. For example, the unit can be a thin-walled film or foil, for example of graphite. Preferably, the film or foil is arranged in a fixed state in the region of the support element facing the accommodation body.

[0027] Thus, advantageously, at least the temperature sensor and in the given case also the reference element and / or the heating element are arranged between the support element and the unit. The unit serves to purposefully distribute heat from the process along the part of the support element facing the accommodation body. Thus, it is ensured that all components of the device arranged on the support element, in particular at least one temperature sensor and in the given case a reference element, are always in thermal equilibrium with one another.

[0028] In a preferred embodiment of the device, the support element is composed of plastic or ceramic. In this case, the support element is preferably of an area shape having a predefinable geometry.

[0029] A further preferred embodiment comprises that at least one guide is present to guide at least one connection line of the at least temperature sensor and in the given case also the reference element and / or the heating element into the support element. For example, the guide can be a cavity, a recess, a channel or a hole in the support element. Also, a sleeve can be introduced into the support element.

[0030] The guide serves for mechanical stabilization of the connection line and prevents undesired tearing. The number of guides depends on the number of connection lines and the number of components fixed to the support element, for example, additional temperature sensors, heating elements or reference elements.

[0031] In a further preferred embodiment, the device comprises at least one flexible circuit board which at least partially serves as a connection line at least for the temperature sensor and in the given case for the heating element and / or the reference element. Since, at least partially, in particular in the region directly adjacent to the temperature sensor, the flexible circuit board serves as a connection line, such a connection line can be guided partially parallel to the support element and in association therewith parallel to the wall of the accommodation body. Like the support element, the flexible circuit board adapts to the contour of the accommodation body. This guiding of the connection line parallel to or along the wall of the accommodation body further reduces the occurrence of undesired heat dissipation into the process environment.

[0032] It is particularly preferred that at least one hollow is provided to introduce at least the temperature sensor and, in the given case, the reference element and / or the heating element into the support element. It is particularly preferred that the hollow is embodied in such a way that the temperature sensor and, in the given case, the reference element and / or the heating element are essentially flush with the surface of the support element.

[0033] The temperature sensor and, in the given case, the reference element and / or the heating element can be fixed to the support element, in particular in the hollow, for example by means of an adhesive. However, according to the application, the fixing by means of an adhesive is not necessary. Rather, all common means of fixing can be used to fix the temperature sensor and, in the given case, the heating element and / or the reference element.

[0034] A further embodiment comprises a device which comprises a fixing means for releasable fixing of the device, in particular to the accommodation body. In this respect, all suitable fixing means which are common to the person skilled in the art can be used, for example tube clamps, and fall within the scope of the application.

[0035] In this case, it is advantageous if the fixing means is embodied in such a way as to ensure a predetermined pressing pressure of the support element on the accommodation body. In this way, a good and repeatable thermal contact between the wall of the accommodation body and the support element can be ensured.

[0036] The fixing means can advantageously comprise at least one magnet which is arranged on the support element, or at least one screw with a screw thread.

[0037] In a further embodiment, the device comprises an enveloping element which at least partially surrounds the support element on the side facing away from the accommodation body.

[0038] In this respect, the enveloping element is advantageously used as a fixing means for fixing the device to the accommodation body, in particular wherein the geometry of the enveloping element comprises at least one recess or at least one hole. BRIEF DESCRIPTION OF DRAWINGS

[0039] The application will now be explained in more detail on the basis of the drawings. The drawings show the following:

[0040] Figure 1 is a thermometer for non-invasive temperature measurement according to the prior art;

[0041] Figure 2 is a first embodiment of the thermometer of the application with a temperature sensor;

[0042] Figure 3 is a second embodiment of the thermometer of the application with two temperature sensors, a heating element and a reference element;

[0043] Figure 4is a third embodiment of the thermometer of the invention with a unit comprising a material with an anisotropic thermal conductivity and a support element provided with a hollow;

[0044] Figure 5 is a fourth embodiment of the thermometer of the invention with a guide and fixation means for the connecting lines; and

[0045] Figure 6 is a fifth embodiment of the thermometer of the invention with an encapsulating element.

[0046] In the drawings, identical elements have identical reference numerals. Furthermore, the embodiments of the different drawings can be combined with each other to the desired extent. DETAILED DESCRIPTION

[0047] Figure 1 A schematic view of a thermometer 1 according to the prior art is shown, which thermometer has a measuring insert 3 and an electronics 4. The thermometer 1 is used for recording the temperature T of a medium M, which medium is located in a containment 2, in this case in the form of a pipe. For this purpose, the thermometer 1 does not protrude into the pipe 2, but is externally superimposed on the wall W of the pipe 2 for non-invasive temperature determination.

[0048] The measuring insert 3 comprises a temperature sensor 5, which in the present case comprises a temperature-sensitive element in the form of a resistance element. The temperature sensor 5 is electrically contacted via connecting lines 6a, 6b and connected with the electronics 4. Although the shown thermometer 1 is embodied in a compact construction with integrated electronics 4, in the case of other thermometers 1 the electronics 4 can also be arranged separately from the measuring insert 3. Also, the temperature sensor 5 does not necessarily have to be a resistance element, nor does the number of connecting lines 6 necessarily have to be two. Rather, the number of connecting lines 6 can be chosen as appropriate depending on the measuring principle of the application and the temperature sensor 5 applied.

[0049] As shown, the measuring accuracy of such a thermometer 1 is highly dependent on the materials used for the thermometer, and in particular on the thermal contact, in particular in the region of the temperature sensor 5. The temperature sensor 5 is indirectly thermally contacted with the medium M, i.e. via the measuring insert 3 and via the wall W of the containment 2. In this respect, the thermal discharge of the medium M into the environment also plays a large role, which can lead to an undesirable temperature gradient in the region of the temperature sensor 5.

[0050] In order to appropriately solve these problems, according to the invention alternative embodiments for a non-invasive thermometer 1 are provided, such as shown in the following drawings on the basis of some preferred embodiments.

[0051] Figure 2A first embodiment of the thermometer 1 of the present application is shown in Fig. 1. The thermometer 1 comprises a flexible thermally insulating support element 7 arranged on the outer surface of the wall W of the containment body 2. For the example shown in this case, in the case of a pipe as containment body 2, the support element 7 is arranged around the outer surface of the wall W of the pipe 2 perpendicularly to the longitudinal axis of the pipe 2. The support element 7 is thus fitted to the profile of the pipe 2. It is noted here that the device 1 of the present application can also be applied with a vessel or other type of containment body. In this case, the support element 7 can be placed on the outer surface of the wall W of the containment body 2 used and fitted accordingly to its profile in the predetermined area.

[0052] The temperature sensor 5 is fixed to the support element 7. The temperature sensor 5 is fixed to the support element 7 in the area of the support element 7 facing the process and thus to the outer surface of the wall W of the containment body 2. In the ongoing operation, the support element 7 serves to reduce or prevent the undesired discharge of heat from the process, i.e. from the medium M to the environment. Since the surface of the support element 7 is arranged on or fixed to the wall W of the containment body 7, a good thermal insulation can be achieved over the entire surface area of the support element facing the containment body. In this way, the temperature sensor 5 is essentially in thermal equilibrium with the medium M, which makes the measurement accuracy of the device 1 high.

[0053] In addition to the temperature sensor 5, the device 1 can also use other components, for example Figure 3 as shown in Fig. 2. In contrast to the embodiment shown in Figure 2 Fig. 1, Figure 3 The device 1 of the present application additionally comprises a heating element 8, a reference element 9 and an additional temperature sensor 10.

[0054] In the embodiment shown in Figure 4 Fig. 2, the thermometer 1 also comprises a unit 11 which at least partially comprises a material with an anisotropic thermal conductivity. The unit is arranged on the support element 7 on the side of the support element 7 facing the medium M and the containment body 2. The unit serves for a uniform heat distribution along the surface O of the support element 7 facing the containment body. For the example shown here, it is assumed that the unit 11 is a thin graphite foil which is fixed to the support element 7.

[0055] The temperature sensor 5, the heating element 8 and the reference element 9 are arranged between the unit 11 and the support element 7. As Figure 4 shown in Fig. 2b, the support element 7 has three hollows 12a-12c to receive the temperature sensor 5, the heating element 8 and the reference element 9, respectively, so that these elements are essentially flush with the surface O.

[0056] In the embodiment shown in Figure 5In the embodiment shown in the figures, the device 1 has four adjacent reference elements 9a to 9d, which have different phase transition temperatures, and which are in electrical contact with two connection lines 6 each via a flexible circuit board 14. However, the flexible circuit board 14 can also be used to contact the temperature sensor 5 and / or the heating element 8. For the electrical contacting of the temperature sensor 5 and the heating element 8, likewise, two connection lines 6 are provided in each case, which are guided through guides 13a, 13b. In this case, the guides 13a, 13b can be, for example, grooves, hollows or channels.

[0057] Furthermore, in order to fix the device 1 on the housing 2, four magnets 16a to 16d are arranged on the support element 7. However, other fixing methods can also be applied and likewise fall within the scope of the present application. In the embodiment shown, the magnets 16a to 16d are arranged on the support element 7 in such a way that they are arranged on the side of the support element 7 facing away from the reference elements 9a to 9d. However, other arrangements are also possible and likewise fall within the scope of the present application. Figure 6 In the embodiment shown, the device 1 also comprises, for example, an enclosing element 17, which surrounds the support element 7 and serves to fix the support element 7 to the housing. For this purpose, for the embodiment shown, the enclosing element comprises two grooves 18, in which, for example, clamps can be arranged in order to be fixed to the housing 2.

[0058] Alternatively, the fixing can also be carried out by means of a bolt with a screw thread. For this case, too, an enclosing element is used, which can be provided, for example, with at least one hole.

[0059] List of reference signs

[0060] 1 device

[0061] 2 housing

[0062] 3 measuring insert

[0063] 4 electronics

[0064] 5 temperature sensor

[0065] 6 connection line

[0066] 7 support element

[0067] 8 heating element

[0068] 9 reference element

[0069] 10 further temperature sensor

[0070] 11 unit

[0071] 12 hollow

[0072] 13 guide

[0073] 14 flexible circuit board

[0074] 15 fixing means

[0075] 16 magnet

[0076] 17 encapsulating element

[0077] 18 recess

[0078] M medium

[0079] T temperature

[0080] W wall of the housing

[0081] O surface of the support element facing the housing

Claims

1. An apparatus (1) for determining and / or monitoring a process variable, said process variable being the temperature (T) or flow rate of a medium (M) in a container (2), said apparatus comprising: Temperature sensor (5), which records temperature (T); A flexible, thermally insulating support element (7) is provided, which can be arranged on the outer surface of the wall (W) of the housing (2). The temperature sensor (5) is fixed on the support element (7), and Unit (11), said unit comprising a material having anisotropic thermal conductivity, The unit (11) is a thin-walled film or foil of graphite fixed to the support element (7). In this embodiment, at least the temperature sensor (5) is arranged between the support element (7) and the unit (11) such that a thin-walled film or a thin-walled foil of graphite is arranged on the surface (O) of the support element (7) facing the container, such that the unit (11) is used for targeted and uniform heat distribution along the surface (O) of the support element (7) facing the container (2).

2. The device (1) according to claim 1, in, The temperature sensor (5) is a resistive element or a thermocouple.

3. The device (1) according to claim 2, It further includes at least one reference element (9) for in-situ calibration and / or verification of at least the temperature sensor (5), wherein, The reference element (9) is fixed to the support element (7) and is at least partially composed of at least one material that has at least one phase transition at at least one predetermined phase transition temperature within a temperature range associated with calibrating the temperature sensor (5), in which the material remains solid.

4. The device (1) according to claim 1, It further includes a heating element (8) which is fixed to the support element (7).

5. The device (1) according to any one of claims 1-4, in, The temperature sensor (5) includes a temperature-sensitive sensor element, which is electrically connected via at least a first connecting line (6a) and a second connecting line (6b). The first connecting line is divided into a first segment and a second segment. The first segment closest to the sensor element is composed of a first material, and The second segment, located away from the sensor element, is composed of a second material different from the first material. The second connecting wire is composed of the second material, and Wherein, the first segment of the first connecting line and at least one sub-region of the second connecting line form a first temperature difference sensor in the form of a thermocouple.

6. The device (1) according to any one of claims 1-4, in, The support element (7) is made of plastic or ceramic.

7. The device (1) according to any one of claims 1-4, in, There is at least one guide (13) to guide at least one connecting line (6) of at least the temperature sensor (5) into the support element (7).

8. The device (1) according to any one of claims 1-4, It further includes at least one flexible circuit board (14), which serves at least in part as a connection line (6) for at least the temperature sensor (5).

9. The device (1) according to any one of claims 1-4, in, At least one hollow portion (12) is provided to introduce at least the temperature sensor (5) into the support element (7).

10. The device (1) according to any one of claims 1-4, It further includes a fixing device (15) for releasably securing the device (1) to the housing (2).

11. The device (1) according to claim 10, in, The fixing device (15) includes at least one magnet (16a-16d) arranged on the support element (7), or at least one bolt with screw threads.

12. The device (1) according to any one of claims 1-4, It further includes an encapsulation element (17) that surrounds the support element at least partially on the side away from the housing (2).

13. The device (1) according to claim 12, in, The encapsulating element (17) serves as a fixing device (15) for securing the device (1) to the housing (2), wherein the geometry of the encapsulating element (17) includes at least one groove (18) or at least one hole.

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