Temperature measuring device

Abstract

The present invention relates to a temperature measuring device for determining the temperature of a surface or medium using the temperature of the surface surrounding the medium. The temperature measuring device comprises at least one measuring sensor and at least one reference sensor, as well as a value processing device, which is connected to the measuring sensor via a first connecting line and to the reference sensor via a second connecting line. Of the two connecting lines, at least the first connecting line is partially implemented as a mineral-insulated sheathed cable providing the measuring sensor, and both connecting lines comprise flexible cables connected to the value processing device.

Description

Technical Field

[0001] The invention relates to a temperature measuring device for determining the temperature of a surface or a medium by means of the temperature of a surface surrounding the medium. Background Art

[0002] Temperature measuring devices are known in industrial process measurement technology, in which one or more temperature sensors are installed in a protective tube that at least partially extends into the interior of a pipeline or container. For this purpose, an opening with an associated seal of the temperature measuring device must be provided in the pipeline or container.

[0003] The disadvantage of these intrusive measurement arrangements is that the components extend into the process chamber, leading to flow energy loss, wear, breakage damage, blockage of the production process and / or cleaning process, and potential leaks. In addition, explosion protection may need to be considered at each pipe and vessel opening.

[0004] The field of application of the invention extends to temperature measuring devices, in which a surface temperature sensor is placed on a surface in order to measure the temperature of this surface and also serves to measure the temperature of a medium located beneath or behind it.

[0005] Ideally, such a sensor should assume the temperature of the medium surrounded by the surface. For example, if the temperature sensor is designed as a thermocouple, the temperature of the sensor and the temperature of the medium can be inferred by measuring the thermoelectric voltage, provided that the two are in thermal equilibrium, i.e. have the same temperature.

[0006] WO 2019 / 063519 A1, a prior art document, discloses a non-invasive temperature measuring device for measuring the temperature of a medium using the wall of a housing surrounding the medium. The temperature measuring device comprises at least one measuring sensor and at least one reference sensor. These two sensors are connected via a common thermally conductive element positioned between the measuring point and the measurement processing device. To provide a robust design for industrial applications and withstand very high and / or very low measurement temperatures, the two sensors are connected to the measurement processing device via a mineral-insulated cable or rod.

[0007] WO 2020 / 035260 A1 discloses a non-invasive temperature measuring device for measuring the temperature of a medium (e.g., a pipe or container) via the wall of a housing surrounding the medium. The device comprises a measuring sensor positioned near a measuring point and a reference sensor positioned between the measuring sensor and a coupling element. The coupling element is connected to mineral-insulated cables connecting the measuring and reference sensors, and the sensors are connected to a value processing device via these cables.

[0008] One drawback of many designs is that they are quite inflexible. The signal processing unit is intended to be mounted head-mounted at one end of one or more mineral-insulated measuring rods. This limits measurements of very high or very low temperatures, as the signal processing electronics must not be exposed to temperatures of approximately 85°C or higher. Very low temperatures can also be a problem. Summary of the Invention

[0009] The problem addressed by the present invention is to provide a temperature measuring device for non-invasive measurement of the temperature of a housing wall or surface under reproducible thermal conditions at the measuring point, with which device very high or very low temperatures can be measured with high measurement accuracy.

[0010] This problem is solved by the temperature measuring device according to the invention. Advantageous embodiments of the invention are described in detail in the detailed description.

[0011] According to the present invention, a temperature measuring device is provided for determining the temperature of a surface or medium using the temperature of the surface surrounding the medium. The temperature measuring device comprises at least one measuring sensor and at least one reference sensor, as well as a value processing device connected to the measuring sensor via a first connecting line and to the reference sensor via a second connecting line. According to the present invention, at least the first of the two connecting lines is partially implemented as a mineral-insulated sheathed cable providing the measuring sensor, wherein both connecting lines comprise flexible cables connected to the value processing device.

[0012] In the special case, if the two connecting lines are thermally coupled, the at least one measuring sensor and the at least one reference sensor are located substantially on the same heat conduction path between the surface and the joint.

[0013] Here, the measuring sensor or reference sensor is essentially located in the tip portion of the connecting line, with which the temperature is to be measured. The sensor is, for example, a resistance sensor, a thermocouple, or any other known thermal sensor element. According to the present invention, at least the first connecting line includes a mineral-insulated sheathed cable provided close to the surface and a flexible cable provided further from the surface. Since the structure of a probe including a mineral-insulated sheathed cable is already known, a detailed description thereof will be omitted.

[0014] The surface temperature is calculated using methods known per se, such as the method described in DE 10 2014 019 365, from the measurement signals of the measuring sensor and the reference sensor.

[0015] To withstand potentially high process temperatures of up to 700°C, mineral insulation must be used. However, this material is rigid. At the joints, the mineral-insulated leads are soldered or fused to the leads of the flexible cable. Flexible cables have lower rigidity than mineral-insulated sheathed cables or rods, making them flexible. Flexible cables enable remote field installation of value processing devices or measurement electronics. Compared to the prior art, the value processing device no longer needs to be head-mounted on the rigid mineral-insulated sheathed cable. This increases measurement flexibility and allows the value processing device to be removed from the high-temperature process.

[0016] In a preferred embodiment, the second connecting line further comprises a mineral insulated sheathed cable. Thus, the reference sensor can also be provided closer to the surface. By doing so, the measurement accuracy and / or response time of the temperature measurement are increased.

[0017] In another preferred embodiment, the flexible cable includes cable insulation having an emissivity greater than 0.9. Consequently, the cable insulation has high thermal radiation. This allows the thermal load on the cable insulation to be reduced more quickly, thereby maintaining the temperature of the cable insulation within the permitted temperature range. Preferably, the emissivity of the cable insulation is greater than 0.95.

[0018] Advantageously, the flexible cable of the first connecting line is provided separately from the flexible cable of the second connecting line. In other words, the connecting lines are not provided as a common wiring harness. Therefore, the flexible cables of both connecting lines are exposed to the ambient air, increasing the surface area of the connecting lines. Each connecting line cools down due to heat radiation and heat conduction, thus allowing the flexible cables to cool down more quickly.

[0019] In a further advantageous development, each flexible cable is divided into several individual wires, including up to four wires. Preferably, the flexible cables are divided in the area of the connector's heat sink structure. Each wire is divided into several parallel individual wires. This increases the total surface area of the wires. By increasing the wire surface, heat radiation and heat conduction also increase, thus maintaining the temperature within an acceptable range. This has the advantage of allowing higher surface temperatures to be measured without damaging the cable insulation due to thermal loads.

[0020] In a preferred embodiment, a heat sink is provided in the area of the joint between at least one mineral insulated sheathed cable and the flexible cable. According to the present invention, a heat sink is a device or measure that further increases heat transfer to the environment. Providing this heat sink in the area of the joint reduces the temperature of the flexible cable. The joint is where the mineral insulated sheathed cable is electrically connected to the flexible cable. This has the advantage of allowing higher surface temperatures to be measured without damaging the cable insulation. It also allows the use of cable insulation with a lower operating temperature. These cable insulations are generally less expensive than those with a higher permissible operating temperature. Consequently, the corresponding temperature measurement equipment is more economical.

[0021] A preferred embodiment provides for the heat sink to be provided as a housing. By using a housing provided on mineral insulation material, the surface area can be significantly increased. This allows for greater heat removal from the mineral insulated sheathed cable. Preferably, the housing is hollow. Alternatively, the housing can contain the connection for the mineral insulated rod and the flexible cable. Thus, the housing is a simple device for reducing temperatures, particularly at the connection points. This allows for a simple reduction in temperature.

[0022] Preferably, the housing has a coating with an emissivity greater than 0.9. Particularly preferably, the coating has an emissivity greater than 0.95. The coating is applied over the entire surface of the housing. Due to the high emissivity of the coating, the thermal radiation of the housing can be further increased. In a preferred embodiment, the housing is powder-coated.

[0023] Advantageously, the housing corresponds to the housing of the head-mounted data processing device. Preferably, the housing has the same dimensions and is positioned identically to the head-mounted data processing device. In other words, the housing represents a virtual data processing device, excluding the electronic measurement equipment within the housing. Such a housing has the advantage of preserving the thermal boundary conditions designed for the head-mounted data processing device. Furthermore, there is no need to recalibrate the device to obtain correct model-based surface temperature measurements. Furthermore, no changes to the calculation software parameters are required.

[0024] In another embodiment of the present invention, at least one end of a mineral insulated sheathed cable includes a region where the mineral insulation is exchanged for a coating having a higher thermal emissivity than the mineral insulation. Preferably, the coating has an emissivity greater than 0.95. By using such a coating, a cooling effect can be achieved, resulting in a lower temperature at the joint than without the coating.

[0025] In an alternative embodiment, or in combination with a heat sink, a thermoelectric cooler is provided in the region of the flexible cable joint, at the mineral insulated sheathed cable. A thermoelectric cooler is an electrical device that utilizes the Peltier effect to generate a heat flux. Such a thermoelectric cooler can be provided as a Peltier element. By providing electrical energy, the heat flux from one side to the other can be increased, thereby actively enhancing the cooling effect of the joint.

[0026] However, thermoelectric coolers can also operate passively. In this mode, the thermoelectric cooler generates energy from the heat at the joint. This energy is preferably supplied to a power supply and / or sensor battery. Since the resistance of the mineral-insulated sheathed cable is known, and the height of the generated current corresponds to the temperature at the joint, this current can also be used as an indicator of the surface temperature.

[0027] In a preferred embodiment, in addition to the first connecting line, the second connecting line is partially provided as a mineral insulated sheathed cable, with the joint for the flexible cables of the first and second connecting lines being provided as a fork. In other words, the mineral insulated sheathed cables of the measuring and reference sensors are separated from each other in the area of the joint. Similarly, the flexible cables of the reference and measuring sensors are separated from each other. Therefore, in the area of the joint, the flexible and mineral insulated cables are not provided as a cable bundle. Consequently, the cables form a forked arrangement. This arrangement has the advantage of increasing the surface area in this area, further improving cooling.

[0028] In another preferred embodiment, a blower such as a piezoelectric fan, synthetic nozzle or even a small fan, phase change material, etc. can be used to stabilize the temperature of the cable sheath connection.

[0029] In another preferred embodiment, the mineral insulated sheath is surrounded by air or some other insulating material well known from other industrial temperature instruments, and a metal neck tube. In a preferred design variant, the rod does not directly contact the neck tube. The neck tube can be secured to the process vessel via a mechanical adapter structure. It can also be connected to a heat sink structure.

[0030] In a preferred embodiment, the device for active or passive cooling comprises at least one additional temperature sensor in its body or close to an outer surface or close to the electronic housing or close to a heat sink structure. These sensors can be connected to the signal processing electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The subject matter of the invention will be explained in more detail in the following description shown in the accompanying drawings, in which:

[0032] Figure 1 is a schematic diagram of a temperature measuring device according to a first embodiment of the present invention;

[0033] Figure 2 is a schematic diagram of a temperature measuring device according to a second embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of a temperature measuring device according to a third embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of a temperature measuring device according to a fourth embodiment of the present invention;

[0036] Figure 5 is a schematic diagram of a temperature measuring device according to a fifth embodiment of the present invention; and

[0037] Figure 6 is a schematic diagram of a temperature measuring device according to a sixth embodiment of the present invention. DETAILED DESCRIPTION

[0038] Figure 1 FIG1 shows a schematic diagram of a temperature measuring device 10 according to a first embodiment of the present invention. The temperature measuring device 10 comprises a measuring sensor 14 and a reference sensor 18. In this embodiment, the measuring sensor 14 is almost in contact with the surface S, while the reference sensor 18 is arranged slightly away from the surface S. With the temperature measuring device 10, the surface temperature T S In this embodiment, the surface S surrounds the medium 22, for example inside a pipe. The medium 22 can thus have a temperature of, for example, up to 100° C., 700° C. or more and down to −50° C. or less.

[0039] In order to evaluate the surface temperature T S The temperature measuring device 10 further comprises a value processing device 26. With the temperature measuring device 10, the surface temperature T can be measured by S The measuring sensor 14 is connected to the value processing device 10 via a first connecting line 30 . Likewise, the reference sensor 18 is connected to the value processing device 26 via a second connecting line 34 .

[0040] Connecting lines 30, 34 include at least a portion provided as a mineral insulated sheathed cable 38 and a portion provided as a flexible cable 42. The mineral insulated sheathed cable 38 has an outer metal sheath surrounding at least two inner cables, which are insulated from the outer sheath with a highly compressed metal oxide powder. The portion provided as the mineral insulated sheathed cable 38 is located on one side of the sensors 14, 18, with the flexible cable 42 connected to the value processing device 26. By using the flexible cable 42, the value processing device 26 can be remotely connected to the surface. The mineral insulated sheathed cable 38 and the flexible cable 42 are connected at a joint 46.

[0041] In this embodiment, the mineral-insulated sheathed cables 38 of the reference and measurement sensors 18 and 14 are at least partially located within a gas-filled neck tube 40, and the mineral-insulated sheathed cables 38 are provided together as a single component. Furthermore, the flexible cables 42 of the measurement and reference sensors 14 and 18 are also provided together as a cable harness. The flexible cables 42 include cable insulation with an emissivity greater than 0.9. This insulation allows a significant amount of heat to be dissipated to the surrounding environment, thereby maintaining the temperature of the flexible cables 42 within an acceptable range.

[0042] exist Figure 2 , a schematic diagram of a temperature measuring device 10 according to a second embodiment of the present invention is shown. Figure 1 The embodiment in FIG. 1 differs in that a heat sink 50 is provided. Heat sink 50 can be provided, for example, as a housing or a body with fins. Housing 50 is positioned at mineral insulated sheathed cable 38 and near connector 46 of flexible cable 42. In this embodiment, housing 50 is essentially hollow but has a coating with an emissivity greater than 0.9. Due to the coating and the high surface area of housing 50, a significant cooling effect is achieved. Heat sink 50 collects heat from the environment when the ambient temperature is higher than that of the cold surface S measured by surface S.

[0043] Figure 3 A schematic diagram of a temperature measurement device 10 according to a third embodiment of the present invention is shown. In this embodiment, a coating 54 is provided on the mineral insulated sheathed cable 38, shortly before the joint 46 of the flexible cable 42. The coating 54 thus has an emissivity that is higher than the emissivity of the mineral insulated sheathed cable 38. Thus, the coating 54 acts as a heat sink, significantly reducing the temperature of the mineral insulated sheathed cable 38 before the joint 46 of the flexible cable 42.

[0044] and Figure 1 and Figure 2 Compared with the embodiment of Figure 3 In this embodiment, the flexible cables 42 are not provided as a single cable harness. In this embodiment, the flexible cables 42 for the first connection 30 and the second connection 34 are provided separately. This increases heat transfer to the environment, thereby reducing the temperature of the flexible cables 42. In another embodiment (not shown), each flexible cable 42 can be split into up to four wires. This further increases the surface area of the flexible cables 42, thereby improving heat exchange with the environment.

[0045] Figure 4 A fourth embodiment of the temperature measuring device 10 is shown in FIG. Figure 1 and Figure 2The embodiment shown differs in that a thermoelectric cooler 58 is provided. The thermoelectric cooler 58 can thus be a Peltier element. In this embodiment, the thermoelectric cooler 58 is provided in the region of the connector 46 of the flexible cable 42. The thermoelectric cooler 58 thus actively cools the temperature to a value acceptable to the flexible cable 42.

[0046] Figure 5 A schematic diagram of a temperature measuring device 10 according to a fifth embodiment of the invention is shown. In this embodiment, the neck 40 is split or widened at its end near the cable connector 46, for example to extend the thermal interaction with the environment.

[0047] At opposite ends of measurement sensor 14 and reference sensor 18, the mineral insulated sheathed cables 38 of reference sensor 18 and measurement sensor 18 are separated from each other. Similarly, the ends of flexible cables 42 are separated. The ends of mineral insulated sheathed cables 38 and corresponding flexible cables 42 are electrically connected to each other in a bifurcated arrangement. This arrangement improves cooling at the joint 46 between the mineral insulated sheathed cables 38 and the flexible cables 42.

[0048] Figure 6 A schematic diagram of a temperature measuring device 10 according to a sixth embodiment of the present invention is shown. Figure 2 The embodiment shown. However, the housing 50 in this embodiment is not arbitrary, but rather is primarily or substantially the same housing, or a housing very similar in terms of its thermal interaction with the environment, as described below for the head-mounted device. In contrast to the head-mounted device, the housing does not include the electronic equipment. This equipment is housed in the value processing device 26. In addition, the housing 50 is also arranged in approximately the same position as in the head-mounted device, namely, in the area of the connector 46.

[0049] Reference Signs List

[0050] 10: Temperature measuring equipment

[0051] 14: Measuring sensor

[0052] 18: Reference sensor

[0053] 22: Medium

[0054] 26: Value processing device

[0055] 30: First connecting line

[0056] 34: Second connecting line

[0057] 38: Mineral insulated sheathed cable

[0058] 40: Neck tube

[0059] 42: Flexible cable

[0060] 46: Connector

[0061] 50: Radiator / housing

[0062] 54: coating

[0063] 58: Thermoelectric Cooler

[0064] S: Surface

[0065] T S : Surface temperature

Claims

1. A temperature measuring device (10) for determining the temperature of a surface (S) or a medium (22) surrounding the medium (22) by means of the temperature of the surface (S) of the medium (22), comprising at least one measuring sensor (14) and at least one reference sensor (18) and a value processing device (26), the value processing device (26) being connected to the measuring sensor (14) via a first connecting line (30) and to the reference sensor (18) via a second connecting line (34), wherein of the two connecting lines (30, 34), at least the first connecting line (30) is partially realized as a mineral insulated sheathed cable (38) providing the measuring sensor (14), and The two connecting lines (30, 34) comprise flexible cables (42) connected to the value processing device (26), and a heat sink (50) is provided in the region of a joint (46) of the flexible cable (42) of the at least one mineral insulated sheathed cable (38).

2. The temperature measuring device (10) according to claim 1, characterized in that The flexible cable (42) includes cable insulation having an emissivity greater than 0.

9.

3. The temperature measuring device (10) according to claim 1 or 2, characterized in that The flexible cable (42) of the first connection line (30) is provided separately from the flexible cable (42) of the second connection line (34).

4. The temperature measuring device (10) according to claim 1 or 2, characterized in that Each flexible cable (42) is divided into a number of individual wires, including up to four wires.

5. The temperature measuring device (10) according to claim 1, characterized in that The heat sink (50) is provided as a housing.

6. The temperature measuring device (10) according to claim 5, characterized in that The housing has a coating with an emissivity greater than 0.

9.

7. The temperature measuring device (10) according to claim 5 or 6, characterized in that The housing corresponds to a housing of a head-mounted data processing device.

8. The temperature measuring device (10) according to claim 1 or 2, characterized in that The end of the at least one mineral insulated sheathed cable (38) includes a region where the mineral insulation is exchanged by a coating (54) having a thermal emissivity higher than that of the mineral insulation.

9. The temperature measuring device (10) according to claim 1 or 2, characterized in that A thermoelectric cooler (58) is provided alternately or together with the heat sink at the mineral insulated sheathed cable (38) in the region of the joint of the flexible cable (42).

10. The temperature measuring device (10) according to claim 1 or 2, characterized in that In addition to the first connecting line (30), the second connecting line (34) is provided partly as a mineral insulated sheathed cable (38), wherein the joint (46) of the flexible cable (42) of the first connecting line and the second connecting line (30, 34) is provided as a fork.

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