Temperature measuring device

Abstract

Temperature measuring device comprising a measuring element (12), a connection element (14) with a housing, a line arrangement (16), wherein the line arrangement (16) comprises at least sectionally connecting lines (46), a data acquisition device (20), wherein the data acquisition device (20) is connected to the measuring element (12) by means of the line arrangement (16), at least one thermocouple with at least two different thermocouple wires (32), each having two opposite ends, wherein the two thermocouple wires (32) are connected to each other at one end in a measuring point (34a, 34b, 34c) and at the other end each to a connecting line forming a connection point, wherein the measuring point (34a, 34b, 34c) is provided in the measuring element (12) and the connection points between connecting leads (46) and thermowire (32) are located inside the housing, characterized in that the conductor arrangement (16) has a first conductor section (40) which comprises an outer sheath (44) with a first end and an oppositely located second end, wherein the at least two connecting leads (46) are guided in the outer sheath (44), the outer sheath (44) is firmly connected to the connecting element (14) in the region of its first end and the outer sheath (44) is filled inside with an electrically insulating, high-temperature-resistant material.

Description

[0001] The present invention relates to a temperature measuring device, in particular a temperature measuring device which is suitable for use at very high temperatures, such as those that occur in the manufacture of glass.

[0002] Melting glass requires very high temperatures, which can range from 1500°C to 1600°C. Most processes for manufacturing glass products from molten glass necessitate monitoring the temperature of the molten glass itself. Due to these extremely high temperatures, the temperature measuring devices used must meet very high standards. In practice, thermocouples have proven to be suitable temperature measuring devices for monitoring the temperature during glass production, particularly for measuring the temperature of molten glass.

[0003] Thermocouples are very versatile and can be used to measure both very low and very high temperatures. A thermocouple consists of two different thermocouple wires connected at a measuring point. To determine the temperature, the thermocouple wires are brought to the point of measurement. The thermally induced voltage in the thermocouple wires is detected by a signal acquisition device, such as a resistance meter, located some distance from the measuring point. Depending on the temperature range in which the thermocouple is used, the materials of the thermocouple wires and the components required for its operation vary.

[0004] Since thermocouples are used in environments where temperatures can cause some materials to melt or decompose, at least the parts of the thermocouple that come into contact with a measuring point at very high temperatures must be made of materials that can withstand high temperatures. Additionally or alternatively, the environmental conditions at the measurement point can trigger chemical reactions in the materials used, especially the thermocouple wires, so these materials, particularly the thermocouple wires, must be protected accordingly.

[0005] For use in very high temperature ranges and / or chemically reactive environments, ceramic-insulated thermocouples have proven effective. In a ceramic-insulated thermocouple, the thermocouple wires required for its function are contained within a ceramic insulating rod. Using this ceramic insulating rod and, if necessary, additional protective devices such as platinum shielding tubes, the thermocouple wires can be positioned at the desired measurement location, for example, in a glass melting furnace, to measure the temperature of the molten glass.

[0006] The voltage difference measurement necessary for determining the temperature is performed remotely from the actual point being measured, in a moderate-temperature environment, so that the signal acquisition devices, especially resistance meters, are not damaged. For this reason, the thermocouple wires often need to be very long.

[0007] Especially when using thermocouples in a melt at very high temperatures, thermocouple wires with very high temperature resistance must be used. Such wires are made of a platinum and rhodium alloy and are therefore comparatively expensive.

[0008] It is known that extending thermocouple wires by using cost-effective compensating leads, for example made of copper, also yields satisfactory measurement results. Compensating leads consist of substitute materials that differ from those of the thermocouple wires but possess the same thermoelectric properties within a permissible temperature range. These compensating leads can be connected to the thermocouple wires using appropriate connectors. Suitable connectors, typically housed in a terminal block, are provided for connecting the thermocouple wires to the compensating leads. For cost reasons, the terminal blocks should therefore be located as close as possible to the measuring point.

[0009] Also for cost reasons, the connection head is usually made of lightweight metal, such as aluminum. Seals and washers required in the connection head are usually made of carbon-based materials, such as plastic. As is well known, carbon-based plastics generally do not have very high temperature resistance. The use of such connection heads and corresponding sealing elements is therefore typically limited to a temperature range between 100°C and 200°C.

[0010] If the connection heads are located too close to the high-temperature point being measured, such as a glass melting furnace, there is a risk that the materials made of organic substances will soften, melt, or burn depending on the temperature, which can damage the connection head. Furthermore, such changes in material state usually lead to a so-called "poisoning" of the thermocouple wires and thus to the failure of the thermocouple.

[0011] In processes involving extremely high temperatures, such as glass manufacturing, there is always a risk of significant temperature fluctuations occurring even at a relatively large distance from the actual measurement point. These fluctuations can generate temperatures so high that they can damage the connecting elements or the sensor head. Therefore, a sufficient safety distance must be maintained, meaning the sensor head must not be positioned too close to the measurement point. However, this safety distance is often impractical and inevitably leads to the use of longer and more expensive thermocouple wires.

[0012] It is therefore an object of the present invention to provide an improved temperature measuring device that is suitable for use in high-temperature environments, for example, in glass manufacturing processes, is cost-effective to manufacture, and reliably provides accurate temperature readings. In particular, it is an object of the present invention to provide a thermocouple with extended thermocouple wires in which the safety distance between the terminal head and the measuring point can be reduced.

[0013] According to the invention, the problem is solved by a temperature measuring device comprising a measuring element, a connection element with a housing, a cable arrangement, wherein the cable arrangement comprises at least sectional connection cables, and a data acquisition device, wherein the data acquisition device is connected to the measuring element by means of the cable arrangement, at least one thermocouple with at least two different thermocouple wires, each having two opposite ends, wherein the two thermocouple wires are connected to each other at one end in a measuring point and at the other end each to a connection cable forming a connection point, wherein the measuring point is provided in the measuring element, the connection points between the connection cable and the thermocouple wire are located inside the housing, wherein the cable arrangement has a first cable section,comprising an outer sheath with a first end and an oppositely located second end, wherein the at least two connecting leads are guided in the outer sheath, the outer sheath is firmly connected to the connecting element in the area of ​​its first end and the outer sheath is filled inside with an electrically insulating, high-temperature-resistant material.

[0014] The temperature measuring device is, for example, a thermocouple in which the measuring element has a protective sheath containing the thermocouple wires. The measuring point is electrically isolated from the sheath. As is known from the prior art, the sheath can be composed of several elements, in particular several layers or sheaths.

[0015] The two thermocouple wires are each extended by means of corresponding connecting leads, so that the voltage difference between the two thermocouple wires can be measured in a data acquisition device located remotely from the measuring point, such as a resistance meter. The connection between the connecting lead and the thermocouple wire is housed in the casing of the connection element. The connection element can be, for example, a terminal block.

[0016] The basic idea of ​​the invention is to make the connection head of existing thermocouples more temperature-resistant by avoiding temperature-sensitive materials such as plastics as much as possible. The concrete implementation of this idea consists of routing the connecting leads inside an outer sheath or casing filled with an electrically insulating, high-temperature-resistant material.

[0017] In the area of ​​the first conductor section, this increases the temperature resistance of the temperature measuring device. The outer sheath can be completely or partially filled with the electrically insulating, high-temperature-resistant material. Crucially, the connecting conductors located within the outer sheath must be electrically insulated from one another. The electrically insulating, high-temperature-resistant material can surround the connecting conductors at least partially. Preferably, the connecting conductors within the outer sheath are each completely surrounded by the electrically insulating, high-temperature-resistant material.

[0018] In a preferred embodiment, the outer casing is filled with high-temperature resistant powder, in particular cast with a high-temperature cement.

[0019] To withstand high ambient temperatures, it is advantageous for the housing of the connection element and / or the outer sheath to be made of stainless steel. Particularly high temperature resistance is achieved by using a high-temperature-resistant stainless steel for the housing of the connection element and / or the outer sheath.

[0020] It is particularly preferred that both the housing of the connection element and the outer sheath are made of stainless steel, especially high-temperature-resistant stainless steel. This allows for a simple, temperature-resistant, and tight connection between the housing of the connection element and the outer sheath. For example, the housing of the connection element and the outer sheath can be joined by welding.

[0021] The measuring element is preferably also firmly and tightly connected to the connecting element, in particular welded to the connecting element.

[0022] In a preferred embodiment, the connecting element comprises a sleeve with a first end face and a second end face, wherein the measuring element is arranged on the first end face and the outer casing on the second end face of the connecting element. This is a very cost-effective design of the connecting element, since the sleeve can be part of the housing.

[0023] To create a tight connection between the outer shell and the connecting element, it is advantageous to have a cover with an opening on the second end face of the connecting element through which the first end of the outer shell protrudes.

[0024] In a preferred embodiment, the measuring element comprises a support tube which is firmly connected at one end to the connecting element. If both the connecting element and the support tube are made of a metal such as stainless steel, the connecting element and the support tube can be joined together, for example, by welding.

[0025] By means of the measures already mentioned, it is possible to reduce the proportion of temperature-sensitive plastic materials in the area of ​​the connection point between connecting cables and thermowires, so that the temperature resistance of the measuring device in the area of ​​the connection point can be increased.

[0026] To further reduce the use of plastic materials, it is advantageous that the connecting wires located within the outer sheath consist solely of electrically conductive materials, at least in the area of ​​the outer sheath's first end. Thus, these connecting wires, at least in the area of ​​the outer sheath's first end, are made entirely of metal wires. In this case, it is understood that the individual metal wires are spaced apart and each is surrounded by electrically insulating, high-temperature-resistant material, preventing any short circuits between the connecting wires.

[0027] If the two connecting cables are embedded at a distance from each other in the thermally insulating material, it is possible to do without the cable insulation of the connecting cables, which is usually made of plastic, and thus without plastic materials.

[0028] It is further advantageous that a second cable section is provided, which forms an extension of the first cable section at the second end of the outer sheath. This second cable section has a first end and an oppositely positioned second end and is flexible. This allows the measuring device to be flexibly installed at any desired location. The flexible second cable section also allows structural obstacles between the data acquisition device and the measuring tip to be overcome.

[0029] For example, the second conductor section can have a flexible sheath in which the at least two connecting leads are guided. In this case, the flexible sheath can be made of a plastic, since it can be assumed that the ambient temperatures decrease with increasing distance between the measuring tip and the conductor section, so that the temperatures are in a range where the plastic no longer deforms. In this embodiment, it is understood that the two connecting leads are each electrically insulated from each other within the flexible sheath. This can be achieved by providing the electrical insulation normally found on connecting leads.

[0030] The transition from the first pipe section to the second pipe section can, for example, be achieved using a transition element. According to a preferred embodiment, a transition element is provided which is firmly connected to the first pipe section in the region of its second end. In particular, the transition element can be a sleeve made of stainless steel. It can be made of high-temperature-resistant stainless steel, but this is no longer strictly necessary.

[0031] As is known from the prior art, it is advantageous for the connecting cable to have an electrical conductor wire that, within a defined temperature range, possesses the same thermoelectric properties as the thermoelectric wires. In this case, the connecting cable is a compensating cable.

[0032] Alternatively, the connecting cable may have a metallic conductor wire with different thermoelectric properties than the thermoelectric wires. In this case, the connecting cable is no longer a compensating cable. For example, the connecting cable could be made of a base metal such as copper or nickel. This has the advantage that the connecting cable has conductor wires made of materials with a higher temperature resistance than those that would have the same thermoelectric properties as the thermoelectric wires if used as a compensating cable.

[0033] Particularly in cases where the connecting leads have an electrical conductor with different thermoelectric properties than the thermoelectric wires, it is advantageous to provide an additional temperature measuring device, especially a resistance sensor or measuring resistor, inside the connecting element. Using the temperatures known inside the connecting element, the voltage difference between the connecting leads detected by the data acquisition device can be corrected accordingly to accurately reflect the temperature actually measured by the temperature measuring device.

[0034] The resistance temperature measuring device could, for example, be a measuring resistor such as a PT100, PT1000 or NTC.

[0035] To measure the temperature inside the connection element, the additional temperature measuring device must have electrical leads that connect it to the data acquisition device. It is advantageous for the electrical leads of the additional temperature measuring device to be routed parallel to and at a distance from the connection leads within the outer sheath.

[0036] In a preferred embodiment, at least two additional thermocouple wires are provided in the measuring tip, wherein each thermocouple wire is connected to a connecting lead and the additional connecting leads are electrically insulated from each other inside the outer sheath, parallel to the existing connecting leads.

[0037] Preferred embodiments are explained in more detail with reference to the accompanying drawings, which show: Fig. 1 a temperature measuring device, Fig. 2 a cross-section through the measuring tip of the measuring element, Fig. 3 a cross-section through the temperature measuring device in the area of ​​the connection element.

[0038] The Fig. Figure 1 shows a temperature measuring device 10 with a measuring element 12, a connection element 14, a cable arrangement 16, a plug 18 and a data acquisition device 20.

[0039] The measuring element 12 comprises a measuring tip 22 with a protective tube 24, a protective sleeve 26, and a support tube 28. The protective tube 24 has a front end and a rear end, with the tubular protective sleeve 26 being located at the front end of the protective tube 24. The support tube 28 is located at the rear end of the protective tube 24 and surrounds it.

[0040] Furthermore, an insulating rod 30 made of a ceramic material is to be inserted, which runs inside the protective cover 26 and the protective tube 24 (see Fig. 2) The insulation rod 30 is connected by means of a Fig. The metallic fixing ring 31 shown in the illustration is firmly connected to the protective tube 24.

[0041] The protective casing 26 is made of platinum and / or rhodium. The protective tube 24 is made of ceramic and the support tube 28 is made of high-temperature-resistant stainless steel.

[0042] Inside the insulating rod 30 are three thermocouple wire pairs, each consisting of two different thermocouple wires 32. The individual thermocouple wires 32 are spaced apart within the insulating rod 30 and aligned parallel to its longitudinal axis. Each thermocouple wire pair has two opposite ends. At one end, both thermocouple wires 32 of each pair are connected at a measuring point 34a, 34b, 34c. The other end of each thermocouple wire 32 protrudes from the insulating rod 30. The measuring points 34a, 34b, 34c are located in the measuring tip 22, while the free ends are located in the area of ​​the support tube 28. The thermocouple wires 32 are made of platinum or a platinum-rhodium alloy.

[0043] The line arrangement 16 comprises a first line section 40 and a second line section 42.

[0044] The first conductor section 40 is formed from a metallic outer sheath 44 with a first end and an oppositely located second end, with connecting conductors 46 being guided inside (see Fig. 3).

[0045] The connecting leads 46 comprise metal wires made of a less expensive material than those of the thermowires 32. For example, these are made of copper or nickel.

[0046] The outer sheath 44 is made of a high-temperature resistant material, such as high-temperature resistant stainless steel. Inside the outer sheath 44 is an electrically insulating, high-temperature resistant material, in particular a high-temperature resistant powder. The connecting leads 46, which are guided within the outer sheath, consist of a pure metal conductor without cable insulation and are spaced apart from one another, aligned parallel to the longitudinal direction of the outer sheath, and embedded in the electrically insulating, high-temperature resistant material.

[0047] The connecting leads 46 protrude from the outer sheath 44 at its end face and are connected to the thermocouple wires 32 protruding from the insulating rod 30. Each thermocouple wire 32 forms a connection point with a connecting lead 46.

[0048] The connection points between connecting leads 46 and thermocouple wire 32 are all located in the connection element 14 to protect the connection points. The connection element 14 comprises a sleeve 48, the sleeve 48 having a first and a second end face.

[0049] The connecting element 14 is connected at its first end face to the support tube 28 of the measuring element 12. The support tube 28 has a smaller outer diameter than the sleeve 48 of the connecting element 14, so that the end section of the support tube 28 projects into the sleeve 48. The sleeve 48 and the support tube 28 are firmly and tightly connected to each other.

[0050] On the second end face is a cover 50 with an opening 52, the opening being surrounded by a nozzle 54. The cover 50 is firmly connected to the sleeve. Both the sleeve 48 and the cover 50 are made of a high-temperature-resistant metal, such as high-temperature-resistant stainless steel, so that the cover 50 can be firmly and tightly connected to the sleeve 48. For example, the cover 50 and the sleeve 48 can be welded together.

[0051] The outer sheath 44 protrudes with its first end section through the opening 52 of the cover 50 and is firmly connected to the cover. Inside the connection element 14 is a measuring resistor 56, which is connected to the data acquisition device 20 via appropriate electrical leads 58. The measuring resistor can be a PT100, PT1000, or an NTC.

[0052] Similar to the connecting leads 46, the electrical leads 58 of the measuring resistor 56 are pure metal wires, arranged without cable insulation, spaced apart from each other and from the connecting leads 46, and aligned parallel to the longitudinal direction of the outer sheath. The electrical leads 58 are also embedded in the electrically insulating, high-temperature-resistant material.

[0053] The second conductor section 42 comprises a flexible sheath in which the connecting leads and the electrical leads of the measuring resistor 56 are guided. The connecting leads and electrical leads in the second conductor section are the same as in the first conductor section 40, except that, unlike the connecting leads 46 and electrical leads 58 in the first conductor section 40, the connecting leads and electrical leads in the second conductor section 42 each have cable insulation to prevent short circuits between the connecting leads and the electrical leads of the measuring resistor.

[0054] The first conductor section 40 and the second conductor section 42 are connected to each other by means of a transition element 60. The transition element 60 is a sleeve that is connected at one end face to the second end of the outer sheath 44 of the first conductor section 40 and at the other end face to the flexible sheath of the second conductor section 42.

[0055] The second line section 42 terminates in the connector 18. The connector 18 is in turn connected to the data acquisition device 20.

[0056] Typically, the connecting leads have an electrical conductor wire that has the same thermoelectric properties as the thermoelectric wires.

[0057] In the illustrated embodiment, however, the connecting leads 46 have an electrical conductor wire that possesses different thermoelectric properties than the thermoelectric wires 32. This has the advantage that materials with a higher temperature resistance can be used for the conductor wires of the connecting leads 46 than the conductor wires of the connecting leads that would have the same thermoelectric properties as the thermoelectric wires 32.

[0058] In the event that the connecting leads 46 have an electrical conductor wire with different thermoelectric properties than the thermoelectric wires 32, the measuring resistor 56 is provided inside the connecting element 14. A temperature measurement can be carried out in the connecting element 14 by means of the measuring resistor 56, and the measured values ​​acquired by the measuring resistor can be used to correct the data acquired in the data acquisition device.

[0059] All of the measures mentioned contribute to making the temperature measuring device in the area of ​​the connection element 14 more heat-resistant, so that the connection element 14 can be positioned relatively close to measuring points that are exposed to very high temperatures.

[0060] To measure the temperature, the measuring tip 22 is placed at the desired location. The resistance between the thermocouple wires 32 and the value obtained from the measuring resistor are recorded in the data acquisition device 20. In a processing unit (not shown), the values ​​from the data acquisition device 20 are processed so that the temperature value present at the measuring point can be determined from the recorded values.

[0061] Instead of the one in the Fig. Other thermocouple measuring elements known from the prior art can also be used instead of the measuring element 12 shown in Figures 1 to 3. In particular, other temperature-resistant materials can be used for the manufacture of the measuring element 12.

[0062] In embodiments not shown, the number of thermocouples may vary. For example, fewer than three or more than three thermocouples may be provided.

[0063] In an embodiment not shown, in which the connecting leads have an electrical conductor wire which has the same thermoelectric properties as the thermowires, the measuring resistor 56 can be omitted.

Claims

[1] Temperature measuring device comprising a measuring element (12), a connection element (14) with a housing, a line arrangement (16), wherein the line arrangement (16) comprises at least sectionally connecting lines (46), a data acquisition device (20), wherein the data acquisition device (20) is connected to the measuring element (12) by means of the line arrangement (16), at least one thermocouple with at least two different thermocouple wires (32), each having two opposite ends, wherein the two thermocouple wires (32) are connected to each other at one end in a measuring point (34a, 34b, 34c) and at the other end each to a connecting line forming a connection point, wherein the measuring point (34a, 34b, 34c) is provided in the measuring element (12) and the connection points between connecting leads (46) and thermowire (32) are located inside the housing,characterized by , that the conductor arrangement (16) has a first conductor section (40) comprising an outer sheath (44) with a first end and an opposite second end, wherein the at least two connecting conductors (46) are guided in the outer sheath (44), the outer sheath (44) is firmly connected to the connecting element (14) in the area of ​​its first end and the outer sheath (44) is filled inside with an electrically insulating, high-temperature resistant material. [2] Temperature device according to claim 1, characterized by , that the outer shell (44) is filled with a high-temperature resistant powder, in particular cast with a high-temperature cement. [3] Temperature device according to one of the preceding claims, characterized by , that the connecting element (14) and / or the outer sheath (44) is made of stainless steel, in particular of high-temperature resistant stainless steel. [4] Temperature device according to one of the preceding claims, characterized by , that the connecting element (14) comprises a sleeve (48) with a first end face and a second end face, wherein the measuring element (12) is arranged on the first end face and the outer shell (44) is arranged on the second end face of the connecting element (14). [5] Temperature device according to claim 4, characterized by , that a cover (50) with an opening (52) is provided on the second end face of the connecting element (14), through which the first end of the outer sheath (44) protrudes. [6] Temperature device according to claim 4 or 5, characterized by , that the measuring element (12) comprises a support tube (28) which is firmly connected at one end to the connecting element (14). [7] Temperature device according to one of the preceding claims, characterized by, that the connecting leads located in the outer sheath (44) consist only of electrically conductive material, at least in the area of ​​the first end of the outer sheath (44). [8] Temperature device according to one of the preceding claims, characterized by , that the line arrangement (16) has a second line section (42) which forms an extension of the first line section (40), wherein the second line section (42) has a first end and an opposite second end and is designed to be flexible. [9] Temperature device according to claim 8, characterized by , that the second conductor section (42) has a flexible sheath in which the at least two connecting conductors are guided. [10] Temperature device according to claim 7 or 8, characterized by, that a transition element (60) is provided which is firmly connected to the first line section (40) in the area of ​​the second end of the first line section (40). [11] Temperature device according to claim 10, characterized by , that the transition element (60) is a sleeve made of stainless steel, in particular made of high-temperature resistant stainless steel. [12] Temperature device according to one of the preceding claims, characterized by , that the connecting leads (46) have an electrical conductor wire which has different thermoelectric properties than the thermoelectric wires (32). [13] Temperature device according to one of the preceding claims, characterized by , that an additional temperature measuring device, in particular a measuring resistor (56) is provided inside the connection element (14). [14] Temperature device according to claim 13, characterized by, that the additional temperature measuring device has electrical leads that connect the additional temperature measuring device to the data acquisition device (20), wherein the electrical leads are guided in the outer sheath (44). [15] Temperature device according to one of the preceding claims, characterized by , that at least two further thermowires (32) of a thermocouple are provided in the measuring element (22), wherein each thermowire (32) is connected to a connecting lead (46) and the additional connecting leads (46) are guided inside the outer sheath (44).

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