SENSOR UNIT WITH HEAT INSULATION

Abstract

The invention relates to a sensor arrangement (100) configured for measuring a fill level, a limit level, and / or a pressure, comprising an antenna (110) for transmitting and / or receiving a measurement signal, a waveguide (120) with a first waveguide section (121) for connecting to the antenna (110) and a second waveguide section (122) configured for transmitting the measurement signal, and a thermal insulation element (130). The thermal insulation element (130) is arranged between the first and second waveguide sections (121, 122) and is configured to at least partially prevent heat conduction between the first and second waveguide sections (121, 122).The invention further relates to a thermal insulation element (130) for a sensor arrangement (100), the use of a thermal insulation element (130) for thermal insulation of electronics (150) of a level, limit level and / or pressure measuring device and the use of a sensor arrangement in a process plant.

Description

Reference to related application

[0001] This application claims priority from German patent application No. 10 2022 213 160.6, filed on December 6, 2022, which is incorporated in its entirety by reference into this document. Field of the invention

[0002] The invention relates to a sensor arrangement for measuring a fill level, a limit level and / or a pressure, a thermal insulation element for a sensor arrangement, the use of a thermal insulation element for thermally insulating electronics with a radar chip of a fill level, limit level and / or pressure measuring device and the use of a sensor arrangement for fill level, limit level and / or pressure measurement in a process plant. Technical background

[0003] In modern process plants, many field devices and measuring instruments are installed both stationary and distributed to collect measurement, parameterization, and diagnostic data. These field devices are often used outdoors or in demanding environments, such as those with high operating temperatures. Such field devices feature, for example, a waveguide that can transmit a measurement beam from the measurement electronics to an antenna or vice versa. The reliability and stability of the field devices are of great importance for long-term use. Summary of the invention

[0004] It is an object of the invention to provide a flexible and robust measuring sensor in a process plant.

[0005] This problem is solved by the features of the independent patent claim. Further developments of the invention emerge from the subclaims and the following description.

[0006] One aspect of the invention relates to a sensor arrangement configured to measure a fill level, a limit level, and / or a pressure, and comprising an antenna configured to transmit and / or receive a measurement signal, a waveguide, and a thermally insulating element. The waveguide comprises a first waveguide section for connection to the antenna and a second waveguide section and is configured to transmit the measurement signal. The second waveguide section can, for example, be configured to connect to a high-frequency electronics unit.

[0007] The thermal insulation element can serve as a connecting element for the waveguide sections for thermal insulation or to reduce the passage of thermal energy from one waveguide section to the other. Therefore, the thermal insulation element can have a higher thermal resistance or a higher specific thermal resistance than the waveguide, or the first waveguide section and the second waveguide section.

[0008] The thermal insulation element is arranged between the first waveguide section and the second waveguide section and is designed to at least partially prevent heat conduction between the first waveguide section and the second waveguide section.

[0009] The sensor arrangement may be a radar sensor arrangement. The sensor arrangement may, for example, comprise a radar sensor, which may be a level sensor, a limit sensor, and / or a pressure sensor.

[0010] The level, limit, and / or pressure sensor may further comprise an external, wired power supply, which may be electrically connected to the electronics to provide the necessary power to operate the sensor assembly. Alternatively, the sensor assembly may comprise a self-contained radar sensor, which may have an internal power supply, such as a battery, accumulator, energy harvesting system, or solar cell.

[0011] According to one embodiment, the antenna of the sensor arrangement is a horn antenna or a parabolic antenna.

[0012] For example, the antenna used as a radar antenna can be a metallic antenna or a plastic antenna, the interior of which can be metallized. Furthermore, the antenna can be connected to the waveguide or the waveguide. For example, the antenna can be integral or integrated with the first waveguide section.

[0013] The first waveguide section, which may be a waveguide lower part, may, for example, be a tubular waveguide section. And the second waveguide section, which may be a waveguide upper part, may, for example, also be a tubular section. The first or second tubular waveguide section may have a circular or rectangular cross-section, for example, for transmitting the measurement signal at a frequency of 240 GHz. Thus, the waveguide for the radar sensor may be discontinuous, allowing the thermal insulation element or thermal insulator to be arranged therebetween.

[0014] The first waveguide section can have the same inner diameter and, if appropriate, the same outer circumference as the second waveguide section. Alternatively, the first waveguide section can have a different outer circumference than the second waveguide section, wherein the inner diameters of the first and second waveguide sections can be kept the same size.

[0015] For example, the waveguide can be made of a metal, such as copper or stainless steel. In particular, the first waveguide section can be made of the same metal as the second waveguide section and / or the antenna.

[0016] With the same inner diameter and the same material or metal of the antenna and the waveguide with the first and second waveguide sections, the sensor arrangement can be designed such that the measurement signal or the radar signal can be transmitted at the transition points without interference and without interruption.

[0017] According to one embodiment, the heat insulating element can be tubular.

[0018] For example, the tubular thermal insulation element may have a circular profile or a rectangular profile for a measurement signal with a frequency of 240 GHz.

[0019] According to a further embodiment, the heat insulating element has an inner wall which is at least partially metallized.

[0020] The inner wall of the thermal insulation element can be formed as a bore or a feedthrough and configured to transmit the measurement signal between the first and second waveguide sections. The metallization of the inner wall can thus serve to optimally transmit the measurement signal, particularly if the inner wall can be metallized with the same metal as the first and second waveguide sections and / or the antenna. The inner wall transitions between the first waveguide section and the thermal insulation element, and between the thermal insulation element and the second waveguide section, can be designed without steps, continuous, and gap-free.

[0021] According to a further embodiment, the heat insulating element consists of a heat insulating material.

[0022] By means of the heat-insulating material, the heat-insulating element can be configured in such a way as to prevent the heat from being drawn up or reaching another component of the sensor arrangement, for example an electronics unit of the sensor arrangement, in particular if a radar chip can be provided on the electronics unit of the sensor arrangement.

[0023] According to a further embodiment, the heat-insulating material is a plastic or a ceramic.

[0024] According to a further embodiment, the heat-insulating material is the plastic PEEK or the ceramic is a silicate ceramic or a zirconium oxide (ZrO) ceramic.

[0025] The thermally insulating material can have a lower thermal conductivity than the metallic waveguide. For example, a copper waveguide can have a conductivity of 401 W / (m·K), or a stainless steel waveguide can have a conductivity of 15 W / (m·K). The high-temperature-resistant thermoplastic polyetheretherketone (PEEK) as the thermally insulating material has a conductivity of 0.25 W / (m·K) and can be used to prevent heat transfer from the sensor assembly to a copper or stainless steel waveguide. Zirconium oxide (ZrO) ceramic with a thermal conductivity of 2 W / (m·K) can also be suitable for a copper or stainless steel waveguide. In contrast, an aluminum oxide (Al2O3) ceramic with a thermal conductivity of 30 W / (m·K) can be a suitable thermally insulating material for a copper waveguide, but not for a stainless steel waveguide.

[0026] According to a further embodiment, the thermal insulation element of the sensor arrangement comprises a first insulation element section configured to receive the first waveguide section and a second insulation element section configured to receive the second waveguide section. The thermal insulation element is configured to lower the temperature of the sensor arrangement along the length of the thermal insulation element between the first insulation element section and the second insulation element section.

[0027] The first insulating element section can have a first passage with a first recess, which can have a larger diameter than the bore of the thermally insulating element. The diameter of the first passage can be larger than the outer circumference of the first waveguide section in order to accommodate the first waveguide section during connection. A first stop surface can be provided between the first passage of the first insulating element section and the inner wall of the thermally insulating element, against which the first waveguide section can abut, wherein the first stop surface can correspond, for example, to the end face of the first waveguide section. It can be provided that the first stop surface can be perpendicular to the inner wall.

[0028] The second insulating element section can have a second passage with a second recess, which can have a larger diameter than the bore of the thermally insulating element. The diameter of the second passage can be larger than the outer circumference of the second waveguide section in order to accommodate the second waveguide section during connection. A second stop surface can be provided between the second passage of the second insulating element section and the inner wall of the thermally insulating element, against which the second waveguide section can abut, wherein the second stop surface can correspond, for example, to the end face of the second waveguide section. It can be provided that the second stop surface can be perpendicular to the inner wall.

[0029] The first passage and the second passage may have the same diameter or different diameters, depending on whether the first waveguide section and the second waveguide section may have the same outer circumference or different outer circumferences.

[0030] The inner wall of the thermal insulation element can be the inner wall along the entire thermal insulation element, i.e., the inner wall can comprise the inner wall of the first thermal insulation element, the first stop surface, the wall of the bore, the second stop surface, and the inner wall of the second thermal insulation element. The inner wall of the thermal insulation element can be completely or continuously metallized. Alternatively, the inner wall of the thermal insulation element can be partially metallized. In other words, for example, only the wall of the bore can be metallized, so that the inner wall of the thermal insulation element, together with the inner wall of the waveguide, can form a continuous or gap-free inner wall of the sensor arrangement after connection, in order to transmit the measurement signal without interference.

[0031] According to a further embodiment, the thermal insulation element is designed to transmit the measurement signal within the thermal insulation element with the inner wall between the first waveguide section and the second waveguide section of the waveguide.

[0032] To keep the thermal conductivity of the thermal insulation element very low even through metallization, the metallization can be applied in tenths or hundredths of a thickness, for example, with a coating thickness of 0.1 to 0.001 mm. For example, the bore of the thermal insulation element can have a diameter of 2.6 mm. To metallize the inner wall or the bore, the thermal insulation element can have a length of, for example, less than 5 mm. Metallizing or coating the bore in the thermal insulation element can advantageously enable a good or optimal radar signal to be obtained for the sensor array.

[0033] According to a further embodiment, the thermal insulation element further comprises a connecting element which is designed to fasten the thermal insulation element to the first waveguide section and / or the second waveguide section.

[0034] According to a further embodiment, the connecting element is a spring connection or a snap connection.

[0035] For example, by means of the connecting element, the waveguide with the first and second waveguide sections and the thermal insulation element can be pressed together by a spring-on-block connection system so that no gap can arise between the waveguide and the thermal insulation element.

[0036] Thus, the heat insulating element can be integrated into the waveguide and form a waveguide arrangement with the waveguide or the first and second waveguide sections, which can consist, for example, of two materials, namely a plastic or a ceramic as a heat insulating material and a metal for the waveguide and the metallization of the inner wall of the heat insulating element.

[0037] According to a further embodiment, the inner wall of the heat insulating element corresponds to the inner wall of the waveguide when connecting the first waveguide section to the first insulating element section and / or when connecting the second waveguide section to the second insulating element section.

[0038] Thus, the measurement signal within the sensor arrangement can be guided or transmitted continuously, steplessly and without interference through the first and second waveguide sections of the waveguide and the thermal insulation element.

[0039] According to a further embodiment, the sensor arrangement further comprises measuring electronics with a radar chip, which is connected to the second waveguide section of the waveguide and is configured to generate a measuring signal and / or to evaluate a measuring signal from the antenna.

[0040] For example, the radar chip can be a high frequency (HF) radar chip, for example with an operating frequency of 80 GHz or higher.

[0041] For example, a stainless steel waveguide can have a thin wall to reduce thermal conductivity. However, the waveguide wall may require a minimum thickness to ensure the waveguide can be manufactured.

[0042] Without the provision of a thermal insulator, the waveguide, which can be made of metal, for example, can have a minimum length to allow the temperature or heat of the sensor arrangement, starting from the antenna or the first waveguide section, where the antenna can be arranged, to be reduced sufficiently at the second waveguide section so that the measuring electronics, which can be arranged on the second waveguide section facing away from the antenna, cannot be damaged. For example, if the waveguide is made of plastic or ceramic, the waveguide with a 2.6 mm bore should be coated to a depth of more than 5 mm for a measurement signal with a frequency of 80 GHz.Metallizing such a waveguide requires significant technical effort, and the waveguide can be manufactured, for example, by metallizing two waveguide half-shells and then assembling them to form the bore. It can be a significant technical challenge for the sensor arrangement with this waveguide to ensure that, after the two waveguide half-shells have been assembled, the measurement beam can be transmitted along the waveguide from the measurement electronics to the antenna, or vice versa, without being influenced by the gap.

[0043] In contrast, the sensor arrangement with the thermal insulator or thermal insulation element can advantageously at least partially prevent or interrupt the heat conduction or heat propagation from the first waveguide section via the second waveguide section to the measuring electronics and / or the radar chip in order to protect the measuring electronics and / or the radar chip from the heat and the high process temperature. For example, the RF radar chip and the measuring electronics can only be exposed to temperatures up to 85°C. If a process temperature reaches a high temperature of 130°C or higher, the provision of the thermal insulation element can advantageously enable the sensor arrangement to be built compactly during use, so that the temperature of the sensor arrangement can be reduced from the high process temperature of 130°C to a temperature below 85°C with the aid of the thermal insulation element.In other words, the sensor assembly comprising the antenna, waveguide, and thermal insulation element can have a short and compact design, allowing heat conduction between the first waveguide section and the second waveguide section to be significantly interrupted or prevented, thus protecting the measuring electrode and radar chip from the high process temperature. The sensor assembly can therefore be used robustly and stably over long periods of time in a process plant with high process temperatures.

[0044] If the sensor arrangement can incorporate a standalone radar sensor, the standalone sensor arrangement can be configured for wireless communication between the measurement electronics or radar chip and an external receiver unit, an external evaluation unit, or a cloud system, for example, for data transmission. Compared to wired communication, where the energy required for the measurement must always be in use, the availability of advanced, energy-saving wireless technologies can make battery-operated sensors for monitoring fill level, limit level, or pressure values ​​increasingly important. Particular advantages arise for applications in the field of process automation in industrial or private environments, such as logistics.

[0045] The term "process automation in industrial or private environments" can be understood as a branch of technology that encompasses all measures for operating machines and systems without human intervention. One goal of process automation is to automate the interaction of individual components of a plant in the chemical, food, pharmaceutical, petroleum, paper, cement, shipping, or mining industries. A variety of sensors can be used for this purpose, each of which is specifically adapted to the specific requirements of the process industry, such as mechanical stability, insensitivity to contamination, extreme temperatures, and extreme pressures. Measured values ​​from these sensors are typically transmitted to a control room, where process parameters such as fill level, limit level, flow, pressure, or density are monitored, and settings for the entire plant can be changed manually or automatically.

[0046] One sub-area of ​​process automation in the industrial environment concerns logistics automation. With the help of distance and angle sensors, processes within a building or within an individual logistics facility are automated in the field of logistics automation. Typical applications for logistics automation systems include baggage and freight handling at airports, traffic monitoring (toll systems), retail, parcel distribution, and building security (access control). The aforementioned examples refer to the fact that the respective application requires presence detection in combination with precise measurement of the size and position of an object. Sensors based on optical measurement methods using lasers, LEDs, 2D cameras, or 3D cameras that measure distances according to the time-of-flight (ToF) principle can be used for this purpose.

[0047] Another sub-area of ​​process automation in the industrial environment concerns factory / production automation. Applications for this can be found in a wide variety of industries, such as automotive manufacturing, food production, the pharmaceutical industry, and packaging in general. The goal of factory automation is to automate the production of goods using machines, production lines, and / or robots, i.e., to run it without human intervention. The sensors used here and the specific requirements regarding measurement accuracy for detecting the position and size of an object are comparable to those in the previous example of logistics automation.

[0048] For example, continuous, automated monitoring of fill levels in mobile containers and the preferably wireless transmission of these values ​​to a central evaluation point in goods logistics can easily implement cross-site inventory management. Depending on the specific problem, the collected data can be used to achieve significant cost reductions, for example, by optimizing the route for delivery vehicles to replenish supplies.

[0049] A further aspect of the invention relates to a thermal insulation element for a sensor arrangement with an antenna and a waveguide, which element has a first insulation element section and a second insulation element section. The first insulation element section is configured to receive a first waveguide section of the waveguide. The second insulation element section is configured to receive a second waveguide section of the waveguide. The thermal insulation element is configured to at least partially prevent heat conduction between the first waveguide section and the second waveguide section.

[0050] A further aspect of the invention relates to the use of a thermal insulation element for thermally insulating electronics with a radar chip of a level, limit level and / or pressure measuring device.

[0051] A further aspect of the invention relates to the use of a sensor arrangement for level, limit level and / or pressure measurement in a process plant.

[0052] Further embodiments are described below. Where the same reference numerals are used in the following figures, they denote identical or similar elements. The representations in the figures are schematic and not to scale. Short description of the characters

[0053] Fig. 1 shows a sensor arrangement according to one embodiment. Detailed description of embodiments

[0054] Fig. 1 shows a sensor arrangement 100 which is designed to measure a fill level, a limit level and / or a pressure and has an antenna 110, a waveguide 120, a heat insulating element 130 and a measuring electronics 150 with a radar chip.

[0055] The antenna 100 may be a horn antenna or a parabolic antenna and may be configured to transmit and / or receive a measurement signal.

[0056] The waveguide 120 can have a first waveguide section 121, which can be configured for connection to the antenna 110, and a second waveguide section 122, which can be configured for connection to the measurement electronics 150 or a high-frequency electronics unit. The waveguide 120 can be configured to transmit the measurement signal from the measurement electronics 150 toward the antenna 110 or vice versa.

[0057] For example, the waveguide 120 may be made of a metal, such as copper or stainless steel.

[0058] The thermal insulation element 130 is arranged between the first waveguide section 121 and the second waveguide section 122 and can be configured to at least partially prevent heat conduction between the first waveguide section 121 and the second waveguide section 122.

[0059] The thermal insulation element 130 may be made of a thermally insulating material, which may be a plastic or a ceramic. For example, the thermally insulating material of the thermal insulation element 130 may be a plastic PEEK or a ceramic, such as a silicate ceramic or a zirconium oxide (ZrO) ceramic.

[0060] It may be necessary for the heat-insulating material to have a lower thermal conductivity than the metallic waveguide 120. For example, the copper waveguide 120 may have a conductivity of 401 W / (m·K) or the stainless steel waveguide 120 may have a conductivity of 15 W / (m·K). The high-temperature-resistant thermoplastic PEEK as the heat-insulating material has a conductivity of 0.25 W / (m·K) and can be provided to prevent heat transfer of the sensor assembly 100 with a copper or stainless steel waveguide 120. A zirconium oxide (ZrO) ceramic with a thermal conductivity of 2 W / (m·K) may also be suitable for the copper or stainless steel waveguide. In contrast, an aluminum oxide (Al2O3) ceramic with a thermal conductivity of 30 W / (m·K) can be a suitable thermal insulating material for the copper waveguide, but not for the stainless steel waveguide.

[0061] The thermal insulation element 130 can be tubular. For example, the thermal insulation element 130 can have a recess or a bore to form a round or rectangular passage in the thermal insulation element 130. For example, the bore for an RF radar chip with an operating frequency of 80 GHz can have a diameter of 2.6 mm.

[0062] Furthermore, the thermal insulation element 130 can have an inner wall that can be at least partially metallized. Alternatively, the thermal insulation element 130 can also be fully metallized. Preferably, the metallization can be applied only in the tenths or hundredths range, such as with a coating thickness of 0.1 to 0.001 mm, whereby the thermal conductivity of the thermal insulation element 130 can also be low after metallization. Thus, heat conduction or heat transport toward the measuring electronics 150 can be effectively prevented, and the radar signal can be transmitted continuously and without interference.

[0063] The thermal insulation element 130 may include a first insulation element portion 131 having a first passage at a first end of the thermal insulation element 130 and a second insulation element portion 132 having a second passage at an opposite second end of the thermal insulation element 130, wherein the first insulation element portion 131 may be configured to receive the first waveguide portion 121 and the second insulation element portion 132 may be configured to receive the second waveguide portion 122.

[0064] The thermal insulation element 130 is configured to reduce the temperature of the sensor assembly along the length of the thermal insulation element 130 between the first insulation element section 131 and the second insulation element section 132. For example, the radar chip, which may be an RF radar chip, and the measurement electronics can only be exposed to temperatures up to 85°C. If a process temperature reaches a high temperature of 130°C or higher, the provision of the thermal insulation element 130 can advantageously enable the sensor assembly 100 to be constructed compactly during use, so that the temperature of the sensor assembly 100 can be reduced from the high process temperature to a temperature below 85°C in a short design with the aid of the thermal insulation element.

[0065] The first passage of the first insulating element section 131 can have a larger diameter than the bore of the thermally insulating element 130, while the second passage of the second insulating element section 132 can have a larger diameter than the bore of the thermally insulating element 130. A first stop surface, against which the first waveguide section 121 can abut, can be provided between the first passage of the first insulating element section 131 and the inner wall of the thermally insulating element 130. The first stop surface can correspond, for example, to the end face of the first waveguide section 121. The first stop surface can be perpendicular to the inner wall.A second stop surface, against which the second waveguide section 122 can abut, can be provided between the second passage of the second insulating element section 132 and the inner wall of the thermally insulating element 130. The second stop surface can correspond, for example, to the end face of the second waveguide section 122. The second stop surface can be perpendicular to the inner wall. The first passage and the second passage can have the same diameter, as shown in FIG. Fig. 1 shown, or have different diameters, depending on whether the first waveguide section 121 and the second waveguide section 122 can have the same outer circumference or different outer circumferences.

[0066] The thermal insulation element 130 may further comprise a connecting element, which may be configured to fasten the thermal insulation element 130 to the first waveguide section 121 and / or the second waveguide section 122. The connecting element may, for example, be a spring connection or a snap connection.

[0067] For example, by means of the connecting element, the waveguide with the first and second waveguide sections and the thermal insulation element can be pressed together by a spring-on-block connection system, so that no gap can arise between the waveguide 120 and the thermal insulation element 130.

[0068] Furthermore, the thermal insulation element 130 can be configured to transmit the measurement signal within the thermal insulation element 130 with the inner wall between the first waveguide section 121 and the second waveguide section 122 of the waveguide. Because the inner wall of the thermal insulation element 130 can be metallized, the measurement signal or the measurement beam can be guided from the measurement electronics or the radar chip of the measurement electronics to the antenna 110, or vice versa, via the first waveguide section 121, the thermal insulation element 130, and the second waveguide section 122.

[0069] The inner wall of the thermal insulation element 130 can correspond to the inner wall of the waveguide 120 when connecting the first waveguide section 121 to the first insulation element section and / or when connecting the second waveguide section 122 to the second insulation element section 132. Thus, the transition between the inner wall of the thermal insulation element 130 and the inner wall of the waveguide 120 or the first waveguide section 121 and / or the second waveguide section can be formed without a gap, so that the measurement signal or the radar signal can be transmitted continuously within the sensor arrangement 100 without interference.

[0070] Furthermore, the thermal insulation element 130 can be integrated into the waveguide 120 and form a waveguide arrangement with the waveguide 120 or the first and second waveguide sections 121, 122, which can consist of two materials, namely a plastic or a ceramic as a thermal insulation material and a metal for the waveguide 120 and the metallization of the inner wall of the thermal insulation element 130.

[0071] Furthermore, the antenna 110 can be formed integrally or integrated with the waveguide 120 or the first waveguide section 121.

[0072] Additionally, it should be noted that "comprising" and "having" do not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered limitations.

Claims

1. A sensor arrangement (100) configured to measure a fill level, a limit level, and / or a pressure, comprising: an antenna (110) configured to transmit and / or receive a measurement signal; a waveguide (120) having a first waveguide section (121) for connection to the antenna (110) and a second waveguide section (122) and configured to transmit the measurement signal; a heat-insulating element (130) arranged between the first waveguide section (121) and the second waveguide section (122) and configured to at least partially prevent heat conduction between the first waveguide section (121) and the second waveguide section (122).

2. Sensor arrangement (100) according to claim 1, wherein the antenna (110) is a horn antenna or a parabolic antenna.

3. Sensor arrangement (100) according to claim 1 or 2, wherein the heat insulating element (130) is tubular.

4. Sensor arrangement (100) according to one of the preceding claims, wherein the thermal insulation element (130) has an inner wall which is at least partially metallized.

5. Sensor arrangement (100) according to one of the preceding claims, wherein the thermal insulation element (130) consists of a thermally insulating material.

6. Sensor arrangement (100) according to claim 5, wherein the heat-insulating material is a plastic or a ceramic.

7. The sensor assembly (100) according to claim 6, wherein the plastic is PEEK; or wherein the ceramic is a silicate ceramic or a zirconium oxide ceramic.

8. Sensor arrangement (100) according to one of the preceding claims, wherein the thermal insulation element (130) has a first insulation element section (131) configured to receive the first waveguide section (121) and a second insulation element section (132) configured to receive the second waveguide section (122), and is configured to allow a temperature of the sensor arrangement to decrease along the length of the thermal insulation element (130) between the first insulation element section (131) and the second insulation element section (132).

9. Sensor arrangement (100) according to claim 4 or 5, wherein the thermal insulation element (130) is configured to transmit the measurement signal within the thermal insulation element (130) with the inner wall between the first waveguide section (121) and the second waveguide section (122) of the waveguide (120).

10. Sensor arrangement (100) according to one of the preceding claims, wherein the thermal insulation element (130) further comprises a connecting element which is configured to fasten the thermal insulation element (130) to the first waveguide section (121) and / or the second waveguide section (122).

11. Sensor arrangement (100) according to claim 10, wherein the connecting element is a spring connection or a snap connection.

12. Sensor arrangement (100) according to one of claims 4 to 11, wherein the inner wall of the heat insulating element (130) corresponds to the inner wall of the waveguide (120) when connecting the first waveguide section (121) to the first insulating element section (131) and / or when connecting the second waveguide section (122) to the second insulating element section (132).

13. Sensor arrangement (100) according to one of the preceding claims, further comprising: measuring electronics (150) with a radar chip, which is connected to the second waveguide section (122) of the waveguide (120) and is configured to generate a measuring signal and / or to evaluate a measuring signal from the antenna (110).

14. A thermal insulation element (130) for a sensor arrangement (100) according to one of claims 1 to 13 with an antenna (110) and a waveguide (120), comprising: a first insulation element section (131) configured to receive a first waveguide section (121) of the waveguide (120), and a second insulation element section (132) configured to receive a second waveguide section (122) of the waveguide (120), wherein the thermal insulation element (130) is configured to at least partially prevent heat conduction between the first waveguide section (121) and the second waveguide section (122).

15. Use of a thermal insulation element (130) according to claim 14 for thermal insulation of an electronics unit (150) with a radar chip of a level, limit level and / or pressure measuring device.

16. Use of a sensor arrangement (100) according to one of claims 1 to 13 for level, limit level and pressure measurement in a process plant.