Fill level measuring device

Abstract

The invention relates to a fill level measuring device (1) for high-precision fill level measurement, which is easy to manufacture, heat-resistant and meets explosion protection requirements, comprising: an IC-based high-frequency unit (10) designed to generate radar signals (S HF ) of 100 GHz or more and to radiate them along a beam axis (a) towards a fill substance (2) and, after their reflection on the fill substance surface, to receive corresponding reception signals (R HF ); an evaluation unit determining a fill level (L) based on at least the reception signals (R HF ). According to the invention, the fill level measuring device (1) is characterized by a package (11) encapsulating the high-frequency unit (10) and at the same time surrounding a radar lens (111) positioned in the beam axis (a). The encapsulation minimizes the assembly and thus simplifies the adjustment of the IC relative to the radar lens (111).

Description

Technical Field

[0001] This invention relates to a radar-based filling level measurement device. Background Technology

[0002] Process automation technologies that use field devices to record relevant process parameters employ corresponding field devices. To record process parameters, appropriate measurement principles are implemented in the field devices. Examples of process parameters include fill level, flow rate, pressure, temperature, pH, redox potential, and conductivity. Various types of field devices and their variations are manufactured and sold by the Endress+Hauser Group.

[0003] For measuring the fill level of media in containers, non-contact measurement methods have proven effective due to their robustness and low maintenance. Another advantage of non-contact methods is their ability to measure fill levels nearly continuously. Therefore, radar-based measurement methods are primarily used in the field of continuous fill level measurement. In the context of this invention, the term "..." radar "" refers to signals or electromagnetic waves with frequencies between 0.03 GHz and 300 GHz. In principle, the higher the frequency, the higher the achievable measurement resolution. Established measurement methods include the pulse travel time method and FMCW ("Frequency Modulated Continuous Wave"). More details on radar-based fill level measurements can be found in, for example, " Radar Level Detection (Radar fill level detection) Peter Devine, 2000 Found in ”.

[0004] Typical frequency bands permitted for radar-based fill level measurements are located at 26 GHz, 60 GHz, 80 GHz, and 120 GHz, and increasingly at 180 GHz and 240 GHz. In such cases, higher frequency bands are advantageous for many applications because better beam focusing is achieved for a given antenna size, and generally more bandwidth is available, which can be used for greater range resolution.

[0005] For higher frequencies of 100 GHz and above, the high-frequency units inside the equipment used to generate and process radar signals are implemented in the form of integrated circuits. In such cases, the transmission and reception of radar signals are directly transmitted through the IC housing (…). AiP = Packaged antenna Or even directly on the semiconductor chip ( AoC = On-chip antenna This occurs. Due to the limited chip area, the structure of such integrated antennas needs to be kept compact, thus resulting in a correspondingly wide beam angle. In such cases, in the context of this invention, the term "..." Beam Angle"This typically refers to a solid angle at which the antenna has a defined, equal transmit strength and receive sensitivity relative to the corresponding beam axis, for example, -3 dB. Furthermore, the term '..." Beam axis "This refers to the vector along which the radar signal is transmitted at maximum intensity."

[0006] To enable sufficient focusing of the radar signal toward the filling material, a focusing radar lens is placed in front of the high-frequency unit (HF unit) despite the presence of IC-based radiation. However, this leads to increased structural and manufacturing complexity. Additional structural conflicts in this case necessitate an explosion-proof package for the HF unit. An alternative is described in WO 2023 / 285300A1, in which the radar signal does not radiate freely from the HF unit toward the radar lens: there, the radar signal is coupled from the HF unit to the antenna via a dielectric waveguide. However, the problem here is that the waveguide cross-section is small for high frequencies, resulting in corresponding finesse and, consequently, manufacturing difficulties.

[0007] Therefore, one object of the present invention is to provide a radar-based fill level measuring device that overcomes these disadvantages. Summary of the Invention

[0008] This invention achieves this objective through a fill level measuring device for determining the fill level of a filler material, the device comprising: - High-frequency unit, which is designed as follows: o generates radar signals and radiates them along the beam axis toward the filling material, and, o After they are reflected by the surface of the filling material, they receive the corresponding received signal. - An evaluation unit designed to determine the fill level based on at least the received signal, and - A potting compound package that at least encapsulates the high-frequency unit and has o The first radar lens is arranged in the beam axis.

[0009] The present invention enables the easy manufacture of a fill level measuring device based on the following method steps: - Provides high-frequency units, potting housings, and enclosures. - Introduce the high-frequency unit into the potting housing. - Casting the potting compound into the potting shell, and - Introduce the potting shell into the housing.

[0010] In this case, neither the delicate waveguide needs to be handled, nor the first radar lens needs to be adjusted relative to the high-frequency unit. When the first radar lens is not enclosed as a hybrid component within a potting compound package, but instead designed as a monolithic component within the potting compound package, the additional manufacturing steps disappear. The first radar lens and / or the potting compound package can be manufactured from, for example, PTFE, PEEK, PEI, PFA, or PEE to induce appropriate refraction of the radar signal.

[0011] The construction of the present invention for a leveling device is particularly advantageous when the high-frequency unit is designed as an IC and the signal is generated and processed accordingly in a frequency band of 100 GHz or higher, particularly 180 GHz. In this case, the construction of the present invention for a leveling device achieves focused radiation of radar signals, even if these radar signals are radiated and received by the IC with a wide beam angle. Advantageously, the potting housing and the high-frequency unit are designed such that an airtight hollow space is formed between the first radar lens and the high-frequency unit. In this way, the hollow space remains free of potting compound during casting, so that the transmission of radar signals is unrestricted during measurement operations.

[0012] When the first radar lens has insufficient focus or requires an aperture with excessively strong focus, within the scope of this invention, a second radar lens can be arranged and appropriately oriented relative to the high-frequency unit in the beam axis after the first radar lens. This is particularly advantageous when the housing of the fill level measuring device in which the high-frequency unit is arranged includes a housing neck for spaced out from the interior of the high-temperature container in a given case. In such a case, the second radar lens can be arranged in the end region of the housing neck toward the fill material. In this way, the first radar lens and the high-frequency unit are correspondingly spaced apart from the second radar lens and the interior of the container via the housing neck, and vice versa. Furthermore, in this case, it is advantageous that the first radar lens has an aperture and is spaced apart from the second radar lens such that the beam angle of the first radar lens coincides with the outer contour of the second radar lens. In this way, the radar signal is transmitted and received with maximum efficiency in terms of transmit / receive power. Of course, to further optimize focusing, a third radar lens can be arranged in the housing neck between the first and second radar lenses.

[0013] Furthermore, especially in the case of radar signal transmission, efficiency can be improved by designing the first radar lens to minimize reflection of radar signals transmitted from the high-frequency unit. This can be achieved in different ways: - The first radar lens can be designed to have a slight tilt relative to the beam axis, so it is between 0.2° and a maximum of 15°.

[0014] - The first radar lens may have a coating on the surface facing the high-frequency unit, or have a groove-like structure having a depth of one-quarter of the wavelength of the radar signal.

[0015] - The first radar lens can be divided into two halves relative to the beam axis, and these two halves are arranged to be offset from each other by one-quarter of the wavelength of the radar signal relative to the beam axis.

[0016] In the context of this invention, the term " unit "Generally, this refers to any design or package of electronic circuitry required for specific applications, such as high-frequency signal processing or as an interface. Therefore, depending on the application, a unit can include corresponding analog circuitry for generating or processing corresponding analog signals. However, a unit can also include digital circuitry, such as FPGAs, microcontrollers, or storage media used in conjunction with a corresponding program. In such cases, the program is designed to perform the required method steps or apply necessary computer operations. In this context, within the scope of this invention, different electronic circuits within a unit can also potentially use shared physical memory or operate by means of the same physical digital circuitry. In such cases, it is irrelevant whether the different electronic circuits within the unit are arranged on a shared circuit board or distributed across multiple connected circuit boards." Attached Figure Description

[0017] The invention will now be described in more detail based on the accompanying drawings, which are shown below: Figure 1 It is a radar-based fill level measurement device on the container, and Figure 2 This is a cross-sectional view of the filling level measuring device of the present invention. Detailed Implementation

[0018] In order to understand the principle of the filling level measuring device 1 of the present invention, Figure 1 A container 3 containing a filling material 2 of undetermined fill level L is shown. In such a case, depending on the type of filling material 2 and the application field, the height of the container 3 can exceed 100 m. The conditions within the container 3 also depend on the type of filling material 2 and the application field. That is, for example, in the case of an exothermic reaction, high temperature and high pressure loads can exist. In the case of containing dust or flammable materials, the interior of the container must maintain the corresponding explosion-proof requirements.

[0019] Typically, the fill level measuring device 1 is connected via a separate interface unit to a higher-level unit 4, such as a local process control system or a distributed server system, in which, for example, " 4-20 mA "", PROFIBUS "", HART"or" Ethernet The protocol is Ethernet. In this way, for example, it is possible to transmit the measured fill level value L so as to control the inflow and / or outflow of container 3 under a given condition. In addition, other information about the overall operating status of the fill level measuring device 1 can also be conveyed.

[0020] To determine the fill level L independently of site conditions, the fill level measuring device 1 is positioned above the fill material 2 at a known installation height h above the bottom of the container 3. In this configuration, the fill level measuring device 1 is pressure-sealed and the fill material is sealed at the appropriate port of the container 3, such that only the second radar lens 12 of the fill level measuring device 1 is guided vertically downward toward the fill material 2 within the container 3, while the additional components of the fill level measuring device 1 are arranged outside the container 3 in a separate housing 13.

[0021] Radar signal S within a predetermined frequency band via the second radar lens 12 HF The signal is emitted in the direction of the surface of the filling material 2. After being reflected on the surface of the filling material, the filling level measuring device 1 then receives the reflected signal R via the second radar lens 12. HF In this situation, in radar signal S HF R HF The signal travel time t between transmission and reception is based on:

[0022] The variable is proportional to the distance d between the filling level measuring device 1 and the filling material 2, where the variable " c "This is at least roughly known radar propagation speed. The signal travel time t can be determined by the fill level measuring device 1, for example, by means of the FMCW method or by means of the pulse travel time method. In this way, the fill level measuring device 1 can assign an appropriate distance d, for example, based on the corresponding calibration of the measured travel time t. Then, when the installation height is provided in the fill level measuring device 1..." h "At that time, the filling level measuring device 1 can then be based on:

[0023] Determine the fill level L. This is based on the incoming received signal R. HF The signal travel time t and the corresponding fill level value L are determined. The fill level measuring device 1 includes a correspondingly designed evaluation unit, in which a suitable measurement principle (FMCW or pulse travel time method) is implemented. This is used to generate the transmitted radar signal S. HF and the received signal R in the fill level measuring device 1 HFThe preprocessing is performed by the corresponding high-frequency unit 10. When the FMCW method is implemented therein, the high-frequency unit 10 can, for example, be based on a PLL ("...") on the transmitter side. Phase-locked loop The high-frequency unit 10 can include Fourier transform logic on the receiving side. This Fourier transform logic is used to detect the signal travel time t, which corresponds to the maximum frequency value in the intermediate frequency signal characteristics of the FMCW, and the intermediate frequency signal is the received signal R. HF With transmitted radar signal S HF Obtained after frequency mixing.

[0024] The high-frequency unit 10 of the filling level measuring device 1 generates radar signal S HF The frequency or band is determined based on the characteristics of the filler material 2. A relatively high frequency band, for example, 180 GHz, is achieved for highly accurate filler level measurements. The construction of the filler level measuring device 1 of the present invention will now be based on... Figure 2 To provide a more detailed description, its features include ease of production at this high frequency band, compliance with explosion-proof requirements, and a temperature-resistant design.

[0025] Basically, the IC-based high-frequency unit 10 includes a circuit board 100, which is further arranged within a housing 13. Thereby, the IC radiates and receives radar signals S and R. HF The beam axis is oriented perpendicular to the circuit board 100. The circuit board 100, and therefore the high-frequency unit 10, is then fixed within a potting compound package 11 within a housing 13. This is achieved during manufacturing by filling with a potting compound (not explicitly shown) to encapsulate the high-frequency unit 10 in an explosion-proof manner. According to the invention, the potting compound package 11 is formed along the beam axis a in the form of a focusing first radar lens 111, wherein... Figure 2 The first radar lens represents a monolithic assembly of the potting compound package 11. In this way, the need for separate components is eliminated. Furthermore, by fixing the circuit board 100 within the potting compound package 11, it is easier to adjust the first radar lens 111 relative to the beam axis a, since the orientation of the circuit board 100 is predetermined by the corresponding stop point in the potting compound package 11.

[0026] In the illustrated embodiment, the housing 13 of the fill level measuring device 1 includes a housing neck 131, such that the high-frequency unit 10 is spaced apart from the container interior for thermal protection. In this case, the housing neck 131, in its assembled state, the end region away from the container interior, is adjacent to the first radar lens 111 along a line of beam axis a. The opposite end region of the housing neck 131 near the fill material 2 is closed by a second radar lens 12, wherein the second radar lens 12 is further arranged and oriented on the same beam axis a as the first radar lens 111.

[0027] like Figure 2 As schematically shown, the aperture and beam angle α of the first radar lens 111 111 It is adjusted to conform to the length of the housing neck 13 and the profile of the second radar lens 12, such that the second radar lens 12 is illuminated over its entire cross-section, for example, according to the following formula:

[0028] In this case, the entire cross-section of the second radar lens 12 corresponds to the radar signal S. HF wavelength λ HF The quantity is an integer multiple of N. In such a case, due to the generally reciprocal nature of radar, the beam angle α of the first radar lens 111 is... 111 Overall, it is unrelated to whether the signal is transmitted or transmitted.

[0029] The second radar lens 12 is also designed to be focused, so that the radar signals S and R directed toward the filling material 2 are focused. HF The beam angle compared to the beam angle α of the first radar lens 111 111 This is further focused on. Plastics such as PTFE, PEEK, PEI, PFA, or PEE affect radar signals S and R due to their dielectric constant. HF The corresponding refraction allows radar lenses 12, 111 and potting housing 11 to be produced from this material, for example by means of injection molding or hot pressing.

[0030] exist Figure 2 In the embodiment of the potting housing 11 of the present invention shown, the potting housing 11 is designed such that after the circuit board 100 is introduced into the potting housing 11, an airtight hollow space 112 is formed between the first radar lens 111 and the high-frequency unit 10. Its advantage is that when, for example, a castable resin is subsequently poured into the potting housing 11, the hollow space 111 remains free of castable resin. Therefore, the radar signal path along the beam axis a is not degraded by the potting compound.

[0031] List of reference numerals

[0032] 1. Fill level measuring equipment

[0033] 2. Filler material

[0034] 3 containers

[0035] 4. Upper-level unit

[0036] 10 high-frequency units

[0037] 11. Encapsulated compound package

[0038] 12 Second radar lens

[0039] 13. Outer shell

[0040] 100 circuit boards

[0041] 111 First Radar Lens

[0042] 112 Hollow Space

[0043] 131 Outer shell neck

[0044] a Beam Axis

[0045] d Distance

[0046] h Installation height

[0047] L fill level

[0048] R HF Received signal

[0049] S HF radar signals

[0050] α 111 Beam angle of the first radar lens

Claims

1. A fill level measuring device for determining the fill level (L) of a filler material (2), comprising: - High-frequency unit (10), said high-frequency unit (10) is designed as follows: o Generate radar signal (S HF And the radar signal (S) HF ) radiates along the beam axis (a) toward the filling material (2), and, o in the radar signal (S HF After being reflected on the surface of the filling material, the corresponding received signal (R) is received. HF ), - An evaluation unit, said evaluation unit being designed to be based on at least the received signal (R HF To determine the fill level (L), and - A potting compound package (11), said potting compound package (11) at least encapsulates the high-frequency unit (10) and has o The first radar lens (111) is arranged in the beam axis (a).

2. The filling level measuring device according to claim 1, wherein, The first radar lens (111) is encapsulated in the potting compound package (11).

3. The filling level measuring device according to claim 1, wherein, The first radar lens (111) is designed as a monolithic component of the potting compound encapsulation (11).

4. The filling level measuring device according to any one of the preceding claims, wherein, The first radar lens (111) and / or the potting compound package (111) are made of PTFE, PEEK, PEI, PFA or PEE.

5. The filling level measuring device according to any one of the preceding claims, wherein, The high-frequency unit (10) is designed to generate and process signals (S, R) in a frequency band of at least 100 GHz, particularly 180 GHz. HF ).

6. The filling level measuring device according to any one of the preceding claims, wherein, The potting compound package (11) is designed to form an airtight hollow space (112) between the first radar lens (111) and the high-frequency unit (10).

7. The fill level measuring device according to any one of the preceding claims, further comprising: - A second radar lens (12) is arranged relative to the high-frequency unit (10) and oriented behind the first radar lens (111) in the beam axis (a).

8. The filling level measuring device according to claim 7, further comprising: - A housing (13) having a housing neck (131), wherein the second radar lens (12) is spaced apart from the first radar lens (111) and the high-frequency unit (10) through the housing neck (131).

9. The filling level measuring device according to claim 7 or 8, wherein, The first radar lens (111) has an aperture and is spaced apart from the second radar lens (12), such that the beam angle (α) of the first radar lens (111) is... 111 The outer contour of the second radar lens (12) coincides with that of the second radar lens (12).

10. The filling level measuring device according to any one of the preceding claims, wherein, The first radar lens (111) has a defined tilt relative to the beam axis (a), particularly between 0.2° and 15°; and / or wherein, The first radar lens (111) has a coating on its surface facing the high-frequency unit (10), or has a particularly groove-shaped structure, which in particular carries the radar signal (S) HF R HF (A quarter of the wavelength) depth.

11. A method for manufacturing a fill level measuring device according to at least one of the preceding claims, wherein, The method includes the following steps: - Provide the high-frequency unit (10), potting housing (11) and outer shell (13). - The high-frequency unit (10) is introduced into the potting housing (11). - Fill the potting compound into the potting housing (11), and - The potting housing (11) is introduced into the outer shell (13).

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