Patent Application
20240003732
The invention relates to a fill level measuring device serving for determining a three dimensional fill level profile.
Applied in process automation technology for registering relevant process parameters are corresponding field devices. For the purpose of registering process parameters of interest in corresponding field devices, suitable measuring principles are implemented, in order to register as process parameter, for instance, a fill level, a flow, a pressure, a temperature, a pH value, a redox potential or a conductivity. The most varied of such field device types are manufactured and sold by the firm, Endress+Hauser.
For fill level measurement of fill substances in containers, contactless measuring methods have proven themselves, since they are robust and low-maintenance. Another advantage of contactless measuring methods is their ability to measure the fill level virtually continuously. In the field of continuous fill level measurement, consequently, primarily radar based measuring methods are applied (according to the invention, the terminology, “radar” refers to signals, or electromagnetic waves, having frequencies between 0.03 GHz and 300 GHz). An established measuring method, in such case, is FMCW (“Frequency Modulated Continuous Wave”). The FMCW based fill level measuring method is described, for example, in Offenlegungsschrift DE 10 2013 108 490 A1.
By means of the FMCW method, it is possible to measure a distance, or the fill level, at least at a point. In such case, the point, at which the fill level is measured, depends on the orientation of the transmitting-/receiving antenna, i.e. on the direction of the lobe of its beam (due to the generally reciprocal properties of antennas, the characteristic, or the beam angle of the beam lobe, of an antenna is independent of whether it is transmitting/sending or receiving; the terminology “angle” or “beam angle” in the context of present invention means the angle, at which the beam lobe has its maximum transmitting intensity, or receiving sensitivity).
In the case of liquid fill substances, whose fill level is uniform, a pointwise fill level measurement is sufficient. In such cases, the fill level measuring device is so oriented that the beam lobe of the antenna is directed, for instance, perpendicularly downwards toward the fill substance and the distance from the fill substance is determined. In the case of solid-type fill substances, such as gravel or grain, the fill level can, however, be nonuniform, for example, as a result of so-called bulk-good cones, such that the fill level value ascertained by the fill level measuring device is only limitedly accurate. Especially in such cases, it is, consequently, desirable, to be able to determine the distance, or the fill level, in the form of a three dimensional fill level profile.
In order to do this, the fill level measuring device needs to be designed to be able to assign an associated solid angle to incoming radar signals. Such can be done, for example, by means of the MIMO principle (“Multiple Input Multiple Output”). Such principle is based on corresponding operating of an antenna arrangement, which is composed of column arranged transmitting antennas and row arranged receiving antennas, in order to implement a digital beam formation of the resulting radar signal. As concerns hardware, such can be implemented, for example, by means of correspondingly programmed MMICs' “(Monolithic Microwave Integrated Circuits”). MIMO based radar systems are described in more detail, for example, in “MIMO Radar Signal Processing ” (Jian Li), 2009.
Above all for explosion protection of the fill level measuring device, often a spatial isolation is required between the active, thus, electrical current supplied, transmitting/receiving unit and the passive antenna arrangement. The transmitting/receiving unit is, consequently, arranged outside of the container, while the antenna arrangement must extend into the container and, thus, be exposed to the process conditions within the container. In order to implement this division, the transmitting/receiving unit is isolated spatially from the antenna arrangement by a corresponding measuring device neck. In such case, the radar signals are led from/to the antenna arrangement through the measuring device neck to the transmitting/receiving unit. For example, for explosion protection, the measuring device neck includes, moreover, in given cases, a process seal, which, after installation, for example, using a flange, seals the container opening provided for the fill level measuring device.
Besides explosion protection requirements, the measuring device neck must fulfill other protection functions: Depending on application, high temperatures, high pressure or dangerous gases can be present in the interior of the container. Therefore, the measuring device neck and the flange must provide a pressure seal, a temperature barrier and a gas seal. These functions and the installation requirements together require between the transmitting/receiving unit and the antenna arrangement a significant distance, over which the measurement signals must be led with as little loss as possible. In pointwise measuring, fill level measuring devices, such distance can be bridged by a single waveguide, wherein, depending on frequency region, coaxial lines, hollow conductor or dielectric waveguide can be applied.
In three dimensionally mapping fill level measuring devices, which work based on digital beam formation, the distance between the transmitting/receiving unit and the antenna arrangement must, however, be not only for a single radar signal, but, instead, as a function of the number of antennas, for correspondingly many radar signals. In the case of technically and economically feasible solutions, this can require more than 200 waveguides. Structurally and from a manufacturing point of view, this is, however, difficult to implement.
It is, accordingly, an object of the invention to provide a three dimensionally mapping fill level measuring device, which is easy to manufacture and can be used under difficult process conditions.
The invention achieves this object by a radar based, fill level measuring device for determining a fill level profile of a fill substance in a container. For this, the fill level measuring device includes components as follows:
In such case, the transmitting waveguides and/or the receiving waveguides can, in principle, be designed as hollow conductors, coaxial cables or dielectric waveguides.
The fill level measuring device of the invention is characterized by features including that the transmitting waveguides are aligned along a first contour, which radially symmetrically surrounds the device neck axis, preferably at regular intervals relative to one another, and the receiving waveguides are aligned either likewise along the first contour or along a second contour, which surrounds the device neck axis likewise radially symmetrically. In such case, also the receiving waveguides can be arranged at regular intervals and alternately with the transmitting waveguides when the receiving waveguides are also arranged along the first contour. For the case, in which the receiving waveguide are arranged along the second contour, it is not essential per se, whether the transmitting waveguides are arranged outside or inside the receiving waveguides with reference to the device neck axis, thus, whether the first contour extends outside the second contour, or not. This can be made dependent, for example, on the implementation of the MIMO principle, or on whether more transmitting antennas or more receiving antennas are required for this and the required number of transmitting- and receiving waveguides.
The terminology “radially symmetric contours” means within the scope of the invention a contour, which with reference to the device neck axis can be divided into at least two, equally large angular segments, wherein the contour in each of the equally large angular segments has an equal course. Accordingly, a radially symmetric contour is, within the scope of the invention, for example, a circular, elliptical or rectangular contour. Advantageous in this regard is when the measuring device neck, the first contour as well as also the second contour have relative to the device neck axis an equal radial symmetry, such as, for example, a circular symmetry. Advantageously, the contours can relative to the measuring device neck be so dimensioned that the waveguides directly adjoin the measuring device neck, or the next outwardly lying waveguide basic body. In this way, there is centrally in the measuring device neck further free space for additional passageways, or components, of the fill level measuring device.
In reference to the transmitting/receiving unit, the terminology “unit” means in the context of the invention, in principle, any electronic circuit, which is suitably designed for the contemplated application. It can, thus, depending on requirement, be an analog circuit for producing, or processing, corresponding analog signals. It can also be a digital circuit, such as an FPGA or a storage medium in cooperation with a program. In such case, the program is designed to perform the corresponding method steps, or to apply the required computer operations of the particular unit. In this context, different electronic units of the measuring device can, within the scope of the invention, potentially also use a shared physical memory, or be operated by means of the same physical, digital circuit. In particular, the transmitting/receiving unit can for operating the antenna arrangement via the waveguides be based, for example, on a corresponding number of MMICs (“Monolithic Microwave Integrated Circuits”), since, depending on design these are able to perform the operations required for implementing the MIMO principle, such as the impressing of phase shifts, amplifying the signal amplitude, or the like.
When MMICs are used, the arrangement of the invention for the transmitting- and receiving waveguides acts, then, advantageously for the transmitting/receiving unit, in that the distance between the individual MMICs can be maximized. Since MMICs have generally a comparatively large thermal power loss, the thermal loading of the MMICs on one another and the thermal loading within the transmitting/receiving unit are, as a whole, minimized by maximizing the distances. For this, the MMICs are arranged above the measuring device neck as well as with reference to the device neck axis along the first contour, in each case, between one of the transmitting waveguides and one of the receiving waveguides, provided that the receiving waveguides are aligned alternately with the transmitting waveguides along the first contour. When the receiving waveguides are arranged not such as the transmitting waveguides along the first contour, but, instead, along the second contour, the MMICs are arranged above the measuring device neck as well as relative to the device neck axis between the first contour and the second contour.
The arrangement of the invention for the waveguides in the measuring device neck can be constructively and productively easily implemented by means of at least one shared, especially monolithic, basic body. In such case, the transmitting waveguides and, when the receiving waveguides are aligned alternately with the transmitting waveguides along the first contour, supplementally also the receiving waveguides can be embodied monolithically by a first basic body, in such a manner that, in each case, a first support structure of the first basic body is arranged between the individual waveguides. When the receiving waveguides are not aligned along the first contour, but, instead, along the second contour, the receiving waveguides can be embodied within the measuring device neck, in turn, by an additional, second basic body, in such a manner that, in each case, a second support structure of the second basic body is arranged between the individual receiving waveguides.
For the case, in which the waveguides are designed as dielectric waveguides, the dielectric waveguides and the first basic body, or the first support structures, can be made as a shared, monolithic, molded part. In such case, the receiving waveguides, when aligned along the second contour, can, in turn, be implemented in such a manner as dielectric waveguides that the receiving waveguides and the second basic body are manufactured as a second, monolithic, molded part. The monolithic, molded parts can especially be made by means of hot forming, injection molding, 3D printing or extrusion, from PTFE, PE or PFA.
In the case of design of the waveguides as hollow conductors, these can be so implemented that at least the first basic body, especially in conjunction with a corresponding interior segment of the measuring device neck, forms the interiors of the hollow conductors. When the receiving waveguides are, in such case, not aligned along the first contour, but, instead, along the second contour, these can, in turn, be implemented as hollow conductors in such a manner that at least the second basic body, especially in connection with the outer or inner, first basic body, forms the interiors of the receiving, hollow conductors. Also, in the case of design of the waveguides as hollow conductors, the one or more basic bodies can be designed as monolithic, molded parts, which are produced, in each case, by means of hot forming, injection molding, extrusion or additive manufacturing, thus, 3D printing, from PTFE, PE or PFA.
The invention will now be explained in greater detail based on the appended drawing. The figures of the drawing show as follows:
For illustrating the principles of radar based fill level measurement,
In order to be able to ascertain the fill level profile L(α,β) independently of the conditions reigning in the container, a fill level measuring device 1 is mounted at a known height h above the fill substance 2 at a corresponding opening on the container 3. In such case, the fill level measuring device 1 is so oriented and secured that it transmits/sends from an antenna arrangement 10 radar signals SHF, for instance, along a vertically directed axis a in the direction of the surface of the fill substance 2. After reflection on the fill substance surface, the fill level measuring device 1, in turn, receives the reflected radar signals RHF via the antenna arrangement 10. In such case, the signal travel time between transmitting and receiving the radar signal SHF, RHF is proportional to the angularly dependent distance d(α,β) between fill level measuring device 1 and fill substance 2, wherein the signal travel time can be determined by the fill level measuring device 1, for example, by means of the FMCW method or the pulse travel time method. Then the fill level measuring device 1 can determine the distance d, for example, based on a corresponding calibration of the measured travel time. In this way, the fill level measuring device 1 can determine the fill level profile L(α,β) according to
d(α,β)=h−L(α,β)
when the installed height h is furnished in the fill level measuring device 1.
As a rule, the fill level measuring device 1 is connected to a superordinated unit 4, such as e.g. a process control system, via an interface, for instance, “PROFIBUS”, “HART” or “Wireless HART”. In this way, the fill level profile L(α,β) can be transmitted, for example, in order, in given cases, to control incoming- or outgoing flows of the container 3. However, also other information concerning general operating state of the fill level measuring device 1 can be communicated.
Since the fill substance 2, such as shown schematically in
The antennas of the antenna arrangement 10 are operated by a transmitting/receiving unit 11 of the fill level measuring device 1. For implementing the digital beam pivoting in the transmitting/receiving unit 11, for example, the MIMO principle can be used. By this, the transmitting/receiving unit 11 can assign the received radar signals RHF their solid angles α,β with reference to the vertical axis a and, based on this, create the three-dimensional fill level profile L(α,β).
As shown in
The high frequency connecting of the transmitting- and receiving antennas of the antenna arrangement 10 to the transmitting/receiving unit 11 occurs via a corresponding number of transmitting waveguides 121, 121′ and receiving waveguides 122, 122′, which correspond, in each case, to the number of transmitting- and receiving antennas and extend within the measuring device neck 12 in parallel with device neck axis a. In such case, the transmitting waveguides 121, 121′ and/or the receiving waveguide 122, 122′ can, in principle, be designed either as hollow conductors 121′, 122′ or as dielectric waveguides 121, 122. In order that the array arranged antennas are connected correctly to the corresponding waveguides 121, 121′, 122, 122′, the fill level measuring device 1 can comprise a manifold (not shown in greater detail) in the form of a lateral redistributor structure, which is arranged between the antenna arrangement 10 and the measuring device neck 12. For explosion protection-conforming closing of the measuring device neck 12, additionally, there can be arranged in its interior a hermetic isolation, which is based, for example, on a glass or a ceramic and is introduced by means of welding in the measuring device neck 12.
In order in the case of the fill level measurement to be able to achieve an effective angular resolution, it is necessary that the antenna arrangement 10 has a minimum number of transmitting- and receiving antennas. In the case of technically and economically sensible solutions, this corresponds to between 16 and 200 transmitting and receiving channels for sufficiently exact implementing of the MIMO principle. With rising number of antennas, it is, however, difficult, so to design, and manufacture, the corresponding number of waveguides 121, 121′, 122, 122′ that they are easily arrangeable within the measuring device neck 12 and take up as little space as possible.
In order to enable this, the transmitting waveguides 121, 121′ are according to the invention aligned relative to one another at regular intervals along a first contour k1, which radially symmetrically surrounds the device neck axis a of the measuring device neck 12. Also the receiving waveguides 122, 122′ are arranged either alternately with the transmitting waveguides 121, 121′ along the first contour k1, or the receiving waveguides 122 are arranged aligned along a second contour k2, which likewise radially symmetrically surrounds the device neck axis a. In such case, the first contour k1 and, in given cases, the second contour k2 ideally follow the cross sectional shape of the measuring device neck 12. This means, in the case of a round cross section of the measuring device neck 12, that the first contour k1 and, in given cases, the second contour k2 are circular.
For manufacturing, this arrangement of the invention for the waveguides 121, 121′, 122, 122′ within the measuring device neck 12 offers the advantage that the waveguides 121, 121′ 122, 122′ can be embodied together in a first basic body 123 and, in given cases, supplementally, a second basic body 124, such as shown in the three-dimensional view of
For the case, in which the waveguides 121, 121′ 122, 122′ are dielectric waveguides 121, 122, the dielectric waveguides 121, 122 are formed along the contours k1, k2 by the thickened segments 1231′, 1241′ of the basic bodies 123, 124. In order to be able to function as dielectric waveguides 121, 122, the basic bodies 123, 124 are correspondingly produced from an electrically insulating material having a dielectric constant of at least two. Utilized for this can be, for example, plastics such as PTFE, PE or PFA. The narrowed segments 1231, 1241 form in the case of dielectric waveguides, in each case, a support structure between the individual dielectric waveguides 121, 122.
When the waveguides 121, 121′ 122, 122′ are embodied as hollow conductors 121′, 122′, they behave as regards the segments 1231, 1231′, 1241, 1241′ exactly oppositely. The thickened segments 1231′, 1241′ of the basic bodies 123, 124 form in the contours k1, k2 support structures between the hollow conductors 121′, 122′, wherein the actual hollow conductors in the contours k2 are defined by the surfaces of the basic bodies 123, 124 in the region of the narrowed segments 1231, 1241. The hollow conductors 121′, 122′ are, thus, embodied virtually as negative-shapes of the narrowed segments 1231′, 1241′ in the basic body 123, 124. In the case of such a design of the waveguides 121, 121′ 122, 122′ as hollow conductors 121′, 122′, it is necessary that the basic bodies 123, 124 at least in the region of the narrowed segments 1231′, 1241′ have electrically conductive surfaces. For this, the basic bodies 123, 124 can be produced, for example, from a plastic and provided with an electrically conductive coating, for example, by means of sputtering or PECVD (“Plasma Enhanced Chemical Vapor Deposition”). Otherwise, the basic body 123, 124 can be made, for example, completely of metal.
In the case of the embodiment shown in
Advantageous for plastic basic bodies 123, 124 as regards their production is that they can be made as yard goods, for example, by means of extrusion, and cut to the desired length and contour k1, k2. Then, the basic body 123, 124 is formed by coiling the tailored plastic yard good in the measuring device neck 12. In such case, the measuring device neck 12 can, in given cases, serve as holder for at least the outer, first basic body 123, such that (depending on whether the transmitting waveguides 121, 121′ or the receiving waveguides 122, 122′ are arranged outwardly lying with respect to the device neck axis a when not all waveguides 121, 121′, 122, 122′ are aligned on a shared contour k1) the corresponding waveguides 121, 121′, 122, 122′ adjoin the inside of the measuring device neck 12. The second basic body 124, and the waveguides 122, 122′ in given cases aligned along the second contour k2, then adjoin the inside of the first basic body 123.
Among other things, in order to achieve a sufficient angular resolution for the beam pivoting, the number of antennas exceeds the available number of transmitting and receiving channels per MMIC by a multiple, such that a corresponding plurality of MMICs 10′ are associated with the transmitting-receiving unit 10. With the rising number of MMICs 10′, however, the danger increases that they thermally load one another excessively, since each individual MMIC 10′ generates a considerable thermal power loss. By the arrangement of the MMICs 10′, as shown in
A second possible embodiment of the measuring device neck 12 is shown in
Analogously to
In contrast with the examples of embodiments of the measuring device neck illustrated in
In the case of the embodiment in
The embodiment of the measuring device neck 12 of the invention shown in
Also the embodiment shown in
Among others, for the case, in which the desired material production technology does not allow the hollow conductors 121′, 122′ of
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 129 765.3 | Nov 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/076265 | 9/23/2021 | WO |
