Spatially resolving filling level measurement

Abstract

The invention relates to a radar-based filling level measuring device (1) for determining location-related filling level values (Lx;y) which is operable with low computing power and low power consumption. For this purpose, the filling level measuring device (1) is based on a converging lens (11) directed toward the filling material (2), such that radar signals (SHF, RHF) are focusedly emittable toward the filling material (2) or focusedly receivable after reflection. A plurality of radar ICs (12, 12') for generating and for receiving the radar signals (SHF, RHF) are arranged, in relation to the filling material (2), behind the converging lens (11) each with a different offset (V1x;y, V2x;y) with respect to the optical axis (a), thus resulting in the spatial resolution. As a result, the radar signals (SHF, RHF) each experience a defined, different deflection toward the filling material (2). In order to determine the corresponding location-related filling level values (Lx;y), a control / evaluation unit (14) correspondingly controls the radar ICs (11, 11'). This arrangement according to the invention makes it possible to dispense with a computationally complex signal evaluation, such as digital beamforming. At the same time, the hardware outlay is limited since, rather than integrated beam arrays as radar ICs (12, 12'), only individual radiators are needed.

Description

[0001] Spatially resolving level measurement

[0002] The invention relates to a spatially resolving level measuring device and a method for operating the level measuring device.

[0003] In process automation technology, appropriate field devices are used to record relevant process parameters. For this purpose, suitable measuring principles are implemented in the respective field devices, allowing them to record the relevant process parameters, such as level, flow, pressure, temperature, pH value, redox potential, or conductivity. A wide variety of such field device types are manufactured and distributed by the Endress + Hauser Group.

[0004] Non-contact measurement methods have become established for measuring the fill level of products in containers because they are robust and low-maintenance. In the context of the invention, the term "container" also includes open containers, such as pools, lakes, or flowing waters. A further advantage of non-contact measurement methods is their ability to measure the fill level virtually continuously. Therefore, radar-based measurement methods are predominantly used for continuous fill level measurement (in the context of this patent application, the term "radar" refers to signals or electromagnetic waves with frequencies between 0.03 GHz and 300 GHz).

[0005] An established measuring principle is FMCW ("Frequency Modulated Continuous Wave"). The measuring principle of FMCW radar-based distance measurement methods is based on the transmission of a continuous radar signal with a modulated frequency. A characteristic of FMCW is that the transmission frequency is periodically changed within a defined frequency band. In consideration of regulatory requirements, higher frequency bands in the range of a standardized center frequency are becoming increasingly common with advancing development: In addition to the 6 GHz band, the 26 GHz band, and the 79 GHz band, frequencies above 100 GHz are now implemented. The advantage of high frequencies is that a larger absolute bandwidth (e.g., 4 GHz in the 100 GHz frequency band) can be used. This, in turn, achieves higher resolution and greater accuracy in level measurement.

[0006] The temporal change of the frequency within the frequency band is linear by default and has a sawtooth or triangular shape. A sinusoidal change can also be implemented in principle. With the FMCW method, the distance is determined based on the instantaneous frequency difference between the currently received high-frequency signal after reflection from the measuring object and the radar signal currently emitted by the measuring device. The FMCW-based level measurement method is described, for example, in the published patent application DE 10 2013 108 490 A1.

[0007] The FMCW method makes it possible to measure the distance or fill level at least at a specific point. The point at which the fill level is measured depends on the orientation of the transmitting / receiving antenna or the direction of its beam lobe (due to the generally reciprocal properties of antennas, the characteristic or beam angle of the beam lobe of the respective antenna is independent of whether it is transmitting or receiving; the term "angle" or "beam angle" in the context of this patent application refers to the angle at which the beam lobe exhibits its maximum transmission intensity or reception sensitivity).

[0008] In the case of liquid products with a homogeneous fill level, a point-based level measurement is sufficient. In these cases, the level measuring device is aligned so that the antenna beam is directed approximately vertically downwards towards the fill material, determining the distance to the fill material. However, with solid-like products such as gravel or grain, the fill level can be inhomogeneous, for example due to bulk material cones, so that the level value determined by the level measuring device is only of limited significance. Especially in such cases, it is therefore desirable to be able to determine the distance or fill level with spatial resolution in the form of a two- or three-dimensional profile. In addition to precise volume estimation, the visual 3D representation of imaging level measuring devices offers particular benefits for the automation of filling and dismantling processes.In addition, visualization can detect and avoid dangerous filling conditions, thus increasing the reliability and safety of corresponding process plants.

[0009] For spatially resolving level measurement, the beam cone of the radar-based level gauge can be designed to be mechanically pivotable, allowing the product profile to be recorded across the entire container cross-section or at least a portion of it. However, due to the increased maintenance effort, such designs are only used in special applications, such as mining.

[0010] Radar-based distance measuring devices with electrically pivotable beams are also known from the state of the art. Among other things, the so-called "phased array" principle can be used, in which the measuring device comprises several antennas, whose radar signals are superimposed for evaluation purposes. The antennas are arranged in rows (beam pivoting along one axis) or in an array (beam pivoting around two axes). To transmit or receive the high-frequency signal at a defined angle, the individual antennas are controlled according to their arrangement sequence with a phase shift that increases for each antenna. The angle a of the beam is adjusted as a function of the phase shift cp according to a~arcsin(cp).

[0011] According to the current state of the art, the necessary hardware can be integrated so compactly that the antennas are housed as patch antennas together with the semiconductor component for signal generation / signal evaluation on a common circuit board or even as a jointly encapsulated radar IC ("integrated circuit"). A distance measuring device operating according to the phased array principle is described, among other things, in the German publication DE 100 36 131 A1.

[0012] In addition to the phased array principle, spatially resolving radar measuring devices can also be designed based on digital beamforming. In this case, each antenna in the antenna array has its own signal processing and digitization. The received signal is digitized using a corresponding process, both in terms of its amplitude and phase position. The summation is performed digitally after a virtual phase shift and amplitude scaling in a special computer, the so-called beamforming processor. With digital beamforming, the radiation pattern of the antenna can be shaped so that it has several independent main lobes for different directions.

[0013] Both digital beamforming and the phased array principle can potentially achieve high lateral spatial resolution in level measurement. However, signal processing in both cases is very complex and requires corresponding hardware and computing power. However, power consumption, in particular, is severely limited in level measurement applications due to explosion protection regulations.

[0014] Accordingly, it is an object of the invention to provide a spatially resolving level measuring device that can be operated with low computing power and correspondingly low power consumption. The invention solves this problem by a radar-based level measuring device for determining location-based level values ​​of a medium in a container, comprising the following components:

[0015] A converging lens with an optical axis which, when attached, is directed towards the filling material so that radar signals can be emitted in a bundled manner towards the filling material or can be received in a bundled manner after their reflection on the filling material surface, at least two radar ICs which are designed o to generate the radar signals to be emitted and / or o to receive the reflected radar signals after reflection on the filling material and to generate from each of these a reception signal by means of which a radar signal propagation time can be determined.

[0016] According to the invention, the at least two radar ICs are arranged behind the converging lens with a defined, respectively different offset from the optical axis relative to the filling material and are aligned towards the converging lens. However, it is not excluded that one of the at least two radar ICs has an offset of zero from the optical axis. A control and evaluation unit is provided, which is designed to control the radar ICs and determine the signal propagation times in order to determine at least two location-related fill level values.

[0017] In the context of the invention, the term "unit" is understood to mean any separate arrangement or encapsulation of those electronic circuits that are intended for the specific application, e.g. for measurement signal processing or as an interface. Depending on the application, the respective unit can therefore comprise corresponding analog circuits for generating or processing analog signals. However, the unit can also comprise digital circuits, such as FPGAs, microcontrollers or storage media in conjunction with corresponding programs. The program is designed to carry out the required method steps or apply the necessary computing operations. In this context, different electronic circuits of the unit within the meaning of the invention can potentially also access a common physical memory or be operated using the same physical digital circuit.It is not relevant whether different electronic circuits within the unit are arranged on a common circuit board or on several connected circuit boards.

[0018] By designing the level gauge according to the invention with a plurality of radar ICs arranged appropriately relative to the converging lens, the area of ​​the product surface can be measured with minimal hardware and evaluation effort, without ambiguity errors or deviations due to incorrect calibration. The level gauge according to the invention is also advantageous from a manufacturing perspective in that the at least two radar ICs can share a common encapsulation.

[0019] In order to achieve sufficient resolution at level measurement points, it is advantageous to coordinate the number of radar ICs, the respective distance between the at least two radar ICs, the distance of the radar ICs to the collecting lens, the diopter of the collecting lens, and the radar frequency of the radar ICs such that the resulting main radiation lobes of the radar ICs into the container have an offset of a maximum of -1 OdB from each other. For homogeneous resolution, it is also advantageous if the at least two radar ICs are arranged mirror-symmetrically with respect to the optical axis. On the other hand, these parameters should be selected such that the main radiation lobes have a maximum offset of -3 dB from each other, since otherwise the spatial unambiguousness of the measured level values ​​can no longer be guaranteed.

[0020] Within the scope of the invention, it is not a priority which radar method is implemented to determine the individual transit times. The at least two radar ICs can, for example, be designed accordingly to generate the radar signals or the received signals according to the FMCW or pulse transit time method. Furthermore, the level measuring device according to the invention can be further developed in such a way that the at least two radar ICs are designed and arranged such that they transmit the radar signals towards the collecting lens or receive them from there with a beam cone that becomes increasingly narrower the greater the offset of the respective radar IC from the optical axis. This allows the lateral resolution of the level values ​​to be kept approximately constant over the height of the container.

[0021] In the simplest case, the monostatic operating method can be implemented in the level measuring device according to the invention. In this case, the radar signal is transmitted and received by the same radar IC in order to derive a corresponding level value L x;yto be determined. Accordingly, the number of lateral positions at each of which a level value can be determined corresponds to the number of radar ICs used. In order to be able to determine level values ​​at significantly more positions with the same number of radar ICs, it is advantageous to design the control and evaluation unit so that it controls the radar ICs using the bistatic radar method or determines the corresponding level values. At least in the case of the bit-static method, it is necessary for all radar ICs to be clocked using a common clock source at high frequency. This ensures that the radar signals emitted by the various radar ICs have the same phase position.

[0022] The bistatic method is also advantageous in that a plausibility check of the measured level values ​​can be performed on the level measuring device according to the invention, thereby increasing the reliability of the process plant. The following process steps are to be applied for the plausibility check:

[0023] Sending a radar signal using the first radar IC,

[0024] Reception of the corresponding radar signal after reflection at the product surface via the second radar IC,

[0025] Determination of a first signal propagation time based on the corresponding received signal,

[0026] Determining a second signal propagation time by repeating the previous process steps, whereby the two radar ICs are swapped as transmitter and receiver, and

[0027] Classification of the level value as implausible if the first signal propagation time and the signal propagation time do not match.

[0028] The invention is explained in more detail with reference to the following figures. They show:

[0029] Fig. 1 : A level measuring device according to the invention on a container,

[0030] Fig. 2: a conceptual structure of the measuring device according to the invention as a cross-sectional view,

[0031] Fig. 3: a conceptual structure of the measuring device according to the invention as a plan view, and

[0032] Fig. 4: a schematic block diagram of the measuring device according to the invention.

[0033] For a basic understanding of the invention, Fig. 1 shows a container 3 with a filling material 2, the fill level L of which is to be determined. Depending on the type of filling material 2 and the area of ​​application, the container 3 can be up to more than 100 m high.

[0034] To determine the fill level L, a radar-based level gauge 1 is mounted above the filling material 2 at a known installation height h above the brine of the container 3. The level gauge 1 is attached to a corresponding opening of the container 3 such that radar signals SHF, RHF can be emitted relative to a defined axis a, which is directed vertically downwards into the container 3 toward the filling material 2, or received after their reflection from the filling material surface. Accordingly, the level gauge 1 can be arranged substantially outside the container 3.

[0035] After reflection of the emitted radar signals Snr at the product surface, the level measuring device 1 receives the reflected radar signals RHF. The resulting signal propagation time t between emission and reception of the respective radar signal SHF, RHF is according to accordingly proportional to the distance d between the level measuring device 1 and the filling material 2. In this context, "c" is the media-dependent radar propagation speed. To determine the signal propagation time t, the FMCW or pulse propagation time method can be implemented in the level measuring device 1. For example, based on an appropriate calibration, the level measuring device 1 can in turn assign the measured signal propagation time t to the respective distance d. Using this, the level measuring device 1 can determine the fill level L at least at a specific point according to d = h - L, provided the installation height h is stored in the level measuring device 1.

[0036] Typically, the level measuring device 1 is connected to a higher-level unit 4, such as a local process control system or a decentralized server system, via a separate interface unit, such as "4-20 mA," "PROFIBUS," "HART," or "Ethernet." The measured level values ​​L can be transmitted via this interface, for example, to control any inflows or outflows of the container 3. However, other information about the general operating status of the level measuring device 1 can also be communicated.

[0037] As shown in Fig. 1, the surface of the filling material 2 is not planar. This can occur particularly with bulk-like filling materials 2, e.g., when cones of material form when filling the container 3. In addition, depressions can occur on the filling material surface when emptying the filling material 2. If the level measuring device 1 only determines the fill level L at a specific point on the surface of the filling material 2, this may lead to an incorrect interpretation of the fill level L. This can erroneously stop an emptying process if the level measuring device 1 detects an empty container 3, even though there is still fill material 2 at the edge of the container interior.In the opposite case, when the container s is full, it may happen that a filling process is not stopped even though a maximum filling level has already been exceeded at one point on the filling material surface, since this is not detected by the level measuring device 1.

[0038] For this reason, the level measuring device 1 shown in Fig. 1 determines the level L x;yspatially resolved, relative to the plane x;y orthogonal to the axis a. The central component here is a lens 11 which focuses the radar signals SHF, RHF. In the embodiment shown in Fig. 1, the converging lens 11 closes off the level measuring device 1 from the filling material 2. In this case, the converging lens 11 is aligned in the attached state of the level measuring device 1 on the container 3 such that its optical axis a, along which the radar signals SHF, RHF can be focused, is directed vertically downwards towards the filling material 2, as shown in Fig. 1. Preferably, the converging lens 11 is mounted on the level measuring device 1 in such a way that the components located inside the level measuring device 1 are encapsulated from the interior of the container 3 in an explosion-proof manner.

[0039] According to the invention, a plurality of radar ICs 12, 12' are provided inside the level measuring device 1, i.e., behind the collecting lens 11 in relation to the filling material 2. Each of the radar ICs 12, 12' has full functionality with regard to point-based distance measurement. This means that radar signals SHF, RHF can be generated, transmitted, and received with each of the radar ICs 12, 12'. Depending on the measuring principle implemented, e.g., FMCW or the pulse transit time method, the respective radar IC 12, 12' generates its own received signal ZF, ZF', to which a radar signal transit time can be assigned. In order to be able to determine the signal propagation time t of the respective radar signal SHF, RHF between transmission and reception based on the received signal ZF, ZF', the radar ICs 12, 12' are connected to a control / evaluation unit 14. The control / evaluation unit 14 determines the respective signal propagation time t or the associated fill level value L x;yin the case of the FMCW principle based on a Fourier transformation of the received signal ZF, ZF'.

[0040] Fig. 2 and Fig. 3 show that the radar ICs 12, 12' are arranged on a circuit board 15 within the level measuring device 1. In the variant shown, all radar ICs 12, 12' are encapsulated together, for example, by a potting compound 16. This eliminates the need for separate encapsulation of the individual radar ICs 12, 12'. The shared encapsulation 16 is designed to be transparent in that the transmission or reception of the radar signals SHF, RHF by the radar ICs 12, 12' is not suppressed. This can be achieved, for example, by having the corresponding primary radiators extend beyond the encapsulation 16 or by exempting them from it. Suitable manufacturing processes include selective dispensing, overprinting with 3D printing, protective molds or protective films over the primary emitters that are not to be cast (“foil assisted molding”), which are then removed.

[0041] The circuit board 15 is positioned inside the level measuring device 1 such that the beam cones A1, A2, within which the radar signals SHF, HF are respectively transmitted and received by the radar ICs 12, 12', are aligned approximately parallel to the axis a towards the collecting lens 11. As can be seen in particular from Fig. 3, the radar ICs 12, 12' are arranged, on the one hand, in different positions x, y on the circuit board 15 with respect to the axis a of the collecting lens 11, specifically mirror-symmetrically to the x and y axes. On the other hand, the radar ICs 12, 12' are divided into two groups of four, wherein the groups are distinguished according to the invention by their lateral offset V1, V2 of the radar ICs 12, 12' relative to the optical axis a of the collecting lens 11.

[0042] As symbolized in Fig. 1, the two different offsets V1, V2 result in the radar ICs 12, 12' transmitting or receiving the radar signals SHF, RHF with respect to the axis a of the collecting lens 11 with two different deviations into the container s or towards the filling material 2. This enables the control / evaluation unit 14 to determine corresponding filling level values ​​L laterally over the widest possible area of ​​the filling material surface. x;y In monostatic operating mode, the number m of detectable level values ​​corresponds to L x;y the number n of radar ICs 12, 12', i.e. eight in the embodiment shown in Fig. 3.

[0043] The lateral position x;y on the product surface, which corresponds to the corresponding level value L x;yis assigned, results from the position or offset V1, V2 of the corresponding radar IC 12, 12' on the circuit board 15 in relation to the axis a of the converging lens 11, the determined distance value d, and the diopter number of the converging lens. In order to determine the level values ​​L x;y To capture the radar beams laterally in a grid that is as uniform or narrow as possible, the diopter number and the positions should preferably be designed so that the resulting main beams of the radar ICs 12, 12' into the container 2 (see Fig. 1) have an offset of -10 dB or less. With an overlap of -3 dB or less, the alignment of the main beams is too large or the viewing angle is too overlapping.

[0044] In the embodiment of the level measuring device 1 according to the invention shown in Fig. 2 and Fig. 3, those four radar ICs 12' which are arranged on the circuit board 15 with the greater offset V2 to the axis a have a narrower beam cone A2 than the beam cone A1 of the inner radar ICs 12. As a result, the corresponding main radiation lobes of the radar signals SHF, HF behind the collecting lens 11 towards the filling material 2 are wider than the main radiation lobes of the inner radar ICs 12 from the offset V1, as is visualized in Fig. 1.

[0045] In this context, Fig. 1 schematically illustrates that the outer main radiation lobes of radar signals SHF, RHF, with respect to the optical axis a, only illuminate higher fill levels L and, at least in the case of a relatively narrow container 3, are not usable for low fill levels L. With the wider main radiation lobes of the outer radar signals SHF, RHF, similar area resolutions can be achieved at the illuminated, higher fill levels L as is the case with the narrow, inner main radiation lobes of the radar signals SHF, RHF at a low fill level L. Since the number of pixels or spatially resolved fill level values ​​L x;yThe number of main radiation lobes or radar ICs 12, 12' corresponds to the number of these, a very large number would be necessary for complete illumination of higher fill levels L with exclusively narrow main radiation lobes. However, since the area resolution for high fill levels L does not need to increase to provide good imaging for the user, wider radiation lobes are sufficient for larger offset angles and higher fill levels L, of which only a limited number are required according to the invention.

[0046] In order to adjust the beam cone A1, A2 of the respective radar ICs 12, 12' accordingly wider or narrower, a radar-focused primary radiator 13, 13' can be connected upstream of the radar ICs 12, 12' in front of their planar antennas. Overall, the inventive design of the level measuring device based on the individual radar ICs 12, 12' in conjunction with the converging lens 11 allows a level profile with laterally sufficient resolution to be achieved over a large height range h of the container 3, without the need for complex and thus power-intensive signal evaluation downstream.

[0047] Based on the level values ​​L determined at different positions x;y x;yThe control and evaluation unit 14 can create a profile of the product surface, for example, by interpolation. The profile of the product surface can be visualized either on a display of the level measuring device 1 or, for example, by the higher-level unit 4.

[0048] In addition to the monostatic operating mode, the level measuring device 1 according to the invention can also, in principle, be operated in the so-called bistatic mode. The operating mode can be set by the control and evaluation unit 14. An exemplary circuit design of two of the radar ICs 12, 12', with which the radar signals SHF, RHF can be generated or received not only monostatically but also bistatically, is shown in Fig. 4. The FMCW principle is implemented in the example shown, so that the radar ICs 12, 12' in Fig.

[0049] 4 are each based on a mixer 125, 125'. This serves to mix the currently transmitted radar signal SHF with the radar signal RHF ZU currently received via the primary radiator 13, 13'. This generates a received signal ZF, ZF' whose frequency changes proportionally to the signal propagation time or the distance d. By reading this frequency—for example, using a Fast Fourier Transformation—the control-evaluation unit 14 can determine the corresponding signal propagation time t according to the FMCW principle.

[0050] Within the respective radar IC 12, 12', the radar signal SHF to be transmitted is fed to the primary radiator 13, 13' via a transmit / receive combiner 123, 123', via which the received radar signal RHF can also be forwarded to the mixer 125, 125'. The radar signal SHF, RHF is amplified as needed before transmission or after reception by an amplifier 122, 122', 123, 123', which is arranged directly before or after the transmit / receive amplifier 123, 123'. With regard to bistatic measurement, it is advantageous if at least the receive amplifiers 124, 124' have sufficient reverse attenuation, in particular > 20 dB.

[0051] In addition to signal amplification, the transmitted radar signal SHF also undergoes frequency multiplication. In the embodiment shown in Fig. 4, a separate frequency multiplier 121, 121', 126, 126' with the same frequency multiplication factor N is provided for each radar IC 12, 12' in both the transmit and receive paths, i.e., upstream of the transmit / receive combiner 123, 123' and upstream of the mixer 125, 125'. This separate amplification in both the transmit and receive paths improves LO suppression, especially for bistable operation.

[0052] The frequency multiplication factor N of the frequency multipliers 121, 121', 126, 126' is the quotient of the desired frequency of the radar signal SHF, RHF divided by the frequency of a clock source 17, which controls the radar ICs 12, 12'. The clock source 17 can be implemented, for example, as an adjustable, phase-locked loop (PLL) for a voltage-controlled regulator (VCO). This allows the frequency of the radar signal SHF to be modulated in a time-dependent ramp according to the FMCW principle.

[0053] In the embodiment shown in Fig. 4, all radar ICs 12, 12' are controlled by the same clock source 17. This can be realized, for example, by the VCO of one of the radar ICs 12, 12' additionally functioning as a clock source 17 for all other radar ICs 12, 12' while their VCOs are deactivated. This ensures phase equality of the radar signals SHF emitted by the various radar ICs 12, 12', which is essential for bistatic operation of the radar ICs 12, 12'. In contrast to monostatic operation, in which the number of location-dependent fill level values ​​L x;y to which the number of existing radar ICs 12, 12' is limited, a bistatic operation enables the recording of level values ​​L x;y at a larger number of positions x; y in the container s than radar ICs 12, 12' are present.

[0054] In addition to the level values ​​L x;y, which in monostatic operating mode (the radar signal SHF, RnF is transmitted and received in monostatic operation by the same radar IC 12, 12' in order to calculate the corresponding level value L x;yTo determine the level of the radar signal (SHF) in bistatic mode, the radar signal SHF is transmitted by the first radar IC 12 and, after reflection, is received by the second radar IC 12'. For this purpose, the components 124, 126, 121', 122' of the radar ICs 12, 12' shown hatched in Fig. 4 must be deactivated accordingly for bistatic mode. The (de-)activation of these components 124, 126, 121', 122' or the coordination of the bistatic measurement can be carried out by the control / evaluation unit 14. Contrary to the illustration in Fig. 4, the bistatic principle for spatially resolved level measurement can also be applied to any number n of radar ICs 12 within the scope of the invention. In general, the theoretical maximum number m of locations at each of which a level value L x;y can be detected in bistatic operation according to calculated according to the Gaussian sum formula.

[0055] Particularly in relation to industrial level measurement, another advantage of the bistatic method is that corresponding level values ​​L x;y can be checked for plausibility. This is possible within the scope of the invention by measuring the level value L x;y is not recorded on a monostatic basis, the paired function of the radar ICs 12, 12' as transmitter and receiver is exchanged. In both constellations, a signal propagation time or a corresponding level value L x;y which logically must have the same value. If this is not the case, for example due to a fault in the level measuring device 1, then an implausible level value L x;yFor such a scenario, the control / evaluation unit 14 can, for example, be designed to generate a corresponding fault message. This enables the level measuring device 1 to perform a corresponding self-diagnosis in order to be able to report any malfunction to the higher-level unit 4. This further reduces the risk of an uncontrolled process state in the container s.

[0056] List of reference symbols

[0057] 1 level gauge

[0058] 2 Filling material

[0059] 3 containers

[0060] 4 Superior unit

[0061] 11 Collecting lens

[0062] 12 radar ICs

[0063] 13 , 13' primary radiator

[0064] 14 Control-evaluation unit

[0065] 15 circuit board

[0066] 16 Encapsulation

[0067] 17 Clock source

[0068] 121 , 121 ' Frequency multiplier in the transmission path

[0069] 122 , 122' transmitter amplifier

[0070] 123 , 123' Transmit-receive switch

[0071] 124 , 124' reception amplifier

[0072] 125 , 125' mixer

[0073] 126 , 126' Frequency multiplier in the receive path

[0074] A1 , A 2 Beam cone width a Optical axis of the collecting lens d Distance h Installation height

[0075] L x;y Level value m Number m of locations x;y where a level value is recorded

[0076] N frequency multiplication factors n number of radar ICs

[0077] R HF SHF (reflected) radar signal

[0078] V1 , V2 offset x;y position coordinates

Claims

Patent claims 1 . Radar-based level measuring device for determining location-related level values ​​(L x;y ) of a filling material (2) in a container (3), comprising: A converging lens (11) with an optical axis (a) which, in the attached state, is directed towards the filling material (2) so that radar signals (SHF, RHF) can be emitted in a bundled manner towards the filling material (2) or can be received in a bundled manner after their reflection on the filling material surface, at least two radar ICs (12, 12') which are designed o to generate the radar signals (SH) to be emitted, and / or o to receive the reflected radar signals (RH) after reflection on the filling material (2) and to generate therefrom a respective reception signal by means of which a radar signal propagation time can be determined, wherein the at least two radar ICs (12, 12') are arranged behind the converging lens (11) with respect to the filling material (2) at a defined, respectively different offset (V1 x;y , V2 x;y) to the optical axis (a) and aligned towards the collecting lens (11), and a control-evaluation unit (14) which is designed to control the radar ICs (11, 11 ') and to determine the signal propagation times in order to obtain at least two location-related fill level values ​​(L x;y ) to determine.

2. Level measuring device according to claim 1, wherein the at least two radar ICs (12, 12') are designed to generate the radar signals (SH) or the received signals according to the FMCW method.

3. Level measuring device according to claim 1 or 2, wherein one of the at least two radar ICs (12, 12') has no offset (V1 x;y , V2 x;y ) to the optical axis (a).

4. Level measuring device according to one of the preceding claims, wherein the at least two radar ICs (12, 12') have a common encapsulation (16).

5. Level measuring device according to one of the preceding claims, wherein the radar ICs (11, 11') are arranged mirror-symmetrically with respect to the optical axis (a) in the event that the level measuring device (1) comprises more than two radar ICs (11, 11').

6. Level measuring device according to at least one of the preceding claims, wherein the at least two radar ICs (12, 12') are designed and arranged such that they transmit the radar signals (SH, RH) with a beam cone (A1, A2) towards the collecting lens (11) or receive them from there, the greater the offset (V1 x;y , V2 x;y ) of the respective radar IC (12, 12') to the optical axis (a).

7. Level measuring device according to at least one of the preceding claims, wherein the number (n) of radar ICs (12, 12'), the respective distance of the at least two radar ICs (12, 12') from one another, the respective distance of the at least two radar ICs (12, 12') from the collecting lens (11), the diopter of the collecting lens (11), and / or the radar frequency of the radar ICs (12, 12') are coordinated with one another in such a way that resulting main radiation lobes of the radar ICs (12, 12') into the container (2) have an offset of at least -3dB and / or a maximum of -10dB from one another.

8. Level measuring device according to at least one of the preceding claims, wherein the control-evaluation unit (14) is designed to control the radar ICs (12, 12') by means of the bistatic radar method or to determine corresponding level values ​​(L x;y ) to determine.

9. Level measuring device according to claim 8, wherein the at least two radar ICs (12, 12') are clocked using high frequency technology by means of a common clock source (17).

10. Procedure for checking the spatially resolved level value (L x;y ) for plausibility by means of the level measuring device (1) according to claim 8 or 9, comprising the following method steps: Emitting a radar signal (SHF) by means of the first radar IC (12), receiving the corresponding radar signal (RHF) after reflection at the filling material surface via the second radar IC (12'), Determination of a first signal propagation time based on the corresponding received signal, Determining a second signal propagation time by repeating the preceding method steps, wherein the two radar ICs (12, 12') are used as transmitters and receivers, respectively. Recipients are swapped, and Classification of the level value (L x;y) as implausible if the first signal propagation time and the signal propagation time do not match.

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