Measuring setup and method for determining the fill level of a medium

Abstract

Measuring arrangement for determining the fill level of a medium (M), comprising: - a transmit-receive module (7, 13, 14, 15) configured to transmit a transmitted measurement signal (8a) towards a surface (4) of the medium (M) and to receive the transmitted measurement signal (8a) again as a returned measurement signal (10a, 10b); and - a forwarding module (9) which is equipped at least for receiving and forwarding the emitted measurement signal (8a) and is arranged such that the emitted measurement signal (8a) reaches the forwarding module (9) as a reflected measurement signal (8b) after the emitted measurement signal (8a) has been reflected at the surface (4) of the medium (M); - wherein the forwarding module (9) is further configured such that the forwarding module (9) sends the reflected measurement signal (8b) back towards the surface (4) of the medium (M) in such a way that the returned measurement signal (10a, 10b) is reflected again at the surface (4) of the medium (M) and only then reaches the transmit-receive module (7); and - wherein a control unit is provided which is configured to determine the fill level of the medium (M) based on a comparison between the emitted measurement signal (8a), the reflected measurement signal (8b) and the returned measurement signal (10a, 10b) and a reference value; characterized in that, - that the transmit / receive module (7, 13, 14, 15) is set up to transmit and receive a radar signal and the relay module (9) is set up to receive and relay a radar signal; - that the transmit-receive module (7, 13, 14, 15) is further configured to transmit and receive a radar-based reference signal (11, 12); and - that the transmit-receive module (7, 13, 14, 15) is configured such that the emitted measurement signal (8a) is emitted in a first main radiation direction (H1) and the reference signal (11, 12) is emitted in a second main radiation direction (H2) that differs from the first main radiation direction (H1).

Description

[0001] The present invention relates to a measuring arrangement for determining the fill level of a medium. Furthermore, the present invention relates to a method for determining the fill level of a medium.

[0002] For example, in the monitoring of rivers, irrigation canals, and watercourses, the water level is an important measurement. In flood protection, the water level is of great significance. Various measuring devices and methods are already known for determining the water level of a medium. For instance, radar-based methods can be used to determine the water level.

[0003] A state-of-the-art measuring arrangement is exemplified in the Fig. 1A and Fig. Figure 1B shows two different measurement situations. The measurement setup includes a transmit-receive module 1, which sends a radar signal via an antenna towards the medium M, in this case the water in a river. Fig. 1A is where the emitted radar signal 2 is represented by the solid arrow. The emitted radar signal 2 returns as a reflected radar signal 3, known as an echo. Fig. 1A represented by the dashed arrow - back to the transmit / receive module 1 after the emitted radar signal 2 has been reflected at the surface 4 of the water.

[0004] The transceiver module 1 then determines the fill level of the medium using a control unit (not shown) by inferring the distance between the transceiver module 1 and the surface 4 of the medium M from the travel time of the radar signal 2, 3. For this purpose, known radar sensors are used, which detect the returned, reflected radar signal 3 as an echo.

[0005] During the evaluation, it is possible, for example, to exploit the fact that the frequency difference between the transmitted and received signals is proportional to the distance between the transceiver module 1 and the surface 4, and thus depends on the fill level. The fill level determined in this way is converted into a corresponding output signal and displayed as a measured value. Alternatively, the distance between the transceiver module 1 and the surface 4, and therefore the fill level of the medium, can also be easily deduced directly from the travel time of the radar signal to return to the transceiver module.

[0006] In the course of the described procedure or the illustrated measurement setup, a wide variety of radar technologies, radar signals and modulation forms can be used, for example pulse radar, FMCW radar (FMCW = Frequency Modulated Continuous Wave), pulse Doppler radar, pulse compression radar, FSK radar (FSK = Frequency Shift Keying) and continuous wave radar (also CW radar, CW = continuous wave).

[0007] Essential to the measurement principle known from the prior art is that a radar signal is first emitted directly from the transceiver module onto the surface of the medium, and the radar signal reflected there returns directly to the transceiver module. For this reason, the transceiver module must also be positioned directly above the medium in the vertical direction, as exemplified in Fig. 1A is shown.

[0008] This is the case at the in Fig. In the measuring arrangement shown in Figure 1A, a mast 5 is provided, which is installed on the bank of the river. At the upper end of the mast 5, a lateral boom 6 is provided, extending perpendicularly to the mast 5, at the end of which the transmit-receive module 1 is attached and which in this way ensures that the transmit-receive module 1 and especially the antenna are arranged above the surface 4 of the river.

[0009] In such measuring arrangements, a special boom 6 must therefore be provided, which moves the transceiver module 1 and the antenna from the riverbank – or more generally from a zone to the side of the medium whose level is to be determined – to an area above the medium. These are structurally complex solutions. In particular, the longer the boom 6 needs to be, the more complex it is to provide a corresponding measuring arrangement. This significantly increases the installation costs of such measuring arrangements.

[0010] The specific length required for setting up the boom in a given application depends on the measurement situation or the expected measurement situations. For example, in the case of a river or channel, the boom might be set to a certain length. Fig. Case 1B shown occurs, in which the boom 6 is used for a certain measuring situation (in Fig. Figure 1B depicts a situation with a low water level) does not protrude far enough, so that the transmit-receive module 1 is not positioned above the surface 4 of the medium M. The emitted radar signal 2 is then – contrary to the scenario shown in Figure 1B – Fig. In the measurement situation shown in 1A, the light is no longer reflected from the surface 4 of the river, but from a section of the riverbed. Therefore, a successful measurement is not possible.

[0011] A disadvantage of the described state-of-the-art measuring arrangements and methods is that a compromise must be made, choosing between, on the one hand, a system for determining the fill level that is as reliable as possible and, on the other hand, a system that is as simple and inexpensive to install as possible. The more reliably the measuring arrangement is to determine the fill level of a medium, the longer the boom must be, and the more complex and expensive the installation of the measuring arrangement becomes.

[0012] Further state of the art is known from JP 2011-174713 A, DE 24 61 945 A1, US 6 071 340 A, CN 106 768 179 B, and CN 101 769 778 B.

[0013] The object of the invention is therefore to provide an improved measuring arrangement and an improved method for determining the fill level of a medium, with which the reliability of the measurement can be increased to such an extent that the fill level can be successfully determined in various measuring situations without having to significantly increase the effort required to assemble the system.

[0014] This problem is solved by a measuring arrangement for determining the fill level of a medium with the features of claim 1, and by a method for determining the fill level of a medium with the features of claim 7. Advantageous further developments of the invention are the subject of the dependent claims.

[0015] The measuring arrangement according to the invention for determining the fill level of a medium comprises a transmit-receive module configured to transmit a measurement signal towards a surface of the medium and to receive the transmitted measurement signal again as a returned measurement signal. Furthermore, the measuring arrangement according to the invention comprises a forwarding module configured at least for receiving and forwarding the transmitted measurement signal and arranged such that the transmitted measurement signal reaches the forwarding module as a reflected measurement signal after being reflected at the surface of the medium.The measuring arrangement according to the invention is characterized in that the forwarding module is further configured such that it sends the reflected measurement signal back towards the surface of the medium in such a way that the returned measurement signal is reflected again at the surface of the medium and only then reaches the transmit-receive module. The measuring arrangement according to the invention is further characterized in that a control unit is provided which is configured to determine the fill level of the medium based on a comparison between the transmitted measurement signal, the reflected measurement signal, the returned measurement signal, and a reference value.

[0016] The key aspect of the present invention is the realization that the measurement signal, which is reflected from the surface of the medium whose fill level is to be determined, does not have to travel directly back to the transmit-receive module. Instead, according to the present invention, the transmission path of the measurement signal is taken a detour, whereby the measurement signal reflected from the medium surface is first forwarded to the relay module and from there sent back towards the medium surface. The measurement signal then reflects once more from the medium surface before finally returning to the transmit-receive module.

[0017] This additional transmission path for the measurement signal means that the transceiver module no longer needs to be positioned directly above the surface of the medium in order for a transmitted measurement signal to be reflected directly back to the transceiver module from that surface. Instead, the transceiver module of the measurement arrangement according to the invention can now be installed laterally offset from the surface of the medium, for example, on the riverbank in the exemplary application of measuring the fill level of a river or irrigation canal.

[0018] Therefore, in the measuring arrangement according to the invention, a boom or other measures that would otherwise have been necessary to position the transceiver module vertically directly above the medium can be dispensed with. Consequently, assembly costs can be saved. Furthermore, the reliability of a successful measurement no longer depends on the length of a boom. Rather, the measuring arrangement according to the invention ensures that the fill level can still be successfully determined even at a low level.

[0019] For evaluation purposes, the entire propagation path of the measurement signal can be used, i.e., the total distance traveled by the transmitted measurement signal, the reflected measurement signal, and the returned measurement signal. Either the total distance of the measurement signal (i.e., the propagation path traveled), the total travel time of the measurement signal, or other parameters characterizing the propagation path, such as frequency shift or phase shift, can be used for evaluation. The evaluation is explained below using the total travel time of the measurement signal as an example.

[0020] The total travel time of the transmitted measurement signal, the reflected measurement signal, and the returned measurement signal can be converted into a distance using methods known from the prior art. This makes it possible to determine the path the measurement signal had to travel. This distance, or the measured value of the total travel time itself, can then be compared with a reference value to determine the fill level. For example, known reference values ​​from previous measurements may be available, from which the fill level can be directly derived. In this case, the reference value(s) are a predefined reference value(s). The reference values ​​may, for example, be stored in a table of values.However, such reference values ​​can also be recorded within the scope of any measurement, as will be described later, so that it is a reference value determined within the scope of the measurement.

[0021] For the purposes of this application, the terms "transmitted measurement signal," "reflected measurement signal," and "returned measurement signal" are used to clarify the distinction between these. These terms can refer to the same measurement signal, but they are used to differentiate between the various stages of the signal's propagation path. The measurement signal, once transmitted by the transceiver module, initially propagates towards the surface of the medium ("transmitted measurement signal"), is reflected there, and then propagates towards the relay module ("reflected measurement signal"), where it is relayed again, this time back to the surface of the medium, from where it is reflected back towards the transceiver module ("returned measurement signal").

[0022] In its simplest form, the relay module can be configured as a reflector from which the measurement signal is reflected and thus sent back towards the surface of the medium or the transmit-receive module of the measurement setup. However, it is also possible for the relay module itself to first receive and process the measurement signal emitted by the transmit-receive module and reflected from the surface of the medium, thereby triggering the transmission of the measurement signal returned by the relay module. For this purpose, the relay module itself can be equipped with a device for transmitting the returned measurement signal.

[0023] Furthermore, the forwarding module is not only configured to receive and forward the transmitted measurement signal, but it can also be configured to perform a reference measurement. For this purpose, a reference signal can be sent from the transmit-receive module to the forwarding module and reflected back to the transmit-receive module.

[0024] The control unit processes the received measurement signals in a manner generally known from the prior art in order to ultimately perform a comparison between the measurement signal, for example between the total transit time of the measurement signal or a value derived from the total transit time, and the reference value, from which the fill level of the medium can ultimately be determined.

[0025] To convert the total travel time of the measurement signal into a value representing a distance, the following procedure can be used, for example: The received, transmitted measurement signal is converted from the time domain to the frequency domain using spectral analysis. A frequency shift of the received signal relative to the transmitted measurement signal is proportional to the distance of a reflection from the transmitter, i.e., to the distance traveled by the measurement signal between the transmit / receive module and the forwarding module. This allows reflections and their distances to the level gauge—in this case, for example, the distance traveled by the measurement signal from the transmit / receive module to the forwarding module and back—to be determined from the received signal.

[0026] For example, a fast Fourier transform (FFT) can be used as a method for spectral analysis. The fast Fourier transform is a widely used and effective method in signal processing for converting signals between the time and frequency domains.

[0027] The transceiver module can be combined with the control unit to form a single measuring device. Alternatively or additionally, the transceiver module can also forward the received values ​​to a dedicated control unit, for example, via wired or wireless transmission.

[0028] In particular, the measuring device can be designed as a two-wire device, for example as a 4-20 mA two-wire device. This allows a measured value to be advantageously transmitted as a current signal via a supply line of the measuring device.

[0029] The measuring arrangement is particularly suitable for determining the fill level of a river or irrigation canal. In a specific measurement scenario, the transceiver module can be positioned on one bank, while the relay module is located on the opposite bank. The transceiver module is then configured so that the transmitted measurement signal strikes the surface of the river at the midpoint between the transceiver module and the relay module. In contrast to direct fill level measurement ( Fig. 1A and Fig. 1B) The new method allows for the use of a smaller transmitting and receiving antenna to achieve the widest possible beam angle. This ensures that the entire flow level is always "illuminated," regardless of the current water level. This enables successful measurements even at extremely low flow levels. The transmitted measurement signal, which strikes the river surface midway between the transmitting-receiving module and the relay module, is then reflected and subsequently reaches the relay module. From there, the measurement signal travels back along the same path in reverse order to the transmitting-receiving module.

[0030] The medium in question can be, for example, water or other liquids. Determining the fill level of the medium, or measuring the fill level or level, can of course be carried out not only in the aforementioned applications of a river or irrigation canal, but also in other bodies of water – such as streams, lakes, reservoirs, etc. – as well as in a basin – for example, in a mine, a settling basin, a sludge basin, a storm overflow basin, etc. – or in containers.

[0031] An advantage of the present invention compared to the prior art methods described above is that the measurement can be taken across the center of the river or lake, i.e., generally across the center of the surface of the medium whose fill level is to be determined, and no longer needs to be taken near the river or lake shore. This eliminates, on the one hand, the limitations inherent in… Fig. The measurement errors described in 1B are avoided. Furthermore, the following disadvantages, which can typically occur when taking measurements at the edge of a body of water, are also avoided: for example, the accumulation of debris at the water's edge that distorts the measurements, or the increased occurrence of plants that distort the measurements, such as algae.

[0032] Preferably, the transmit-receive module and the relay module are arranged at the same height horizontally. In this way, an imaginary connecting line between the transmit-receive module and the relay module—that is, a propagation path running directly between the transmit-receive module and the relay module—runs essentially parallel to the surface of the medium whose fill level is to be determined. This results in a particularly simple triangle for determining the fill level using trigonometric calculations, as shown below.

[0033] Preferably, the transmit-receive module and the relay module are equidistant from the center of the medium whose fill level is to be determined (e.g., the center of a flow), relative to the direct path between the transmit-receive module and the relay module. This ensures that the path traveled by the transmitted measurement signal to the center of the flow is exactly the same as the path traveled by the measurement signal reflected at the center of the flow. This results in a particularly simple triangle for determining the fill level using trigonometric calculations, as shown below.

[0034] The direct distance between the transmit / receive module and the forwarding module can be chosen as a reference value. Alternatively, an angle can be selected for the triangle used to calculate the fill level. This allows for the determination of a value representing the fill level, and ultimately the fill level itself, through simple trigonometric calculations.

[0035] The following is an example of how to calculate the water level of a river using the proposed measurement setup. The variable "a" represents the direct distance between the transmit / receive module and the relay module, both of which are located at the same horizontal height. The variable "b" represents the propagation path traveled by the transmitted and reflected measurement signal, i.e., the distance from the transmit / receive module to the water surface in the middle of the river and to the relay module. The variable "d" corresponds to the distance from the surface of the river's water level to the horizontal line connecting the transmit / receive module and the relay module. The variable "g" corresponds to the total distance from the riverbed to the horizontal line connecting the transmit / receive module and the relay module. Finally, the variable "h" represents the water level of the river to be determined. (a2)2+d2=(b2)2 d=(b2)2−(a2)2 h=g−d a direct distance between the transmit-receive module and the forwarding module, both of which are arranged at a common horizontal height; a / 2 half the distance “a”; b the propagation path traveled by the emitted and reflected measurement signal, i.e. the distance from the transmit / receive module to the water surface in the middle of the river and to the forwarding module; b / 2 is half the distance “b”, i.e., the propagation path traveled by the emitted measurement signal, i.e., the distance from the transmit-receive module to the center of the river; d distance from the surface of the river's water level to the horizontal connecting line between the transmit-receive module and the relay module; g Distance from the bottom of the river to the horizontal connecting line between the transmit-receive module and the relay module; and h is the fill level of the river to be determined.

[0036] Because the triangle formed by the three elements – the transmitting module, the relaying module, and the flow center located between the transmitting and relaying modules – is an isosceles triangle, the quantity to be determined, in the form of the fill level, can be derived using simple trigonometric relationships, as can be seen from equations (1) to (3) above. Equation (1) corresponds to the Pythagorean theorem for the right-angled triangle formed by the variables "a / 2", "d", and "b / 2". From this, the intermediate result "d" can be calculated using equation (2), and finally, the final result for the fill level "h" can be calculated using equation (3). In this calculation example, the reference value therefore corresponds to the direct distance between the transmitting and relaying modules, which can be known beforehand or measured during each measurement.

[0037] An alternative calculation example can be performed analogously to the previously described relationships of the isosceles triangle, whereby the reference value is not the direct distance between the transmit-receive module and the relay module, but rather the angle "α" that exists between the horizontal connecting line between the transmit-receive module and the relay module and the direction of propagation of the emitted measurement signal, which spreads from the transmit-receive module towards the center of the flow. The corresponding equations (4) to (6) for calculating the fill level are given below: sin α=(db / 2) d=b2∗sin α h=g−d α the angle between the horizontal connecting line between the transmit-receive module and the forwarding module and the direction of the propagation path of the emitted measurement signal, which spreads from the transmit-receive module towards the center of the flow; b the propagation path traveled by the emitted and reflected measurement signal, i.e. the distance from the transmit-receive module to the center of the flow and to the forwarding module; b / 2 is half the distance “b”, i.e., the propagation path traveled by the emitted measurement signal, i.e., the distance from the transmit-receive module to the center of the river; d distance from the surface of the river's water level to the horizontal connecting line between the transmit-receive module and the relay module; g Distance from the bottom of the river to the horizontal connecting line between the transmit-receive module and the relay module; and h is the fill level of the river to be determined.

[0038] In a first preferred embodiment of the measuring arrangement, the transmission module is designed as an angled reflector. This angled reflector is configured such that an incident signal, regardless of the angle of incidence, is reflected back in the direction from which the incident signal originated. The angled reflector can be a retroreflector in the form of a triple mirror, a triangular angled reflector, or a retroreflector. Crucially, the measurement signal arriving at the transmission module is reflected back in the direction from which it originated, i.e., back to the surface of the medium at the point where the measurement signal was previously reflected as a signal emitted by the transmit-receive module. This results in a particularly simple measuring arrangement in terms of design. Simultaneously, the reflected signals are reduced.This means that less computational effort is required for signal evaluation in the transmit and receive module, and the clearer signals also ensure higher measurement accuracy and reliability.

[0039] According to the measuring arrangement according to the invention, the transmit / receive module is configured for transmitting and receiving a radar signal, and the relay module is configured for receiving and relaying a radar signal. The measuring signal can therefore be a radar signal, whereby a wide variety of radar technologies, radar signals, and modulation forms can be used, for example, pulse radar, FMCW radar (FMCW = Frequency Modulated Continuous Wave), pulse Doppler radar, pulse compression radar, FSK radar (FSK = Frequency Shift Keying), and continuous wave radar (also CW radar, CW = continuous wave). In this way, the fill level of a wide variety of media, especially liquids, can be measured in a contactless and safe manner.

[0040] According to the measuring arrangement according to the invention, the transmit-receive module is further configured to transmit and receive a radar-based reference signal. The reference signal can also be a radar signal based on one of the aforementioned different radar technologies.

[0041] The reference signal can be transmitted in such a way that the propagation time of the reference signal to the relay module and back to the transmit-receive module is provided as a reference value for the control unit. Preferably, the reference signal is transmitted directly to the relay module and reflected back from the relay module. This allows the immediate distance between the transmit-receive module and the relay module to be determined as described above, and this immediate distance to be used as a reference value for determining the fill level of the medium. The transmission path of the reference signal is therefore the direct transmission path between the transmit-receive module and the relay module, while the previously described measurement signal takes an indirect transmission path between the transmit-receive module and the relay module, namely the "detour" via the surface of the medium whose fill level is to be determined.It is possible that the transmitted measurement signal and the reference signal are emitted separately from the transceiver module. However, it is also possible that they originate from the same source and exhibit a wide radiation angle when emitted from the transceiver module. In this case, the transmitted measurement signal, which returns as the transmitted measurement signal, and the reference signal are only distinguished upon the transceiver module's subsequent reception of the signals. The reference signal will return to the transceiver module first because the direct transmission path of the reference signal is shorter than the indirect transmission path (across the surface of the medium) of the transmitted measurement signal.If the reference value is also determined via a reference signal which is exposed to the same environmental conditions as the measurement signal, then error compensation advantageously takes place.

[0042] Furthermore, according to the invention, the transmit-receive module is configured such that the transmitted measurement signal can be emitted in a first main radiation direction and the reference signal in a second main radiation direction that differs from the first main radiation direction. The transmitted measurement signal and the reference signal can be emitted separately or independently of each other by the transmit-receive module. The signals can then be emitted in a more concentrated or focused manner – i.e., with a smaller radiation angle or opening angle. In particular, the second main radiation direction points directly from the transmit-receive module to the relay module, while the first main radiation direction points from the transmit-receive module to a point on the surface of the medium located midway between the transmit-receive module and the relay module.Advantageously, the reference signal can then be sent only when needed, while the measurement signal is sent for each measurement to determine the fill level.

[0043] According to a further preferred embodiment of the measuring arrangement, the transmit-receive module is pivotably positioned between a first position, in which the transmitted measurement signal can be emitted in the first main radiation direction, and a second position, in which the reference signal can be emitted in the second main radiation direction. This provides a structurally simple embodiment of a measuring arrangement for realizing two different main radiation directions for two signals. Advantageously, it eliminates the need for two separate sources for the two signals, the measurement signal and the reference signal.The swivel capability also makes it advantageous to ensure that, regardless of the specific fill level present in a measurement situation, the first main radiation direction is correctly set, i.e., that a point on the surface of the medium is hit by the emitted measurement signal in the middle between the transmit-receive module and the forwarding module.

[0044] According to an alternative preferred embodiment of the measuring arrangement, the transmit-receive module has at least two differently oriented transmitting antennas for emitting the transmitted measurement signal in the first main radiation direction and for emitting the reference signal in the second main radiation direction. In this way, a structurally simple and cost-effective measuring arrangement can be provided, in which standard components for the transmitting antennas can be used.

[0045] According to a further, alternative preferred embodiment of the measuring arrangement, the transmit-receive module features a phased array antenna for transmitting the measurement signal in the first main radiation direction and for transmitting the reference signal in the second main radiation direction. This allows the different main radiation directions to be easily controlled using beamforming. A phased array antenna can be understood as a phased array antenna with strong directivity. The radiated energy can be focused by arranging and connecting individual radiators. The radiation direction, i.e., in this case the differently adjustable main radiation directions, is thus electronically adjustable.

[0046] According to a further preferred embodiment of the measuring arrangement, an additional relay module is provided, which is configured to receive and relay the emitted measurement signal. The additional relay module is arranged such that the emitted measurement signal reaches the relay module as a reflected measurement signal after being reflected off the surface of the medium. Furthermore, the additional relay module is configured such that it sends the reflected measurement signal back towards the surface of the medium in such a way that the reflected signal is again reflected off the surface of the medium and only then reaches the transmit-receive module. The additional relay module can have the same properties as the relay module described above.In this way, two measurement signals can be generated for each measurement: one from the previously described forwarding module and one from the additional forwarding module. This improves measurement reliability.

[0047] According to a further aspect of the present invention, a method according to the invention for determining the fill level of a medium is provided, wherein the method comprises the following steps: a) emitting a measurement signal towards a surface of the medium by means of a transmit-receive module; and b) reflecting the emitted measurement signal at the surface of the medium such that the emitted measurement signal is forwarded as a reflected measurement signal to a forwarding module. The method according to the invention further comprises the following step c): forwarding the reflected measurement signal as a returned measurement signal back towards the surface of the medium by means of the forwarding module.The method according to the invention further comprises the following step d): re-reflecting the returned measurement signal at the surface of the medium such that, after re-reflecting at the surface of the medium, the returned measurement signal again reaches the transmit-receive module. Finally, the method according to the invention further comprises the following step e): determining the fill level of the medium by a control unit based on a comparison between the transmitted measurement signal, the reflected measurement signal, and the returned measurement signal, as well as a reference value.

[0048] The advantages previously described in connection with the measuring setup also apply analogously to the method according to the invention. In particular, the key insight for the present invention is that the measurement signal, which is reflected from the surface of the medium whose fill level is to be determined, does not have to travel directly back to the transmit-receive module. Rather, according to the present invention, a detour is taken for the transmission path of the measurement signal, whereby the measurement signal reflected from the surface of the medium is first forwarded to the relay module and from there sent back towards the surface of the medium. The measurement signal then reflects once more from the surface of the medium before finally returning to the transmit-receive module. This provides, in particular, a reliable method by which the fill level of the medium can be determined even at low fill levels.

[0049] In a first preferred embodiment of the method, an angle reflector, in particular a triple mirror, is used as a transmission module, wherein the angle reflector is arranged such that an incident signal is reflected back into an origin direction regardless of the angle of incidence, from which origin the incident signal came.

[0050] According to the invention, a radar-based signal is used as the emitted measurement signal.

[0051] According to the invention, the transit time of a radar-based reference signal, transmitted directly from the transceiver module to the relay module and relayed back from the relay module to the transceiver module, is used as the reference value. In particular, the directly transmitted and relayed reference signal propagates between the transceiver module and the relay module without contact with the medium whose fill level is to be determined.

[0052] Furthermore, the reference signal and the transmitted measurement signal can preferably be transmitted simultaneously by the transmit-receive module.

[0053] Alternatively, the reference signal and the transmitted measurement signal can preferably be emitted by the transmit-receive module with a time delay. Preferably, the main radiation direction of the transmit-receive module can also be changed between the emission of the reference signal and the emission of the measurement signal.

[0054] The advantages previously described in the context of the advantageous embodiments of the measuring arrangement also apply accordingly to the advantageous embodiments of the method according to the invention.

[0055] The aforementioned method according to the invention, as well as its preferred embodiments, can in particular be carried out with a aforementioned measuring arrangement according to the invention, as well as with the preferred embodiments of the measuring arrangement according to the invention.

[0056] The measuring arrangement described above, as well as its preferred embodiments, can in particular be set up to carry out a method described above, as well as the preferred embodiments of the method according to the invention.

[0057] The present invention is explained in detail below with reference to exemplary embodiments and the accompanying figures. These show: Fig. 1A: a simplified representation of a measurement setup according to the state of the art in a measurement situation at a high water level of a river (already covered), Fig. 1B: the state-of-the-art measuring arrangement according to Fig. 1A in another measurement situation at a low river level (already discussed), Fig. 2A: a measuring arrangement according to the present invention in one of the Fig. 1A corresponding measurement situation at a high water level of a river, Fig. 2B: the measuring arrangement according to Fig. 2A in another, the Fig. 1B corresponding measurement situation at low river level, Fig. 3A and Fig. 3B: Exemplary embodiments of a transmit-receive module of the measuring arrangement according to the invention, Fig. 4A and Fig. 4B: Exemplary embodiments of a forwarding module of the measuring arrangement according to the invention, and Fig. 5A and Fig. 5B: Triangle underlying a specific determination of the fill level of a river according to two different embodiments.

[0058] In the Fig. 2A and Fig. Figure 2B shows a measurement setup according to the present application, in two different measurement situations, which corresponds to the Fig. 1A and Fig. The measurement situations shown in Figure 1B and described at the beginning correspond to the state of the art. Firstly, in Fig. 2A represents a flow with the medium M in the form of water, where one measurement situation is at a high water level, while the other is in Fig. Figure 2B shows a measurement situation at a low water level.

[0059] The illustrated measuring arrangement for determining the fill level of the medium M includes, among other things, a transmit-receive module 7, which is configured to emit a measurement signal 8a towards the surface 4 of the medium M. The transmit-receive module 7 is in Fig. 2A or Fig. 2B is mounted on a mast 5 on the left bank of the river, the mast 5 being a conventional mast 5 according to the state of the art (cf. Fig. 1A and Fig. 1B). Only one boom can be advantageously dispensed with in the measuring arrangement, so that the transmit-receive module 7 is arranged on the riverbank itself and is not located directly vertically above the surface 4 of the medium M.

[0060] The transmit-receive module 7 according to the described embodiment is basically, in its simplest form, constructed like radar measuring devices known from the prior art that are used for level measurement - for example, according to the transmit-receive module 1 known from the prior art ( Fig. 1A and Fig. 1B). In the illustrated embodiments, a radar-based signal is used as the measurement signal.

[0061] To successfully measure the fill level, the emitted measurement signal 8a is first directed diagonally downwards - as in Fig. 2A shown at a first tilt angle α1 and in Fig. 2B is emitted from the transmit-receive module 7 at a second tilt angle α2, which is greater than the first tilt angle α1, and strikes the surface 4 of the medium M. The emitted measurement signal 8a is then reflected from the surface 4 of the medium M and propagates further as the reflected measurement signal 8b until it reaches a relay module 9. The propagation path of the emitted measurement signal 8a and the reflected measurement signal 8b is described in the Fig. 2A and Fig. 2B - and furthermore in Fig. 3A - marked by a solid arrow.

[0062] The inclination angles α1 and α2 are measured relative to the horizontal, in the Fig. 2A and Fig. 2B with respect to the horizontally running, direct connecting line between transmit-receive module 7 and forwarding module 9. The transmit-receive module 7 and the forwarding module 9 are preferably arranged horizontally opposite each other at the same height.

[0063] The forwarding module 9 is configured to receive and forward the emitted measurement signal 8a and is arranged such that the emitted measurement signal 8a reaches the forwarding module 9 as a reflected measurement signal 8b after the emitted measurement signal 8a has been reflected at the surface 4 of the medium M. In the illustrated and thus preferred embodiment according to Fig. 2A or Fig. 2B, the relay module 9, is located on the riverbank shown on the right, i.e., on the riverbank opposite the transmit-receive module 7. The emitted measurement signal 8a strikes the surface 4 of the medium M in the middle between the transmit-receive module 7 and the relay module 9, i.e., in the middle of the river.

[0064] As soon as the reflected measurement signal 8b reaches the relay module 9, it is reflected again there, in such a way that it is sent back as a returned measurement signal 10a in the direction from which the reflected measurement signal 8b originated. For this purpose, the relay module 9 in the illustrated embodiment is designed as a so-called triangular angle reflector. Such an angle reflector reflects radar-based signals in precisely the direction from which the signal came when it arrived at the angle reflector.

[0065] The forwarding module 9 is therefore set up such that the reflected measurement signal 8b is sent back in the direction of the surface 4 of the medium M in such a way that the returned measurement signal 10a is reflected again at the surface 4 of the medium M and only then does it reach the transmit-receive module 7 as a returned measurement signal 10b.

[0066] The propagation path of the returned measurement signal 10a, 10b is in the embodiments according to Fig. 2A and Fig. 2B - and furthermore in Fig. 3A - marked by a dashed arrow.

[0067] The transmit / receive module 7 is therefore also configured to receive the transmitted measurement signal 8a again as a returned measurement signal 10a, 10b. As soon as the transmit / receive module 7 has received the returned measurement signal 10b, the level or fill level of the medium M or the flow can be determined from the measurement signal, for example, from the total travel time of the measurement signal – that is, from the travel time of the transmitted measurement signal 8a, the reflected measurement signal 8b, and the returned measurement signal 10a, 10b. A control unit, not shown separately, is provided in the measuring arrangement for this purpose.

[0068] For the sake of simplicity, the emitted measurement signal 8a, the reflected measurement signal 8b, and the returned measurement signal 10a, 10b can all be collectively referred to as the measurement signal, since in the illustrated and described embodiments they constitute one and the same measurement signal. The individual linguistic distinctions are made solely for clarity, to differentiate between the various sections of the measurement signal's propagation path.

[0069] For the purpose of evaluating the measurement, the measurement signal can first be converted into a distance using methods known from the prior art. For this purpose, the propagation time of the measurement signal can be used, for example. Furthermore, the direct, immediate distance between the transmit-receive module 7 and the relay module 9 is also known. This distance may, for example, have been initially measured or may be determined within the scope of a single measurement. For this purpose, the transmit-receive module 7 can emit a reference signal 11 – also radar-based in the illustrated embodiment – ​​which travels directly to the relay module 9, is reflected there, and returns to the transmit-receive module 7 as a reference signal 12. This reference signal 11, 12, specifically, for example, its propagation time, can again be converted into the distance traveled by the reference signal 11, 12 using a known method.

[0070] The propagation path of the reference signal 11 transmitted to the forwarding module 9 is in the Fig. 2A and Fig. 2B, and furthermore in Fig. 3A, marked by a solid arrow, while the propagation path of the reference signal 12 reflected from the forwarding module 9 back to the transmit-receive module 7 in the Fig. 2A and Fig. 2B, and furthermore in Fig. 3A, is marked by a dashed arrow.

[0071] Once the individual paths of both the emitted measurement signal 8a, the reflected measurement signal 8b, and the returned measurement signal 10a, 10b – i.e., the path of the measurement signal – as well as the reference signal 11, 12 are known, the fill level or the position of the surface 4 of the medium M can be determined by means of simple geometric calculations. As can be seen from the Fig. 2A and Fig. As can be seen in Figure 2B, the corresponding lines form an isosceles triangle, the lengths of which are all known based on the aforementioned measurements. From this, the distance d1 and d2 can be easily calculated. These distances correspond to the perpendicular distance from the surface 4 of the medium M to the direct connecting line between the transmit-receive module 7 and the relay module 9. Since the heights of the mounted transmit-receive module 7 and relay module 9, as well as the general geometry of the flow, in particular the depth of the medium M and the position of the riverbed, are also known, the fill level of the medium M can be successfully determined by means of a simple geometric calculation.

[0072] A specific calculation example is given at the end of the detailed description and refers to the illustrations in Fig. 5A and Fig. 5B.

[0073] The direct distance between the transmit-receive module 7 and the forwarding module 9 can therefore serve as a reference value for determining the fill level and can, as described above, either be determined as part of each individual measurement or determined in advance.

[0074] This "direct measurement" between the transceiver module 7 and the relay module 9 is therefore not strictly necessary for every measurement. However, it can be performed regularly for monitoring purposes, for example, even with each individual measurement. The value characterizing the reference signal 11, 12, such as the propagation time of the reference signal 11, 12, or the direct distance between the transceiver module 7 and the relay module 9, must be constant. This value is independent of the fill level of the medium M. Therefore, a change in such a value during the "direct measurement" or reference measurement indicates that the system has a fault and requires further investigation.

[0075] In determining the fill level, it is not necessary to calculate the individual distances based on the measurement signal and the reference signal 11, 12. Since the travel times or the frequency shift—depending on which characteristic value of the signal is used as the basis for the calculation—of the individual radar signals are proportional to the distance traveled, it suffices to arrange the travel times or the characteristic values ​​themselves—once for the measurement signal and once for the reference signal 11, 12—in the ratio of the isosceles triangle described above. This then results in a kind of imaginary travel time or an imaginary characteristic value of an imaginary radar signal, which, positioned midway above the river, would have traveled a distance corresponding to the dashed line representing the distance d1 or d2. This imaginary travel time or characteristic value...This imaginary characteristic value can also be converted into the distance d1 or d2.

[0076] The method according to the present application for determining the fill level of the medium M, which can be carried out with the described measuring arrangement, can be summarized as follows: a) Emitting the emitted measurement signal 8a in the direction of the surface 4 of the medium M by means of the transmit-receive module 7; b) Reflecting the emitted measurement signal 8a on the surface 4 of the medium M such that the emitted measurement signal 8a is forwarded as a reflected measurement signal 8b to the forwarding module 9; c) Forwarding the reflected measurement signal 8b as a returned measurement signal 10a, 10b back towards the surface 4 of the medium M by means of the forwarding module 9; d) re-reflecting the returned measurement signal 10a, 10b at the surface 4 of the medium M such that the returned measurement signal 10a, 10b, after re-reflecting at the surface 4 of the medium M, again reaches the transmit-receive module 7, and e) Determining the fill level of the medium M by the control unit based on a comparison between the emitted measurement signal 8a, the reflected measurement signal 8b and the returned measurement signal 10a, 10b as well as a reference value.

[0077] As can be seen from the described embodiment, the terms level measurement or determination of the fill level of a medium in the present application can be understood to mean both the determination of the distance from the surface of the medium to a specific height above the level – in this case, the connecting line between the transmit-receive module 7 and the forwarding module 9 – and the measurement of the distance of the surface of the medium from the bottom of a river or irrigation canal or, for example, a channel. In the present measuring arrangement, these values ​​are each convertible into one another.

[0078] The control unit is suitable for performing the described operations. Accordingly, the control unit is configured to determine the fill level of the medium M based on a comparison between the emitted measurement signal 8a, the reflected measurement signal 8b, and the returned measurement signal 10a, 10b, as well as a reference value. The total transit time of the measurement signal can be used for this purpose, and the reference value can be, in particular, the transit time of the reference signal 11, 12.

[0079] In the Fig. 3A, Fig. 3B and Fig. Figure 3C shows various embodiments of the transmit-receive module 13, 14, 15, all of which, as in the Fig. 2A and Fig. 2B described, which can be used according to the transmit / receive module 7.

[0080] In the case of the transmit-receive module 13 according to Fig. 3A provides a very wide initial beam angle β1, or opening angle, for the emitted measurement signal 8a and also the reference signal 11. In this way, both the reference signal 11 and the emitted measurement signal 8a can be emitted as a single signal by the transmit-receive module 13.

[0081] However, it is also possible, as illustrated by the example shown in the illustration. Fig. As can be seen in Figure 3B, individual or different signals are emitted as reference signal 11 or transmitted measurement signal 8a by the transmit-receive module 14. In the Fig. In the embodiment shown in Figure 3B, the signals are then more concentrated or focused, so that a small, second radiation angle β2 is provided for the reference signal 11 and a small, third radiation angle β3 is also provided for the emitted measurement signal 8a. The emitted measurement signal 8a then propagates along the first main radiation direction H1 and the reference signal 11 along the second main radiation direction H2.

[0082] To enable the different main emission directions – first main emission direction H1 and second main emission direction H2 – to be provided by the transmit-receive module 14, various embodiments of the transmit-receive module 14 can be used. For example, the transmit-receive module 14 can be pivotably configured between a first position, in which the transmitted measurement signal 8a can be emitted in the first main emission direction H1, and a second position, in which the reference signal 11 can be emitted in the second main emission direction H2.

[0083] Alternatively, a phased array antenna can be provided in the transmit-receive module 14 for transmitting the transmitted measurement signal 8a in the first main radiation direction H1 and for transmitting the reference signal 11 in the second main radiation direction H2.

[0084] Alternatively, several individual radar antennas with different radiation directions can simply be provided.

[0085] The first main radiation direction H1 and the second main radiation direction H2 enclose the third tilt angle α3. If this occurs in the course of Fig. 3B described transmit / receive module 14 in the in Fig. In the measurement situation shown in 2A, the third inclination angle α3 corresponds to the first inclination angle α1, and in the Fig. The measurement situation shown in 2B corresponds to the second inclination angle α2.

[0086] A described orientation of the first main radiation direction H1 or on Fig. The third tilt angle α3, as defined in section 3B, can be adjusted in various ways, such as by pivoting the transmit / receive module 14 or by using a phased array antenna. The specific orientation, or third tilt angle α3, can be continuously adjusted. This can also be used to calibrate the measurement setup or for each measurement. The third tilt angle can be changed until the emitted measurement signal 8a, along the first main radiation direction H1, reaches the required point on the surface 4 of the medium M, for example, the center of the flow. As soon as the corresponding orientation of the first main radiation direction H1 is reached, the corresponding echo signal of the returned measurement signal 10b is also at its strongest, since the reflection at the relay module 9 then causes the emitted measurement signal 8a to be reflected at its maximum strength.the reflected measurement signal 8b returns to the transmit-receive module 7 via the same path as the returned measurement signal 10a, 10b.

[0087] The specific tilt angle thus set, i.e. the angle between the first main radiation direction H1 and the second main radiation direction H2, can also be measured and used to calculate the previously described isosceles triangle for determining the fill level of the medium M.

[0088] A specific calculation example is given at the end of the detailed description, which relates to the representation in Fig. 5B and refers to.

[0089] In Fig. Figure 3C shows another embodiment of a transmit-receive module 15, which has a radio unit 16 for communicating measured values ​​to external systems and a solar cell 17 for generating electrical energy to supply a battery of the transmit-receive module 15 (not shown).

[0090] In the Fig. 4A and Fig. Figure 4B shows two embodiments of the forwarding module 9, both of which are described in the Fig. 2A and Fig. The measurement setups or situations described in 2B can be used.

[0091] Each additional forwarding module 18, 19 is provided, which is configured to receive and forward the emitted measurement signal 8a. The additional forwarding module 18, 19 is also arranged such that the emitted measurement signal 8a reaches the forwarding module 9 as a reflected measurement signal 8b after the emitted measurement signal 8a has been reflected at the surface 4 of the medium M.

[0092] In general, what was previously described in connection with forwarding module 9 also applies to the additional forwarding module 18, 19. In particular, the additional forwarding module 18, 19 is also configured such that the reflected measurement signal 8b is reflected from it in the direction of the surface 4 of the medium M in such a way that a returned measurement signal is reflected again at the surface 4 of the medium M and only then reaches the transmit-receive module 7.

[0093] In this way, two feedback measurement signals can be generated during a measurement, thereby increasing the reliability of the measurement or enabling targeted coding. As described in Fig. As shown in Figure 4B, the additional forwarding module 19 is positioned offset forward by a certain distance (e). In the illustrated embodiments, the additional forwarding module 18, 19 is arranged above the forwarding module 9. A reverse arrangement is also possible, such that the additional forwarding module is located below the forwarding module 9. An offset in the opposite direction, opposite to the offset e, i.e., to the rear, is also possible.

[0094] The following example illustrates the following: Fig. 5A and Fig. Section 5B provides a calculation of the fill level h of a river. The reference symbols are based on the previously described embodiment according to... Fig. 2A or Fig. 2B. The variable “a” represents the direct distance between the transmit / receive module 7 and the relay module 9, both of which are located at the same horizontal height. The variable “b” represents the propagation path traveled by the transmitted and reflected measurement signal 8a, 8b, i.e., the distance from the transmit / receive module 7 to the center of the river and to the relay module 9. The variable “d” corresponds to the distance from the surface 4 of the river's water level to the horizontal line connecting the transmit / receive module 7 and the relay module 9. The variable “g” corresponds to the total distance from the riverbed to the horizontal line connecting the transmit / receive module 7 and the relay module 9. Finally, the variable “h” corresponds to the river's water level to be determined.

[0095] Due to the fact that the triangle formed by the three elements transmit-receive module 7, relay module 9 and the flow center located between transmit-receive module 7 and relay module 9 is an isosceles triangle, the quantity to be determined in the form of the fill height h can be derived via simple trigonometric relationships, as shown in the following equations (1) to (3) in conjunction with the representation according to Fig. As can be seen in section 5A. Equation (1) corresponds to the Pythagorean theorem for the right-angled triangle formed by the variables "a / 2", "d", and "b / 2", from which the intermediate result "d" can be calculated via equation (2) and finally the final result to be determined for the fill level "h" via equation (3). In this calculation example, the reference value therefore corresponds to the direct distance a between the transmit-receive module 7 and the forwarding module 9, which may be known in advance or can be measured during each measurement. (a2)2+d2=(b2)2 d=(b2)2−(a2)2 h=g−d a direct distance between transmit-receive module 7 and forward module 9, both of which are arranged at a common horizontal height; a / 2 half the distance “a”; b the propagation path traveled by the emitted and reflected measurement signal 8a, 8b, i.e. the distance from the transmit / receive module 7 to the center of the flow and to the forwarding module 9; b / 2 half the distance “b”, i.e. the propagation path traveled only by the emitted measurement signal 8a, i.e. the distance from the transmit-receive module 7 to the center of the river; d distance from the surface 4 of the water level of the river to the horizontal connecting line between transmit-receive module 7 and forward module 9; g Distance from the bottom of the river to the horizontal connecting line between transmit-receive module 7 and forward module 9; and h is the fill level of the river to be determined.

[0096] An alternative calculation example can be performed analogously to the previously described relationships of the isosceles triangle, whereby the reference value is not the direct distance a between transmit-receive module 7 and relay module 9, but rather the angle "α" that exists between the horizontal connecting line between transmit-receive module 7 and relay module 9 and the direction of propagation of the emitted measurement signal 8a, which propagates from transmit-receive module 7 towards the center of the flow. The corresponding equations (4) to (6) for calculating the fill level are given below and are related to the representation according to Fig. 5B to be understood: sin α=(db / 2) d=b2∗sin α h=g−d α the angle between the horizontal connecting line between transmit / receive module 7 and forward module 9 and the direction of propagation of the emitted measurement signal 8a, which propagates from the transmit / receive module 7 towards the center of the flow; b the propagation path traveled by the emitted and reflected measurement signal 8a, 8b, i.e. the distance from the transmit / receive module 7 to the center of the flow and to the forwarding module 9; b / 2 half the distance “b”, i.e. the propagation path traveled only by the emitted measurement signal 8a, i.e. the distance from the transmit-receive module 7 to the center of the river; d distance from the surface 4 of the water level of the river to the horizontal connecting line between transmit-receive module 7 and forward module 9; g Distance from the bottom of the river to the horizontal connecting line between transmit-receive module 7 and forward module 9; and h is the fill level of the river to be determined. Reference symbol list 1 Transceiver module 2. Emitted measurement signal 3 reflected measurement signal 4 Surface area (of the medium) 5 masts 6 outriggers 7, 13, 14, 15 Transceiver module 8a emitted measurement signal 8b reflected measurement signal 9, 18, 19 Forwarding module 10a, 10b returned measurement signal 11, 12 Reference signal 16 radio units 17 solar cells H1 first main radiation direction H2 second main direction of radiation M Medium a distance between the transmit / receive module and the forwarding module b. Propagation path traveled by the emitted and reflected measurement signal (8a, 8b) d, d1, d2 Distance (from the surface 4 of the water level of the river to the horizontal connecting line between transmit / receive module and forward module) e offset g Total distance from the bottom of the river to the horizontal connecting line between the transmit-receive module and the forwarding module h Filling level α Angle between horizontal connecting line between transmit-receive module and forwarding module and the direction of propagation path of the emitted measurement signal α1 first angle of inclination α2 second angle of inclination α3 third inclination angle β1 first radiation angle β2 second beam angle β3 third beam angle

Claims

[1] Measuring arrangement for determining the fill level of a medium (M), comprising: - a transmit-receive module (7, 13, 14, 15) configured to transmit a transmitted measurement signal (8a) towards a surface (4) of the medium (M) and to receive the transmitted measurement signal (8a) again as a returned measurement signal (10a, 10b); and - a forwarding module (9) which is equipped at least for receiving and forwarding the emitted measurement signal (8a) and is arranged such that the emitted measurement signal (8a) reaches the forwarding module (9) as a reflected measurement signal (8b) after the emitted measurement signal (8a) has been reflected at the surface (4) of the medium (M); - wherein the forwarding module (9) is further configured such that the forwarding module (9) sends the reflected measurement signal (8b) back towards the surface (4) of the medium (M) in such a way that the returned measurement signal (10a, 10b) is reflected again at the surface (4) of the medium (M) and only then reaches the transmit-receive module (7); and - wherein a control unit is provided which is configured to determine the fill level of the medium (M) based on a comparison between the emitted measurement signal (8a), the reflected measurement signal (8b) and the returned measurement signal (10a, 10b) and a reference value; characterized by , - that the transmit / receive module (7, 13, 14, 15) is set up to transmit and receive a radar signal and the relay module (9) is set up to receive and relay a radar signal; - that the transmit-receive module (7, 13, 14, 15) is further configured to transmit and receive a radar-based reference signal (11, 12); and - that the transmit-receive module (7, 13, 14, 15) is configured such that the emitted measurement signal (8a) is emitted in a first main radiation direction (H1) and the reference signal (11, 12) is emitted in a second main radiation direction (H2) that differs from the first main radiation direction (H1). [2] Measuring arrangement according to claim 1, characterized by , that the forwarding module (9) is designed as an angle reflector, in particular as a triple mirror, wherein the angle reflector is arranged such that an incident signal is reflected back into an origin direction regardless of the angle of incidence, from which origin direction the incident signal came. [3] Measuring arrangement according to claim 1 or 2, characterized by, that the transmit-receive module (7, 13, 14, 15) is pivotably arranged between a first position in which the emitted measurement signal (8a) can be emitted in the first main radiation direction (H1) and a second position in which the reference signal (11, 12) can be emitted in the second main radiation direction (H2). [4] Measuring arrangement according to claim 3, characterized by , that the transmit-receive module (7, 13, 14, 15) has at least two differently oriented transmitting antennas for transmitting the transmitted measurement signal (8a) in the first main radiation direction (H1) and for transmitting the reference signal (11, 12) in the second main radiation direction (H2). [5] Measuring arrangement according to claim 3, characterized by, that the transmit-receive module (7, 13, 14, 15) has a phased array antenna for transmitting the transmitted measurement signal (8a) in the first main radiation direction (H1) and for transmitting the reference signal (11, 12) in the second main radiation direction (H2). [6] Measuring arrangement according to any one of claims 1 to 5, characterized by, that an additional forwarding module (18, 19) is provided, which is configured to receive and forward the emitted measurement signal (8a) and is arranged such that the emitted measurement signal (8a) reaches the forwarding module (9) as a reflected measurement signal (8b) after the emitted measurement signal (8a) has been reflected at the surface (4) of the medium (M), wherein the additional forwarding module (18, 19) is further configured such that the additional forwarding module (18, 19) sends the reflected measurement signal (8b) back towards the surface (4) of the medium (M) in such a way that a returned measurement signal of the additional forwarding module (18, 19) is reflected again at the surface (4) of the medium (M) and only then reaches the transmit-receive module (7). [7] Method for determining the fill level of a medium (M), comprising the following steps: a) Emitting a transmitted measurement signal (8a) towards a surface (4) of the medium (M) by means of a transmit-receive module (7, 13, 14, 15); b) Reflecting the emitted measurement signal (8a) at the surface (4) of the medium (M) such that the emitted measurement signal (8a) is forwarded as a reflected measurement signal (8b) to a forwarding module (9); c) Forwarding the reflected measurement signal (8b) as a returned measurement signal (10a, 10b) back towards the surface (4) of the medium (M) by means of the forwarding module (9); d) re-reflecting the returned measurement signal (10a, 10b) at the surface (4) of the medium (M) such that the returned measurement signal (10a, 10b) after re-reflecting at the surface (4) of the medium (M) again reaches the transmit-receive module (7, 13, 14, 15), and e) Determining the fill level of the medium (M) by a control unit based on a comparison between the emitted measurement signal (8a), the reflected measurement signal (8b) and the returned measurement signal (10a, 10b) and a reference value; characterized by , that a radar-based signal is used as the emitted measurement signal (8a), and that the time of flight of a radar-based reference signal (11, 12) emitted directly from the transmit-receive module (7, 13, 14, 15) to the forwarding module (9) and forwarded back from the forwarding module (9) to the transmit-receive module (7, 13, 14, 15) is used as the reference value. [8] Method according to claim 7, characterized by, that an angle reflector, in particular a triple mirror, is used as a transmission module (9), wherein the angle reflector is arranged such that an incident signal is reflected back into an origin direction regardless of the angle of incidence, from which origin direction the incident signal came. [9] Method according to claim 7 or 8, characterized by , that the reference signal (11, 12) and the transmitted measurement signal (8a) are transmitted simultaneously by the transmit-receive module (7, 13, 14, 15). [10] Method according to claim 7 or 8, characterized by , that the reference signal (11, 12) and the emitted measurement signal (8a) are emitted by the transmit-receive module (7, 13, 14, 15) with a time delay, preferably that a main radiation direction (H1; H2) of the transmit-receive module (7, 13, 14, 15) is changed between the emission of the reference signal (11, 12) and the emitted measurement signal (8a). [11] Method according to any one of claims 7 to 10, characterized by that the method is carried out with a measuring arrangement according to one of claims 1 to 6.

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