Method for commissioning a level measuring device

Abstract

The invention relates to a method for commissioning a level measuring device (100), comprising the following steps: detecting an echo curve (200) by means of a radar sensor unit (120) of the level measuring device (100), wherein the echo curve (200) comprises at least a first echo (210); selecting a first echo (210) having a first distance (211) and a first amplitude (212) from the echo curve (200), wherein the first amplitude (212) has the highest amplitude of the echo curve (200); determining a calculated first amplitude (214), wherein the calculated first amplitude (214) is a function of the first distance (211); and evaluating the echo curve (200) as acceptable for commissioning if the first amplitude (212) is higher than the calculated first amplitude (214).

Description

Technical Field

[0001] The invention relates to a method for commissioning a level measuring device. The invention also relates to a level measuring device, a program element, a computer-readable medium and a use. Background Art

[0002] During the commissioning of level measuring devices, which in particular use radar sensor units for measurement, a large number of measurements are often required in order to achieve a high level of safety and / or a high measurement accuracy after the commissioning of the level measuring device. For example, for limit level determination, which only detects the upper and lower limits of the level in the container, at least two measurements are required for commissioning. For fill level measurement (so-called range monitoring), five measurements are often required. Here, for each measurement, the medium is filled into the container to the desired level. Such measurements can result in a certain (sometimes very high) expenditure on material and time. Summary of the invention

[0003] The object of the invention is to reduce the number of measurements during operation of a level measuring device, at least in some cases.

[0004] One aspect relates to a method for commissioning a level measuring device, the level measuring device being configured to measure the level of a filling material in a container. The method comprises the following steps:

[0005] detecting a (detected) echo curve by means of a radar sensor unit of the level measuring device, wherein the echo curve comprises at least a first echo;

[0006] selecting a first (detected) echo having a first distance and a first amplitude from the (detected) echo curve, wherein the first amplitude is a highest amplitude of the echo curve;

[0007] determining a calculated first amplitude, wherein the calculated first amplitude is a function of the first distance;

[0008] If the (detected) first amplitude is higher than the calculated first amplitude, the echo curve is assessed as acceptable for commissioning.

[0009] When the level measuring device is put into operation, the container whose fill level, limit level and / or topology is to be measured can be empty or can be (at least partially) filled with a medium. It can be useful to fill the container incompletely so that there is a distance of at least a few centimeters between the medium and the so-called "neighborhood" of the radar sensor unit.

[0010] During the measurement, the radar sensor unit of the level measuring device detects an echo curve. The detection of the echo curve can be achieved, for example, by receiving a radar wave, which is generated, for example, by a transmitter of the radar sensor unit and reflected by the medium and / or the container part, by the radar sensor unit. The received reflected radar wave is then converted into a so-called echo curve, for example, in an evaluation unit (and / or radar sensor unit) of the level measuring device. For the measurement, for example, a frequency modulated continuous wave (FMCW) radar method, a pulse radar method and / or other radar methods can be used. The echo curve is usually represented by a graph, whose X-axis represents the distance (usually linear) and the Y-axis represents the amplitude (usually logarithmic, i.e., linear in dB). The (local) maximum of the echo curve usually corresponds to a reflection, for example, from the medium and / or the container part. The global maximum usually occurs in the vicinity of the radar sensor unit and is produced, for example, by a reflection from a horn antenna of the radar sensor unit. In practice, it has been shown that not only the expected maximum values ​​but also interferences that can falsify the measurement result occur in such an echo curve. These interferences can have many different causes.

[0011] Here, the actual measured echo curve has at least one echo. If the echo curve has more than one echo, the echo with the highest amplitude of the echo curve is selected from the multiple echoes as the "first echo". Here, at least in some cases, the amplitude in the vicinity of the transmitter (which may be higher than the amplitude of the first echo) can be ignored. If the echo curve has only one echo, this echo is selected as the "first echo". The distance of the first echo is called the "first distance", and the amplitude of the first echo is called the "first amplitude".

[0012] The calculated first amplitude is the result of applying the function to the first distance. In this case, the function can represent a decrease in the intensity of the reflected radar waves, for example, when the filling material surface is far away from the antenna of the transmitter. In this case, it is assumed that the filling material surface reflects radar waves more strongly, for example, in the case of liquids, or in the case of reflections from the bottom of the container. Filling material surfaces that do not reflect radar waves more strongly are, for example, coarse-grained loose materials and / or liquids with small DK values ​​(dielectric constants) such as liquefied petroleum gas, oils and solvents. The function can be calculated (for example, inversely proportional) and / or derived from measurements. For example, a reference point ("maximum value") of the function that can be used to calculate this intensity decrease can be obtained based on empirical values, for example from the characteristics of different antenna systems.

[0013] If the first amplitude is higher than the calculated first amplitude, the echo curve can be assessed as acceptable for commissioning. In many cases, commissioning can therefore be completed. If the first amplitude is lower than the calculated first amplitude, there may be several reasons. For example, interference may have occurred and / or the radar waves are "absorbed" by the container wall, for example by the fillings and adhesions in the container. If the first amplitude is lower than the calculated first amplitude, this may mean that the measurement performed with the level measuring device may be wrong. Therefore, in this case, the echo curve is assessed as unacceptable for commissioning. It may then be successful to perform multiple or additional measurements for commissioning.

[0014] Thus, by means of this method, the number of measurements during the commissioning of the level measuring device can be reduced, at least in some cases. This can advantageously contribute to reducing the workload for commissioning. In particular, the method can help the plant operator to dispense with startup with medium, and the plant operator can still achieve a high level of safety during commissioning, or in significantly fewer cases only a large number of measurements need to be carried out during commissioning. This can be particularly useful, since for the plant operator, startup with a switch point or the entire measuring range is not always possible and / or not always desirable, for example in cases where rapid commissioning is required or when no medium is available at the time of commissioning.

[0015] In some embodiments, the container is empty or at least partially filled with a liquid. For example, the liquid may also be an emulsion or a suspension. In particular, the surface of the filling material of the liquid may strongly reflect radar waves.

[0016] In some embodiments, for the measured echo curve to be assessed as acceptable, the first amplitude is higher than the calculated first amplitude by a safety margin, wherein the safety margin is 1 dB, 2 dB, 5 dB, 10 dB, 15 dB or more. Here, the safety margin may, for example, take into account measurement inaccuracies due to, for example, irregular designs of the container, container walls, smaller inserts, etc. Such stricter criteria for assessing an echo curve as acceptable for commissioning may reduce the number of "false positives", sometimes significantly.

[0017] In one embodiment, the method further comprises the steps of determining at least one second echo, wherein the second echo has a second distance and a second amplitude, wherein the second distance is smaller than the first distance; and if the second amplitude is greater than a second reference amplitude of a reference echo curve at the second distance, evaluating the measured echo curve as unacceptable for commissioning.

[0018] One or more second echoes may be measured. Here, the amplitude of the second echo may be lower than the amplitude of the first echo. For example, the second echo may be caused by a loading part, adhesion, etc. arranged in the container between the filling material surface and the transmitting antenna.

[0019] In some embodiments, the reference echo curve substantially corresponds to an echo curve measured in an empty container of infinite length.Furthermore, a tolerance band may be considered; for example +1 dB, +2 dB, +3 dB around the calculated reference echo curve.

[0020] In some embodiments, echoes from the vicinity of the level measurement device are ignored. For example, the vicinity of the level measurement device may be at a distance of less than 10 cm or 20 cm from the transmitter (e.g., from the transmitter chip). For example, the echoes from the vicinity may be caused by a horn antenna (as a transmitting antenna) or by a so-called "dome" (e.g., a through-tube), in which the transmitter is arranged and in at least some cases the "dome" is arranged at the top of the inner side of the container. The echoes from the vicinity may have a higher amplitude. The echoes from the vicinity may have a so-called antenna ringing, i.e., interference caused, for example, during antenna coupling. For example, the echoes from the vicinity may have been excluded from the evaluation (e.g., as a "real" echo from the surface of the filling material) at the manufacturer by the so-called "factory interference signal suppression". If an amplitude that does not increase is identified in the echo of the current measurement compared to the factory interference signal suppression, the measurement can be evaluated as acceptable for commissioning.

[0021] One aspect relates to a level measuring device for measuring the level of a filling material in a container. The level measuring device comprises: a radar sensor unit configured to transmit radar waves and receive reflected radar waves; and an evaluation unit configured to convert the reflected radar waves into an echo curve and evaluate the echo curve in the above and / or below manner. For example, the radar sensor unit can use an FMCW method or a pulse radar for measurement. At least in some cases, the radar sensor unit and the evaluation unit can be implemented as integrated hardware (for example, integrated into the same circuit board or on the same chip).

[0022] One aspect relates to the use of a level measuring device described above and / or below for measuring a filling level, a topology and / or a limit level of a filling material in a container.

[0023] One aspect relates to a program element which, when executed on an evaluation unit and / or another computing unit of a fill-level measuring device described above and / or below, instructs the evaluation unit and / or computing unit to execute the method described above and / or below.

[0024] An aspect relates to a computer-readable medium having stored thereon a program element as described herein.

[0025] It should also be noted that the various embodiments described above and / or below may be combined with each other.

[0026] For further explanation, the present invention will be described based on the embodiments shown in the accompanying drawings. These embodiments should be understood as examples only, not limitations. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a level measuring device according to an embodiment is shown.

[0028] Figure 2 An example of an echo curve according to an embodiment is shown.

[0029] Figure 3 Another example of an echo curve according to an embodiment is shown.

[0030] Figure 4 A flow chart of a method according to an embodiment is shown.

[0031] Figure 5 A commissioning scheme according to an embodiment is shown.

[0032] Figure 6 A commissioning scheme according to another embodiment is shown.

[0033] Figure 7 A commissioning scheme according to another embodiment is shown.

[0034] Figure 8 Some examples of echo amplitudes according to another embodiment are shown. DETAILED DESCRIPTION

[0035] Figure 1A level measuring device 100 and a container 150 according to an embodiment are schematically shown. The level measuring device 100 and the container 150 are not shown to scale. In particular, the container 150 is usually significantly larger than the level measuring device 100. At least in some cases, the level measuring device 100 can be arranged in a so-called "dome", for example, in a through tube (Schacht), which is arranged at least in some cases at the top of the inside of the container. The level measuring device 100 is configured to measure the level 170 of the filling material 160 in the container 150. The level measuring device 100 includes a radar sensor unit 120, which is configured to transmit radar waves and receive reflected radar waves 125. The transmission and reception of the radar waves are carried out by an antenna 122, which is schematically represented as a horn antenna. For example, the reflected radar wave 125 is reflected from the filling material surface 170 and / or from the bottom 152 of the container 150. Furthermore, the radar waves can be reflected from the inserts and / or adhesives 155, in particular located on or near the wall of the container 150. In this case, the reflected radar waves 125 are received by the radar sensor unit 120 (via the antenna 122) and transmitted to the evaluation unit 140, which is configured to convert the reflected radar waves 125 into an echo curve 200 (see, for example, Figure 2 or Figure 3 ). The evaluation unit 140 is also configured to evaluate the echo curve 200 in the manner described above and / or below. The evaluated measured values ​​are then transmitted to another system, for example to a control station, via the line 145. For example, the line 145 can be designed as a two-wire system and / or support other protocols. For example, the line 145 can also be connected to a radio module capable of wirelessly transmitting measured values.

[0036] In order to commission the level measurement device 100, the level measurement device 100 is arranged on or in the container 150, for example on the top or in a so-called "dome" (not shown) of the container 150. The level measurement device 100 can then emit radar waves and form an echo curve 200 from the reflected radar waves 125. The echo curve 200 can then be evaluated and, at least in some cases, it can be decided based on the echo curve 200 whether the echo curve 200 (and therefore the level measurement device 100) is evaluated as acceptable for commissioning.

[0037] Figure 2 An example of an echo curve 200 according to an embodiment is shown, which echo curve is measured, for example, in a container 150 which is empty or at least partially filled with a liquid (see, for example, Figure 1). The echo curve 200 is represented by a graph, the X-axis of which represents the distance d (linear representation) and the Y-axis of which represents the amplitude A (in dB). For example, the origin can have an amplitude value A=0 dB and a distance d=0 m from the transmitter. In this case, the highest amplitude 202 of the echo curve 200 is measured in the vicinity of the transmitter. In addition, the neighboring area (Nahbereich) 204 has higher amplitude values. Since the amplitude values ​​measured in the neighboring area 204 generally do not reflect "useful information (i.e. reflections from the surface of the filling material)", the echoes from the neighboring area can be excluded from the evaluation at the manufacturer, for example, by so-called "factory interference signal suppression". This can be done, for example, by subtracting the calculated echo curve 240 from the measured echo curve 200 (before evaluating the echo curve). The calculated echo curve or reference echo curve 240 can essentially correspond to an echo curve measured in an empty container of infinite length. Furthermore, for the reference echo curve 240 , a tolerance band may be taken into account, for example +1 dB, +2 dB, +3 dB may be added to the calculated reference echo curve.

[0038] When the level measuring device is put into operation, the echo curve 200 can be evaluated. In this case, during the actual measurement, the echo curve 200 has a first echo 210. For example, the first echo 210 can be a reflection from the filling material surface 170 (in the case of an at least partially filled container) or a reflection from the bottom 152 of the container 150 (in the case of an empty container). In the case of an at least partially filled container, the echo curve 200 can also have (at least) two echoes, namely an echo from the filling material surface 170 and an echo from the bottom 152; in this case, the echo from the bottom 152 has a lower amplitude, in particular a significantly lower amplitude, than the echo from the filling material surface 170. In this case, the first echo 210 has a first distance 211 and a first amplitude 212. In this case, the echo with the highest amplitude of the echo curve 200, excluding the echo from the adjacent area 204, can be selected as the first echo 210. For example, the first echo 210 can be determined by the fact that it stands out highest relative to the reference echo curve 240. Furthermore, a calculated first amplitude 214 can be determined, wherein the calculated first amplitude 214 is a function of the first distance 211. For example, a function that decreases monotonically with the distance d can be used, which function is then applied to the highest amplitude 202, and the calculated first amplitude 214 is obtained by subtracting the amplitude value 241 from the highest amplitude 202. Figure 2 In the example of FIG. 2 , the first amplitude 212 is higher than the calculated first amplitude 214, and even higher than the calculated first amplitude 214 by a safety margin 217. Figure 2 The echo curve 200 shown is evaluated as acceptable for commissioning.

[0039] Figure 3 FIG. 3 shows another example of an echo curve 300 according to an embodiment. Figure 2 The same reference numerals in the figure denote the same or similar elements. In addition to the first echo 210, the echo curve 300 also shows a second echo 320. In actual measurement, one or more second echoes 320 may be measured. Here, the amplitude of the second echo 320 may be lower than the amplitude of the first echo 210. The second echo 320 may be caused, for example, by an insert, an adhesive 155 (see FIG. 1 ) arranged in a container between the surface of the filling material and the transmitting antenna. Figure 1 ) etc. Figure 3 The second echo 320 shown has a second distance 321 and a second amplitude 322, wherein the second distance 321 is smaller than the first distance 211. If the second amplitude 322 is greater than the second reference amplitude 342 of the reference echo curve 240 at the second distance 321, the measured echo curve is assessed as unacceptable for commissioning.

[0040] In some embodiments, echoes from neighboring areas 204 may also be considered. In this regard, if increased amplitudes are seen in the currently measured echoes compared to plant interference signal suppression, the measurement results may be assessed as unacceptable for commissioning.

[0041] Figure 4 A method for operating a level measurement device 100 according to an embodiment is shown (see, for example, Figure 1 ) is a flowchart 400 of a method. In step 402, the radar sensor unit 120 of the level measuring device 100 detects the echo curve 200 (see, for example, Figure 2 or Figure 3 ), wherein the echo curve 200 comprises at least a first echo 210. In step 404, a first echo 210 having a first distance 211 and a first amplitude 212 is selected from the echo curve 200. Here, the first amplitude 212 has the highest amplitude of the echo curve 200 (excluding the amplitude in the adjacent area 204). In step 406, a calculated first amplitude 214 is determined, wherein the calculated first amplitude 214 is a function of the first distance 211. In step 408, it is queried whether the first amplitude 212 is higher than the calculated first amplitude 214. If the first amplitude 212 is higher than the calculated first amplitude 214, then in step 410, the echo curve 200 is evaluated as acceptable for commissioning. Otherwise, in step 412, the echo curve 200 is evaluated as unacceptable for commissioning. In this case, for example, additional measurements for commissioning can be performed.

[0042] Figure 5A commissioning scheme 500 according to one embodiment is shown. Here, for applications for measuring the limit levels of filling materials, at least two measurements are required, for example, one measurement of the highest level ("max") in the container and one measurement of the lowest level ("min"). Here, the echo curve is detected and evaluated by a radar sensor unit. Here, for each limit level, an actual measurement value is detected, which corresponds to, for example, an actual current in a two-wire system (for example, in accordance with the HART protocol). The actual measurement value or the actual current is compared with a target measurement value or a target current. Based on these measurement values, the level measuring device for measuring the limit level can be evaluated as acceptable for commissioning. In the case of correct measurement results, these values ​​can be stored, for example, for archiving. In the case of incorrect measurement results, commissioning can be aborted.

[0043] For applications for measuring the filling level of a filling material, at least five measurements are required, for example a "maximum" measurement of the highest level, a "minimum" measurement of the lowest level and, for example, three other measurements at other selected levels. Here, for each limit level, an actual measured value is detected, which corresponds to, for example, an actual current. The actual measured value or the actual current is compared with a target measured value or a target current. Based on these measured values, the level measuring device for measuring the filling level and / or topology can be evaluated as acceptable for commissioning. In the case of correct measurement results, these values ​​can be stored, for example, for archiving. In the case of incorrect measurement results, commissioning can be aborted.

[0044] At least in some cases, especially when applying the above and / or below methods, the commissioning schedule can be shortened.

[0045] Figure 6 A commissioning scheme 600 according to another embodiment is shown. Here, the container 150 (see, for example, Figure 1 ) can be at least partially filled or empty, i.e. can be started at any level without medium or with medium present. If an agitator is present in the vessel for measurement, a distinction can be made based on the position of the agitator: when the agitator is arranged in the measuring channel of the radar sensor, different commissioning methods can be selected. If the agitator is not in the measuring channel of the sensor, the above and / or the following methods can be used.

[0046] Subsequently, the echo quality can be evaluated as described above and / or as described below. In the case of a correct measurement result, the value can be stored, for example, for archiving. In the case of an incorrect measurement result, commissioning can be aborted. Alternatively or additionally, the measurement can also be performed as described in commissioning scheme 500 (see above).

[0047] Figure 7A commissioning scheme 700 according to another embodiment is shown, in which an agitator is arranged in the container. If the agitator is arranged in the measuring channel of the radar sensor, another commissioning method can be selected. If the agitator is not in the measuring channel of the sensor, the method described above and / or below can be used. Here, the container can be empty; for example, there may be the possibility that no medium is filled. Here, the sensor is installed in or on the container and the empty container is measured. The measuring range (for example, "from... to" or "maximum") can be specified by the plant operator and / or service personnel. Then, an interaction step can be set, that is, the plant operator (etc.) can be asked whether the measurement is reasonable. If it is confirmed that the measurement is reasonable, the sensor can be considered to be "correctly set". Therefore, the first larger echo can be interpreted as a reflection in the bottom area of ​​the container. In a further step, the area between the antenna and the end of the measuring range can be divided into two areas: the adjacent area 204 (see, for example Figure 2 or Figure 3 ) and the remaining areas. In the neighboring area 204, the so-called "plant interference signal suppression" can be applied, which subtracts the calculated echo curve or reference echo curve 240 from the currently measured echo curve 200. If no increased amplitude is seen in the previously measured echo curve 200 compared to the plant interference signal suppression, the measurement can be evaluated as acceptable for commissioning. Since the amplitude in the neighboring area 204 usually has a higher intensity, it can be well identified after subtracting the reference echo curve 240.

[0048] For the remaining areas, the following options are available:

[0049] If no echo is identified in this area, the measurement is assessed as acceptable for commissioning.

[0050] If an echo is identified in this area, the amplitude of this echo must be evaluated. The sensor settings can be used for this purpose. If an aqueous solution is expected, a higher amplitude can be tolerated than in the case of an oily liquid where a smaller useful echo amplitude is expected.

[0051] Other options for evaluating the echo curve may include: If there is a medium or product in the container, multiple echoes can be evaluated. If multiple echoes are present, the sensor or operating tool can compare the amplitude of the multiple echoes with the amplitude of the level echo. If the multiple echo is sufficiently smaller than the level echo, this aspect of the measurement is evaluated as acceptable for commissioning. Multiple echoes outside the actual measurement range can also be used for evaluation.

[0052] For assessing acceptable measurements, for example, settings or parameters entered by an expert (eg, by a service person) can be used. In addition to information about the medium, the settings or parameters can also be information about the application or the container.

[0053] For example, information about the medium may include:

[0054] Medium-sized loose materials: The echo amplitude may fluctuate strongly here. Therefore, the measurement may be more difficult.

[0055] Medium-sized liquids: The DK value can be taken into account here. For example, if the DK value is less than 2, the reflection characteristics may be too low and it may make sense to choose a non-automatic commissioning method.

[0056] DK values: For smaller DK values, the method shown is only applicable to a limited extent.

[0057] For example, information about an application may include:

[0058] Storage tanks: Measurement can be more reliable here, since only slow level changes are expected.

[0059] • Metering tanks: Here rapid level changes are expected, so it may be advantageous to use greater safeguards (eg larger safety margins).

[0060] For example, information about a container may include:

[0061] Presence of agitators: Uneven surfaces can generate strongly fluctuating echo amplitudes, making reliable measurements almost impossible.

[0062] Dish-shaped vessel top: This vessel geometry can produce stronger multiple echoes.

[0063] Figure 8 Some examples of echo amplitudes according to another embodiment are shown. Here, the echo amplitude is shown as part of an echo curve 200, whose X-axis represents the distance d in m and whose Y-axis represents the amplitude A in dB. Here, curve 810 shows the expected increase in amplitude for an antenna system with a flange. Curve 820 shows the expected increase in amplitude for an antenna system with a thread. Curve 830 shows the expected increase in amplitude for an antenna system with a horn antenna. These curves can be used, for example, as reference echo curves depending on the antenna used.

[0064] CROSS-REFERENCE TO RELATED APPLICATIONS

[0065] This application claims priority from European patent application No. 21 206 634.4 filed on November 5, 2021, the entire contents of which are incorporated herein by reference.

[0066] Reference numerals list

[0067] 100 Level measuring devices

[0068] 120 radar sensor units

[0069] 122 Antenna

[0070] 125 Reflected radar waves

[0071] 140 evaluation units

[0072] Route 145

[0073] 150 containers

[0074] 152 container bottom

[0075] 155 Adhesion

[0076] 160 Filling material

[0077] 170 Filling level, filling material surface

[0078] 200 echo curve

[0079] 202 highest amplitude

[0080] 204 Neighborhood

[0081] 210 First Echo

[0082] 211 First Distance

[0083] 212 First Amplitude

[0084] 214 Calculated first amplitude

[0085] 217 Safety margin

[0086] 240 Calculated echo curve, reference echo curve

[0087] 241 Amplitude value

[0088] 242 Second reference amplitude

[0089] 300 echo curve

[0090] 320 Second Echo

[0091] 321 Second Distance

[0092] 322 Second Amplitude

[0093] 342 Second reference amplitude

[0094] 400 Flowchart

[0095] Steps 402-412

[0096] 500~700 Operation Plan

[0097] 810~830 curve

Claims

1. A method for commissioning a level measuring device (100), the level measuring device being configured to measure a filling level (170) of a filling material (160) in a container (150), the method comprising the following steps: Detecting an echo curve (200) by means of a radar sensor unit (120) of the level measurement device (100), wherein the echo curve (200) comprises at least a first echo (210); Selecting the first echo (210) having a first distance (211) and a first amplitude (212) from the echo curve (200); determining a calculated first amplitude (214), wherein the calculated first amplitude (214) is a function of the first distance (211); and If the first amplitude (212) is higher than the calculated first amplitude (214), the echo curve (200) is evaluated as acceptable for commissioning, It is characterized in that The first amplitude (212) is the highest amplitude of the echo curve (200); determining at least one second echo (320), wherein the second echo (320) has a second distance (321) and a second amplitude (322), wherein the second distance (321) is smaller than the first distance (211); and If the second amplitude (322) is greater than a second reference amplitude (242) of a reference echo curve (240) at the second distance (321), the measured echo curve (200) is evaluated as unacceptable for commissioning.

2. The method according to claim 1, in, The container (150) is empty or at least partially filled with a liquid.

3. The method according to claim 1 or 2, in, For assessing the measured echo curve (200) as acceptable, the first amplitude (212) is higher than the calculated first amplitude (214) by a safety margin (217), Wherein, the safety margin (217) is 1 dB, 2 dB, 5 dB, 10 dB, 15 dB or above.

4. The method according to claim 1, in, The reference echo curve (240) substantially corresponds to an echo curve (200) measured in an empty container (150) of infinite length.

5. The method according to claim 1 or 2, in, Echoes from a vicinity (204) of the level measurement device (100) are ignored.

6. A level measuring device (100) for measuring a filling level (170) of a filling material (160) in a container (150), the level measuring device (100) comprising: a radar sensor unit (120) configured to transmit radar waves and receive reflected radar waves (125); as well as An evaluation unit (140) is configured to convert the reflected radar wave (125) into an echo curve (200) and to evaluate the echo curve (200) according to the method according to any one of claims 1 to 5.

7. Use of the level measuring device (100) according to claim 6 for measuring a filling level (170), a topology and / or a limit level of a filling material (160) in a container (150).

8. A program product which, when executed on an evaluation unit (140) and / or another computing unit of a level measuring device (100) according to claim 6, instructs the evaluation unit (140) and / or the computing unit to execute the method according to any one of claims 1 to 5.

9. A computer-readable medium storing the program product according to claim 8.

Images