Radar level gauge and method for detecting cleaning processes using radar level gauge

Abstract

A radar level gauge and a method for detecting cleaning processes using the radar level gauge are disclosed. The method and system for detecting cleaning processes using a radar level gauge are described. The radar level gauge is configured to determine the fill level of articles contained in a tank. The radar level gauge includes a transceiver configured to provide a transmit signal S to be propagated toward the articles via a propagation device. T It is configured to receive the reflected signal S generated by the reflection of the emitted signal at the surface of the article. R And configured to determine the fill level in the tank based on the received reflected signal, wherein the method includes: determining (300) the signal amplitude difference between at least two different fill level measurements at a measurement location at a known distance above the fill level and near a reference location near the ceiling of the tank; and determining (302) that cleaning processing in the tank is in progress if the determined signal amplitude difference exceeds a predetermined threshold.

Description

Technical Field

[0001] This invention relates to radar level gauges and to a method for detecting cleaning processes using guided wave radar level gauges. Specifically, the invention aims to use radar level gauges to detect and determine the characteristics of cleaning processes in tanks. Background Technology

[0002] Radar level gauge (RLG) systems are widely used to determine the fill level of items contained in tanks. Radar level measurement is typically performed using either non-contact measurement or contact measurement (often referred to as guided wave radar (GWR)). In non-contact measurement, an electromagnetic signal is radiated toward the items contained in the tank; in contact measurement, the electromagnetic signal is guided toward and into the items by a probe acting as a waveguide. The probe is typically arranged to extend vertically from the top of the tank toward the bottom.

[0003] The emitted electromagnetic signal is reflected at the surface of the article, and the reflected signal is received by a receiver or transceiver included in the radar level gauge. Based on the emitted and reflected signals, the distance to the surface of the article can be determined. More specifically, the distance to the surface of the article is typically determined based on the time between the emission of the electromagnetic signal and the reception of its reflection at the interface between the environment in the container and the article contained therein. To determine the actual fill level of the article, the distance from the reference position to the surface is determined based on the aforementioned time (so-called time of flight) and the propagation speed of the electromagnetic signal.

[0004] In some applications, tank cleaning is a critical part of the production cycle. This can be applied, for example, to food production or chemical processing. During tank cleaning, filling level determination may be difficult or impossible to perform due to disturbances associated with the cleaning process. Therefore, a solution for handling cleaning processes using radar level gauges is desired. Summary of the Invention

[0005] In view of the above problems, the object of the present invention is to provide a method and system for determining whether a cleaning process is taking place in a tank.

[0006] According to a first aspect of the invention, a method is provided for detecting cleaning processes using a radar level gauge configured to determine the fill level of articles contained in a container. The radar level gauge includes a transceiver configured to provide a transmitted signal, i.e., a Tx signal, to be propagated toward the articles via a propagation device, configured to receive a reflected signal generated by reflection of the transmitted signal at a surface of the articles, and configured to determine the fill level in the container based on the received reflected signal. The method includes: determining a signal amplitude difference between at least two consecutive fill level measurements for a given distance from the ceiling of the container; and determining that cleaning processes are in progress in the container if the determined signal amplitude difference exceeds a predetermined threshold.

[0007] A jar can be any container or vessel capable of holding items, and can be metallic or partially or entirely non-metallic, open, semi-open, or closed.

[0008] A "transceiver" can be a functional unit capable of transmitting and receiving electromagnetic signals, or a transceiver can be a system comprising separate transmitter and receiver units.

[0009] In addition, the propagation device can be an antenna in a free radiation radar level gauge system, but it can also be a probe in a guided wave radar (GWR) application.

[0010] This invention is based on the understanding that cleaning processes within a tank can be detected by observing changes in the amplitude of a received signal corresponding to a position above the filling level. Cleaning processes can be performed, for example, by means of a spray ball located near the ceiling of the tank, wherein the spray ball comprises one or more nozzles that spray water and / or other cleaning agents toward the inner surface of the tank. This implies the presence of a turbulent environment within the tank, which can be detected by observing the signal amplitude at a known measurement location. Therefore, if an operator initiates a cleaning process, or if the cleaning process is initiated automatically, the radar level gauge can provide verification that the cleaning process has actually begun. Furthermore, it can also detect whether the cleaning process was initiated by an operator or as a controlled function of the system and subsequently failed to start or did not start as intended.

[0011] Cleaning is typically performed in empty or nearly empty tanks. However, cleaning can also be performed in tanks containing items, in which case the measurement position is above the fill level. If it is determined that cleaning is being performed in a tank containing items, this can be communicated to the operator, or the process can be handled by automatically compensating for the fill level measurement as long as cleaning is in progress, as will be described in further detail below.

[0012] According to one embodiment of the invention, determining the signal amplitude difference includes determining the relative difference in signal amplitude. Therefore, the detected signal amplitude change does not depend on whether the amplitude increases or decreases from one measurement to another. The signal amplitude difference can be viewed as a measure of signal fluctuations in the tank or throughout the tank at the measurement location, where high fluctuations, i.e., fluctuations above a threshold, are considered an indication of ongoing cleaning processes.

[0013] According to one embodiment of the invention, the method further includes: providing a transmitted signal in the form of a frequency scan signal; and sampling the received reflected signal at predetermined intervals, wherein each sample corresponds to a unique distance from a reference position. The frequency scan signal can be, for example, a frequency-modulated continuous wave (FMCW) signal commonly used in radar level gauge systems. Each sample of the FMCW signal corresponds to a known distance from the reference position. Therefore, by sampling the received signal at regular intervals, the amplitude of the signal can be determined for different distances from the reference position at regular intervals. For a free-radiating antenna, the reference position can be at the antenna itself, i.e., at the location where the antenna transmits the signal into the container. By using the described frequency scan signal, the signal amplitude at multiple locations between the antenna and the surface of the object can be compared with predetermined thresholds, thereby improving the reliability of determining that cleaning is in progress.

[0014] According to one embodiment of the present invention, determining the signal amplitude difference includes: determining the relative difference between the signal amplitudes of multiple different samples of a frequency scan signal; determining the median of the determined signal amplitude differences; and comparing the median with a predetermined threshold. Each sample corresponds to a unique distance from a reference position, and each scan can be regarded as representing a point in time. By using the median of the signal amplitude difference of a single scan to perform the comparison with the threshold, the influence of outliers and echoes not generated by the cleaning process can be reduced.

[0015] According to one embodiment of the invention, determining a signal amplitude difference includes: determining a relative difference in the signal amplitudes of multiple different samples of a frequency scan signal; determining the median of the signal amplitude differences of the frequency scan signals; determining a change in the median compared to at least one median of an earlier frequency scan signal; and determining that a cleaning process in the tank is in progress if the change in the median is higher than a predetermined threshold. In the described embodiment, comparing the signal amplitude difference with the signal amplitude difference from a previous frequency scan signal further increases the reliability of determining that a cleaning process is in progress. Since fluctuations in the signal amplitude difference are expected to be introduced by the cleaning process, fluctuations in the median between different frequency scans can also be expected. The median of more than two frequency scans can also be compared, and the condition for a cleaning process to be in progress can be, for example, that the median should be higher than a threshold for a predetermined number of consecutive frequency scans.

[0016] According to one embodiment of the invention, determining the signal amplitude difference includes: determining the relative difference of signal amplitudes of multiple different samples of a plurality of frequency scan signals; determining the median of the relative difference of signal amplitudes for each frequency scan signal; determining the change in the median compared to at least one median of an earlier frequency scan signal; and determining that in-tank cleaning is in progress if the change in the median is higher than a predetermined threshold. Therefore, the relative difference of signal amplitudes cannot be compared to a specific threshold. Instead, a change in the median of the relative difference of signal amplitudes is observed.

[0017] According to one embodiment of the present invention, the method further includes: determining a background difference based on samples corresponding to a first range of distances from a reference location; determining a near-region difference based on samples corresponding to a second range of distances from a reference location, wherein the second range is a sub-range of the first range, the sub-range starting at the endpoint of the first range corresponding to the location closest to the reference location; and determining that cleaning processing is in progress if at least one of the background difference and the near-region difference is higher than a corresponding background threshold and a near-region threshold.

[0018] The background region can be viewed as the area extending from the reference position toward the surface of the object in the can (or, if the can is empty, toward the bottom of the can) into the can, while the near region is the area closest to the antenna, also starting from the reference position. The precise extensions of the background and near regions can be determined for each specific application based on a range of parameters such as antenna and signal characteristics, antenna type, can size, etc. Generally, the background region can be viewed as the area where no echo is expected—that is, neither surface echo nor echo from other objects in the can. Therefore, the background region provides a measure of the signal amplitude change caused by the cleaning process. The near region can be viewed as the area closest to the antenna and can be considered as the area where the cleaning process is expected to affect the characteristics of the antenna itself, such as the transition of the transmitted signal from the transmitting antenna to the can environment.

[0019] According to one embodiment of the invention, the method may further include: determining that a cleaning process is in progress only when both the background difference and the near-area difference are higher than corresponding thresholds. This further ensures that the detected signal amplitude difference is a result of the cleaning process, and not a result of other events in the tank.

[0020] According to one embodiment of the invention, the method may further include: if it is determined that a cleaning process is in progress, comparing the signal amplitude difference of the current cleaning process with the signal amplitude difference obtained in a previous cleaning process; and if the change in the signal amplitude difference is higher than a threshold, providing a notification that the characteristics of the cleaning process have changed. Therefore, not only can the initiation of a cleaning process be detected, but the quality of the cleaning process can also be monitored. Specifically, a decrease in cleaning performance can be detected because fluctuations occurring during a cleaning process can be expected to be the same for repeated cleaning processes, at least provided that other conditions in the tank are similar. The signal amplitude difference determined in the most recent cleaning process can also be compared with a reference difference obtained when the tank is new and empty, or under other controlled conditions that can verify that the cleaning process is operating at full capacity.

[0021] Furthermore, by observing the cleaning characteristics of both the near-field and background areas, it is possible to estimate whether the entire tank has been properly cleaned, or whether there are specific areas where cleaning has been reduced. The tank can also be divided into even more zones, and the cleaning characteristics of each zone can be observed separately.

[0022] According to one embodiment of the invention, the method further includes reducing the sensitivity of the fill level measurement if a cleaning process is detected to be in progress in the tank. Alternatively or in combination, the method may include discarding fill level measurements acquired during the cleaning process. Since the cleaning process introduces interference in the tank, reducing the sensitivity of level measurements performed during the cleaning process to reduce the risk of artifacts generated by the cleaning process being interpreted as surface echoes may be advantageous. Furthermore, in some applications, it may be desirable to completely discard measurements performed during the cleaning process. However, measurement signals may still be emitted so that measurements can be restarted once the cleaning process is detected to be complete.

[0023] According to a second aspect of the invention, a radar level gauge is provided, configured to determine the fill level of an article contained in a container. The radar level gauge includes: a transceiver configured to provide a transmitted signal, i.e., a Tx signal, to be propagated toward the article via a propagation device; configured to receive a reflected signal generated by reflection of the transmitted signal at a surface of the article; and configured to determine the fill level in the container based on the received reflected signal. The radar level gauge further includes measurement control circuitry configured to: determine a signal amplitude difference between at least two consecutive fill level measurements at a measurement position above the fill level and at a known distance from a reference position near the ceiling of the container; and determine that cleaning processing in the container is in progress if the determined signal amplitude difference exceeds a predetermined threshold.

[0024] The effects and features of the second aspect of the invention are largely similar to those described above in conjunction with the first aspect of the invention.

[0025] Further features and advantages of the invention will become apparent as the claims are presented and the following description is given. Those skilled in the art will recognize that different features of the invention can be combined to create embodiments other than those described below, without departing from the scope of the invention. Attached Figure Description

[0026] These and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, which illustrate exemplary embodiments of the invention, in which:

[0027] Figure 1 An exemplary tank device including a radar level gauge system according to an embodiment of the present invention is illustrated schematically;

[0028] Figure 2 yes Figure 1 A schematic diagram of the measuring units included in the radar level gauge system;

[0029] Figure 3 This is a flowchart outlining the general steps of a method according to an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram illustrating a portion of a can that shows the features of the present invention;

[0031] Figure 5 This is a graphic representation schematically outlining the signals used in embodiments of the invention;

[0032] Figure 6 It is a graphical representation of a curve obtained by the method according to an embodiment of the present invention;

[0033] Figure 7 It is a graphical representation of a curve obtained by the method according to an embodiment of the present invention;

[0034] Figure 8 This is a flowchart outlining the general steps of a method according to an embodiment of the present invention; and

[0035] Figure 9 This is a graphic illustration that schematically summarizes the features of the invention. Detailed Implementation

[0036] In this specific embodiment, various embodiments of the system and method according to the invention are described primarily with reference to radar level gauges installed in tanks located on land. However, the described system and method are suitable for use in other fields, such as marine applications. Furthermore, various embodiments of the invention are discussed primarily with reference to free-radiation radar level gauge systems having signal propagation devices in the form of antennas for transmitting and receiving measurement signals. However, the various embodiments of the invention are equally applicable to guided wave radar systems including probes along which signals propagate.

[0037] Figure 1 A radar level gauge system 100, including a measuring unit 102 and a signal propagation device shown herein as a horn antenna 103, is schematically illustrated. However, it should be noted that the signal propagation device could similarly be another type of radiating antenna or transmission line probe. The radar level gauge system 100 is arranged on top of the tank 105 for determining the filling level of the articles 106 within the tank 105.

[0038] When measuring the filling level of the item 106 in the tank 105, the radar level gauge system 100 emits an electromagnetic signal S towards the surface 107 of the item 106 via the horn antenna 103. T In this process, the signal is reflected as an electromagnetic surface echo signal S. R Then, based on the electromagnetic surface echo signal S R The distance to the surface 107 of the article 106 is determined by the propagation time (from the radar level system 100 to the surface 107 and back from the surface 107 to the radar level system 100). Based on the propagation time, the distance to the surface (generally referred to as the ullage) can be determined. Based on this distance (ullage) and the known dimensions of the tank 105, the filling level can be calculated.

[0039] Using radar level gauge systems according to various embodiments of the present invention, the propagation time is determined based on the frequency difference between the frequency-modulated transmitted signal and the surface reflected signal. This type of measurement scheme is commonly referred to as FMCW (Frequency Modulated Continuous Wave), and the measurement signal can be described as a signal sweep with a finite and known duration.

[0040] Figure 1A cleaning device in the form of a spray ball 108 located at or near the top of tank 105 is further shown. In the example shown, the spray ball is suspended from the ceiling 109 of tank 105. The spray ball 108 is arranged to clean tank 105 by providing a flow of water, for example, through multiple openings in the ball. Other types of cleaning devices are also possible, and the cleaning device need not be static and fixed to the tank. In principle, the claimed invention is capable of detecting any type of cleaning that affects the tank environment near an antenna or propagation device.

[0041] Reference Figure 2 Schematic block diagram in Figure 1 The measurement unit 102 of the radar level gauge system 100 includes a transceiver 110, a measurement control unit (MCU) 111, a wireless communication control unit (WCU) 112, a communication antenna 113, an energy storage device such as a battery 114, and a tank feeder 115.

[0042] like Figure 2 As schematically shown, MCU 111 controls transceiver 110 to generate, transmit, and receive electromagnetic signals. The transmitted signal is transmitted to horn antenna 103 via canister feedthrough 115. Figure 2 (not shown in the image), and the received signal is transmitted from the horn antenna 103 to the transceiver 110 via the canister feeder 115.

[0043] As shown above (refer to the reference) Figure 1 Briefly described, MCU 111 is based on the transmitted signal S T With surface echo signal S R The phase difference between the two phases determines the fill level of the item 106 in tank 105. The fill level is provided from MCU 111 via WCU 112 and communication antenna 113 to an external device, such as a control center. The radar level gauge system 100 can be advantageously configured according to the so-called WirelessHART communication protocol (IEC 62591).

[0044] Although the measuring unit 102 is shown to include an energy storage device 114 and means for enabling wireless communication (e.g., WCU 112 and communication antenna 113), it should be understood that power supply and communication can be provided in different ways, for example, via a communication line (e.g., a 4mA to 20mA line, HART), in which case the WCU 112 can be replaced by a control unit for wired communication.

[0045] Figure 3 This is a flowchart outlining the steps of a method according to an embodiment of the present invention, and will be further referenced to the tank 105 in which the horn antenna 103 is located. Figure 4 To describe this method.

[0046] The method includes determining 300 at the measurement position d meas The signal amplitude difference between at least two different fill level measurements at the measurement location d meas At the filling level d fill Above and at a reference position d approximately 109 meters from the ceiling of the tank ref At a known distance. The reference position can, for example, be set to the location closest to the antenna where the reflected signal can be detected, and then the reference position can be considered as describing the transition from the antenna to the environment. It should be noted that the location of the known filler level is not explicitly required for performing the described method for determining whether cleaning is in progress. Therefore, a fixed measurement location d can be used. meas To execute this method.

[0047] Figure 5 The signal amplitude of the received measurement signal is schematically shown, where zero on the x-axis corresponds to the reference position d. ref The large echo 502, located before zero, originates from the transition from the antenna to the environment and is therefore ignored. The second, larger echo 504, located at a certain distance from the antenna, corresponds to the filling level d. fill And therefore the position d is measured. meas Selected to be located at d ref With d fill Between. Figure 5 The points on the curve represent sampling points at different distances where the signal amplitude can be determined.

[0048] Therefore, for two different measurements, i.e., for two different signal scans, the amplitude at the selected measurement location is determined. For example, the two measurements to be compared can be consecutive measurements. Depending on the type of radar level gauge and the application at hand, the duration and repetition frequency of the signal scan can vary considerably. In exemplary embodiments, the duration of the signal scan can be in the range of 100 μs to 100 ms and the repetition frequency is typically on the order of 1 Hz to 5 Hz, but it can also be outside these ranges. However, FMCW measurements are well known to those skilled in the art and will not be discussed further in detail herein.

[0049] The method further includes determining that cleaning is underway in tank 302 if the determined signal amplitude difference exceeds a predetermined threshold. A large signal amplitude difference between two measurements that are relatively close in time indicates a turbulent environment at the measurement location, which is typical for cleaning processes where water splashes around the antenna and / or throughout the tank. The signal amplitude difference is advantageously determined as a relative difference, such that the sign or absolute amplitude does not affect the difference value. Relative difference = |A S1 -AS2 | / MIN(A S1 A S2 ), where A S1 and A S2 These are two independent signal amplitudes obtained from different measurements. Therefore, a positive scalar value representing the relative change in signal amplitude is determined, which can be compared to a predetermined threshold.

[0050] Therefore, if the determined signal amplitude difference exceeds a predetermined threshold, it can be determined that cleaning is in progress in the tank. For example, the threshold can be preset by characterizing the signal amplitude fluctuations of cleaning under controlled conditions.

[0051] like Figure 5 As can be seen, multiple sampling points are shown, each corresponding to a known distance from the reference position. The distance resolution between sampling points in the example system ranges from 1 cm to 5 cm.

[0052] For a radar level gauge that provides a transmitted signal in the form of a frequency scan signal, the received reflected signal can therefore be sampled at predetermined intervals, where each sample corresponds to a unique distance from a reference position. Determining the signal amplitude difference may then include determining the relative difference in signal amplitudes of multiple different samples of the frequency scan signal, determining the median of the determined signal amplitude differences; and comparing the median with a predetermined threshold, and if the median exceeds the threshold, determining that cleaning is being performed in the tank.

[0053] Figure 6 Multiple curves are shown, each corresponding to a specific distance from a reference position, with the x-axis representing the number of scans proportional to time. It can be assumed that all shown measurement scans were performed at fixed intervals. Based on... Figure 6 The information shown allows for the determination of the median of the relative difference for each signal scan, i.e., practically for each time point. The median is therefore considered the median value along the vertical line intersecting all curves, thus representing the median of the signal variation across all sampling points / sampling distances of a single signal scan. This avoids the influence of outliers. The median of the acquired signal scan is... Figure 7 As shown in the diagram. Therefore, Figure 7 Curve 700 in the diagram can be viewed as describing the fluctuation of the signal amplitude as a function of time. At approximately scan number 180, a significant increase in fluctuation (i.e., the signal amplitude difference) can be observed, and this can be considered an indication that cleaning processing has begun. In previous examples, comparing the signal amplitude difference to a threshold has been described. However, when observing… Figure 7At that time, it becomes clear that other parameters can be used to determine when the cleaning process in the tank has begun. For example, the derivative of the curve can be studied or the moving average of the values ​​can be viewed. Other signal processing methods for detecting and characterizing changes are also feasible and are entirely within the scope of this invention. For example, a low-pass filter can be applied to the difference curve to reduce noise, and changes in the difference can also be derived as changes in the standard deviation.

[0054] Based on, for example Figure 7 The curve 700 can also be used to characterize the cleaning process. This is achieved by observing the average absolute value of the relative amplitude difference (from...). Figure 7 Line 702 (illustrated in the diagram) can, for example, determine whether the quality of the cleaning process has declined. A lower average indicates lower fluctuations, which may be a result of a reduced cleaning process. The decline in cleaning process could be caused by clogged spray nozzles or a decrease in the fluid pressure of the spray nozzles. By... Figure 7 The information derived from the curve can be compared with one or more corresponding curves from one or more earlier cleaning processes to determine whether the reduction in cleaning processes is gradual or sudden, which in turn can provide guidance on the cause of the reduction.

[0055] According to Figure 8 The flowchart illustrates one embodiment of the invention, in which the method may include: determining a background difference 800 based on samples corresponding to a first range 900 of distance from a reference location; determining a near-region difference 802 based on samples corresponding to a second range 902 of distance from the reference location, wherein the second range is a subrange of the first range, the subrange starting at the endpoint of the first range corresponding to the location closest to the reference location; and determining that a cleaning process 804 is in progress if at least one of the background difference and the near-region difference is higher than a corresponding background threshold and a near-region threshold.

[0056] like Figure 9 As shown, the second range 902 is a subrange of the first range 900, wherein the subrange begins at the endpoint of the first range 900 corresponding to the position closest to the reference location. The first range 900 and the second range 902 may also be non-overlapping. The near-area difference characterizes the behavior closest to the antenna, while the background difference can be considered as representing the environment between the antenna and the filling site. Therefore, the condition can be set such that at least one or both of the near-area difference and the background difference exceed a corresponding threshold or exhibit sufficient change over time to determine that cleaning is in progress.

[0057] The result of determining that a cleaning process is in progress can be a reduction in the sensitivity of level measurements, the discarding of measured values, or the suspension of level measurements. Similarly, it can be determined that a cleaning process is complete and that normal operating conditions can be restored. Furthermore, other parameters of the cleaning process, such as duration and performance over time, can be determined and evaluated. Therefore, a cleaning process can be performed and monitored without altering or suspending level measurements, and accurate level measurements can be obtained even during the cleaning process.

[0058] Various embodiments of the invention described can be used in tanks for food industries, chemical, pharmaceutical or other processes, and for marine applications such as oil, natural gas, and liquefied natural gas.

[0059] Although the present invention has been described with reference to specific exemplary embodiments, many different changes, modifications, etc., will become apparent to those skilled in the art. Furthermore, it should be noted that parts of the system and method may be omitted, interchanged, or arranged in various ways, while the system and method still perform the functions of the present invention.

[0060] Furthermore, based on a study of the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments when practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used for profit.

Claims

1. A method for detecting cleaning processes using a radar level gauge (100), the radar level gauge being configured to determine the fill level of an article (106) contained in a container (105), the radar level gauge including a transceiver (110) configured to provide a transmitted signal to be transmitted toward the article via a propagation device, configured to receive a reflected signal generated by reflection of the transmitted signal at a surface (107) of the article, and configured to determine the fill level in the container based on the received reflected signal, wherein, The method includes: At a measurement location at a known distance above the filling level and near a reference position close to the ceiling of the tank, determine (300) the signal amplitude difference between at least two different filling level measurements; and If the determined signal amplitude difference exceeds a predetermined threshold, then it is determined that the cleaning process in the tank (302) is in progress.

2. The method according to claim 1, wherein, Determining the signal amplitude difference includes determining the relative difference in signal amplitude.

3. The method according to claim 1 or 2, further comprising: The transmitted signal is provided in the form of a frequency scanning signal; as well as The received reflected signal is sampled at predetermined intervals, wherein each sample corresponds to a unique distance from the reference position.

4. The method according to claim 3, wherein, Determining the signal amplitude difference includes: Determine the relative difference in signal amplitude among multiple different samples of a frequency scan signal; Determine the median of the determined signal amplitude difference; and The median value is compared with a predetermined threshold, and if the median value exceeds the threshold, it is determined that the cleaning process in the tank is in progress.

5. The method according to claim 3, wherein, Determining the signal amplitude difference includes: Determine the relative difference in signal amplitude among multiple different samples of a frequency scan signal; Determine the median of the signal amplitude difference of the frequency scanning signal; Determine the change in the median compared to at least one median of the earlier frequency scan signal; and If the change in the median value is higher than a predetermined threshold, it is determined that the cleaning process in the tank is in progress.

6. The method according to claim 3, wherein, Determining the signal amplitude difference includes: Determine the relative difference in signal amplitudes of multiple different samples of a multi-frequency scan signal; Determine the median of the relative differences in signal amplitudes for each frequency scan signal; Determine the change in the median compared to at least one median of the earlier frequency scan signal; and If the change in the median value is higher than a predetermined threshold, it is determined that the cleaning process in the tank is in progress.

7. The method according to claim 3, further comprising: (800) background difference is determined based on samples corresponding to a first range of distances from the reference location; (802) Near-region difference is determined based on samples corresponding to a second range of distances from the reference location; as well as If at least one of the background difference and the near region difference is higher than the corresponding background threshold and near region threshold, then it is determined that (804) cleaning processing is in progress.

8. The method according to claim 7, further comprising: A cleaning process is determined to be in progress only when both the background difference and the near-area difference are higher than the corresponding threshold.

9. The method according to claim 1 or 2, further comprising: If it is determined that a cleaning process is in progress, the signal amplitude difference of the current cleaning process is compared with the signal amplitude difference obtained in an earlier cleaning process; as well as If the change in signal amplitude difference exceeds a threshold, a notification is provided that the cleaning process characteristics have changed.

10. The method according to claim 1 or 2, further comprising: If a cleaning process is detected to be in progress in the tank, the sensitivity of the fill level measurement is reduced or the fill level measurement acquired during the cleaning process is discarded.

11. A radar level gauge configured to determine the filling level of an article contained in a tank, the radar level gauge comprising: A transceiver configured to provide a transmitted signal to be transmitted toward the article via a propagation device, configured to receive a reflected signal generated by the reflection of the transmitted signal at the surface of the article, and configured to determine the filler level in the can based on the received reflected signal; as well as Measurement control circuit, the measurement control circuit being configured to: At a measurement location located at a known distance from a reference position above the filling level and near the ceiling of the tank, determine the signal amplitude difference between at least two consecutive filling level measurements; as well as If the determined signal amplitude difference exceeds a predetermined threshold, it is determined that the cleaning process in the tank is in progress.

12. The radar level gauge according to claim 11, wherein, The measurement control circuit is also configured to: The transmitted signal is provided in the form of a frequency scanning signal; and The received reflected signal is sampled at predetermined intervals, wherein each sample corresponds to a unique distance from the reference position.

13. The radar level gauge according to claim 11 or 12, wherein, The measurement control circuit is also configured to: Determine the relative difference in signal amplitude among multiple different samples of a frequency scan signal; Determine the median of the determined signal amplitude difference; and The median value is compared with a predetermined threshold, and if the median value exceeds the threshold, it is determined that the cleaning process in the tank is in progress.

14. The radar level gauge according to claim 11 or 12, wherein, The measurement control circuit is also configured to reduce the sensitivity of the fill level measurement during the cleaning process if it is detected that cleaning is in progress in the tank.

15. The radar level gauge according to claim 11 or 12, wherein, The measurement control circuit is also configured to discard fill level measurements acquired during the cleaning process if it is detected that a cleaning process is in progress in the tank.

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