This application claims priority to European Patent Application No. 21 206 634.4 filed on 5 Nov. 2021, the entire content of which is incorporated herein by reference.
The invention relates to a method for putting a level measuring device into operation. Furthermore, the invention relates to a level measuring device, a program element, a computer-readable medium and a use.
When commissioning, e.g., putting into operation, a level measurement device that uses, in particular, a radar sensor unit for the measurement, a large number of measurements are required in many cases in order to obtain a high level of safety and/or measurement accuracy after the level measurement device has been commissioned. For example, for a limit level measurement that is intended to detect only an upper and lower limit of the level in the vessel, at least two measurements are required for commissioning. For a level measurement (so-called range monitoring), five measurements are required in many cases. For each of these measurements, a medium is filled into the vessel at the desired level. Such measurements can cause a certain—sometimes high—expenditure of material and time.
There may be a desire to reduce the number of measurements during a start-up (putting into operation) of a level measuring device (level meter) in at least some cases.
One aspect relates to a method of commissioning a level measuring device arranged to measure a level of a product in a container. The method comprises the following steps:
detecting, by means of a radar sensor unit of the level meter, a (detected) echo curve, wherein the echo curve comprises at least a first echo;
selecting, from the (detected) echo curve, the first (detected) echo having a first distance and a first amplitude, the first amplitude having the highest amplitude of the echo curve;
determining a calculated first amplitude, wherein the calculated first amplitude is a function of the first distance;
if the (detected) first amplitude is higher than the calculated first amplitude, rate the echo curve as acceptable for start-up of the level measuring device.
When the level measuring device is put into operation, the vessel whose level, limit level and/or topology is to be measured can be empty or (at least partially) filled with a medium. It may be useful not to fill the container completely, so that the medium is at least a few centimeters away from a so-called “close range” of the radar sensor unit.
During a measurement, the radar sensor unit of the level measuring device detects the echo curve. The detection of the echo curve can be realized, for example, in such a way that radar waves—generated, for example, by a transmitter of the radar sensor unit—reflected by the medium and/or by parts of the container are received by a receiver of the radar sensor unit. The received reflected radar waves are then converted, e.g. in an evaluation unit (and/or in the radar sensor unit) of the level meter, into the so-called echo curve. For the measurement, e.g. an FMCW method (FMCW: frequency modulated continuous wave radar), a pulse radar and/or other radar methods can be used. The echo curve is often displayed in a diagram whose x-axis represents a distance (usually linear) and whose y-axis represents an amplitude (usually logarithmic, e.g., linear in dB). A (local) maximum of the echo curve usually corresponds to a reflection, e.g. from the medium and/or from parts of the vessel. A global maximum usually occurs in the close range of the radar sensor unit and is generated e.g. by reflections from a horn antenna of the radar sensor unit. In practice, it has been shown that not only desired maxima appear in such an echo curve, but also disturbances that can falsify the measurement. The disturbances can have many different causes.
An echo curve of a real measurement has at least one echo. If the echo curve has more than one echo, then the one whose amplitude has the highest amplitude of the echo curve is selected as the “first echo” from the multitude of echoes. An amplitude in the near range of the transmitter (which may be higher than the amplitude of the first echo) can be neglected in at least some cases. If the echo curve has only one echo, then this is selected as the “first echo”. The distance of the first echo is called “first distance” and the amplitude of the first echo is called “first amplitude”.
The calculated first amplitude results from the application of a function to the first distance. The function can represent a decrease in the intensity of the reflected radar wave, as it occurs, for example, when the product surface moves away from an antenna of the transmitter. It is assumed that the product surface reflects radar waves strongly, as is the case, for example, with liquids, or also with a reflection from the bottom of the vessel. A product surface that does not strongly reflect radar waves would be, for example, a coarse-grained bulk material, and/or liquids with small DK—values (dielectric constants), such as LPG (Liquified Petroleum Gas), oils and solvents. The function may be calculated (e.g., inversely proportional) and/or derived from measurements. A reference point (“maximum value”) of the function, from which this decrease in intensity can be calculated, can be obtained e.g. from experience values, e.g. from the characteristics of different antenna systems.
If the first amplitude is higher than the calculated first amplitude, the echo curve can be evaluated as acceptable for commissioning. In many cases, commissioning can be completed with this. If the first amplitude is lower than the calculated first amplitude, this can have several causes. For example, interference may have occurred and/or the radar waves have been “swallowed” by the walls of the vessel, e.g., by internals in the vessel, by buildup, etc. If the first amplitude is lower than the calculated first amplitude, this can mean that measurements with the level measuring device can be faulty. Therefore, in this case, the echo curve will be evaluated as non-acceptable for commissioning. It may then be successful to perform several or additional measurements for commissioning.
With this method, it may therefore be possible to reduce the number of measurements during commissioning of a level measuring device in at least some cases. Advantageously, this can help to reduce the time and effort required for commissioning. In particular, it can help to save a plant operator from having to start up with medium, and the plant operator can still have a high level of safety during commissioning, or a large number of measurements during commissioning is only required in significantly fewer cases. This can be all the more useful because starting up the switching points or the entire measuring range is not always feasible and/or desired by the plant operator, for example in cases where rapid commissioning is required or if no medium is available at the time of commissioning.
In some embodiments, the container is either empty or at least partially filled with a liquid. The liquid may also be an emulsion or suspension, for example. In particular, the fill surface of liquids can strongly reflect radar waves.
In some embodiments, for evaluating the measured echo curve as acceptable, the first amplitude is higher than the calculated first amplitude by a safety margin, where the safety margin is 1 dB, 2 dB, 5 dB, 10 dB, 15 dB, or more. The safety distance can take into account, for example, inaccuracies in the measurement caused, for example, by an irregular design of the vessel, its walls, by smaller internals, etc. This tightened criterion to evaluate the echo curve as acceptable for commissioning can reduce the number of “false positive” evaluations, sometimes significantly.
In an embodiment, the method comprises further steps of: determining at least a second echo, the second echo having a second distance and a second amplitude, the second distance being less 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 non-acceptable for commissioning.
One or more second echoes can be measured. The second echoes can have a lower amplitude than the first echo. The second echoes can be caused, for example, by installations in the vessel, by buildup, etc., which are located between the product surface and the transmitting antenna.
In some embodiments, the reference echo curve substantially corresponds to an echo curve measured in an infinitely long empty vessel. Further, a tolerance band may be considered; e.g., +1 dB, +2 dB, +3 dB around a calculated reference echo curve.
In some embodiments, an echo from a close range of the level measuring device is neglected. For example, the close range of the level measuring device may have a distance of less than 10 cm or 20 cm from the transmitter (e.g., from a transmitter chip). The echo from the close range may be caused, for example, by a horn antenna (as a transmitting antenna), or by a so-called “dome”, e.g. a shaft, in which the transmitter is located and which in at least some cases is located at the top of an inner side of the vessel. The echo from the close range may have a high amplitude. The echo from the close range may exhibit so-called antenna ringing, e.g., interference caused, for example, during antenna coupling. The echo from the near range can be excluded from an evaluation—e.g. as a “real” echo, from a product surface—by a so-called “factory noise suppression” already at the manufacturer. In cases where no increased amplitude can be detected in the currently measured echo compared to the factory false signal suppression, the measurement can be evaluated as acceptable for commissioning.
One aspect relates to a level measuring device for measuring a level of a product in a container. The level measuring device comprises a radar sensor unit configured to transmit radar waves and to receive reflected radar waves, and an evaluation unit which is configured to convert the reflected radar waves into an echo curve and to evaluate the echo curve as described above and/or below. The radar sensor unit can, for example, use an FMCW method or a pulse radar for measurement. The radar sensor unit and the evaluation unit may in at least some cases be implemented as one integrated hardware—e.g. on the same board, or on the same chip.
One aspect relates to a use of a level measuring device as described above and/or according to following for measuring a level, a topology and/or a boundary level of a filling material in a container.
One aspect relates to a program element which, when executed on an evaluation unit of a level measuring device as described above and/or below and/or on another computing unit, instructs the evaluation unit and/or the computing unit to perform the method as described above and/or below.
One aspect relates to a computer-readable medium on which the program element described herein is stored.
It should also be noted that the various embodiments described above and/or below may be combined.
For further clarification, the invention is described with reference to embodiments illustrated in the figures. These embodiments are to be understood only as examples and not as limitations.
To put the level measuring device 100 into operation, the level measuring device 100 is arranged on or in the container 150, e.g. on top of the container 150 or in a so-called “dome” (not shown). Radar waves may then be transmitted to the level measuring device 100, and an echo curve 200 may be formed from the reflected radar waves 125. The echo curve 200 can then be evaluated, and in at least some cases, a decision can be made based on the echo curve 200 as to whether the echo curve 200—and thus the level measuring device 100—is judged acceptable for use.
When the level measuring device is put into operation, the echo curve 200 can then be evaluated. In this case, the echo curve 200 exhibits a first echo 210 during real measurement. The first echo 210 may, for example, (in the case of an at least partially filled container) have been reflected from the product surface 170 or (in the case of an empty container) from a bottom 152 of the container 150. In the case of an at least partially filled container, the echo curve 200 can also have (at least) two echoes, namely from the product surface 170 and from the bottom 152; in this case, the echo from the bottom 152 has a lower amplitude than the echo from the product surface 170, in particular a substantially lower amplitude. The first echo 210 has a first distance 211 and a first amplitude 212. The echo which has the highest amplitude of the echo curve 200—apart from the echoes from the close range 204—can be selected as the first echo 210. The first echo 210 may be determined, for example, by the fact that it protrudes highest from the reference echo curve 240. Further, a calculated first amplitude 214 may be determined, wherein the calculated first amplitude 214 is a function of the first distance 211. For example, a function that monotonically decreases with distance d may be used, which is then applied to the highest amplitude 202 and, by subtracting an amplitude value 241 from the highest amplitude 202, yields the calculated first amplitude 214. In the example of
In some embodiments, echoes from the close range 204 may also be considered. In this regard, in cases where an increased amplitude is seen in the currently measured echo compared to the factory noise suppression, the measurement may be judged to be unacceptable for commissioning.
An application for measuring a level of a product requires at least five measurements, for example a “max” measurement at an upper level, a “min” measurement at a lower level and e.g. three further measurements with further selected levels. For each limit level, one actual measured value is recorded, which corresponds to an actual current, for example. This actual measured value or actual current is —compared—with a target measured value or target current. Based on these measured values, a level measuring device for measuring the level and/or a topology can be evaluated as acceptable for commissioning. The values can, in case of correct measurements, be stored e.g. for documentation. In case of non-correct measurements, the commissioning can be aborted.
In at least some cases, the commissioning scenario can be shortened, particularly for applications of any of the processes as described above and/or below.
Subsequently, the echo quality can be evaluated as described above and/or below. If the measurements are correct, the values can be saved, e.g. for documentation. If the measurements are not correct, the commissioning can be aborted. Alternatively or additionally, measurements can be performed as e.g. for the commissioning scenario 500 (see above).
For the remaining area, the following scheme can be applied:
Other options for echo curve evaluation may include: If a medium or product is present in the vessel, it may be possible to evaluate multiple echoes. If multiple echoes are present, the sensor or the operating tool can compare the amplitude of the multiple echoes with the amplitude of the level echo. If the multiple echoes are sufficiently smaller than the level echo, the measurement is considered acceptable for commissioning in this aspect. Multiple echoes outside the actual measuring range can also be used for evaluation.
In order to assess an acceptable measurement, it is possible, for example, to refer to settings or parameters that have been entered by a specialist, e.g. by service personnel. In addition to information about the medium, this can also be information about the application or the vessel.
Information about the medium may include, for example:
Information about the container may include, for example:
Number | Date | Country | Kind |
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21 206 634.4 | Nov 2021 | WO | international |