Fill level measuring device for process automation in an industrial or private setting

Abstract

The invention relates to a fill level measuring device, configured for process automation in an industrial or private setting, having a measurement signal generation and control circuit, configured to generate a first measurement signal for carrying out a signal propagation measurement and a second measurement signal for carrying out a measurement signal damping measurement, wherein the measurement signal generation and control circuit is configured to switch between the generation of the first measurement signal and the generation of the second measurement signal.

Description

[0001] Level measuring device for process automation in industrial or private environments

[0002] Reference to related applications

[0003] This application claims priority from German patent application No. 10 2023 203 927.3, filed on April 27, 2023, which is incorporated in its entirety by reference into this document.

[0004] Field of the invention

[0005] The invention relates to level measurement technology. In particular, the present disclosure relates to a level measuring device designed for process automation in industrial or private environments.

[0006] Technical background

[0007] In level measurement technology, both in industrial and private settings, level measuring devices are used that transmit measurement signals toward the product surface and receive the reflected signals. From this, an echo curve can be calculated, in which the level echo can be identified. From this, the level can then be calculated. In this context, this is also referred to as a time-of-flight measurement method, or ToF method. The measurement signals can be transmitted in the form of signal pulses (so-called pulse method) or in the form of frequency-modulated continuous wave signals (so-called MFCW method).

[0008] However, it has been found that these measuring methods provide inaccurate or no level values ​​under certain circumstances, for example because foam has formed on the product surface or the measuring signal is reflected by vessel internals and this false echo is incorrectly classified as a level echo.

[0009] Summary

[0010] Against this background, it is an object of the present disclosure to provide a level measuring device which provides level measurement results with increased reliability.

[0011] This object is achieved by the features of the independent patent claims. Further developments of the invention emerge from the subclaims and the following description of embodiments.

[0012] A first aspect of the present disclosure relates to a level measuring device configured for process automation in an industrial or private environment. It comprises a measurement signal generation and control circuit configured to generate a first measurement signal for performing a signal propagation time measurement and a second measurement signal for performing a measurement signal attenuation measurement.

[0013] An antenna is provided which is configured to radiate the first measurement signal and / or the second measurement signal in the direction of the filling material surface and to receive the first and / or second measurement signal reflected at the filling material surface in order to calculate the filling level.

[0014] The measurement signal generation and control circuit is in particular configured to switch between the generation of the first measurement signal and the generation of the second measurement signal.

[0015] This makes it possible to perform a signal propagation time measurement and a signal attenuation measurement consecutively. According to one embodiment, these two different measurements are performed consecutively. According to another embodiment, these two measurements are performed simultaneously. Hello Mr. Hengstier, hello Mr. Schmidt, I know that last sentence makes little technical sense; but it doesn't do any harm, which is why I recommend keeping it.

[0016] The measurement with the second measurement signal can be used to detect overfilling, i.e., when the antenna of the level measuring device is immersed in the medium or completely covered by it. Additional sensors, such as capacitive sensors, are not required to detect flooding of the measuring device housing. In particular, the present disclosure provides a level radar sensor that can safely and reliably detect that it is immersed in the medium or even flooded. For this purpose, the level measuring device not only operates according to the ToF method (pulse or MFCW), but also switches to a continuous wave signal in a time-controlled manner or alternately depending on the signal in order to then measure the attenuation.

[0017] The term "process automation in industrial environments" can be understood as a branch of technology that includes measures for operating machines and systems without human intervention. One goal of process automation is to automate the interaction of individual components of a plant in the chemical, food, pharmaceutical, petroleum, paper, cement, shipping, or mining industries. A variety of sensors can be used for this purpose, which are specifically adapted to the specific requirements of the process industry, such as mechanical stability, insensitivity to contamination, extreme temperatures, and extreme pressures. Measured values ​​from these sensors are usually transmitted to a control room, where process parameters such as fill level, limit level, flow rate, pressure, or density are monitored, and settings for the entire plant can be changed manually or automatically.

[0018] A sub-area of ​​process automation in the industrial environment concerns the logistics automation of plants and the logistics automation of supply chains. With the help of distance and angle sensors, processes inside or outside a building, or within a single logistics facility, are automated in the field of logistics automation. Typical applications for logistics automation systems include baggage and freight handling at airports, traffic monitoring (toll systems), retail, parcel distribution, and building security (access control). What the aforementioned examples have in common is that the respective application requires presence detection in combination with precise measurement of the size and location of an object.For this purpose, sensors based on optical measuring methods using lasers, LEDs, 2D cameras or 3D cameras that measure distances according to the time of flight (ToF) principle can be used.

[0019] Another sub-area of ​​process automation in the industrial environment concerns factory-to-production automation. Applications for this can be found in a wide variety of industries, such as automotive manufacturing, food production, the pharmaceutical industry, and packaging in general. The goal of factory automation is to automate the production of goods using machines, production lines, and / or robots, i.e., to run the process without human intervention. The sensors used here and the specific requirements regarding measurement accuracy for detecting the position and size of an object are comparable to those in the previous example of logistics automation.

[0020] The terms used in the claims should be construed to give them the broadest possible reasonable interpretation consistent with the foregoing description. For example, the use of the article "a" or "the" in introducing an element should not be construed to exclude a plurality of elements. Likewise, the mention of "or" should be construed to include a plurality of elements, so that the mention of "A or B" does not exclude "A and B" unless it is clear from the context or the preceding description that only one of A and B is intended.Furthermore, the phrase "at least one of A, B, and C" should be understood as one or more elements from a group of elements consisting of A, B, and C, and should not be interpreted as requiring at least one of each of the listed elements A, B, and C, whether A, B, and C are related as categories or otherwise. Furthermore, the reference to "A, B, and / or C" or "at least one of A, B, or C" should be interpreted to include each individual unit of the listed elements, e.g., A, each subset of the listed elements, e.g., A and B, or the entire list of elements A, B, and C.

[0021] According to one embodiment of the present disclosure, the first measurement signal is a frequency-modulated continuous wave (FMCW) signal. According to another embodiment of the present disclosure, the second measurement signal is a constant frequency continuous wave (CW) signal.

[0022] According to a further embodiment of the present disclosure, the measurement signal generation and control circuit is configured to switch between the generation of the first measurement signal and the generation of the second measurement signal, in particular only when no level echo can be detected in the measurement with the first measurement signal, or, alternatively, the level echo cannot be clearly detected.

[0023] According to a further embodiment of the present disclosure, the measurement signal generation and control circuit is configured to periodically switch between the generation of the first measurement signal and the generation of the second measurement signal. Alternatively or additionally, it can be configured to switch between the generation of the two measurement signals in an event-controlled manner.

[0024] According to one embodiment of the present disclosure, the measurement signal generation and control circuit is configured to measure the energy of the reflected second measurement signal and to determine that the antenna is immersed in the filling material when the measured energy is above a predetermined threshold value.

[0025] According to a further embodiment of the present disclosure, the level measuring device is configured for a user to perform a calibration measurement in which the threshold value is determined by immersing the antenna into the filling material and performing the measurement signal attenuation measurement.

[0026] According to one aspect of the present disclosure, a method for determining a fill level of a filling material is provided, comprising the following steps: generating a first measurement signal for performing a signal propagation time measurement; radiating the first measurement signal by an antenna in the direction of a filling material surface and receiving the first measurement signal reflected at the filling material surface for calculating the fill level by the antenna; calculating the fill level; switching from the generation of the first measurement signal to the generation of the second measurement signal; generating the second measurement signal for performing a measurement signal attenuation measurement; and radiating the second measurement signal by the antenna and receiving the reflected second measurement signal by the antenna for deciding whether the antenna is covered by the filling material or not.

[0027] According to a further aspect of the present disclosure, a program element is provided which, when executed on a measurement signal generation and control circuit of a level measuring device, instructs the level measuring device to perform the method steps described above and below.

[0028] Another aspect of the present disclosure relates to a computer-readable medium on which the program element described above is stored.

[0029] Further embodiments of the present disclosure are described below with reference to the figures. The representations in the figures are schematic and not to scale. Where the same reference numerals are used in the following description of the figures, they denote identical or similar elements.

[0030] Short description of the characters

[0031] Fig. 1 shows two echo curves of a signal propagation time measurement at different fill levels.

[0032] Fig. 2 shows containers and measurement curves at two different filling levels.

[0033] Fig. 3 shows a flowchart of a method according to an embodiment of the present disclosure.

[0034] Detailed description of embodiments Fig. 1 shows two measurement curves 105, 106. The measurement curve 105 was recorded with a first measurement signal for performing a signal propagation time measurement, as was the measurement curve 106.

[0035] In measurement curve 105, the filling material surface 103 of the filling material 104 is located at a significant distance from the antenna 102 of the level measuring device 100. The x-axis of this measurement curve represents the distance between the filling material surface and the antenna 102, and the y-axis represents the amplitude of the reflected measurement signal. The level echo 107 is clearly visible here. The so-called antenna ringing 108 in the vicinity of the antenna 102 is also visible.

[0036] If the level echo 107 now moves close to the antenna 102 because the level rises, the level echo 107 disappears in the antenna ringing 108 and can no longer be reliably detected.

[0037] The level measuring device 100, which is a radar sensor, can switch from FMCW measuring mode or pulse measuring mode (first measuring signal) to continuous wave radar measuring mode (second measuring signal) in order to measure the attenuation of the second measuring signal. The switchover can be triggered temporally or by a control signal. This allows flooding or immersion of the antenna in the filling material to be reliably detected. In particular, this can also be reliably detected immediately after the level measuring device 100 is switched on. This offers particular advantages for autonomous sensors that only measure at certain time intervals. In particular, the level measuring device can be configured to record additional information about the installation situation in the container or at the measuring point.

[0038] The level radar measuring device records an echo curve. However, since this curve may not reveal a (clear) level echo under certain circumstances, for example, when the container is empty, when there is significant foam formation, or when the container is flooded, the sensor cannot distinguish whether the container is full / flooded up to the radar antenna or not. By switching to the second measurement signal and measuring the reflected amplitude, the sensor can reliably and safely detect whether the container / sensor is flooded. Level radar measuring devices based on the pulse or FMCW principle, as well as other sensors that operate according to the ToF principle, such as ultrasonic sensors or laser sensors, often have sensitivity issues at close range due to the coupling and decoupling of the measurement signal.

[0039] In the case of radar level measuring devices, this means that the level measuring device can measure the level with less accuracy or not at all in the close range. If the antenna 102 is completely submerged or if the level measuring device 100 is completely below the surface of the filling material (flooded), the level measuring device can no longer detect a signal. An echo curve in the close range always has a deflection in amplitude at the coupling (antenna), the so-called antenna ringing. If the sensor / antenna is completely submerged, for example in the case of flooding, no echo signal can be detected on the echo curve. However, the antenna ringing is not affected by this, which can be disadvantageous because the sensor cannot recognize or detect it as an error or as an indication of flooding.

[0040] There can be many reasons why no level echo can be seen in the right-hand measurement curve.

[0041] Therefore, only the antenna ringing is visible on the right echo curve. This condition can occur for various reasons. Examples include:

[0042] The antenna and / or level measuring device are completely immersed in the filling material, for example water;

[0043] Foam on the liquid surface;

[0044] Level echoes outside the measuring range;

[0045] The container is empty and due to the geometry of the container (e.g. sloping container bottom) the reflection signal from the bottom is not reflected to the level measuring device but away from it;

[0046] Liquids with low dielectric constant and processes with difficult process conditions (turbulent surfaces, gas inclusion, etc.); attenuation of the radar signal by the gas atmosphere in the vessel (ammonia, vinyl chloride, acetone, etc.);

[0047] Reflector under the sensor or manipulation of the measuring point (sensor measures into the sky).

[0048] To detect flooding or submersion of the antenna 102, the level measuring device 100 switches to a continuous wave signal. The term "continuous wave" is not 100% physically correct, as a microwave signal is only emitted at a constant frequency for a short period of time. The level measuring device measures the reflected energy of the measurement signal, similar to a microwave barrier, such as in the VEGA MIP measuring device. This allows it to be detected whether the sensor / antenna is submerged or flooded.

[0049] It also allows a short area in front of the antenna to be effectively monitored. The antenna doesn't have to be fully submerged. If the level gauge has no signal but only detects the antenna ringing, it can detect flooding by switching to continuous wave mode.

[0050] Fig. 2 shows a container A with a low fill level and a container B with a very high fill level, where the overfill situation can be seen. The fill level measuring device 100 is mounted on the top outside of the container. In this embodiment, the container is a plastic container that is permeable to the radar signal.

[0051] The radar level gauge 100 has a measurement problem at close range. At close range, no level echo can be detected in the echo curve 111 during the time-of-flight measurement 110 because the container is overfilled. A level echo 107 can be detected in the echo curve 112, which was recorded in state A, i.e., at a lower level.

[0052] If the level measuring device 100 now switches to the second operating mode, in which the second measurement signal is used (continuous wave signal), the reflected energy can be measured. An example of such a continuous wave signal is shown in measurement curve 113, with the time axis t and the frequency axis F. In situation A, the reflected energy is measured according to curve 114, i.e., a relatively low amplitude. In the overfill situation B, a significantly higher amplitude is measured (see measurement curve 115).

[0053] This can be used to conclude that there is overcrowding, as the amplitude exceeds a predetermined threshold.

[0054] According to one embodiment, the level measuring device can be factory-preset for the amplitude values ​​for evaluating the damping (continuous wave, at which threshold the sensor is flooded). According to one embodiment, the level measuring device detects this threshold itself and learns, since the threshold can vary depending on the installation situation.

[0055] Fig. 3 shows a flow diagram of a method according to one embodiment. In step 301, a measurement signal is generated for performing a signal propagation time measurement and, in step 302, is radiated towards the filling material surface, where it is reflected, and the reflected measurement signal is received again by the antenna. In step 303, the fill level is calculated from this, in particular by evaluating an echo curve. If it is then determined that the fill level echo cannot be identified with sufficient accuracy or cannot be found at all, the fill level measuring device switches to generating a second measurement signal, which is, for example, a continuous wave signal (see step 304). This measurement signal is then generated and radiated in step 305. In step 306, the reflected second measurement signal is received, and by evaluating the amplitude of the received measurement signal, a decision is made as to whether the antenna is covered by the filling material or not.In step 307, the measuring device switches back to the first measuring mode, in which the first measuring signal is used for level measurement.

Claims

Patent claims 1. A level measuring device (100) configured for process automation in an industrial or private environment, comprising: a measurement signal generation and control circuit (101) configured to generate a first measurement signal for performing a signal propagation time measurement and a second measurement signal for performing a measurement signal attenuation measurement; an antenna (102) configured to radiate the first and second measurement signals toward a filling material surface and to receive the first or second measurement signals reflected at the filling material surface for calculating the fill level; wherein the measurement signal generation and control circuit (101) is configured to switch between the generation of the first measurement signal and the generation of the second measurement signal.

2. Level measuring device (100) according to claim 1, wherein the first measuring signal is a frequency modulated continuous wave signal, FMCW.

3. Level measuring device (100) according to one of claims 1 or 2, wherein the second measuring signal is a continuous wave signal with a constant frequency.

4. Level measuring device (100) according to one of the preceding claims, wherein the measurement signal generation and control circuit (101) is configured to switch between the generation of the first measurement signal and the generation of the second measurement signal when no level echo can be detected in the measurement with the first measurement signal.

5. Level measuring device (100) according to one of the preceding claims, wherein the measurement signal generation and control circuit (101) is configured to periodically switch between the generation of the first measurement signal and the generation of the second measurement signal.

6. Level measuring device (100) according to one of the preceding claims, wherein the measurement signal generation and control circuit (101) is configured to measure the energy of the reflected second measurement signal and to determine that the antenna (102) is immersed in the filling material when the measured energy is above a predetermined threshold value.

7. Level measuring device (100) according to claim 6, arranged for carrying out a calibration measurement by a user, in which the threshold value is determined by immersing the antenna (102) in the filling material and carrying out the measurement signal attenuation measurement.

8. A method for determining a fill level, comprising the steps: Generating a first measurement signal for performing a signal propagation time measurement; Radiating the first measurement signal by an antenna (102) in the direction of a filling material surface and receiving the first measurement signal reflected at the filling material surface for calculating the filling level by the antenna (102); Calculate the fill level; Switching from the generation of the first measurement signal to the generation of a second measurement signal; Generating the second measurement signal for performing a measurement signal attenuation measurement; Emitting the second measurement signal through the antenna (102) and receiving the reflected second measurement signal through the antenna (102) to decide whether the antenna is covered by the filling material or not.

9. A program element which, when executed on a measurement signal generation and control circuit (101) of a level measuring device (100), instructs the level measuring device (100) to perform the following steps: Generating a first measurement signal for performing a signal propagation time measurement; Radiating the first measurement signal by an antenna (102) in the direction of a filling material surface and receiving the first measurement signal reflected at the filling material surface for calculating the filling level by the antenna (102); Calculate the fill level; Switching from the generation of the first measurement signal to the generation of a second measurement signal; Generating the second measurement signal to perform a measurement signal attenuation measurement; Emitting the second measurement signal through the antenna (102) and receiving the reflected second measurement signal through the antenna (102) to determine whether the antenna is covered by the filling material or not.

10. A computer-readable medium on which a program element according to claim 9 is stored.

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