Calibration of modular level meters
By combining the transmitter module, sensor module, and electronic module, the manufacturing and calibration process of the modular level gauge is simplified, the calibration accuracy is improved, and the production cost is reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ENDRESS & HAUSER GMBH & CO KG
- Filing Date
- 2021-08-16
- Publication Date
- 2026-05-29
AI Technical Summary
The calibration process for existing modular level gauges is complex and difficult to simplify in manufacturing and calibration.
By employing a combination of a transmitter module, a sensor module, and an electronic module, an AC voltage signal is transmitted between the level gauge and the reflector to record the received variables, a calibration function is created, and the electronic module is connected during final assembly, simplifying the calibration process.
It simplifies the manufacturing and calibration process of level gauges, improves calibration accuracy, reduces the number of production lines, and lowers calibration costs.
Smart Images
Figure CN116057356B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for producing and calibrating modular level gauges. Background Technology
[0002] In automation technology, particularly for process automation, field devices are frequently used to record various measurement variables. These variables can be, for example, the level, flow rate, pressure, temperature, pH value, redox potential, conductivity, or dielectric value of a medium in a plant. To record the corresponding measurements, field devices include appropriate sensors and are based on suitable measurement principles. The Endress+Hauser Group manufactures and sells a wide variety of different types of field devices.
[0003] For level measurement of materials filling containers, capacitance-based, radar, and ultrasonic measurement principles have been proven robust and low-maintenance. A key advantage of these principles is their ability to virtually continuously measure level. In this context, the term "ultrasonic" refers to sound waves with frequencies between 14 kHz and 1 GHz. The term "radar" refers to radar signals with frequencies between 0.03 GHz and 300 GHz, with typical radar bands for performing level measurements located, for example, 2 GHz, 26 GHz, 79 GHz, and 120 GHz. In the application of ultrasound, the typical measurement principle is based on measuring pulse propagation time. In the case of radar, in addition to the pulse propagation time principle (also known as "pulse radar"), the FMCW ("Frequency Modulated Continuous Wave") principle is used to determine distance and level. A level gauge operating according to the pulse propagation time method is described, for example, in publication DE 10 2012 104858 A1. A typical construction of an FMCW-based level gauge is illustrated in publication DE 10 2013 108 490A1. The measurement principles of FMCW and pulse radar are described in detail in "RadarLevel Detection, Peter Devine, 2000".
[0004] Besides the free-radiation radar signals transmitted and received between the antenna and the filling material in the pulse propagation time principle and the FMCW principle, there is also the guided wave radar principle (more commonly known as "TDR, time domain reflectometer"). In this case, the radar signal is not radiated from the antenna, but coupled to a conductive measuring probe, which extends, for example, vertically into the filling material and just above the bottom of the container. In the case of TDR, the radar signal is reflected in the measuring probe at the height of the filling material surface, so that the reflected received signal can be used to determine the material level.
[0005] Similar to guided wave radar, level measurement is also performed using a measuring probe based on the capacitive measurement principle. In the capacitive measurement principle, the capacitance of the measuring probe depends on the level. To determine the capacitance, an AC voltage signal is coupled into the measuring probe, and the level is determined based on corresponding determined received variables, such as impedance or resonant frequency.
[0006] Capacitive, radar, and ultrasonic level gauges share a common characteristic: they are typically modularly constructed, comprising sensor modules, transmitting modules, and electronic modules. This allows for the creation of different level gauges and field device types based on common electronic modules. In this case, the electronic module of the field device primarily converts the sensor signal obtained by a specific sensor module into a standardized measurement signal used in a specific plant. A common standard is, for example, the 4-20mA range according to DIN-IEC 60381-1. Within the sensor module, the selected measurement principle is implemented to determine the distance to the filling material, enabling the sensor module to output the distance value as a corresponding sensor signal. In this case, the sensor module often generates sensor signals as digital signals. Therefore, the electronic module is designed to receive and process these digital sensor signals.
[0007] The design of the transmitting module is guided by the measurement principles implemented in the sensor module: in the case of free radiation radar (FMCW and pulse propagation time measurement), the transmitting module essentially consists of an antenna frequency-matched, and the radar signal is coupled to the antenna, for example, through a hollow conductor. In the case of capacitive measurement principles and guided wave radar, the transmitting module is implemented as a conductive probe, the extension of which is mounted in a container. In the case of ultrasonic measurement, the transmitting module effectively functions as a speaker / microphone and includes, for example, piezoelectric elements for signal output and input coupling.
[0008] Especially in applications requiring certification, it is necessary to create a so-called calibration protocol for the manufactured level gauges. In this case, the manufacturer needs to demonstrate that the measuring device measures correctly within the required error tolerance range. Therefore, a calibration protocol is created in a corresponding test series by coordinating or correspondingly setting the level measurements determined using the level gauge to each other for setting the level (or the setting distance to the reflector in the calibration device).
[0009] Because the modules are manufactured separately, and calibration or calibration protocols are required for all level gauges, the calibration process is logically complex. Therefore, the object of this invention is to provide a logically simplified manufacturing and calibration process for continuous level gauges. Summary of the Invention
[0010] This invention achieves this objective through a method for manufacturing and calibrating a modular level gauge based on capacitance, ultrasonic, or radar measurement principles, and comprising the following modules:
[0011] - A transmitting module, to which an AC voltage signal can be coupled, so that the AC voltage signal is emitted in the direction of the filling material or other reflector, and received as a corresponding receiving variable after reflection.
[0012] - Sensor module, which includes:
[0013] The signal generation unit is designed to generate an AC voltage signal based on a suitable measurement principle.
[0014] The evaluation unit is designed to convert received variables into sensor signals representing the distance between the level gauge and the reflector using a calibration function.
[0015] - An electronic module designed to convert sensor signals into standardized measurement signals representing material level (e.g., according to a 4-20mA standard) using a known installation height, and it includes...
[0016] The first interface of the evaluation unit is used to receive sensor signals, and
[0017] The second interface is designed to output measurement signals to the higher-level unit.
[0018] The term "reflector" within the scope of this invention refers to a calibration device and can be defined differently depending on the measurement principle implemented: in the case of free radiation radar and ultrasound, it is a reflective surface, such as a plate disposed in the calibration device. In the case of guided wave radar and capacitive measurement principles, the term "reflector" is, for example, a fixing device that terminates the measuring probe after an appropriate distance.
[0019] The method of the present invention includes the following steps:
[0020] - Connect the transmitter module to the sensor module, and
[0021] Then, calibrate the sensor module using a suitable calibration device as described below.
[0022] o Transmits an AC voltage signal when there is at least a defined distance between the level gauge and the reflector.
[0023] o records the corresponding received variable in each case, and
[0024] Based on the received variables of at least one record and the corresponding distance in each case, a calibration function is created, and
[0025] - Instruct the electronic module as follows
[0026] For example, the installation height of the level gauge can be input via a touchscreen module.
[0027] According to the present invention, this method simplifies the manufacturing process of the level gauge because the electronic module does not need to be connected during the calibration of the sensor module, but is only connected during final assembly or at the latest at the field of use.
[0028] The more distances and corresponding receiver variables considered when creating a calibration function, the more accurate the calibration of the sensor module can be. Therefore, it is advantageous to transmit AC voltage signals when there are two or more defined distances between the level gauge and the reflector, and to create a calibration function based on these distances and corresponding receiver variables.
[0029] According to the present invention, a calibration protocol can be created based on this method as follows:
[0030] o If at least a defined set distance exists to the reflector, transmit the signal to be transmitted, and after reflection, receive the corresponding received variable.
[0031] o generates sensor signals based on received variables and calibration functions stored in the sensor module.
[0032] o Use the expected installation height to convert the sensor signal into a standardized measurement signal, and
[0033] o coordinates at least one material level represented by a measured value signal with a set distance or corresponding material level value.
[0034] In this configuration, the sensor signal generated by the sensor module is specifically stored in an external memory unit, allowing the sensor signal to be transmitted from the external memory unit to the electronic module, for example, via a first interface. An advantage of creating a calibration protocol according to the present invention is that the electronic module and the sensor module do not need to be connected together at the point the calibration protocol is created.
[0035] The calibration of the sensor module can be improved by performing supplementary temperature compensation. In this case, temperature compensation can be performed as follows:
[0036] The sensor module generates an AC voltage signal at at least one defined distance and at least two different temperatures—for this purpose, the sensor module can operate, for example, in a temperature-controlled room.
[0037] After reflection, o records the corresponding received variable, and
[0038] o Create a compensation function based at least on the received variable and the corresponding temperature.
[0039] In subsequent measurement operations, when the sensor module includes a temperature sensor, temperature compensation can be applied, through which the ambient temperature can be measured. In this case, the sensor unit can output a sensor signal that has been temperature-compensated by means of a compensation function and the measured ambient temperature.
[0040] In the context of this invention, the terms "module" and "unit" generally refer to any circuit and any sensor appropriately designed for the intended application. Thus, it can be an analog circuit for generating or processing a corresponding analog signal, as needed. It can also be digital circuitry, such as an FPGA or a storage medium that interacts with a program. In this case, the program is designed to perform corresponding method steps or the necessary computer operations of a particular unit. In this context, within the scope of this invention, different electronic units of the level gauge can also potentially use shared physical memory or operate by means of the same physical digital circuitry. Attached Figure Description
[0041] The invention will now be explained in more detail with reference to the accompanying drawings, which are shown below:
[0042] Figure 1 A schematic arrangement of a time-of-propagation level gauge installed on a container is shown.
[0043] Figure 2 Detailed views of the various modules of the level gauge are shown, as well as
[0044] Figure 3 A schematic diagram of the calibration method of the present invention for a level gauge with a modular construction is shown. Detailed Implementation
[0045] In order to provide a basic understanding of the present invention, Figure 1 A free-radiation level gauge 1 is shown, which operates based on radar or ultrasonic measurement principles and is arranged on a container 3. In this case, filler material 2 is located in the container 3, and the level L of filler material 2 is determined by the level gauge 1. To determine the level L, the level gauge 1 is placed at a known installation height h at the top of the container 3.
[0046] Because radar and ultrasound involve measurement principles based on propagation time, the level gauge 1 is designed to emit or transmit radar or ultrasound-based signals S approximately perpendicular to the direction of the filling material 2. HF .exist Figure 1In the example of the illustrated embodiment, the level gauge 1 includes a horn-shaped antenna. Conversely, in the case of guided wave radar (“TDR”) and in the case of capacitive measurement principles, the level gauge 1 typically has a rod-shaped or cable-shaped measuring probe instead of an antenna, extending vertically from the level gauge 1 directly above the bottom plate of the container. In this case, the corresponding AC voltage signal S... HF It is coupled into the measurement probe.
[0047] At the surface of filling material 2, signal S HF The signal is reflected and received by the level gauge 1 as a received signal R after the corresponding signal propagation time. HF In this case, signal S HF R HF The signal propagation time depends on the distance d between the level gauge 1 and the surface of the filling material. Based on the received signal R... HF Determine signal S HF R HF The signal propagation time is used. Based on the signal propagation time, the level gauge 1 then determines the distance d to the filling material 2. The installation height h of the level gauge 1, stored in the level gauge 1, allows the level L to be determined based on the measured distance d using the relationship d = h – L. In the case of a capacitive measurement principle (not shown), the level gauge 1 determines the impedance or eigenfrequency, rather than the received signal R from radar or ultrasound. HF As a received variable, the level-related capacitance of the measuring probe can be determined based on the impedance or intrinsic frequency, and thus the distance d, i.e., the length of the measuring probe that is not wetted by the filling material, can be determined.
[0048] Typically, in the case of field equipment, the level gauge 1 is connected to the upper-level unit 4, such as a process control system or distributed database, via an interface 122, such as "4-20mA", "Ethernet", "PROFIBUS", "HART", or "Wireless HART". In this way, the level value L can be transmitted primarily to control the flow rate into and out of the container 3 under given conditions. However, information about the operating status of the level gauge 1 can also be transmitted in addition.
[0049] The various functions of the level gauge 1 are executed by the corresponding modules. Figure 2 The module arranged within the equipment housing is schematically shown. For communication with the higher-level unit 4, the interface 122 of the level gauge 1 is a component of the electronic module 12, suitable for a wide variety of field equipment types. In addition to transmitting peripheral data, this module 12 is particularly capable of standardizing the measured value signal S using one of the aforementioned protocols (“4-20mA”, “Ethernet”, “PROFIBUS”, “HART”, or “Wireless HART”). 4-20The material level value L is forwarded to the upper-level unit 4 in the form of [the signal]. Because determining the material level L requires knowing not only the distance value d but also the installation height h of the material level gauge 1, the electronic module 12 includes a predetermined memory for storing the installation height h. To input the installation height h, the electronic module 12 can, for example, be connected to an input module (not shown), such as a touchscreen.
[0050] Electronic module 12 obtains the distance value d from sensor module 11 via second interface 121, which, under given conditions, is presented as a digitized sensor signal x. In this case, sensor module 11 is housed within the device housing below electronic module 12. To generate sensor signal x, evaluation unit 111 of sensor module 11 appropriately converts the received signal R according to the pulse propagation time principle or the FMCW principle. HF In order for evaluation unit 111 to correctly evaluate the received signal R... HF The propagation time information in the signal is associated with the distance d to the surface of the filling material, when the received signal R... HF When converted into sensor signal x, the evaluation unit 111 references the calibration function d stored separately by the level gauge 1. i (R HF,i Furthermore, in the case of TDR or capacitive level measurement, a corresponding calibration function d is required. i (R HF,i This is so that the evaluation unit 111 can correctly assign the corresponding received variable R. HF This is associated with the length of the measuring probe that is not wetted by the filler material 2 (e.g., corresponding to the distance d to the filler material 2). In this way, independent of the implemented measurement principle, it is ensured that the sensor signal x correctly contains the distance d from the level gauge 1 to the surface of the filler material 2.
[0051] Figure 1 The horn antenna of the level gauge 1 shown is a component of the transmitting module 10, by means of which radar signals or ultrasonic signals S HF It is emitted into the filling material 2 and, after reflection, serves as the received signal R. HF Received. For example... Figure 2 As shown, the transmitting module 10 is located below the sensor module 11 in the installed state, and is transmitted by the sensor module 11 via the corresponding AC voltage signal S. HF To operate. In this case, the AC voltage signal S HF The frequency depends on the chosen measurement principle. In the case of free radiation radar and TDR, the AC voltage signal S HF The frequency ranges from 0.03 GHz to 300 GHz, while in the case of ultrasound, the frequency ranges from 14 kHz to 1 GHz. According to the principle of capacitance measurement, the AC voltage signal S...HF It has a frequency between 0.5kHz and 5kHz. This is used to generate an AC voltage signal S. HF The sensor module 11 includes a signal generation unit 110, which generates an AC voltage signal S according to the selected measurement principle. HF It is then coupled into the transmitter module 10.
[0052] On the one hand, the modular construction facilitates the adaptation of the level gauge 1 to different application areas, for example, by providing a transmitting module 10 with an antenna or a measuring probe mounted to an installation height h. On the other hand, individual modules of the level gauge 1, such as, in particular, the electronic module 12, can be used for other types of field equipment. This reduces the number of production lines required.
[0053] However, the modular construction and adaptability to handle special needs make the calibration of level gauge 1 more difficult, because calibration involves the entire level gauge 1 and container geometry, and the calibration of individual modules 100 cannot be omitted, such as, in particular, the calibration of sensor module 11. Most importantly, this also involves calibration protocols [d] i ;d ij The possible creation of ].
[0054] Figure 3 The diagram schematically illustrates a process flow chart of the present invention, which minimizes the calibration work associated with the manufacture of the modular level gauge 1. In this case, calibration 100 begins by first electrically and mechanically connecting the transmitter module 10 and the sensor module 11 together. Then, calibration 100 is performed using a calibration device for the sensor module 11 and the specific transmitter module 10. In this case, the calibration device includes a reflector that simulates the surface of the filling material, having a defined distance d from the level gauge 1 between, for example, 1 m and 25 m. i For example, EP 03390982 A1 contains more details about a similar setup for a free radiation radar measuring instrument.
[0055] In this device, the signal generation unit 110 of the sensor module 11 is positioned at a defined number of i different distances d between the level gauge 1 and the reflector 2. i An AC voltage signal S is generated at the location. HF To perform calibration 100 on sensor module 11, so that the corresponding radar or ultrasonic signal S HF,i At different distances d i The signal is transmitted to the reflector via the transmitting module 10. Correspondingly, the evaluation unit 111 of the sensor module 11 receives the received signal R via the transmitting module 10. HF,i In this case, the recorded received signal R HF,i and corresponding distance di The data is stored together. This can be stored in the evaluation unit 111 or the external memory unit 5. Based on this data, the evaluation unit 111 of the sensor module 11 creates and stores the calibration function d. i (R HF,i In this case, the calibration function d i (R HF,i It can be created in the form of an analytical function, for example, using an approximation algorithm or a calibration function d. i (R HF,i It can be stored as a pure lookup table. In both cases, the accuracy of calibration 100 increases with the distance d used. i The number i increases. In order to perform these steps of calibration 100 in sensor module 11, sensor module 11 does need to be designed so that it can be placed in the corresponding calibration mode.
[0056] By adding temperature compensation 400, the accuracy of calibration 100 can be further improved. In this regard, the term "temperature compensation" means that the distance value d represented by the sensor signal x is not corrupted by the ambient temperature deviating from room temperature. For the level gauge 1 to perform compensation, the level gauge 1 (e.g., sensor module 11) does need to be able to measure the ambient temperature, for example, by means of the corresponding integrated PT 100 temperature sensor. Temperature compensation can be performed in the device in the context of a standalone test series or in the context of the aforementioned calibration test series.
[0057] In this case, by subjecting the signal generation unit 110 to at least two different temperatures T j Below at least one set distance d i An AC voltage signal S is generated at the location. HF A series of compensation tests are performed, similar to the calibration method. For this purpose, the sensor module 11 can be housed in the device, for example, in an artificial climate chamber, which ensures that the corresponding ultrasonic or radar signal S is transmitted via the transmitting module 10. HF Transmitted to the reflector. In this case, preferably, at least two set temperatures T j Within the upper and lower limits of the design specifications, such as -15°C and +45°C. Furthermore, at two (or more) different temperatures T... j The more distance d below i Used to generate and transmit AC voltage signal S HF The more accurate the temperature compensation becomes.
[0058] In signal S HF After reflection on reflector 2, various corresponding received signals R are then recorded. HF Therefore, sensor module 11, such as evaluation unit 111, can be based on such received signal RHF,i and based on the corresponding temperature T j Create a compensation function, similar to the calibration function d. i (R HF,i The compensation function can also be an analytical function or a pure lookup table. Another option in this regard is that the compensation function is not created as a standalone function, but rather a calibration function d is created based on data from the compensation test series. i (R HF,i ,T j This allows it to include ambient temperature as another variable. Therefore, in the corresponding design, sensor module 11 can output a value using a compensation function (or an extended calibration function d). i (R HF,i ,T j The sensor signal x, which is compensated for the ambient temperature measured, is used for measurement. i temperature.
[0059] According to the present invention, no additional modules need to be calibrated except for the sensor module 11. Furthermore, the method of the present invention has the advantage that the electronic module 12 does not need to be connected during the calibration of the sensor module 11. This can be performed subsequently during the final assembly of the level gauge 1, and thus, in a given case, even at another location. Moreover, the command 200 for the electronic module 12 relative to the installation height h does not need to be performed during the calibration of the sensor module 11.
[0060] Similar considerations apply to the creation of the 300 calibration protocol [d] i ;d ij For this purpose, a separate series of protocol tests is performed on the calibrated sensor module 11 within the device. First, at one or more defined set distances d... j At each location, in every case, the AC voltage signal S HF The signal is generated by the signal generation unit 110 and transmitted to the reflector 2 via the transmission module 10. Upon receiving the corresponding received signal R via the transmission module 10... HF,i Subsequently, the evaluation unit 111 evaluates the received signal R HF,j And based on the already generated calibration function d i (R HF,i The sensor signal x is generated as a result. j,j In this case, the calibration protocol [d] is used. i ;d ij Sensor signal x j,j The data is stored in external memory unit 5. In this respect, memory unit 5 does not necessarily need to be a fixed component of the device. Memory unit 5 may also include mobile devices, such as smartphones or tablet computers, which can be wirelessly connected to the device, sensor module 11, and / or electronic module 12.
[0061] In order to execute the protocol creation 300 steps in the sensor module 11, the sensor module 11 must then be designed to be able to be placed in the corresponding protocol mode for this purpose.
[0062] Following the protocol test series of sensor module 11, in order to create protocol 300, the sensor signals x obtained in the protocol test series of sensor module 11 are provided from external memory unit 5 to electronic module 12. i,j In this case, it is advantageous that the memory unit 5 can be connected to the electronic module 12 via the first interface 121. Furthermore, the electronic module 12 is provided with an installation height h. Using the installation height h, the electronic module 12 can transmit the acquired sensor signal x... i,j Converted into a properly standardized measurement signal S 4-20i,j In order to perform the above method steps in electronic module 12 to create a calibration protocol [d] i ;d ij Similarly, electronic module 12 is designed so that it can be placed in the corresponding protocol mode when needed.
[0063] The measurement signal S generated by electronic module 12 in protocol mode 4-20i,j Converted into the corresponding material level value L i,j For this purpose, electronic module 12 can be connected to an external data processing unit, for example, via a second interface 122. The distance d used in the measurement series... j Alternatively, the data can be manually entered into the data processing unit, or the data processing unit can be connected to the corresponding control unit used in the device.
[0064] Then, in order to create the 300 calibration protocol [d i ;d ij The data processing unit will process the measurement signal S generated by the electronic module 12 in the agreed mode. 4-20 and corresponding distance d j Taken together, this distance is used in the device within the agreed-upon test series of sensor module 11. In this case, due to the corresponding distance d i d ij and material level L ij The coordination makes the possible differences between corresponding values apparent, thus resulting in a settling. This is documented as the calibration protocol [d]. i ;d ij For example, in paper form or a suitable electronic form. In the present invention for creating calibration protocols [d] i ;d ijAnother advantage of this method is that the sensor module 11 and the electronic module do not need to be connected at the points in time during the execution of the agreed test series. This is advantageous for the production of the level gauge 1, as the expensive device does not need to be maintained at the final manufacturing site. Instead, the device is stored at the site where the sensor module is manufactured.
[0065] List of reference numerals
[0066] 1. Level gauge
[0067] 2 reflectors / filling material
[0068] 3 containers
[0069] 4. Upper-level unit
[0070] 5 External Memory Units
[0071] 10. Transmission Module
[0072] 11 Sensor Module
[0073] 12 Electronic Modules
[0074] 100 Calibration Sensor Module
[0075] 110 Signal Generation Unit
[0076] 111 Evaluation Unit
[0077] 121 First Interface
[0078] 122 Second Interface
[0079] 200 instruction electronic module
[0080] 300 Create Calibration Protocol
[0081] 400 Compensation Sensor Module
[0082] d Distance
[0083] [d i ;d ij Calibration Protocol
[0084] d i (R HF,i Calibration function
[0085] R HF Receive variable
[0086] h Installation height
[0087] i, j set the distance between the reflectors
[0088] L material level
[0089] S HF Signal
[0090] S 4-20 Measured value signal
[0091] T j Temperature during compensation
[0092] x i Sensor signals
Claims
1. A method for manufacturing and calibrating a modular level gauge (1), the modular level gauge being based on a capacitance, ultrasonic, or radar-based measurement principle, and comprising the following components: - Transmitter module (10), AC voltage signal (S) HF ) can be coupled to the transmitting module, so that the signal (S) HF The signal is emitted in the direction of reflector (2) and, after reflection, serves as the corresponding received variable (R). HF ) was received, - Sensor module (11), the sensor module includes o signal generation unit (110), said signal generation unit (110) is designed to generate said AC voltage signal (S) according to appropriate measurement principles. HF ),as well as o Evaluation unit (111), said evaluation unit (111) is designed to use a calibration function (d i (R HF,i The received variable (R) HF ) is converted into sensor signal (x) i The sensor signal (x) i ) represents the distance (d) between the level gauge (1) and the reflector (2). i ),as well as - Electronic module (12), said electronic module (12) is designed to use a known installation height (h) to transmit the sensor signal (x) i ) is converted into a standardized measurement signal (S) representing the material level (L). 4-20 ), and the electronic module (12) includes o to the first interface (121) of the evaluation unit (111) in order to receive the sensor signal (x) i ),as well as o Second interface (122), the second interface (122) is designed to transmit the measured value signal (S 4-20 Output to the upper unit (4). The method includes the following steps: Connect the transmitting module (10) to the sensor module (11). - The sensor module (11) is calibrated (100) by means of the following method when the electronic module (12) is not connected: There is at least one defined distance (d) between the level gauge (1) and the reflector (2). i In the case of transmitting the AC voltage signal (S) HF ), o records the corresponding received variable in each case, and o is based on the received variable of at least one record and the corresponding distance (d) in each case. i ), create the calibration function (d i (R HF,i )),as well as -The electronic module (12) is instructed (200) as follows: Enter the installation height (h) of the level gauge. in, The electronic module (12) is connected to the sensor module (11) during the final assembly of the level gauge (1).
2. The method according to claim 1, wherein, There are two or more defined distances (d) between the level gauge (1) and the reflector (2). i In the case of transmitting the AC voltage signal (S) HF ), for calibrating (100) the sensor module (11), and wherein, based on these distances (d i The calibration function (d) is created using the corresponding received variables and the corresponding received variables. i (R HF,i )).
3. The method according to claim 1 or 2, further comprising: - Create a (300) calibration protocol as follows ([d i ; d ij ]): o In the presence of at least one defined setting distance (d) j In the case of the signal (S) HF The data is transmitted to the reflector (2), and after reflection, the corresponding received variable is received. o Based on the received variable and the calibration function (d) i (R HF,i The sensor signal is generated. o Use the known installation height (h) to convert the sensor signal into a standardized measurement signal (S). 4-20 ),as well as o will be determined by the measured value signal (S) 4-20 At least one level value (L) represents i,j ) and the defined setting distance (d) j (To be coordinated) 4. The method according to claim 3, wherein, The sensor signals generated by the sensor module (11) are stored in the external memory unit (5), and The sensor signal is transmitted from the external memory unit (5) to the electronic module (12) via the first interface (121).
5. The method according to claim 1 or 2, wherein, The electronic module (12) is designed to generate the measured value signal (S) according to the 4-20 mA standard. 4-20 ).
6. The method according to claim 1 or 2, wherein, The sensor module (11) is designed to generate the sensor signal (x) as a digital signal. i ), and wherein the electronic module (12) is designed to process digital sensor signals (x i ), receiving the digital sensor signal (x) via the first interface (121) i ).
7. The method according to claim 1 or 2, wherein, In the calibration (100) of the sensor module (11), temperature compensation (400) is performed as follows: o at at least a defined distance (d) i ) and at least two different temperatures (T) j The signal (S) is generated under these conditions. HF ), After reflection, o records the corresponding received variable (R). HF ),as well as o is based at least on the received variable and the corresponding temperature (T) j Create a compensation function. The sensor module (11) is designed to measure ambient temperature, and the sensor module (11) is designed to output a temperature-compensated sensor signal (x) by means of the compensation function and the measured ambient temperature. i ).