A wireless liquid level remote monitoring liquid level meter and monitoring system

Abstract

The present application belongs to the field of instruments and internet of things monitoring technology, and particularly relates to a wireless liquid level remote monitoring liquid level meter and a monitoring system, aiming to solve the problems of insufficient temperature resistance, hanging material interference, low precision and poor stability caused by lack of automatic calibration in high-temperature molten salt liquid level measurement. The system comprises a 1000 DEG C-resistant double-layer coaxial capacitance sensing probe, an adaptive signal conditioning module, a wireless transmission unit, a remote monitoring terminal and a dynamic calibration engine. The signal precision is improved by suppressing hanging material through a porous ceramic electrode, differential capacitance and temperature compensation. Based on the dielectric properties of molten salt, online calibration without manual intervention is realized. Remote visualization and intelligent alarm are supported, and the system is suitable for extreme working conditions such as solar thermal power generation.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of instruments and Internet of Things monitoring technology, and particularly relates to a wireless liquid level remote monitoring liquid level meter and a monitoring system. BACKGROUND

[0002] In high-temperature industrial systems such as photo-thermal power generation and molten salt energy storage, liquid level monitoring is a key link to ensure process safety and operation efficiency. As a highly efficient heat transfer and storage medium, molten salt has a working temperature usually exceeding 500℃ and has strong corrosiveness and high viscosity, which puts high requirements on liquid level measurement technology. The liquid level monitoring device not only needs to operate stably for a long time in an extreme thermal environment, but also needs to effectively cope with multiple challenges such as medium material hanging, signal interference and material aging. Therefore, developing a liquid level remote monitoring solution with high temperature resistance, corrosion resistance, material hanging prevention and high reliability has become a core requirement in this field.

[0003] Among them, the wireless liquid level remote monitoring technology gradually becomes an important development direction for high-temperature molten salt storage tank liquid level monitoring due to its advantages of no need for wiring, easy deployment and suitability for dangerous or closed environments. This technology aims to realize real-time, continuous and remote monitoring of the molten salt liquid level by integrating a high-stability sensing unit and a wireless communication module, thereby improving the system automation level and operation safety.

[0004] The prior art still faces significant bottlenecks in achieving the above objectives. Although the radar liquid level meter has the advantage of non-contact, it is easily affected by signal attenuation and false reflection interference in the high-temperature molten salt vapor environment. Although the optical fiber liquid level meter is resistant to electromagnetic interference, the wavelength drift caused by coating aging at high temperatures requires frequent calibration. Although the magnetostrictive liquid level meter can be continuously measured, the float is easily affected by the viscosity of the molten salt, and the waveguide wire thermal expansion introduces measurement errors. In particular, the capacitive liquid level meter generally has insufficient temperature resistance, electrode hanging material leading to capacitive drift, serious electromagnetic and parasitic capacitance interference, and lack of adaptive calibration capability for dynamic changes in dielectric constant in high-temperature molten salt scenarios, which makes it difficult to ensure measurement accuracy, reduces system reliability, and increases maintenance costs. Therefore, there is an urgent need for a wireless liquid level remote monitoring liquid level meter and monitoring system that can comprehensively solve the problems of high temperature resistance, anti-hanging material, strong anti-interference and automatic calibration. SUMMARY

[0005] The purpose of the present application is to provide a wireless liquid level remote monitoring liquid level meter and a monitoring system to solve the problems of low measurement accuracy, poor system stability and high maintenance cost in existing high-temperature molten salt liquid level measurement technology due to insufficient temperature resistance, weak anti-hanging material capability, poor anti-interference performance and lack of automatic calibration mechanism.

[0006] The technical scheme of the present application comprises: a high-temperature-resistant capacitance sensing probe, an adaptive signal conditioning module, a wireless data transmission unit, a remote monitoring terminal, and a dynamic calibration engine; the high-temperature-resistant capacitance sensing probe adopts a double-layer coaxial electrode structure, the inner electrode is a solid molybdenum rod, the outer electrode is a porous ceramic-coated molybdenum mesh, and high-purity alumina ceramic is used between the inner and outer electrodes for isolation; the adaptive signal conditioning module is integrated in the high-temperature sealed cavity at the bottom of the probe, used to convert the weak capacitance signal output by the capacitance sensing probe into a digital signal, and to perform temperature compensation and material hanging interference suppression processing on the signal; the wireless data transmission unit adopts a low-power wide-area communication protocol, encrypts the liquid level data after conditioning, and remotely transmits it to the remote monitoring terminal; the remote monitoring terminal is used to receive, store and visually display the liquid level data, and simultaneously sends a calibration trigger instruction to the dynamic calibration engine; the dynamic calibration engine is based on a physical model of the change of the dielectric constant of molten salt with temperature and composition, combines real-time temperature data and historical liquid level trends, dynamically corrects the capacitance-liquid level mapping relationship, and realizes online automatic calibration without manual intervention.

[0007] Further, in the double-layer coaxial electrode structure, the pore size of the porous ceramic of the outer electrode is controlled to be between 5 microns and 20 microns, and the porosity is set to be 30% to 50%, so as to allow slow penetration of molten salt vapor while ensuring structural strength and reducing surface material accumulation; the radial spacing between the inner electrode and the outer electrode is set to be 2 mm to 5 mm, so as to optimize the balance between capacitance sensitivity and voltage resistance performance.

[0008] Further, the adaptive signal conditioning module comprises a high-precision capacitance digital converter, a temperature compensation unit, and a material suppression algorithm unit; the high-precision capacitance digital converter adopts a differential capacitance measurement architecture, which uses the same high-temperature environment for the reference capacitance and the sensing capacitance to offset environmental drift; the temperature compensation unit obtains temperature data in real time through the platinum-rhodium thermocouple integrated in the probe, and dynamically corrects the capacitance value according to the pre-stored electrode thermal expansion coefficient and dielectric constant temperature characteristic curve of the insulating medium; the material suppression algorithm unit identifies the slow drift component caused by material hanging based on the time domain fluctuation characteristics of the capacitance signal, and filters it out through high-pass filtering and trend elimination algorithm.

[0009] Further, the wireless data transmission unit adopts LoRa or NB-IoT communication protocol, the radio frequency front end is packaged in a metal shield, and electrical isolation with the high-temperature sealed cavity is realized through a ceramic feedthrough; the data transmission period can be configured to be 1 second to 60 minutes, supporting event-triggered mode, when the liquid level change rate exceeds the preset threshold, the reporting interval is automatically shortened.

[0010] Further, the dynamic calibration engine runs on a remote monitoring terminal or a cloud server, and a calibration model thereof is constructed based on a molten salt component database and a temperature-dielectric constant mapping table; when the system detects that a molten salt batch is replaced or a temperature interval is significantly deviated, corresponding dielectric constant parameters are automatically called, and a liquid level height is recalculated in combination with a current capacitance measurement value; the calibration process does not need to interrupt measurement and does not need manual intervention.

[0011] Further, the lead of the high-temperature-resistant capacitance sensing probe adopts a double-layer insulation structure, the inner layer is magnesium oxide powder compaction insulation, the outer layer is stainless steel braided armor, the signal line core is a nickel-chromium alloy wire, and the whole can withstand a continuous working temperature of 800 DEG C; the connection between the lead and the signal conditioning module adopts a high-temperature ceramic substrate welding process, and the welding point is subjected to laser sealing treatment to prevent molten salt vapor from invading.

[0012] Further, the remote monitoring terminal has multi-device access capability, can simultaneously manage multiple liquid level meter nodes, and supports liquid level trend early warning, abnormal fluctuation alarm and historical data backtracking functions; alarm thresholds can be dynamically set according to process requirements, and alarm information is pushed to operators through SMS, email or industrial protocol.

[0013] Further, the system further comprises a power management module, which adopts a hybrid power supply architecture of a wide-temperature-range lithium battery and an energy harvesting unit; the energy harvesting unit utilizes the temperature difference between the outer walls of the storage tanks to generate electricity and provides auxiliary power for the wireless transmission unit, thereby prolonging the service life of the battery; the power management module has a low power warning function and automatically reports a maintenance request when the remaining capacity of the battery is less than 20%.

[0014] Compared with the prior art, the application has the following advantages and positive effects:

[0015] The application fundamentally solves the problems of electrode aging and insulation failure of traditional capacitance liquid level meters in a high-temperature molten salt environment by constructing a double-layer coaxial capacitance sensing probe resistant to 1000 DEG C high temperature; the design of the porous ceramic outer electrode effectively suppresses the capacitance drift caused by molten salt hanging material, significantly improving the long-term measurement stability; the self-adaptive signal conditioning module integrates differential capacitance measurement, temperature dynamic compensation and hanging material suppression algorithm, eliminating environmental interference from both hardware and software dimensions to ensure high-fidelity conversion of weak capacitance signals; the wireless remote transmission architecture eliminates the wiring problem in the high-temperature area, reducing the installation complexity and maintenance risk; the dynamic calibration engine realizes online calibration without manual intervention based on a molten salt property model, overcoming systematic errors caused by changes in dielectric constant with temperature and composition, and greatly reducing the frequency of manual calibration; the overall system has high reliability, strong anti-interference and intelligent operation and maintenance capability, and is suitable for continuous liquid level monitoring in extreme conditions such as concentrated solar power and molten salt energy storage, providing key technical support for safe and efficient operation of high-temperature molten salt systems. BRIEF DESCRIPTION OF DRAWINGS

[0016] Fig. 1 is the overall technical scheme architecture schematic diagram of the wireless liquid level remote monitoring liquid level meter and monitoring system provided by the present application;

[0017] Fig. 2 is the core principle framework schematic diagram of the dynamic calibration engine in the present application;

[0018] Fig. 3 is the structure diagram of the wireless liquid level remote monitoring liquid level meter of the present application. DETAILED DESCRIPTION Embodiment 1

[0019] Please refer to Figs. 1 to 3 The present application provides a wireless liquid level remote monitoring liquid level meter and monitoring system to solve the technical problems of insufficient temperature resistance, weak anti-hanging material ability, poor anti-interference performance and lack of automatic calibration mechanism in high-temperature molten salt liquid level measurement. Through integrated hardware design and intelligent software algorithm, the present application realizes precise, stable and maintenance-free remote monitoring of high-temperature molten salt liquid level.

[0020] The overall technical scheme of the system includes a high-temperature resistant capacitive sensing probe, a self-adaptive signal conditioning module, a wireless data transmission unit, a remote monitoring terminal and a dynamic calibration engine. The core workflow of the system is as follows: the high-temperature resistant capacitive sensing probe converts the change of the molten salt liquid level into a weak capacitive signal; the self-adaptive signal conditioning module amplifies, digitizes, temperature compensates and suppresses the hanging material interference of the weak signal; the processed liquid level data is encrypted by the wireless data transmission unit and then remotely sent to the remote monitoring terminal; the remote monitoring terminal receives and displays the data, and triggers the dynamic calibration engine under certain conditions; the dynamic calibration engine dynamically corrects the measurement error according to the physical model and real-time data to ensure long-term measurement accuracy.

[0021] The high-temperature-resistant capacitive sensing probe is the core measurement component of the system, directly contacting the high-temperature molten salt. Its design aims to withstand high-temperature conditions above 1000°C. The probe adopts a double-layer coaxial electrode structure. The inner electrode is a solid molybdenum rod, which has excellent high-temperature strength, corrosion resistance, and good electrical conductivity. The surface of the molybdenum rod is finely ground to ensure a smooth electrode surface and reduce physical adsorption with the molten salt. The outer electrode is a porous ceramic-coated molybdenum mesh. The molybdenum mesh structure provides a large surface area while maintaining a certain mechanical strength. The porous ceramic layer directly contacts the molten salt, with a pore size strictly controlled between 5 microns and 20 microns, and a porosity set between 30% and 50%. This porous structure not only effectively isolates the direct corrosion of the molten salt body on the molybdenum mesh, but also allows the slow penetration and condensation of molten salt vapor inside the micropores, thereby reducing the formation of a continuous hanging layer of liquid molten salt on the probe surface, avoiding the drift of the capacitance value caused by hanging material. The sintering process of the porous ceramic ensures its structural stability and chemical inertness at high temperatures. High-purity alumina ceramic is used to separate the inner electrode from the outer electrode. Alumina ceramic has extremely high dielectric strength, excellent insulation performance, and excellent thermal stability, and can maintain a stable dielectric constant in extreme high-temperature environments. The insulating medium and the electrode are tightly combined through special high-temperature adhesive or co-sintering technology to prevent delamination or medium failure at high temperatures. The gap between the sleeve and the electrode assembly is sealed with inert gas (such as high-purity nitrogen) to prevent oxidation and molten salt vapor intrusion. The lead wire outside the probe adopts a double-layer insulation structure, with the inner layer being a magnesium oxide powder compacted insulation, providing excellent electrical insulation and high-temperature resistance; the outer layer is a stainless steel braid, providing mechanical protection and anti-electromagnetic interference capability. The signal wire core uses a nickel-chromium alloy wire, which has good high-temperature conductivity and thermal stability, and the entire lead wire can withstand a continuous working temperature of 800°C. The connection between the lead wire and the adaptive signal conditioning module uses a high-temperature ceramic substrate welding process to ensure the reliability of the electrical connection. The welding point area is treated with laser sealing to further enhance the airtightness and prevent any trace of molten salt vapor from penetrating along the lead wire path to the internal circuit. The radial distance between the inner electrode and the outer electrode is precisely set to 2-5 mm. The choice of this distance is based on the comprehensive optimization of capacitive sensitivity and probe voltage resistance performance. Too small a distance will result in a too large capacitance value, which may exceed the measurement range and reduce voltage resistance performance; too large a distance will reduce capacitive sensitivity and affect measurement resolution. This optimized distance ensures measurement accuracy and stability while meeting the structural integrity requirements of high-temperature and high-pressure conditions.

[0022] The adaptive signal conditioning module is precisely integrated within a dedicated high-temperature sealed cavity at the bottom of the high-temperature-resistant capacitive sensing probe. The cavity is made of high-temperature-resistant alloy materials (such as Hastelloy or Inconel) and has undergone strict air tightness tests to ensure that the internal electronic components can operate stably at relatively low temperatures (through heat dissipation design or local refrigeration, such as air circulation cooling outside the storage tank). The main function of the module is to convert the extremely weak analog capacitive signals output by the high-temperature-resistant capacitive sensing probe into high-precision digital signals and perform a series of complex signal processing. The module includes a high-precision capacitive digital converter, a temperature compensation unit, and a hang-up suppression algorithm unit. The high-precision capacitive digital converter adopts a differential capacitive measurement architecture. This architecture obtains liquid level information by simultaneously measuring one sensing capacitor and one reference capacitor and calculating the difference between the two. The reference capacitor and the sensing capacitor are designed to share the same high-temperature environment or be in similar temperature gradients. This design significantly offsets errors caused by environmental temperature drift, component aging, or common-mode noise, greatly improving the stability and accuracy of the measurement. The capacitive digital converter integrates a high-resolution analog-to-digital converter inside, which can accurately convert capacitive changes in the order of picofarads or even smaller into digital quantities. Its sampling frequency can be configured according to actual working conditions, such as 10 times per second to 100 times per second, to capture rapid changes in liquid level or perform more intensive signal analysis.

[0023] The temperature compensation unit obtains real-time temperature data of the probe's contact with the molten salt region through a platinum-rhodium thermocouple integrated inside the probe. As a high-temperature-resistant and high-precision temperature sensor, the platinum-rhodium thermocouple's thermoelectric potential directly reflects the real-time temperature of the molten salt. The temperature compensation unit has pre-stored thermal expansion coefficients of electrode materials and dielectric constant temperature characteristic curves of the insulating medium. These curve data are usually obtained through precise calibration experiments in the laboratory and stored in the module's non-volatile memory in the form of polynomial fitting or lookup tables. When real-time temperature data is obtained, the temperature compensation unit will dynamically correct the raw capacitance values output by the high-precision capacitive digital converter according to these pre-stored curves. The correction process includes calculating the size change of the electrode due to thermal expansion and its effect on the capacitance, as well as the change of the dielectric constant of the insulating medium with temperature. For example, if the temperature rise causes the dielectric constant of the insulating medium to decrease slightly, the correction algorithm will adjust the measured capacitance value accordingly to restore its equivalent value at the standard temperature. This dynamic and real-time temperature compensation mechanism ensures the accuracy of the capacitive measurement results and is not affected by the temperature fluctuations of the molten salt.

[0024] The dross suppression algorithm unit is the key to cope with the interference of molten salt dross. Based on the in-depth analysis of the time-domain fluctuation characteristics of the capacitance signal, this unit identifies and suppresses the dross effect. The molten salt dross is a slow formation and accumulation process on the probe surface, which causes the capacitance value to drift, showing a low-frequency, long-term trend. While the real liquid level change, especially under normal operating conditions, usually changes rapidly, showing a high-frequency, instantaneous characteristic. The dross suppression algorithm unit takes advantage of this difference and uses a combination of high-pass filtering and trend removal algorithm for processing. The high-pass filter will filter out the low-frequency components in the capacitance signal, i.e. the slow drift caused by dross, and retain the high-frequency components produced by the liquid level change. At the same time, the trend removal algorithm estimates and removes the long-term trend component in the signal by sliding window averaging or least squares fitting of historical capacitance data. For example, the algorithm calculates the average drift rate of the capacitance value within a set time window (e.g. 10 to 60 minutes) and subtracts it from the current measurement value. This double mechanism can effectively separate the real liquid level signal from the dross interference signal, ensuring that the output liquid level data is pure data purified by dross effect. The parameters of the dross suppression algorithm unit, such as the cutoff frequency of the high-pass filter, the size of the sliding window, etc., can be adjusted and optimized according to different types of molten salt and operating environments to ensure its adaptability. The capacitance value after temperature compensation and dross suppression is further converted into liquid level height and sent to the wireless data transmission unit through the internal digital bus.

[0025] The wireless data transmission unit is responsible for transmitting the liquid level data processed by the adaptive signal conditioning module to the remote monitoring terminal in a safe and reliable manner. This unit uses a low-power wide-area communication protocol for data transmission. In specific implementation, LoRa or NB-IoT communication protocol can be chosen. The reason for choosing these protocols is that they have the characteristics of wide coverage, low power consumption, strong anti-interference ability and suitability for Internet of Things applications. The radio frequency front end of the unit is packaged in a metal shield, which can effectively block electromagnetic interference from high temperature environments, protect sensitive radio frequency circuits from external noise, and ensure the stability and reliability of communication. The metal shield and the high temperature sealed cavity are electrically isolated by a ceramic feedthrough. As a high temperature insulation penetration component, the ceramic feedthrough allows radio frequency signals to pass through without loss while maintaining airtightness, and effectively isolates the heat conduction in the high temperature cavity. The liquid level data will be encrypted before transmission, for example using the AES-128 encryption algorithm, to ensure the confidentiality and integrity of the data during transmission and prevent malicious eavesdropping or tampering. The data transmission period can be flexibly configured, for example from 1 second to 60 minutes. By default, the system may report data at a lower frequency (e.g. every 5 minutes) to save power. However, the unit supports event-triggered mode. When the adaptive signal conditioning module detects that the liquid level change rate exceeds the preset threshold (e.g. the liquid level changes more than 10 mm per minute), the wireless data transmission unit will immediately shorten the reporting interval, for example switching to reporting every 1 second, to ensure timely response to emergency situations. This on-demand transmission mechanism ensures real-time data while maximizing the service life of the system battery. The wireless data transmission unit is also responsible for reporting its own operating status, including battery power, signal strength, and any internal fault diagnosis information.

[0026] The remote monitoring terminal is a comprehensive platform integrating data reception, storage, display, analysis, and instruction issuance. The terminal can be a dedicated industrial computer or a cloud server client running specific application programs. Its core function is to receive encrypted liquid level data from the wireless data transmission unit in real time, and perform decryption, verification, and storage. Data storage uses an efficient time-series database (such as InfluxDB or OpenTSDB) that can record timestamped liquid level, temperature, battery level, and other data at high throughput and support fast queries. The terminal has data visualization display capabilities, which can display current and historical liquid level status to operators in an intuitive graphical interface (such as real-time trend graphs, historical curves, and digital displays). The terminal also supports multi-device access, allowing it to manage liquid level data from multiple level gauge nodes and display them on the same interface for centralized monitoring. The system provides liquid level trend warning functions, which use machine learning analysis (such as ARIMA models or Kalman filtering) on historical liquid level data to predict future trends and issue warnings when the predicted trend exceeds the safety range. At the same time, the terminal has an abnormal fluctuation alarm function. When the real-time liquid level value, liquid level change rate, or acceleration exceeds the pre-set static or dynamic threshold, the system will immediately trigger an alarm. Alarm thresholds can be dynamically set according to specific process requirements, such as different molten salt types and different operation stages corresponding to different alarm limits. Alarm information will be pushed to operators through various channels, including SMS, email, and standard industrial protocols integrated with industrial control systems (such as Modbus TCP or OPC UA), ensuring timely delivery and processing of alarm information. In addition, the remote monitoring terminal also has a historical data backtracking function, allowing operators to query liquid level historical data for any time period for fault diagnosis, process optimization, and compliance auditing. The terminal is also the hub for interacting with the dynamic calibration engine, responsible for sending calibration trigger instructions to the dynamic calibration engine and updating the system's internal liquid level calculation parameters after receiving the calibration results.

[0027] The dynamic calibration engine is the key innovation of the system to achieve online automatic calibration without human intervention. The engine can run on the local server of the remote monitoring terminal or be deployed on a more powerful cloud server to take advantage of the elastic computing resources of cloud computing. The core mechanism of the engine is based on the physical model of the change of the dielectric constant of molten salt with temperature and composition, combined with real-time temperature data and historical liquid level trends, to dynamically correct the capacitance-liquid level mapping relationship. The dielectric constant of molten salt is a key physical parameter that affects capacitance measurement, but its value will change with the actual temperature and chemical composition of the molten salt (such as the difference in trace element content of different batches of molten salt). Traditional liquid level meters often need to be calibrated manually at regular intervals, which is time-consuming and labor-intensive and prone to errors. The dynamic calibration engine quantifies these effects by establishing an accurate physical model. The calibration model is based on a large molten salt composition database and a temperature-dielectric constant mapping table. The molten salt composition database contains the typical chemical composition of different types, different suppliers, and different batches of molten salt and their corresponding dielectric constant data. The temperature-dielectric constant mapping table records the dielectric constant values of each type of molten salt at different temperatures in detail. When the system detects a change in molten salt batch (such as through manual input by the operator or through other industrial system interfaces) or a significant shift in the temperature range of the current molten salt (such as a change in average temperature of more than 20 degrees Celsius) through the remote monitoring terminal, the dynamic calibration engine will be automatically triggered. After triggering, the engine will first query the composition database and the mapping table, automatically calling the dielectric constant parameters that best match the current molten salt composition and temperature range. Then, the engine combines the current capacitance measurement value provided by the high-temperature-resistant capacitance sensing probe to recalculate the liquid level height. This recalculating process takes into account the impact of the new dielectric constant value on the capacitance-liquid level mapping curve, such as using linear interpolation, polynomial fitting, or more complex nonlinear regression algorithms to update the mapping function. The entire calibration process is fully automated and does not require interrupting liquid level measurement or human intervention. After calibration is complete, the engine sends the updated calibration parameters (such as the new mapping curve coefficients or correction factors) to the remote monitoring terminal, which updates its internal liquid level calculation logic, thereby achieving accurate correction of subsequent liquid level measurement values. This online dynamic calibration mechanism fundamentally solves the systematic measurement errors caused by dielectric constant drift, significantly improving the long-term running accuracy and reliability of the system.

[0028] The power management module provides stable and reliable energy support for the entire wireless liquid level remote monitoring liquid level meter. The module adopts a hybrid power supply architecture of wide-temperature-range lithium batteries and energy harvesting units. The wide-temperature-range lithium batteries can work stably in a wide ambient temperature range of -40°C to 85°C, ensuring power supply in extreme working conditions. The energy harvesting unit is the key to realizing long service life and low maintenance operation of the system. The unit utilizes the temperature difference between the outer wall of the storage tank and the ambient air to convert thermal energy into electrical energy through the thermoelectric effect (e.g., thermoelectric generator using the Seebeck effect). The thermoelectric generator is usually composed of semiconductor materials, and when there is a temperature difference between its two ends, an electromotive force will be generated. This energy harvesting method can provide auxiliary power for the wireless data transmission unit, and even provide the main operating power in some stable conditions, significantly extending the service life of the main lithium battery. The power management module integrates high-efficiency power conversion circuits (e.g., high-efficiency DC-DC converters) inside, ensuring that the unstable voltage output by the energy harvesting unit can be converted into a stable voltage that can be used by the system components. At the same time, the module also contains intelligent charging management circuits for overcharge, overdischarge, and overcurrent protection of the lithium battery. The power management module has a low power warning function. When the remaining capacity of the lithium battery is lower than the preset threshold (e.g., 20%), the module will send a low power warning message to the remote monitoring terminal through the wireless data transmission unit. After receiving the warning, the remote monitoring terminal will generate a maintenance request or alarm information and push it to the operator, prompting timely replacement or repair of the battery to ensure uninterrupted operation of the system. This hybrid power supply and intelligent management strategy greatly reduces the maintenance frequency and operating cost of the system.

[0029] In summary, the present application builds a wireless liquid level remote monitoring system for high-temperature molten salt environment through the organic cooperation and intelligent management of the above-mentioned units. The high-temperature-resistant capacitive sensing probe solves the problems of electrode aging, insulation failure and material hanging interference at extreme temperatures with its innovative double-layer coaxial electrode structure and porous ceramic design. The self-adaptive signal conditioning module ensures accurate conversion and high-fidelity output of weak signals through differential measurement, temperature compensation and material hanging suppression algorithms. The wireless data transmission unit realizes safe and reliable remote transmission of data. The remote monitoring terminal provides powerful data management, visualization, early warning and alarm functions. The dynamic calibration engine overcomes systematic errors caused by changes in the dielectric constant of molten salt with a physical model and automated mechanism, achieving online calibration without human intervention. The hybrid power supply architecture of the power management module ensures long-term autonomous operation of the system. The comprehensive application of these technical solutions significantly improves the measurement accuracy, long-term stability, anti-interference ability and intelligent operation and maintenance level of the system in high-temperature molten salt working conditions, providing key technical support for the photothermal power generation, molten salt energy storage and other fields, and reducing the operation risk and maintenance cost.

[0030] The core difference of the present scheme is that, on the basis of traditional liquid level sensing technology, the multi-hole ceramic coated outer electrode design, differential capacitance measurement architecture, material hanging suppression algorithm based on time domain characteristics, and dynamic calibration engine based on molten salt physical model are innovatively introduced. These innovations collectively solve the problems of measurement drift, weak anti-interference ability and complex calibration that traditional liquid level meters cannot overcome in extreme high-temperature molten salt environment. The multi-hole ceramic outer electrode not only improves the corrosion resistance of the probe, but also suppresses the formation of molten salt hanging material through its unique physical structure, reducing the influence of hanging material on measurement from the source. The differential capacitance measurement architecture of the adaptive signal conditioning module uses the common mode rejection characteristic of the reference capacitance and the sensing capacitance to effectively resist environmental temperature drift and system common mode noise. The hanging material suppression algorithm intelligently identifies and eliminates the slow drift component caused by hanging material through digital signal processing technology. Most importantly, the introduction of the dynamic calibration engine realizes real-time correction of the physical model of the dielectric constant of molten salt with temperature and composition changes, achieving true online automatic calibration without human intervention. This greatly improves the long-term running accuracy and stability of the system, and transforms the complex manual calibration process that requires expert experience into an autonomous and continuously optimized intelligent process. These differentiated features make the present invention significantly superior to existing technology in terms of measurement accuracy, stability, reliability, maintenance convenience and intelligence level, bringing revolutionary progress to the field of high-temperature molten salt level monitoring. Embodiment 2

[0031] This embodiment further elaborates on the specific implementation scheme of the wireless data transmission unit and its performance optimization in extreme environments based on the previous embodiment 1.

[0032] The low-power wide-area communication protocol used by the wireless data transmission unit focuses on the implementation details of the LoRa protocol in this embodiment. LoRa protocol is particularly suitable for complex industrial environments due to its long-range, low-power, and high-penetration characteristics. The internal structure of the wireless data transmission unit includes a LoRa radio frequency transceiver chip, a low-power microcontroller, and related power management and sensor interface circuits. The LoRa radio frequency transceiver chip is responsible for physical layer modulation and demodulation, encoding digital liquid level data into LoRa spread spectrum signals and transmitting them through the antenna. The microcontroller runs the LoRaWAN protocol stack, manages data packet assembly, encryption, transmission scheduling, and reception confirmation.

[0033] The assembly process of data packets strictly follows the LoRaWAN protocol specification. Each data packet contains necessary header information such as device address, frame counter, and port number. Payload data such as liquid level data, temperature data, battery level, and diagnostic information are encrypted using AES-128 with a session key before transmission. The encryption process is completed within the microcontroller or a dedicated encryption hardware accelerator, ensuring data security. The frame counter is used to prevent replay attacks and is automatically incremented after each data packet transmission, with the receiving end verifying its order.

[0034] The configuration of LoRa communication parameters is crucial to the performance of the system. These parameters include spreading factor (SF), bandwidth (BW), and coding rate (CR). The spreading factor determines the transmission distance and interference resistance of the signal, with a higher SF value resulting in a longer transmission distance and stronger interference resistance but a lower data rate. Bandwidth affects data rate and reception sensitivity, with a wider BW resulting in a higher data rate but possibly lower reception sensitivity. Coding rate provides forward error correction capability. In actual deployment, these parameters are dynamically or pre-set optimized according to the actual wireless environment on site (such as distance, obstruction, and interference source). For example, for a liquid level meter node that is far away from the remote monitoring terminal, a higher spreading factor can be configured to ensure reliable transmission; for areas with strong electromagnetic interference, a higher coding rate can be configured to enhance data robustness. The optimization of these parameters aims to minimize power consumption while ensuring communication reliability.

[0035] The radio frequency front end of the wireless data transmission unit is packaged in a metal shield. This metal shield is made of high-conductivity materials such as nickel-plated steel or copper alloy and is connected to the common ground plane of the system through a ground wire. The design of the shield takes into account the Faraday cage effect, effectively suppressing electromagnetic radiation from external power equipment or industrial environments of high-temperature molten salt storage tanks that interferes with the radio frequency circuit. The inside of the shield is also coated with an absorbing material to further reduce internal electromagnetic wave reflection and standing wave, optimizing radio frequency performance. The electrical isolation between the metal shield and the high-temperature sealed cavity is achieved through a custom ceramic feedthrough. The ceramic feedthrough uses high-frequency low-loss dielectric ceramic materials and adopts a coaxial structure design to ensure that the radio frequency signal maintains low insertion loss and good impedance matching when passing through the feedthrough. The mechanical fixation of the feedthrough uses high-temperature brazing or glass sealing technology to ensure its airtightness and mechanical stability under extreme temperature cycles.

[0036] The configurability of data transmission cycles and the implementation of event-triggered mode are the key to the energy saving and responsiveness of the wireless data transmission unit. In the conventional mode, the microcontroller wakes up the LoRa transceiver at a pre-set longer cycle (e.g. every 10 minutes), sends data, and then enters a deep sleep mode. This low-duty-cycle operation significantly reduces the average power consumption. When the adaptive signal conditioning module's hang-up suppression algorithm unit or temperature compensation unit detects that the liquid level change rate exceeds the pre-set threshold, it sends an interrupt signal to the microcontroller of the wireless data transmission unit through the internal digital interface (e.g. SPI or I2C bus). In response to this interrupt, the microcontroller immediately wakes up from the deep sleep mode and switches to the event-triggered mode. In the event-triggered mode, the data transmission cycle is automatically shortened to a high-frequency mode (e.g. every 1 second). At this time, the system prioritizes sending the latest liquid level data to ensure that the remote monitoring terminal can obtain detailed information about the emergency in a timely manner. When the liquid level change returns to normal and lasts for a period of time, the microcontroller automatically switches the system back to the conventional low-frequency mode to restore the power consumption optimization state. This intelligent transmission strategy achieves dynamic adjustment, balancing data real-time and energy efficiency.

[0037] The wireless data transmission unit also has a built-in link quality monitoring function. The microcontroller regularly monitors the received signal strength indication (RSSI) and signal-to-noise ratio (SNR) of the LoRa signal. When the RSSI or SNR is below the pre-set threshold, it indicates that the wireless link quality is poor, and there may be interference or the distance is too far. In this case, the microcontroller can try to adjust the LoRa communication parameters (such as increasing the spreading factor or sending power), or report a link quality warning to the remote monitoring terminal for the operator to check or adjust the antenna position. At the same time, the unit also verifies the network connection status with the remote monitoring terminal by periodically sending heartbeat packets and receiving confirmation. If consecutive heartbeats are not confirmed, it is judged that the network is lost, and the local storage mechanism will be triggered to temporarily store the liquid level data in the microcontroller's non-volatile memory, and then perform batch upload after the network is restored, avoiding data loss. Example 3

[0038] This embodiment further elaborates on the specific implementation of the dynamic calibration engine in two different deployment modes, i.e. running on the remote monitoring terminal (local deployment) and running on the cloud server (cloud deployment), the differences in architecture, their respective advantages and optimization strategies.

[0039] Firstly, when the dynamic calibration engine runs on a remote monitoring terminal, it is usually deployed on a high-performance industrial PC or embedded server. The main advantage of this local deployment mode is high data security, all calibration logic and data are processed locally, avoiding the risk of sensitive data transmission through public networks. At the same time, due to the physical proximity of computing resources and data sources (time series database of remote monitoring terminal), data access delay is extremely low, response speed is fast, and it can run independently even in unstable industrial environment.

[0040] In the local deployment mode, the specific implementation of the dynamic calibration engine includes:

[0041] Data interface module: This module is responsible for obtaining real-time temperature data, historical liquid level data, and current capacitance measurement values from the local time series database of the remote monitoring terminal. It uses efficient database query language (such as SQL or API call) to ensure the timeliness and integrity of data acquisition. At the same time, this module also receives input from the operators of the remote monitoring terminal, such as explicit instructions for molten salt batch replacement.

[0042] Calibration trigger evaluation module: This module continuously monitors real-time running data to evaluate whether the calibration trigger condition is met. Trigger conditions include but are not limited to:

[0043] Molten salt batch replacement: When receiving the batch replacement instruction from the operator, the calibration is triggered immediately.

[0044] Temperature interval significant deviation: This module will calculate the average value and standard deviation of the molten salt temperature in the past period (for example, 24 hours), and compare it with the reference temperature range set at system initialization. If the current average temperature deviates from the reference value by more than the pre-set threshold (for example, 20 degrees Celsius), and this deviation lasts for a period of time (for example, 2 hours), it is judged that the temperature interval has a significant deviation, and the calibration is triggered.

[0045] Historical liquid level trend anomaly: This module will analyze historical liquid level data. If it is found that the measured value of the liquid level in a relatively stable physical state (for example, the known storage tank liquid level has no actual change) has a long-term slow drift beyond the pre-set allowable error range, the calibration is triggered to correct the potential dielectric constant change.

[0046] Physical Model Calculation Module: This is the core of the engine, which implements the physical model of the molten salt dielectric constant changing with temperature and composition. Inside this module contains a molten salt physical parameter library, which stores the dielectric constant data of various commonly used molten salts (such as solar molten salt components: mixture of sodium nitrate, potassium nitrate) at different temperatures and component ratios. These data are usually stored in the form of multi-dimensional lookup table, polynomial regression model or neural network model. When receiving the calibration trigger signal and the latest temperature and molten salt component information, the module will use its built-in physical model to accurately calculate the actual dielectric constant value of the molten salt under the current working condition according to the input. The calculation result is directly used for subsequent correction of the capacitance-liquid level mapping relationship.

[0047] Mapping Relationship Correction Module: This module receives the latest dielectric constant value calculated by the physical model, and recalculates and generates an optimized capacitance-liquid level mapping relationship based on the current capacitance measurement. This is usually achieved by adjusting the coefficients of the pre-stored capacitance-liquid level function (such as linear function, quadratic function) or updating the lookup table entries. The corrected mapping relationship can more accurately reflect the real liquid level under the current molten salt state.

[0048] Parameter Issuance and Verification Module: The corrected calibration parameters will be sent to the software module responsible for liquid level calculation through the internal communication bus (such as shared memory, IPC mechanism) of the remote monitoring terminal, and the liquid level calculation logic will be updated in real time. In order to ensure the effectiveness of the calibration, the module also performs post-calibration verification. For example, within a certain period of time after calibration, the stability of the liquid level measurement value is continuously monitored and compared with the historical trend. If there is a new anomaly, it may trigger a rollback to the previous stable state or re-calibration.

[0049] Secondly, when the dynamic calibration engine runs on a cloud server, its architecture will be more distributed and flexible. The main advantage of cloud deployment is that it has almost unlimited computing and storage resources, which can handle more complex physical models and larger historical data volumes, and implement more advanced calibration algorithms (such as deep learning-based dielectric constant prediction model). In addition, cloud deployment facilitates centralized management of multi-site, large-scale liquid level meter networks and unified updating and maintenance of calibration models.

[0050] In the cloud deployment mode, the specific implementation of the dynamic calibration engine is different from the local deployment:

[0051] Cloud Data Ingestion Service: The remote monitoring terminal uploads the real-time liquid level, temperature data, system diagnostic information and manually input batch replacement information to the cloud data ingestion service after encryption through a secure network protocol (such as HTTPS, MQTT over TLS). This service is responsible for data decryption, verification, format conversion, and writing to the cloud's big data platform (such as data lake or cloud-native time series database).

[0052] Cloud Calibration Trigger Service: This service runs on elastic compute instances in the cloud, continuously fetching data streams from the big data platform, and evaluating calibration trigger conditions for all connected level gauge nodes. Due to its powerful computing capabilities, this service can perform more complex statistical analysis and machine learning algorithms to identify potential dielectric constant drifts, not just simple threshold judgments. For example, it can use anomaly detection algorithms to identify liquid level data that deviates significantly from expected behavior patterns as an implicit trigger condition for calibration.

[0053] Distributed Physical Model Calculation Service: Cloud deployment allows the distributed deployment of the physical model calculation service, utilizing multiple servers for parallel processing. This service not only stores a more detailed molten salt property database and dielectric constant mapping table, but also integrates more advanced physical simulation models. When receiving a calibration trigger request, this service can perform parallel evaluations on multiple alternative calibration models and select the optimal model for parameter calculation. In addition, it can also update its property parameter library in real time based on global molten salt market data and supplier information, improving the universality of calibration.

[0054] Model Optimization and Deployment Service: In the cloud, not only can the capacitance-liquid level mapping relationship be corrected, but the underlying dielectric constant physical model itself can also be continuously optimized. This service can automatically adjust the parameters of the physical model or even retrain the model using historical calibration data and actual operation feedback through machine learning algorithms such as reinforcement learning or Bayesian optimization. Optimized calibration models can be updated remotely to all connected level gauge nodes or remote monitoring terminals through cloud deployment pipelines.

[0055] API and Notification Service: Calibration results are provided to remote monitoring terminals through API interfaces. Terminals obtain the latest calibration parameters through regular polling or WebHook callback mechanisms. At the same time, the cloud service can send calibration reports and status notifications to relevant personnel through various means such as email, SMS, and mobile application push.

[0056] Regardless of local deployment or cloud deployment, the core goal of the dynamic calibration engine is to achieve the adaptive ability of the measurement system to environmental changes. Local deployment emphasizes security and low latency, suitable for industrial scenarios sensitive to network dependence; while cloud deployment emphasizes scalability, advanced analysis capabilities, and centralized management, suitable for large-scale, multi-site deployment. The choice of the two modes can be flexibly configured according to specific application requirements, network infrastructure, and security policies. This dual deployment strategy ensures that the invention can provide efficient and reliable dynamic calibration services in various industrial application scenarios, significantly reducing the frequency and cost of manual calibration, and improving the overall intelligent level of the system.

Claims

1. A monitoring system for a wireless liquid level remote monitoring liquid level meter, characterized by, The application relates to a high-temperature-resistant capacitive sensing probe, an adaptive signal conditioning module, a wireless data transmission unit, a remote monitoring terminal and a dynamic calibration engine. The high-temperature-resistant capacitive sensing probe adopts a double-layer coaxial electrode structure, the inner electrode is a solid molybdenum rod, the outer electrode is a molybdenum mesh coated with porous ceramic, and high-purity alumina ceramic is filled between the inner and outer electrodes as a high-temperature insulation medium. The adaptive signal conditioning module is integrated in a high-temperature sealed cavity at the bottom of the probe, is used for converting weak capacitive signals output by the capacitive sensing probe into digital signals, and performs temperature compensation and material interference suppression processing on the signals. The wireless data transmission unit adopts a low-power wide-area communication protocol, encrypts the liquid level data after conditioning, and remotely transmits the liquid level data to the remote monitoring terminal. The remote monitoring terminal is used for receiving, storing and visually displaying the liquid level data, and sending a calibration trigger instruction to the dynamic calibration engine. The dynamic calibration engine is based on a physical model of the change of the dielectric constant of molten salt with temperature and composition, combines real-time temperature data and historical liquid level trends, dynamically corrects the capacitive-liquid level mapping relationship, and realizes online automatic calibration without manual intervention. The adaptive signal conditioning module comprises a high-precision capacitive digital converter, a temperature compensation unit and a material suppression algorithm unit; the high-precision capacitive digital converter adopts a differential capacitive measurement architecture, the reference capacitor and the sensing capacitor share the same high-temperature environment; the temperature compensation unit obtains temperature data in real time through a platinum-rhodium thermocouple integrated in the probe, and dynamically corrects the capacitive value according to the pre-stored thermal expansion coefficient of the electrode and the dielectric constant temperature characteristic curve of the insulation medium; the material suppression algorithm unit identifies the slow drift component caused by the material based on the time domain fluctuation characteristics of the capacitive signal, and removes the slow drift component through high-pass filtering and trend elimination algorithm. The trend elimination algorithm dynamically estimates and removes the long-term trend component in the signal by performing sliding window averaging or least square fitting on the historical capacitive data; the time length of the sliding window is 10 minutes to 60 minutes. The dynamic calibration engine runs on the remote monitoring terminal or a cloud server, and the calibration model is constructed based on a molten salt component database and a temperature-dielectric constant mapping table; when the system detects that the molten salt batch is replaced or the temperature interval is significantly deviated, corresponding dielectric constant parameters are automatically called, and the liquid level height is recalculated in combination with the current capacitive measurement value. In the double-layer coaxial electrode structure, the pore diameter of the porous ceramic of the outer electrode is 5 microns to 20 microns, and the porosity is 30% to 50%; the radial spacing between the inner electrode and the outer electrode is 2 mm to 5 mm.

2. The monitoring system of a wireless liquid level remote monitoring liquid level meter according to claim 1, characterized in that, The wireless data transmission unit adopts LoRa or NB-IoT communication protocol, the radio frequency front end is packaged in a metal shield, and electrical isolation with the high-temperature sealed cavity is realized through a ceramic feedthrough; the data transmission period is configured to be 1 second to 60 minutes, and an event trigger mode is supported, when the liquid level change rate exceeds a preset threshold, the reporting interval is automatically shortened.

3. The monitoring system of a wireless liquid level remote monitoring liquid level meter according to claim 1, wherein, ​ 4. The monitoring system of a wireless liquid level remote monitoring liquid level meter according to claim 1, wherein, The lead of the high-temperature-resistant capacitive sensing probe adopts a double-layer insulation structure, the inner layer is magnesium oxide powder compaction insulation, the outer layer is stainless steel braided armor, the signal line core is nickel-chromium alloy wire, and the whole can withstand 800 DEG C continuous working temperature; the connection between the lead and the signal conditioning module adopts high-temperature ceramic substrate welding process, and the welding point is subjected to laser sealing treatment.

5. The monitoring system of a wireless liquid level remote monitoring liquid level meter according to claim 1, wherein, The remote monitoring terminal has multi-device access capability, simultaneously manages multiple liquid level meter nodes, and supports liquid level trend early warning, abnormal fluctuation alarm and historical data backtracking functions; the alarm threshold is dynamically set according to process requirements, and alarm information is pushed to operators through SMS, email or industrial protocol.

6. The monitoring system of a wireless liquid level remote monitoring liquid level meter according to claim 1, wherein, The system also includes a power management module, which adopts a hybrid power supply architecture of wide-temperature-range lithium batteries and energy harvesting units; the energy harvesting unit utilizes the temperature difference of the outer wall of the storage tank to generate electricity and provides auxiliary power for the wireless transmission unit; the power management module has a low power warning function, and when the remaining capacity of the battery is less than 20%, a maintenance request is automatically reported.

7. A wireless liquid level remote monitoring liquid level meter applied to the monitoring system according to any one of claims 1 to 6, characterized in that: It comprises a high-temperature-resistant capacitive sensing probe, an adaptive signal conditioning module, a wireless data transmission unit, a remote monitoring terminal and a dynamic calibration engine.

Images