A resistive liquid level monitoring device

Abstract

This invention discloses a resistive liquid level monitoring device, mainly comprising a main control module, a resistance detection module, a communication module, a power management module, a data analysis module, an electrode assembly, and a wave suppression module. During operation, the main control module monitors the resistance values ​​between the electrode assemblies. When the difference between the resistance value between contacts at a certain height and the resistance value between contacts at a higher height reaches a set threshold, it indicates that the liquid level is between these two heights. To reduce the impact of liquid level fluctuations, the electrode assembly is placed within a recess. When waves surge into the recess, the central waves are directly blocked by the baffle columns, while the waves on both sides are suppressed by the baffle units at the inlet. Waves flowing past the baffle columns then pass through the baffle units on both sides before reaching the electrode assembly. During this process, the addition of the baffle columns creates two multiple-turn, buffered flow channels within the recess, which, together with the baffle units, effectively suppress waves, minimizing wave fluctuations and thus improving the stability of the resistance detection.

Description

Technical Field

[0001] This invention relates to the field of liquid level monitoring technology, and in particular to a resistive liquid level monitoring device with strong anti-interference capabilities and long-term maintenance-free operation, suitable for scenarios such as river channels, reservoirs, chemical storage tanks, and integrated monitoring of multiple parameters of the water environment. Background Technology

[0002] Liquid level is a crucial monitoring parameter in fields such as water conservancy, environmental protection, and chemical engineering. Traditional liquid level gauges require manual, periodic observation, resulting in low levels of automation. Existing automatic water level monitoring technologies mainly include float-type, pressure-type, ultrasonic, and radar-type gauges. Float-type water level gauges require the construction of logging wells, leading to high costs and inconvenient maintenance; pressure-type water level gauges are easily affected by impurities and sediment content in the water; ultrasonic and radar-type water level gauges are significantly affected by environmental factors such as temperature and humidity, and also have high equipment and installation costs.

[0003] Image-based water level detection methods are emerging, but these methods are greatly affected by environmental factors such as lighting, weather, and water quality, and their reliability is poor under complex conditions. Water level gauges carried by drones or unmanned vessels have poor sustainability under extreme conditions of strong winds and heavy rain.

[0004] Therefore, existing technologies need further improvement and refinement. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a resistive liquid level monitoring device.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows: A resistive liquid level monitoring device mainly includes a main control module, a resistance detection module, a communication module, a power management module, a data analysis module, an electrode assembly, and a wave suppression module. The power management module is electrically connected to the main control module, resistance detection module, communication module, data analysis module, and electrode assembly, providing power to these modules. The main control module is data-connected to the resistance detection module, communication module, and data analysis module. The wave suppression module is vertically fixed at the shoreline to suppress the influence of waves on the measured values. The electrode assembly is vertically installed inside the wave suppression module and electrically connected to the resistance detection module. The resistance detection module measures the resistance values ​​between different locations using the electrode assembly and feeds the results back to the data analysis module. After obtaining the analysis results, the main control module feeds the results back to the monitoring platform via the communication module, thereby obtaining the latest liquid level monitoring data.

[0007] As a preferred embodiment of the present invention, the main control module is an STM32L4 series microcontroller as the core processing unit.

[0008] As a preferred embodiment of the present invention, the resistance detection module adopts the AD5933 impedance conversion chip.

[0009] Furthermore, the communication module adopts the LoRa wireless transmission protocol and connects to the main control module via a UART serial port. It is responsible for sending the encapsulated data packets to a remote LoRa gateway or server using LoRa modulation. Preferably, the communication module also supports RS485, Ethernet, 4G, or NB-IoT communication methods.

[0010] Furthermore, the power management module adopts a hybrid power supply design of solar energy and mains power, including a solar panel, a charge / discharge management module, and a battery pack. The charge / discharge management module has two sets of power input terminals that can be switched between each other, one set connected to the solar panel and the other set connected to the mains power, and the output terminal of the charge / discharge management module is connected to the battery pack.

[0011] Specifically, the electrode assembly mainly includes a first electrode plate, a second electrode plate, a first contact, and a second contact. The first and second electrode plates are both vertically mounted and fixed, with a gap between them. A plurality of first contacts are vertically distributed on the first electrode plate and electrically connected to the resistance detection module, with the first contacts spaced apart from each other. A plurality of second contacts are vertically distributed on the second electrode plate and electrically connected to the resistance detection module, with the second contacts spaced apart from each other.

[0012] In a preferred embodiment of the present invention, the electrode assembly further includes a plurality of spare electrode plates and spare contacts. The spare electrode plates are vertically mounted on one side of the first electrode plate. The plurality of spare contacts are vertically distributed on the spare electrode plates and are electrically connected to the resistance detection module respectively, and the spare contacts are spaced apart from each other.

[0013] Furthermore, the electrode assembly also includes an ultrasonic cleaning module. The ultrasonic cleaning module is mounted on the first and second electrode plates and connected to the main control module and power management module. It utilizes cavitation to remove deposits and some corrosion products from the surfaces of the first and second contacts, exposing the metal surfaces.

[0014] Furthermore, the wave suppression module includes a T-shaped recess, a flow-blocking column, and flow-blocking units. The flow-blocking column is vertically fixed in the center of the recess, opposite to the recess's inlet, and has gaps between it and the recess's edges. The flow-blocking units are arranged in pairs on the left and right sides of the recess's inlet and the flow-blocking column. The electrode assembly is installed inside the recess, opposite to the recess's inlet, located between the flow-blocking column and the inner side of the recess.

[0015] Furthermore, the flow-blocking unit includes a mounting plate, a first baffle, and a second baffle. The mounting plate is vertically installed and fixedly connected to the recessed inner wall. Both the first and second baffles are vertical and fixed to the mounting plate, and are perpendicular to each other. Both the first and second baffles are installed at an angle, and are installed alternately from top to bottom. The bottom of the upper first baffle is lower than the top of the adjacent lower second baffle, and the bottom of the upper second baffle is lower than the top of the adjacent lower first baffle, with a gap between adjacent baffles. During operation, since the first and second baffles are inclined relative to each other, there is no space left for waves to pass through directly in the longitudinal direction. When waves hit the first or second baffle, the two baffles act as buffers, and the wave surge only acts on the baffles. Since there are gaps between the first and second baffles and between adjacent flow-blocking units, the liquid can flow calmly through the gaps. The waves or surges are suppressed to the maximum extent by the action of the first baffle, the second baffle, and the gaps, thus ensuring the calmness of the liquid surface in the depression.

[0016] The working process and principle of this invention are as follows: During operation, the main control module monitors the resistance value between the electrode groups through the resistance detection module. Since the first and second contacts in the electrode group are vertically distributed, with a portion separated by liquid and another portion by air, and because the resistance between liquid and air is different, when the difference between the resistance between contacts at a certain height and the resistance between contacts at a higher height reaches a set threshold, it indicates that the liquid level is between these two heights. To reduce the impact of liquid surface fluctuations or waves on resistance detection, the electrode group is placed within a recess. When waves surge into the recess, the central waves are directly blocked by the baffle column, and the waves on both sides are suppressed by the baffle unit at the recess opening. The waves flowing through the baffle column then pass through the baffle units on both sides before reaching the electrode group. During this process, the addition of the baffle column creates two multiple turning and buffering flow channels inside the recess, which, together with the baffle unit, effectively suppress the waves, minimizing wave fluctuations at the electrode group and thus maximizing the stability of resistance detection. This invention also has the advantages of simple structure, convenient operation, and ease of implementation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the services required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the electrode assembly provided by the present invention.

[0019] Figure 2 This is a top view of the structure of the electrode assembly and wave suppression module provided by the present invention.

[0020] Figure 3 This is a schematic diagram (side view) of the flow-blocking unit provided by the present invention.

[0021] Figure 4 A schematic diagram of the working process of the resistive liquid level monitoring device provided by the present invention.

[0022] Figure label: 1-First electrode plate, 2-Second electrode plate, 3-First contact, 4-Second contact, 5-Recess, 6-Baffle post, 7-Baffle unit, 8-Mounting plate, 9-First baffle, 10-Second baffle, 11-Spare electrode plate. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments: Example

[0024] like Figures 1 to 4 As shown, this embodiment provides a resistive liquid level monitoring device, mainly including a main control module, a resistance detection module, a communication module, a power management module, a data analysis module, an electrode assembly, and a wave suppression module. The power management module is electrically connected to the main control module, resistance detection module, communication module, data analysis module, and electrode assembly, providing power to these modules. The main control module is data-connected to the resistance detection module, communication module, and data analysis module. The wave suppression module is vertically fixed at the shoreline to suppress the influence of waves on the measured values. The electrode assembly is vertically installed inside the wave suppression module and electrically connected to the resistance detection module. The resistance detection module measures the resistance values ​​between different locations using the electrode assembly and feeds the results back to the data analysis module. After obtaining the analysis results, the main control module feeds the results back to the monitoring platform via the communication module, thereby obtaining the latest liquid level monitoring data.

[0025] As a preferred embodiment of the present invention, the main control module is an STM32L4 series microcontroller as the core processing unit.

[0026] As a preferred embodiment of the present invention, the resistance detection module adopts the AD5933 impedance conversion chip.

[0027] Furthermore, the communication module adopts the LoRa wireless transmission protocol and connects to the main control module via a UART serial port. It is responsible for sending the encapsulated data packets to a remote LoRa gateway or server using LoRa modulation. Preferably, the communication module also supports RS485, Ethernet, 4G, or NB-IoT communication methods.

[0028] Furthermore, the power management module adopts a hybrid power supply design of solar energy and mains power, including a solar panel, a charge / discharge management module, and a battery pack. The charge / discharge management module has two sets of power input terminals that can be switched between each other, one set connected to the solar panel and the other set connected to the mains power, and the output terminal of the charge / discharge management module is connected to the battery pack.

[0029] Specifically, the electrode assembly mainly includes a first electrode plate 1, a second electrode plate 2, first contacts 3, and second contacts 4. The first electrode plate 1 and the second electrode plate 2 are both vertically mounted and fixed, with a gap between them. A plurality of first contacts 3 are vertically distributed on the first electrode plate 1 and electrically connected to the resistance detection module, with the first contacts 3 spaced apart from each other. A plurality of second contacts 4 are vertically distributed on the second electrode plate 2 and electrically connected to the resistance detection module, with the second contacts 4 spaced apart from each other.

[0030] In a preferred embodiment of the present invention, the electrode assembly further includes a plurality of spare electrode plates 11 and spare contacts. The spare electrode plates 11 are vertically mounted on one side of the first electrode plate 1. The plurality of spare contacts are vertically distributed on the spare electrode plates 11 and are electrically connected to the resistance detection module respectively, and the spare contacts are spaced apart from each other.

[0031] Furthermore, the electrode assembly also includes an ultrasonic cleaning module. The ultrasonic cleaning module is mounted on the first electrode plate 1 and the second electrode plate 2, and is connected to the main control module and the power management module. It utilizes cavitation effect to remove deposits and some corrosion products from the surfaces of the first contact point 3 and the second contact point 4, exposing the metal surfaces.

[0032] Furthermore, the wave suppression module includes a T-shaped recess 5, a flow-blocking column 6, and flow-blocking units 7. The flow-blocking column 6 is vertically fixed in the center of the recess 5, opposite to the inlet of the recess 5, and has gaps between it and the edge of the recess 5. The flow-blocking units 7 are arranged in pairs on the left and right sides of the inlet of the recess 5 and the flow-blocking column 6. The electrode assembly is installed inside the recess 5, opposite to the inlet of the recess 5, and located between the flow-blocking column 6 and the inner side of the recess 5.

[0033] Furthermore, the flow-blocking unit 7 includes a mounting plate 8, a first baffle 9, and a second baffle 10. The mounting plate 8 is vertically installed and fixedly connected to the inner wall of the recess 5. The first baffle 9 and the second baffle 10 are both vertical and fixed on the mounting plate 8, and the first baffle 9 and the second baffle 10 are perpendicular to each other. The first baffle 9 and the second baffle 10 are both installed at an angle, and the first baffle 9 and the second baffle 10 are installed alternately from top to bottom. The bottom of the upper first baffle 9 is lower than the top of the adjacent lower second baffle 10, and the bottom of the upper second baffle 10 is lower than the top of the adjacent lower first baffle 9, with a gap between the adjacent baffles. During operation, since the first baffle 9 and the second baffle 10 are both inclined to each other, there is no space left for waves to pass through directly in the longitudinal direction. When waves hit the first baffle 9 or the second baffle 10, the two baffles act as buffers, and the wave surge only acts on the baffles. Since there is a gap between the first baffle 9 and the second baffle 10, and there is also a gap between adjacent flow-blocking units 7, the liquid can flow calmly through the gaps, and the waves or surges will be suppressed to the maximum extent by the action of the first baffle 9, the second baffle 10, and the gaps, thereby ensuring the calmness of the liquid surface in the depression 5.

[0034] The working process and principle of this invention are as follows: During operation, the main control module monitors the resistance value between the electrode groups through the resistance detection module. Since the first contact 3 and the second contact 4 in the electrode group are vertically distributed, with a portion separated by liquid and another portion by air, and because the resistance between the liquid and the air is different, when the difference between the resistance between the contacts at a certain height and the resistance between the contacts at a higher height reaches a set threshold, it indicates that the liquid level is between these two heights. To reduce the impact of liquid surface fluctuations or waves on resistance detection, the electrode group is placed inside the recess 5. When waves surge into the recess 5, the waves in the middle are directly blocked by the baffle column 6, and the waves on both sides are suppressed by the baffle unit 7 at the entrance of the recess 5. The waves flowing through the baffle column 6 then pass through the baffle units 7 on both sides before reaching the electrode group. During this process, the addition of the baffle column 6 creates two multiple turning and buffering flow channels inside the recess 5, which, together with the baffle unit 7, effectively suppress the waves, minimizing the wave fluctuations at the electrode group, thereby maximizing the stability of resistance detection. The present invention also has the advantages of simple structure, convenient operation and easy implementation. Example

[0035] Combination Figure 1 and Figure 4 As shown in the figure, this embodiment provides a specific implementation of a resistive liquid level monitoring device, which is described in detail below: I. System Hardware Configuration The core hardware components of the system are as follows: Main control module: The core processing unit is an STM32L4 series ultra-low power microcontroller (MCU). This MCU is based on the Arm® Cortex®-M4 core, which combines high performance with extremely low operating and sleep power consumption. It is responsible for controlling the entire measurement process, data processing, protocol encapsulation and power scheduling.

[0036] Resistance detection module: The resistance detection module (20) contains two electrode groups, A1~A3 and B1~B3, which are placed in the liquid to be tested (10). The excitation signal frequency used in the low-voltage AC measurement method is preferably in the range of 100Hz to 100kHz. This invention uses the low-voltage AC measurement method, and the excitation signal frequency used is preferably in the range of 100Hz to 100kHz. The selection of this frequency range is based on the following considerations: if the frequency is too low, the polarization effect of the electrode cannot be effectively suppressed, which will lead to measurement error; if the frequency is too high, the influence of parasitic capacitance will be aggravated, which will also reduce the measurement accuracy. Within this preferred frequency range, the best balance can be achieved between suppressing polarization and reducing capacitive interference.

[0037] One method is to fix electrode A1 and measure the resistance values ​​of electrodes B1 to B3, then fix electrode A2 and measure the resistance values ​​of electrodes B1 to B3 again, and so on, until electrode A3 is fixed and the resistance values ​​of electrodes B1 to B3 are measured again. The height of the electrode with a high resistance state (>10MΩ) is above the liquid level (air); the height of the electrode with a low resistance state (<10MΩ) is below the liquid level. The highest electrode with a low resistance state (<10MΩ) is the current liquid level (water depth). If the electrode measurement state is unstable, sometimes in a low resistance state (<10MΩ) and sometimes in a high resistance state (>10MΩ), then the current liquid level is fluctuating near this electrode. Alternatively, the interface value can be determined by using the highest electrode with a low resistance state (<10MΩ) from the previous measurement as the interface value, and then searching upwards and downwards for the interface between the high resistance state (>10MΩ) and the low resistance state (<10MΩ) electrode to determine the current liquid level.

[0038] The design of the electrode array is one of the key factors for achieving long-term maintenance-free operation of this device. Therefore, this invention employs a multi-layered comprehensive protection strategy: The first line of defense: material selection. The electrode body is selected based on different application scenarios and cost budgets, prioritizing corrosion-resistant materials. For general applications or clean water bodies, inexpensive and mechanically strong 316 / 316L stainless steel can be used; for high-chloride environments (such as seawater and chemical plants), titanium (Gr2) materials with excellent chloride ion corrosion resistance are preferred; for extreme corrosive environments (strong acids, strong alkalis), Hastelloy C-276 can be used; if both excellent conductivity and chemical inertness are required, platinum-coated electrodes can be selected; as a non-metallic option, acid and alkali resistant graphite electrodes can also be used, but their mechanical strength is relatively poor.

[0039] The second line of defense: surface treatment and protection. The electrode surface is covered with a hydrophobic functional coating, such as a PTFE coating, to prevent scaling and biofouling. This coating forms a non-stick surface, effectively preventing dirt adhesion and indirectly avoiding under-deposit corrosion. For stainless steel electrodes, surface passivation treatment can also be performed to enhance the stability and corrosion resistance of the chromium oxide film on its surface.

[0040] Regarding the impact of surface coatings on conductivity, this invention ensures measurement reliability through the following methods: PTFE and other coatings are not absolutely dense at the microscopic level, exhibiting microscopic discontinuities such as pinholes. More importantly, this invention employs a low-voltage AC measurement method. In an AC circuit, current can pass through the coating via microscopic physical channels and capacitive coupling effects, forming a conductive loop. While the coating introduces a stable and finite additional impedance, the resistance measurement circuit of this invention possesses a wide measurement range and automatic gain adjustment capability, capable of completely covering and compensating for this impedance variation, ensuring reliable resistance jump detection even under coating protection.

[0041] The third line of defense: system design and operational strategy. First, a redundant electrode design with one electrode in use and one in standby is employed. The main control module can periodically or automatically diagnose the electrode status based on performance indicators (such as signal quality degradation or abnormal resistance), and seamlessly switch to the standby electrode when the main electrode fails. Second, an ultrasonic cleaning module is integrated into the electrode array base. This module can be activated periodically or triggered to powerfully and non-destructively remove deposits and some corrosion products from the electrode surface using cavitation effects, exposing fresh metal surfaces. Finally, robust circuit and algorithm design, such as appropriately increasing the strength of the AC excitation signal to "break down" the high-impedance layer and analyzing the electrode impedance spectrum for early fault diagnosis and data validity marking, collectively ensures that the system can maintain functionality even with slight electrode degradation.

[0042] Regarding the potential contamination of the tested samples by electrode materials, by selecting the aforementioned inert materials (such as titanium and platinum), their ion dissolution rates are extremely low, and the contamination risk is negligible for monitoring rivers, reservoirs, and most industrial processes. For extremely pure scenarios such as semiconductor ultrapure water and pharmaceutical water, it is recommended that users choose platinum-coated electrodes or high-purity graphite electrodes with the lowest dissolution rates, or switch to non-contact level gauges.

[0043] The preset threshold for water pollution early warning can be dynamically set based on historical monitoring data. In a preferred embodiment, a water pollution early warning is triggered when the system detects that the relative rate of change of the resistance value compared to the baseline value continuously exceeds 30% and remains so for more than three measurement cycles. This threshold strategy effectively avoids false alarms caused by transient interference, ensuring the accuracy of the early warning.

[0044] Communication module: A LoRa wireless transmission module (such as the Semtech SX1276 / 78 series) is used. This module connects to the STM32L4 MCU via a UART serial port and is responsible for sending the encapsulated data packets to a remote LoRa gateway or server in LoRa modulation mode. The transmission distance can reach several kilometers, perfectly adapting to the needs of field deployment.

[0045] The power system consists of a 100W solar panel, a 20Ah lithium battery pack, and a high-efficiency power management module (PMIC). The power management module performs the following functions: Maximum power point tracking (MPPT) is performed on the solar panel input to optimize charging efficiency.

[0046] Intelligent charge and discharge management for 20Ah lithium batteries, including charging status indication and overcharge and over-discharge protection.

[0047] Provides a stable and switchable 3.3V power rail for STM32L4 MCUs, AD5933, LoRa modules, etc.

[0048] II. Operating Modes and Power Consumption Management The system adopts a low-power operating mode of "heartbeat packet + event triggering": Deep sleep: The device is in this state most of the time, with only the STM32L4's RTC, some SRAM and power management modules working, and the overall power consumption can be as low as 5μA or less.

[0049] Timed wake-up (heartbeat mode): After reaching the preset acquisition interval (e.g., every 30 minutes) of the RTC, the RTC wakes up the STM32L4 main controller. The main controller sequentially powers on the AD5933, performs level and resistance measurements, encapsulates the data, and then powers on the LoRa module to upload the data. After completion, all peripherals are powered off, and the MCU re-enters deep sleep mode. The duration of a single activity window is controlled within 60 seconds.

[0050] Event-triggered mode: If the MCU detects a sudden change in liquid level (such as exceeding the rate of change limit) or abnormal resistance value (indicating contamination) during measurement, it will immediately interrupt the normal process and prioritize waking up the LoRa module to send an emergency alarm data packet.

[0051] III. Communication Protocol Design The system defines a set of efficient and reliable binary application layer communication protocols for all data interactions between devices and the cloud platform. The protocol frame structure is unified, and key instructions / status codes are defined as follows: Uplink (Platform → Device): 0x01 (Remote Wake-up), 0x02 (Data Query), 0x10 (Parameter Setting).

[0052] Downlink (device → platform): 0x81 (heartbeat response), 0x83 (water level data), 0x84 (power data), 0x8F (alarm data).

[0053] IV. Communication Examples The system communicates by combining different data packets. The following is a typical example of a device proactively reporting data: Water level data reporting Function: Report the calculated liquid level results at regular intervals.

[0054] Status code: 0x83 Example of a data frame (hexadecimal): AA 55 01 00 5E 23 00 10 83 09 65 3A 4A 60 33 33 1B 42 00 A0 2B Load analysis: includes timestamp (0x604A3A65), liquid level (42.775 meters), and status (0: normal).

[0055] Power data reporting Function: Synchronize power supply status.

[0056] Status code: 0x84 Data frame example: AA 55 01 00 5E 23 00 10 84 09 65 3A 4A 60 E8 03 3C 90 01 4F 2D Load analysis includes timestamp, battery voltage (1000mV), battery level (60%), and charging current (400mA).

[0057] Maintenance alarm reporting Function: Proactively report system anomalies.

[0058] Status code: 0x8F Data frame example: AA 55 01 00 5E 23 00 10 8F 06 65 3A 4A 60 F1 02 D3 C1 Load analysis: includes timestamp, alarm code (0xF1: electrode contamination), and details (0x02: electrode 2).

[0059] V. System Workflow Initialization: STM32L4 reads device ID (0x235E0001), operator ID (0x1000) and other configurations.

[0060] Low-power cycle: The MCU is in deep sleep and is woken up by an RTC or LoRa interrupt.

[0061] Data Acquisition and Processing: After waking up, the MCU controls the AD5933 to measure the impedance of each electrode and calculate the liquid level and resistance value.

[0062] Encapsulation and transmission: The MCU encapsulates the data into corresponding data packets (such as water level packet 0x83) according to the protocol and transmits them via LoRa.

[0063] Hibernation: After completion, the power supply to the external devices is cut off, and the MCU re-enters deep hibernation.

[0064] Anomaly Handling: When a sudden change in liquid level (>10cm / hour) or an abnormal change in resistance (>30%) is detected, the system will immediately wake up, increase the sampling frequency to 1 time / minute, and send an alarm message.

[0065] Maintenance Function: The system automatically activates the ultrasonic cleaning function monthly for 30 seconds. When electrode performance is detected to be degraded, the system prompts maintenance personnel to replace the electrodes. Example

[0066] like Figure 1 and Figure 4 As shown in this embodiment, the resistive liquid level monitoring device is widely used in many fields such as water conservancy and hydrology (e.g., river and reservoir water level monitoring), environmental protection (e.g., sewage treatment plant and discharge outlet monitoring), industrial production (e.g., chemical and food industry storage tank liquid level management), and agricultural irrigation (e.g., canal system and reservoir water level control). Especially in scenarios with complex media characteristics (high viscosity, easy foaming, strong corrosion), harsh environments (field, unattended), and special requirements for cost and control logic, this invention has significant technical advantages and economic benefits compared to traditional float-type, pressure-type, ultrasonic-type, or radar-type liquid level gauges.

[0067] The following technical solution is adopted in this embodiment: A resistive liquid level monitoring device includes an electrode array, a resistance measurement circuit, a data analysis module, a communication module, and a power management module.

[0068] The electrode array includes at least one pair of measuring electrodes, preferably made of corrosion-resistant materials such as 316 stainless steel, titanium, graphite, or platinum-coated electrodes. The electrode surface is covered with a hydrophobic functional coating that prevents scaling and biofouling. The electrodes are fixed to the base via detachable connections using snap-fit, magnetic, or threaded connections, supporting quick replacement. Furthermore, the electrode array employs a redundant design, including one or more backup electrode pairs. The main control module can automatically activate the backup electrode pair when the main electrode pair fails, greatly improving system reliability. In addition, an ultrasonic cleaning module is integrated into the electrode array base, which can be activated periodically or triggered under the control of the main control module to remove biofouling or polarization deposits from the electrode surface, achieving long-term maintenance-free operation. The resistance measurement circuit employs a low-voltage AC measurement method with a frequency range of 100Hz to 100kHz to eliminate electrode polarization effects. To further improve the measurement range and accuracy, the circuit integrates an automatic range switching function, automatically adjusting the amplification factor through a comparator and a multiplexer to ensure accurate measurement across the entire range, from extremely high resistance in air (>10MΩ) to relatively low resistance in liquids (<10Ω). The circuit can be implemented using a constant current source method, a voltage divider method, or a scheme based on an analog-to-digital converter chip. The AC excitation signal is generated by a square wave oscillator composed of a timer chip, a PWM signal generated by a microcontroller, or generated internally by a dedicated measurement chip.

[0069] Regarding the influence of surface coatings on conductivity, this invention ensures measurement reliability through the following methods: Hydrophobic coatings such as PTFE are inherently insulators. However, in practical applications, discontinuities such as microscopic pinholes in the coating provide a limited conductive path for current. More importantly, this invention employs a low-voltage AC measurement method. In this mode, the metal electrode, insulating coating, and conductive solution together constitute a capacitor, and the AC signal can penetrate the coating through capacitive coupling, forming a displacement current. Therefore, the total impedance of the measurement circuit is composed of the resistive component of the microscopic pinholes and the capacitive component of the intact coating in parallel.

[0070] Although the coating introduces a stable and finite additional impedance, the resistance measurement circuit of this invention features a wide measurement range and automatic gain adjustment capability. Its design goal is to accommodate a wide range of measurements, from extremely high impedance (>10MΩ, where capacitive coupling dominates) to lower impedance (<10Ω, where solution resistance dominates). As long as the coating itself has stable physicochemical properties, the systematic errors it introduces can be compensated for through circuitry and algorithms, thereby ensuring reliable resistance jump detection even under coating protection.

[0071] The resistance detection module uses the AD5933 impedance conversion chip, which integrates a direct digital frequency synthesizer (DDS), a 12-bit analog-to-digital converter (ADC), and a digital signal processing (DSP) unit, enabling automatic signal excitation, acquisition, and processing. This chip provides a programmable frequency output from 100Hz to 100kHz, supports impedance measurement from 100Ω to 10MΩ, achieves a system accuracy of 0.5%, and communicates via an I²C interface. Operating at 2.7V-5V, it is suitable for high-precision liquid level monitoring systems, greatly simplifying peripheral circuit design. As an alternative, the AC excitation signal can also be generated by filtering a PWM signal generated by a microcontroller, or by a square wave oscillator constructed from a timer chip (such as a 555).

[0072] The data analysis module executes an intelligent liquid level determination algorithm: First, it measures the resistance value between each electrode pair in the electrode array through polling; second, it accurately determines the gas-liquid interface and liquid level height based on the abrupt change in resistance value (>10MΩ in air, <10MΩ in liquid); furthermore, the module continuously tracks the long-term trend of the resistance value of each electrode pair, establishing a liquid resistivity baseline. When the resistance value deviates from the baseline by more than a preset threshold, a water pollution warning is triggered. This module can also be configured to correlate liquid level data with water quality anomaly data and report it via a communication module, providing data support for network-based source tracing.

[0073] The resistance measurement time interval of the analysis module can be set by local / remote devices, or based on historical experience data, or by remote wake-up testing.

[0074] The communication module supports multiple communication methods, including wired (such as RS485, Ethernet) and wireless (such as LoRa, 4G, NB-IoT). It features intelligent data management functions, including local data caching during network interruptions, resume transmission after network recovery, and efficient interaction with the cloud platform based on IoT protocols (such as MQTT), enabling remote data visualization, monitoring command issuance, and alarm management.

[0075] The power management module adopts a hybrid power supply design, compatible with renewable energy sources such as solar, wind, and tidal power, and integrates a battery pack and mains power switching circuit. The solar cell module can be equipped with a high-efficiency power management chip (PMIC) with maximum power point tracking (MPPT) function, which can intelligently optimize energy harvesting efficiency and manage and protect the battery charging and discharging, ensuring that the system can operate stably 24 / 7 in harsh outdoor environments.

[0076] As another important aspect of the invention, the device can be used independently as a liquid level monitoring device or as part of a water quality monitoring system. When used for multi-parameter monitoring of the water environment, its electrode array simultaneously serves liquid level measurement and water conductivity measurement, realizing the reuse of hardware resources and collaborative data analysis.

[0077] Compared with existing technologies, this invention has the following significant advantages: it detects liquid level by resistive change, unaffected by environmental factors such as water quality and light; it adopts a low-voltage AC measurement method combined with an automatic sizing circuit, effectively avoiding electrode polarization and achieving high-precision measurement over a wide range from air to liquid; through a multi-layered protection strategy of "material selection + surface coating + redundant design + ultrasonic cleaning", it significantly improves electrode life and achieves long-term maintenance-free operation; it can realize early warning of water pollution; and it supports multiple power supply and communication methods, making it suitable for unattended field applications.

[0078] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, any changes made in accordance with the shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A resistive liquid level monitoring device, characterized in that, The system includes a main control module, a resistance detection module, a communication module, a power management module, a data analysis module, an electrode assembly, and a wave suppression module. The power management module is electrically connected to the main control module, resistance detection module, communication module, data analysis module, and electrode assembly, providing power to these modules. The main control module is data-connected to the resistance detection module, communication module, and data analysis module. The wave suppression module is vertically fixed at the shoreline to suppress the influence of waves on the measured values. The electrode assembly is vertically installed inside the wave suppression module and electrically connected to the resistance detection module. The resistance detection module measures the resistance values ​​between different locations using the electrode assembly and feeds the results back to the data analysis module. After obtaining the analysis results, the main control module feeds the results back to the monitoring platform through the communication module, thereby obtaining the latest liquid level monitoring data.

2. The resistive liquid level monitoring device according to claim 1, characterized in that, The main control module, an STM32L4 series microcontroller, serves as the core processing unit.

3. The resistive liquid level monitoring device according to claim 1, characterized in that, The resistance detection module uses the AD5933 impedance conversion chip.

4. The resistive liquid level monitoring device according to claim 1, characterized in that, The communication module adopts the LoRa wireless transmission protocol and is connected to the main control module via a UART serial port. It is responsible for sending the encapsulated data packets to a remote LoRa gateway or server in LoRa modulation mode.

5. The resistive liquid level monitoring device according to claim 1, characterized in that, The power management module adopts a hybrid power supply design of solar energy and mains power, including a solar panel, a charge and discharge management module, and a battery pack. The charge and discharge management module has two sets of power input terminals that can be switched between each other, one set is connected to the solar panel and the other set is connected to the mains power, and the output terminal of the charge and discharge management module is connected to the battery pack.

6. The resistive liquid level monitoring device according to claim 1, characterized in that, The electrode assembly includes a first electrode plate, a second electrode plate, a first contact, and a second contact; the first electrode plate and the second electrode plate are both vertically installed and fixed, with a gap between them; a plurality of first contacts are vertically distributed on the first electrode plate and are electrically connected to the resistance detection module respectively, and the first contacts are spaced apart from each other; a plurality of second contacts are vertically distributed on the second electrode plate and are electrically connected to the resistance detection module respectively, and the second contacts are spaced apart from each other.

7. A resistive liquid level monitoring device according to claim 6, characterized in that, The electrode assembly also includes several spare electrode plates and spare contacts; the spare electrode plates are vertically mounted on one side of the first electrode plate; the spare contacts are vertically distributed on the spare electrode plates and are electrically connected to the resistance detection module respectively, and the spare contacts are spaced apart from each other.

8. A resistive liquid level monitoring device according to claim 6, characterized in that, The electrode assembly also includes an ultrasonic cleaning module; the ultrasonic cleaning module is disposed on the first electrode plate and the second electrode plate, and is connected to the main control module and the power management module. It uses the cavitation effect to remove the deposits and some corrosion products on the surfaces of the first contact and the second contact, exposing the metal surface.

9. A resistive liquid level monitoring device according to claim 1, characterized in that, The wave suppression module includes a T-shaped recess, a flow-blocking column, and flow-blocking units. The flow-blocking column is vertically fixed in the middle of the recess, opposite to the inlet of the recess, and has gaps between it and the edge of the recess. The flow-blocking units are arranged in pairs on the left and right sides of the recess inlet and the flow-blocking column. The electrode assembly is installed in the recess, opposite to the recess inlet, and located between the flow-blocking column and the inner side of the recess.

10. A resistive liquid level monitoring device according to claim 9, characterized in that, The flow-blocking unit includes a mounting plate, a first baffle, and a second baffle; the mounting plate is vertically installed and fixedly connected to the recessed inner wall; the first baffle and the second baffle are both vertical and fixed on the mounting plate, and the first baffle and the second baffle are perpendicular to each other; the first baffle and the second baffle are both installed at an angle, and the first baffle and the second baffle are installed alternately from top to bottom, and the bottom of the upper first baffle is lower than the top of the adjacent lower second baffle, the bottom of the upper second baffle is lower than the top of the adjacent lower first baffle, and there is a gap between the adjacent baffles.

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