Chloride ion on-line monitoring device for earthquake precursor observation

Abstract

This invention belongs to the field of earthquake monitoring technology, specifically relating to an online chloride ion monitoring device for earthquake precursor observation. It includes a base frame and a control cabinet and drive mechanism mounted on the base frame, as well as a chloride ion sensor and a central controller. The central controller is installed inside the control cabinet and is communicatively connected to the drive mechanism and the chloride ion sensor. The drive mechanism drives the chloride ion sensor to move up and down. When the chloride ion sensor descends into groundwater, it monitors the chloride ion concentration in the groundwater. This invention uses a drive mechanism to periodically drive the chloride ion sensor down into the groundwater, achieving timed measurement of chloride ions in the groundwater. This avoids the chloride ion sensor being immersed in excessively hot groundwater for extended periods, further extending its service life. It also achieves online non-destructive sampling, unaffected by manual or pipeline sampling, thus achieving real-time monitoring.

Description

Technical Field

[0001] This invention belongs to the field of earthquake monitoring technology, specifically relating to an online chloride ion monitoring device for earthquake precursor observation. Background Technology

[0002] An earthquake is a large-scale ground shaking caused by a sudden event inside the Earth's crust. The pores or crystal defects in the rocks inside the Earth are filled with fluids, and deep fluids play an important role in the earthquake gestation process. Therefore, by monitoring underground fluids, earthquake prediction can be effectively achieved, earthquake information can be promptly alerted, and people can be given more time to evacuate, thereby reducing the negative impact of earthquakes.

[0003] Groundwater fluids are mainly substances such as water, gas, and oil that flow through the pores of the Earth's crust. Chloride ions are the most widely distributed ions in groundwater, present in almost all groundwater. Monitoring the dynamic changes of chloride ions in groundwater is helpful for earthquake precursor monitoring and forecasting.

[0004] Currently, groundwater chloride ion detection mainly relies on manual sampling or long pipeline transportation to deliver samples to the testing pool. Manual sampling is discontinuous and heavily influenced by human experience; long-distance pipeline transportation is susceptible to pipeline adsorption and contamination, resulting in samples that are no longer in the original quantity or composition, failing to objectively and completely reflect the real-time dynamic changes in chloride ions in groundwater, thus affecting the accuracy of earthquake precursor predictions.

[0005] Traditional online chloride ion monitoring instruments rely on sensors that are constantly immersed in groundwater for measurement. However, the groundwater temperature at hot spring monitoring sites is typically quite high, which challenges the lifespan of these traditional online chloride ion sensors. Furthermore, most earthquake precursor monitoring sites are located in remote areas without mains power supply, further complicating online chloride ion monitoring.

[0006] Therefore, there is an urgent need in this field to develop an online chloride ion monitoring device that features non-destructive sampling, high temperature resistance, and low power consumption. Summary of the Invention

[0007] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide an online chloride ion monitoring device for earthquake precursor observation that meets one or more of the aforementioned requirements.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] An online chloride ion monitoring device for earthquake precursor observation includes a base frame and a control cabinet and drive mechanism installed on the base frame. It also includes a chloride ion sensor and a central controller. The central controller is installed in the control cabinet and is communicatively connected to the drive mechanism and the chloride ion sensor. The drive mechanism is used to drive the chloride ion sensor to move up and down. When the chloride ion sensor descends into the groundwater, it monitors the chloride ion concentration in the groundwater.

[0010] As a preferred embodiment, the driving mechanism includes a telescopic bracket, pulleys, a cable reel, and a communication cable. The pulleys and cable reel are respectively installed at both ends of the telescopic bracket along the telescopic direction. The cable reel includes a reel body, a stepper motor mounted on the reel body, and a spool. The reel body is fixedly installed on the telescopic bracket, and the spool rotates in conjunction with the reel body. The stepper motor is used to drive the spool to rotate and is communicatively connected to the central controller. One end of the communication cable is wound around the spool and connected to the central controller, and the other end passes around the pulley to connect to the chloride ion sensor.

[0011] As a preferred embodiment, the pulse digital signal of the stepper motor is controlled by a timer interrupt method for input.

[0012] As a preferred embodiment, the telescopic bracket is a hollow structure, and the communication cable runs along the inside of the telescopic bracket.

[0013] As a preferred embodiment, the online chloride ion monitoring device for earthquake precursor observation also includes a distance sensor for measuring the distance from the chloride ion sensor to the groundwater surface; the distance sensor is communicatively connected to the central controller.

[0014] As a preferred embodiment, the online chloride ion monitoring device for earthquake precursor observation also includes a wireless communication module, which is connected to the central controller for wireless transmission of online chloride ion monitoring information.

[0015] As a preferred embodiment, the online chloride ion monitoring device for earthquake precursor observation also includes a power supply module for supplying power to each electrical component.

[0016] As a preferred embodiment, the power supply module includes a solar photovoltaic panel and a solar controller. The solar photovoltaic panel is mounted on the top of the base frame via a photovoltaic bracket, and the solar controller is mounted on the control cabinet. The solar photovoltaic panel is communicatively connected to the solar controller, and the solar controller is communicatively connected to the central controller.

[0017] As a preferred embodiment, the power supply module further includes a lithium battery, which is installed in the control cabinet; the solar photovoltaic panel is electrically connected to the lithium battery, and the lithium battery is electrically connected to the central controller.

[0018] As a preferred embodiment, the chloride ion sensor includes an insulating substrate and a working electrode, a reference electrode, and an auxiliary electrode disposed on the insulating substrate.

[0019] Compared with the prior art, the beneficial effects of this invention are: (1)

[0021] This invention uses a drive mechanism to periodically lower a chloride ion sensor into groundwater, enabling timed measurement of chloride ions in the groundwater. This avoids the chloride ion sensor being immersed in excessively hot groundwater for extended periods, further extending its service life. It also achieves online, non-destructive sampling, unaffected by manual or pipeline sampling, thus achieving real-time monitoring.

[0022] (2) This invention can be powered by new energy sources such as solar or wind power, which solves the problem that most earthquake precursor monitoring points are located in remote areas and have no mains power supply.

[0023] (3) This invention has wireless data transmission function, which can remotely query monitoring results in real time and is suitable for unattended continuous observation of earthquake precursors in the field. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the online chloride ion monitoring device for earthquake precursor observation according to Embodiment 1 of the present invention;

[0025] Figure 2 This is a communication architecture diagram of the online chloride ion monitoring device for earthquake precursor observation according to Embodiment 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the chloride ion sensor according to Embodiment 1 of the present invention;

[0027] Figure 4 This is a cross-sectional view of the working electrode of Embodiment 1 of the present invention;

[0028] Figure 5 This is an exploded view of the working electrode structure of Embodiment 1 of the present invention;

[0029] Figure 6 This is a cross-sectional view of the reference electrode in Embodiment 1 of the present invention;

[0030] Figure 7 This is a cross-sectional view of the auxiliary electrode in Embodiment 1 of the present invention;

[0031] Figure 8 This is a schematic diagram of the structure of the mask plate in Embodiment 1 of the present invention. Detailed Implementation

[0032] To more clearly illustrate the embodiments of the present invention, specific implementation methods will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0033] Example 1:

[0034] like Figure 1 and 2 As shown, the online chloride ion monitoring device for earthquake precursor observation in this embodiment includes a base frame, a control cabinet 100, a drive mechanism, a central controller 200, a chloride ion sensor 300, a distance sensor 400, a wireless communication module, and a power supply module.

[0035] Specifically, the base frame includes upright a, pole base b, and base c. Upright a is a galvanized pole with a diameter of 40-80mm. Pole base b is fixed to base c with nuts, and the surface of the nuts is coated with cement to prevent corrosion. Upright a is a hollow structure, which facilitates the wrapping of cables and prevents them from being exposed.

[0036] The control cabinet 100 is installed on the upper part of the upright a and is used to install electrical components.

[0037] The central controller 200 is installed inside the control cabinet 100. The central controller 200 is communicatively connected to the drive mechanism and the chloride ion sensor 300. The drive mechanism is used to drive the chloride ion sensor to move up and down. When the chloride ion sensor descends into the groundwater, it monitors the chloride ion concentration in the groundwater.

[0038] Specifically, the drive mechanism includes a telescopic bracket 50, a pulley 60, a cable reel 70, and a communication cable 80. The telescopic bracket is fixedly installed in the middle of the upright a, and the telescopic bracket 50 extends laterally, allowing its length to be adjusted by telescoping along the lateral direction. The length of the telescopic bracket is adjusted according to the distance between the groundwater and the upright. The telescopic bracket 50 is made of hollow aluminum alloy tubing, which facilitates the routing of the communication cable 80.

[0039] The telescopic bracket 50 has a cable reel 70 and a pulley 60 installed at its left and right ends along the telescopic direction, respectively. The cable reel 70 includes a reel body, a stepper motor 9 mounted on the reel body, and a spool. The reel body is fixedly mounted on the telescopic bracket, and the spool rotates in conjunction with the reel body. The stepper motor 9 drives the spool to rotate and is connected to the central controller 1 via a cable. One end of the communication cable 80 is wound around the spool and connected to the central controller 1, while the other end passes around the pulley 60 to connect to the chloride ion sensor 300. The reel body has a communication cable outlet so that the communication cable can enter the control cabinet 100. The pulse digital signal of the stepper motor is controlled by a timer interrupt, thereby driving the stepper motor to move at regular intervals. This enables the chloride ion sensor 300 to be vertically lowered into the groundwater every 10 minutes to 2 hours to measure the chloride ion concentration, achieving autonomous real-time monitoring.

[0040] In this embodiment, the communication cable 80 is a PVC cable with steel wire rope, which has high communication stability and high strength.

[0041] The ranging sensor 400 in this embodiment is used to measure the distance from the chloride ion sensor to the groundwater surface; the ranging sensor is communicatively connected to the central controller. Specifically, the ranging sensor 400 is installed on the top exterior of the chloride ion sensor 300, measures the distance from the chloride ion sensor to the groundwater surface, and transmits the measurement signal to the central controller.

[0042] In this embodiment, the wireless communication module is connected to the central controller for wireless transmission of online chloride ion monitoring information. Specifically, the wireless communication module is installed inside the control cabinet, and its antenna 10 is installed at the top of the control cabinet 100. It is used to transmit the chloride ion concentration monitored by the chloride ion sensor to the Internet cloud for cloud storage and cloud query of data.

[0043] The power supply module in this embodiment is used to supply power to various electrical components. Specifically, the power supply module includes a solar photovoltaic panel 11, a solar controller 12, and a lithium battery 13. The solar photovoltaic panel 11 is mounted on the top of column a via a photovoltaic bracket. The solar controller 12 and lithium battery 13 are installed inside a control cabinet. The solar photovoltaic panel 11 is connected to the solar controller 12 and lithium battery 13 via cables. The solar controller 12 and lithium battery 13 are also connected to the central controller 200 via cables. Each cable connection circuit employs a surge protection circuit, which can release the large amount of energy accumulated in the circuit to the ground in the shortest possible time, thereby preventing the electrical components from burning out due to excessive current.

[0044] In this embodiment, the device is powered by a dual power source: a solar photovoltaic panel 11 and a lithium battery 13. During the day, the solar photovoltaic panel powers the device while charging the lithium battery, and at night or on cloudy days, the lithium battery powers the device.

[0045] The central controller and solar controller use the low-power MSP430 microprocessor. The entire device can be powered by lithium batteries for a long time without solar photovoltaic power, ensuring normal operation and enabling real-time monitoring of chloride ion concentration in groundwater around the clock.

[0046] like Figure 3-7 As shown, the chloride ion sensor of this embodiment includes an insulating substrate 7 and a reference electrode 1, a working electrode 2, an auxiliary electrode 3, and electrode solder joints 5 corresponding to each electrode located on the insulating substrate 7. The working electrode 2 is located between the reference electrode 1 and the auxiliary electrode 3.

[0047] In this embodiment, the insulating substrate 7 is a rigid silicon wafer, i.e., an insulating silicon substrate.

[0048] Among them, the working electrode 2, the reference electrode 1 and the auxiliary electrode 3 are respectively connected to their corresponding electrode solder joints 5 through electrode wires 4. Each electrode wire is independent of each other and is covered with an insulating layer 6. Specifically, silicone rubber is applied to the surface of the electrode wire as an insulating layer 6 to protect the electrode wire.

[0049] Each electrode solder joint 5 is used to connect to an external control circuit to output electrode change signals.

[0050] The working electrode 2 in this embodiment includes a first conductive layer 2-1 and a reactive layer 2-2 sequentially stacked on an insulating substrate 7. Specifically, the first conductive layer 2-1 is an interdigitated electrode, fabricated by photolithography. The interdigitated electrode array pattern includes a pair of sparse microelectrodes, each with 3 to 10 fingers. Dozens of fingers on the two sparse microelectrodes are arranged in an interlaced manner to form the interdigitated electrode. The fingers are 3 to 8 mm long and 5 μm wide, with a spacing of 5 μm between adjacent fingers. The micro-spacing of the interdigitated electrodes can amplify the detection signal, further improving the sensor's detection sensitivity and accuracy. A conductive Cu film is deposited on the insulating substrate by electron beam evaporation vacuum deposition, with a film thickness of 50 nm to 1 μm.

[0051] The reaction layer 2-2 comprises a conductive nanofiber film layer 2-2A, an Ag thin film layer 2-2B, and an AgCl thin film layer 2-2C sequentially stacked on the first conductive layer 2-1. Specifically, the reaction layer is fabricated on the first conductive layer using an electrospinning method to obtain a conductive nanofiber thin film, followed by the deposition of a metallic Ag layer and an AgCl layer on the conductive nanofiber. Due to the high porosity, large specific surface area, and uniform structure of the conductive nanofibers, they can increase the loading capacity of the analyte, thereby significantly increasing the electrochemical active sites of the sensor. This enables the nanofibers to accelerate and amplify the electrical signal, improving the sensor's sensitivity to chloride ion detection, shortening the detection time, and enhancing sensor performance.

[0052] Among them, the conductive nanofiber membrane layer 2-2A is made by electrospinning with polyvinylidene fluoride polymer as spinning precursor and conductive active material and coupling agent added.

[0053] Polyvinylidene fluoride polymers possess excellent chemical stability, including corrosion resistance, high temperature resistance, oxidation resistance, and UV resistance. This improves the chemical stability of chloride ion sensors and extends their lifespan.

[0054] Conductive active materials include one or more of doped metal nanoparticles, fullerenes, graphene, and carbon nanotubes. The addition of conductive active materials improves the electron transfer performance of the material. Taking carbon nanotube doping in nanofibers as an example, carbon nanotubes possess excellent mechanical properties, high mechanical strength, high conductivity, and high electrochemical stability, which enhances the effective electrical signal generated by the chloride ion reaction layer. Furthermore, the good chemical stability of carbon nanotubes helps reduce signal fluctuations caused by complex components in the test solution, minimizes interference from irrelevant substances, and improves the repeatability and stability of chloride ion detection.

[0055] The coupling agent can be one or a mixture of several of the following: aminopropyltriethoxysilane (KH550), glycidyl methoxypropyltrimethoxysilane (KH560), methacryloxypropyltrimethoxysilane (KH570), vinyltriethoxysilane (A151), vinyltriethoxysilane (A171), mercaptopropyltrimeth(eth)oxysilane (KH580, KH590), ethylenediaminepropyltriethoxysilane (KH792), and ethylenediaminepropylmethyldimethoxysilane (KBM602). The addition of the coupling agent increases the adhesion between the fiber film and the electrode, prevents film detachment, and extends the sensor's lifespan.

[0056] The thickness of the conductive nanofiber film is 100 nm to 5 μm, the thickness of the Ag film is 200 nm to 5 μm, and the thickness of the AgCl film is 500 nm to 10 μm.

[0057] The reference electrode 1 in this embodiment includes a second conductive layer 1-1, an Ag thin film layer 1-2, an AgCl thin film layer 1-3, and a hydrogel layer 1-4 sequentially stacked on an insulating substrate 7. The second conductive layer 1-1 is a conductive Cu film deposited on the insulating substrate by electron beam evaporation vacuum deposition, with a film thickness of 50 nm to 1 μm; the Ag thin film layer 1-2 has a film thickness of 200 nm to 5 μm; the AgCl thin film layer 1-3 has a film thickness of 500 nm to 10 μm; and the hydrogel layer 1-4 has a thickness of 0.5 to 1 μm. Specifically, the reference electrode is formed by depositing a conductive Cu film on an insulating substrate, then depositing an Ag thin film on the conductive Cu film, then depositing an AgCl thin film layer on the Ag thin film layer, and finally coating the AgCl thin film layer with a hydrogel layer.

[0058] The hydrogel layer comprises the following components: 2-hydroxyethyl methacrylate, polyvinylpyrrolidone, 2,2-dimethoxy-2-phenylacetophenone, ethylene glycol dimethacrylate, and potassium chloride, with a weight ratio of 10:1:0.4:0.05:2.75.

[0059] In this embodiment, the auxiliary electrode 3 includes a third conductive layer 3-1 and a Pt thin film layer 3-2 sequentially stacked on an insulating substrate 7. The third conductive layer 3-1 is a conductive Cu film deposited on the insulating substrate 7 by electron beam evaporation vacuum deposition, with a film thickness of 50 nm to 1 μm; the Pt thin film layer has a film thickness of 200 nm to 10 μm. Specifically, the auxiliary electrode is formed by depositing a conductive Cu film on an insulating substrate, and then depositing a stable Pt thin film on the conductive Cu film.

[0060] The fabrication process of the chloride ion sensor in this embodiment is as follows:

[0061] (1) The insulating silicon substrate was placed in an ultrasonic cleaner and cleaned sequentially with hydrogen peroxide, acetone, and anhydrous ethanol, then dried. In a vacuum chamber, the insulating silicon substrate was heated to 300°C, and the vacuum level reached 10. -5 A Cu thin film of 50 nm to 1 μm is deposited on an insulating silicon substrate at a pressure of Pa or higher, and then a pre-designed photomask (e.g., ...) is used. Figure 8 As shown, Cu thin films are photolithographically ...

[0062] The working electrode interdigitated electrode array pattern includes a pair of sparse microelectrodes, each of which has 3 to 10 fingers. The 3 to 10 fingers on the two sparse microelectrodes are arranged in an interlaced manner to form an interdigitated electrode. The fingers are 3 to 8 mm long, 5 μm wide, and the distance between adjacent fingers is 5 μm.

[0063] (2) A layer of conductive nanofibers was prepared on the interdigitated electrode using electrospinning: 2g of polyvinylidene fluoride was dissolved in 25mL of acetone and stirred until dissolved. Then, 0.3g of carbon nanotubes and 0.1g of aminopropyltriethoxysilane (KH550) were added and stirred to obtain a uniform and stable polyvinyl alcohol electrospinning precursor solution. An appropriate amount of precursor solution was injected into a syringe, and a stainless steel needle was used as the spinning nozzle. The electrostatic high voltage DC was set to 18KV~25KV, and the precursor solution was propelled at a rate of 1mL / h~2.5mL / h. The spinning time was set to 5~25s. Under the action of the electric field, a conductive composite fiber film with a high specific surface area and high porosity of 100nm~5μm was formed on the interdigitated electrode.

[0064] (3) The fiber film substrate is placed in the vacuum coating chamber again for secondary electron beam evaporation vacuum coating. An Ag film is first deposited on the thin film fibers of the reference electrode and the working electrode, with a coating thickness of 200 nm to 5 μm. Then an AgCl film is deposited, with a coating thickness of 500 nm to 10 μm. A Pt film is deposited on the auxiliary electrode, with a coating thickness of 200 nm to 10 μm. The coating method is the same as that of Cu film.

[0065] (4) A layer of hydrogel is then coated on the outer surface of the reference electrode. The hydrogel is prepared and coated with 2-hydroxyethyl methacrylate, polyvinylpyrrolidone, 2,2-dimethoxy-2-phenylacetophenone (DMPAP), ethylene glycol dimethacrylate and potassium chloride in a mass ratio of 10:1:0.4:0.05:2.75.

[0066] (5) Apply silicone rubber to the surface of the electrode wire as an insulating layer to protect the electrode wire.

[0067] In this embodiment, the working electrode of the chloride ion sensor is an Ag / AgCl chloride ion selective electrode. Chloride ions and silver chloride form a dynamic equilibrium in the test solution. When the chloride ion concentration in the solution changes, the potential of the Ag / AgCl electrode also changes accordingly. The reference electrode potential remains stable in the test solution. By combining the Nernst equation, the chloride ion concentration can be obtained. The auxiliary electrode forms a circuit with the working electrode to maintain a smooth and stable current flow, ensuring that all reactions occur at the working electrode, making the measurement more accurate.

[0068] The workflow of the online chloride ion monitoring device for earthquake precursor observation in this embodiment is as follows:

[0069] The input of pulse digital signals is controlled by timer interrupt, and the stepper motor is driven to control the forward and reverse rotation of the reel, so as to realize the timed measurement of chloride ion concentration.

[0070] When measurement is required, the stepper motor controls the reel to rotate forward, causing the chloride ion sensor to descend to 10cm underwater, activating the chloride ion sensor to detect and measure the chloride ion concentration in the groundwater. The concentration result is transmitted to the central controller via a communication cable, and after being converted by the central controller, it is transmitted to the cloud via a wireless communication module to achieve cloud storage and cloud query.

[0071] After the measurement is completed, the stepper motor controls the reel to reverse, raising the chloride ion sensor to a height of 0.5 meters above the water surface, ready for the next measurement.

[0072] When the groundwater level rises, if the distance between the chloride ion sensor and the water surface is less than a certain distance as measured by the ranging sensor, the signal is transmitted to the central controller. The central controller then sends a signal to reverse the stepper motor, causing the chloride ion sensor to rise to a certain distance from the water surface. This prevents the chloride ion sensor from being submerged in water for extended periods of non-operation, thus extending its service life.

[0073] Example 2:

[0074] The difference between the online chloride ion monitoring device for earthquake precursor observation in this embodiment and that in Embodiment 1 is:

[0075] Powered by lithium batteries, solar energy, or wind power, it adopts a single power supply method to meet the needs of different applications;

[0076] Other structures can be found in Example 1.

[0077] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A device for monitoring chloride ions on-line for earthquake precursors, characterized by, It includes a base frame and a control cabinet and drive mechanism mounted on the base frame, as well as a chloride ion sensor and a central controller. The central controller is installed in the control cabinet and is communicatively connected to the drive mechanism and the chloride ion sensor. The drive mechanism is used to drive the chloride ion sensor to perform lifting and lowering movements. Chloride ion sensors are lowered into groundwater to monitor the concentration of chloride ions in the groundwater; real-time dynamic changes in chloride ion concentration in groundwater are used to observe earthquake precursors. It also includes a wireless communication module, which communicates with the central controller and is used to wirelessly transmit online chloride ion monitoring information; The drive mechanism includes a telescopic bracket, pulleys, a cable reel, and a communication cable. The telescopic bracket has pulleys and a cable reel installed at both ends along the telescopic direction. The cable reel includes a reel body, a stepper motor mounted on the reel body, and a spool. The reel body is fixedly mounted on the telescopic bracket, and the spool rotates within the reel body. The stepper motor drives the spool to rotate and is communicatively connected to the central controller. One end of the communication cable is wound around the spool and connected to the central controller, while the other end passes around the pulley to connect to the chloride ion sensor. The pulse digital signal of the stepper motor is controlled by a timer interrupt method for input; The telescopic bracket is a hollow structure, and the communication cable runs along the inside of the telescopic bracket. A chloride ion sensor includes an insulating substrate and a reference electrode, a working electrode, an auxiliary electrode, and electrode solder joints corresponding to each electrode, all located on the insulating substrate. The working electrode is located between the reference electrode and the auxiliary electrode. Among them, the working electrode, the reference electrode and the auxiliary electrode are connected to their respective electrode solder joints through electrode wires, and each electrode wire is independent of each other and is covered with an insulating layer. Each electrode solder joint is used to connect to an external control circuit to output electrode change signals; The working electrode includes a first conductive layer and a reactive layer sequentially stacked on an insulating substrate. The first conductive layer is an interdigitated electrode. The interdigitated electrode array pattern includes a pair of sparse microelectrodes, each of which has 3 to 10 fingers. Dozens of fingers on the two sparse microelectrodes are arranged in an interlaced manner to form an interdigitated electrode. The fingers are 3 to 8 mm long, 5 μm wide, and the distance between adjacent fingers is 5 μm. The reactive layer includes a conductive nanofiber film, an Ag film, and an AgCl film layer sequentially stacked on the first conductive layer. The conductive nanofiber membrane is made by electrospinning with polyvinylidene fluoride polymer as the spinning precursor and conductive active material and coupling agent added; the conductive active material includes one or more of doped metal nanoparticles, fullerenes, graphene and carbon nanotubes. The thickness of the conductive nanofiber film is 100 nm to 5 μm, the thickness of the Ag film is 200 nm to 5 μm, and the thickness of the AgCl film is 500 nm to 10 μm. The reference electrode comprises a second conductive layer, an Ag thin film layer, an AgCl thin film layer, and a hydrogel layer sequentially stacked on an insulating substrate. The second conductive layer is a conductive Cu film deposited on the insulating substrate by electron beam evaporation vacuum deposition, with a film thickness of 50 nm to 1 μm; the Ag thin film layer has a film thickness of 200 nm to 5 μm; the AgCl thin film layer has a film thickness of 500 nm to 10 μm; and the hydrogel layer has a thickness of 0.5 to 1 μm. The hydrogel layer comprises the following components: 2-hydroxyethyl methacrylate, polyvinylpyrrolidone, 2,2-dimethoxy-2-phenylacetophenone, ethylene glycol dimethacrylate, and potassium chloride, with a weight ratio of 10:1:0.4:0.05:2.

75. The auxiliary electrode includes a third conductive layer and a Pt thin film layer stacked sequentially on an insulating substrate. The third conductive layer is a conductive Cu film deposited on the insulating substrate by electron beam evaporation vacuum deposition, with a film thickness of 50 nm to 1 μm. The Pt thin film layer has a film thickness of 200 nm to 10 μm.

2. The on-line monitoring apparatus for chloridion in earthquake precursor observation according to claim 1, characterized by, It also includes a distance sensor for measuring the distance from the chloride ion sensor to the groundwater surface; the distance sensor is connected in communication with the central controller.

3. The on-line monitoring apparatus for the earthquake precursor observation according to any one of claims 1 to 2, characterized by, It also includes a power supply module, which is used to supply power to each electrical component.

4. The online chloride ion monitoring device for earthquake precursor observation according to claim 3, characterized in that, The power supply module includes a solar photovoltaic panel and a solar controller. The solar photovoltaic panel is installed on the top of the base frame via a photovoltaic bracket, and the solar controller is installed in the control cabinet. The solar photovoltaic panel is communicatively connected to the solar controller, and the solar controller is communicatively connected to the central controller.

5. The online chloride ion monitoring device for earthquake precursor observation according to claim 4, characterized in that, The power supply module also includes a lithium battery, which is installed in the control cabinet; the solar photovoltaic panel is electrically connected to the lithium battery, and the lithium battery is electrically connected to the central controller.

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