A multi-channel acquisition and control integrated soil gas flux monitoring system and monitoring method

Abstract

The present invention provides a multi-channel acquisition and control integrated soil gas flux monitoring system and a monitoring method, which includes a controller, a sensor unit, a gas chamber unit, and a human-machine interaction interface. The controller uses an MCU, an ARM application processor, and a Linux operating system to achieve a high degree of integration of system control and data acquisition, supports a visual human-machine interaction interface, GPS time synchronization and positioning, Wi-Fi wireless communication, and remote control of the PC / mobile phone web page, and supports the arbitrary addition and combination of various gas sensors such as CO2 / O2 / CO / CH4; the user side supports functions such as monitoring parameter setting, real-time data display, and file transfer management; the system is based on the concept of in-situ monitoring, avoiding the problems of "gas barrier" and uneven air pressure in the gas chamber, and eliminating the influence of external forces such as air pumps on the gas release rate; it can be widely used for long-term continuous monitoring of soil gas flux and scientific research experiments in complex environments under unattended conditions in the wild.

Description

Technical Field

[0001] The present invention relates to the technical field of gas flux monitoring in the fields of ecology, environmental protection, mining, and safety, and particularly relates to a multi-channel acquisition and control integrated soil gas flux monitoring system and a monitoring method. Background Art

[0002] Soil is the most important core component of the terrestrial ecosystem. It is both the producer of the earth, conserving water and nutrients to maintain plant growth and supplying terrestrial organisms through the food chain; it is also the decomposer of the earth, decomposing the waste generated by the environment into small molecules such as carbon dioxide or inorganic nitrogen and inorganic phosphorus through microorganisms, and then entering the material cycle again. While regulating plant growth and material cycle, the soil continuously exchanges gases (such as CO2, nitrogen oxides, sulfides, etc.) with the atmospheric environment, maintaining the stability of the atmospheric composition. Therefore, long-term continuous monitoring of the surface soil gas flux is of great significance for aspects such as soil ecosystem assessment and determination of the deep formation state.

[0003] Based on the publicly disclosed patent "An Intelligent Soil Gas Flux Monitoring Data Acquisition System" (Patent Application No.: CN201920807690.X, Authorization Publication (Announcement) No.: CN 210037800 U), the following problems exist: 1) Single monitoring channel. In the assessment of soil greenhouse gas respiration, only one of CO2 or O2 is monitored, and the coupled effects of soil respiration and surface vegetation photosynthesis cannot be comprehensively considered, affecting the credibility of the data; in the monitoring and early warning of coal spontaneous combustion in coal seams or goafs, the index gases include CO2, CO, CH4, sulfides, etc. Synchronous data collection and mutual verification of multiple characteristic gases at the same point are required to accurately and reliably determine the combustion state, fire area range, movement direction, and movement speed. If multiple gases cannot be synchronously monitored online, the monitoring efficiency and assessment accuracy will be greatly reduced. 2) Unreasonable structural design. The monitoring system uses industrial control modules with high costs and large volumes, resulting in the necessity of separate design for the control system and the acquisition system. There are disadvantages such as complex wiring, large volume, heavy weight, large floor area, and difficulty in handling. Therefore, the monitoring work has relatively large limitations on surface conditions, sampling distance, and field conditions, and the portability and field adaptability are relatively poor. 3) Imperfect details of the gas chamber. The gas sensor unit is placed inside the soil ring. During the manual installation and disassembly of the sensor, vibrations will inevitably be caused to the precision electronic components inside the gas sensor unit, shortening its service life and affecting the monitoring accuracy. On the other hand, there is no rain-proof facility outside the air exchange port of the gas chamber, increasing the probability of the gas sensor unit inside the gas chamber being immersed in water during rainy and snowy weather, greatly reducing the service life of the sensor. 4) Inflexible function settings. The user end cannot freely set and change monitoring parameters such as the monitoring cycle number, monitoring time, and sampling interval time. If parameter changes are required, they can only be achieved through program debugging on an external computer, which cannot meet different experimental requirements and is not conducive to solving different engineering practice problems. 5) Unintelligent system operation. There is no visualization interface, and the system operation status and data collection situation cannot be grasped in real time. It can only be viewed by manually exporting files to the PC end through a USB medium. On the other hand, wireless remote control cannot be achieved, and special personnel are required to be responsible for on-site observation of the system operation status and file transfer management, making it difficult to improve the monitoring efficiency. Summary of the Invention

[0004] Aiming at the deficiencies of the above-mentioned prior art, the present invention aims to provide a soil gas flux monitoring system and monitoring method that can simultaneously examine multiple gases and environmental factors, have better portability, stronger field adaptability, more intelligent and flexible operation, and are more safe and reliable.

[0005] To achieve the above technical effects, the present invention proposes a multi-channel integrated acquisition and control soil gas flux monitoring system, including a controller, a sensor unit, a gas chamber unit, and a man-machine interaction interface;

[0006] The controller includes an MCU single-chip microcomputer and an ARM application processor. The MCU single-chip microcomputer conducts data interaction with the ARM application processor through the USART method;

[0007] The sensor unit includes a gas sensor unit, a temperature sensor, a barometric pressure sensor, and a soil moisture sensor. The gas sensor unit includes, but is not limited to, a CO2 sensor, an O2 sensor, a CO sensor, and a CH4 sensor;

[0008] The air chamber unit includes a cylinder body equipped with a sluice gate, a ventilation fan, an upper limit switch, a lower limit switch, and a soil ring. The sluice gate consists of a sealed partition board, a stepper motor, a lifting shaft, a flexible connector, and a dust-proof cover;

[0009] The human-machine interaction interface includes a display screen, an indicator light, an operation button, and a web page end;

[0010] The CO2 sensor, O2 sensor, CO sensor, CH4 sensor, temperature sensor, and soil moisture sensor respectively conduct data transmission with the MCU single-chip microcomputer through RS485 communication. The barometric pressure sensor conducts data transmission with the MCU single-chip microcomputer through IIC communication. The stepper motor is connected to the MCU single-chip microcomputer through a wire. The ventilation fan, upper limit switch, and lower limit switch are respectively connected to the MCU single-chip microcomputer through wires. The display screen, indicator light, and operation button are respectively connected to the MCU single-chip microcomputer through wires. The web page end conducts data interaction with the ARM application processor through a Wi-Fi hotspot signal;

[0011] The CO2 sensor is used to collect the CO2 concentration data in the air chamber in real time. The O2 sensor is used to collect the O2 concentration data in the air chamber in real time. The CO sensor is used to collect the CO concentration data in the air chamber in real time. The CH4 sensor is used to collect the CH4 concentration data in the air chamber in real time;

[0012] The temperature sensor is used to collect the air chamber temperature data in the air chamber in real time;

[0013] The barometric pressure sensor is used to collect the barometric pressure data in the air chamber in real time;

[0014] The soil moisture sensor is used to collect the soil temperature and soil moisture data of the ground surface around the air chamber in real time;

[0015] The MCU single-chip microcomputer includes a central processing unit, an RS485 communication unit, an IIC communication unit, a sluice gate control unit, an I / O control unit, and a GPS timing and positioning unit;

[0016] The central processing unit is used to realize the operation control of the sluice gate control unit and the I / O control unit, and is also used to process the real-time data collected by each sensor;

[0017] The RS485 communication unit is used to implement the issuance of acquisition instructions and data reading for the gas sensor unit, temperature sensor, and soil moisture sensor by the central processing unit, and to realize that the monitoring system is not restricted by the types and numbers of sensors connected by means of the modbus protocol and polling reading of each sensor;

[0018] The IIC communication unit is used to implement the issuance of acquisition instructions and data reading for the barometric pressure sensor by the central processing unit;

[0019] The gate control unit is used to control the stepping motor to lift or lower the airtight partition, control the ventilation fan to ventilate the air chamber, and is also used to control the static time of the air chamber for monitoring;

[0020] The I / O control unit is used to implement the control of the display screen, indicator lights, and operation buttons by the central processing unit;

[0021] The GPS timing and positioning unit includes a GPS receiver. The GPS receiver transmits data to the MCU single-chip microcomputer through a wire, obtains the standard clock signal and geographical location information from the satellite through the GPS receiver, and transmits the standard clock signal and standard geographical location information to the central processing unit to realize the calibration of the time of the monitoring system and the positioning of the real-time location;

[0022] The ARM application processor includes a Wi-Fi hotspot unit, a web control unit, a file management unit, and a storage unit. The ARM application processor integrates web control functions and file management functions;

[0023] The web end of the human-computer interaction interface realizes the information interaction between the web end and the ARM application processor through the Wi-Fi hotspot unit and the web control unit, realizes the functional operations of storing, searching, exporting, and deleting data in the storage unit through the file management unit, and can also realize the data interaction function with the external USB storage medium through the file management unit;

[0024] The Wi-Fi hotspot unit is used to transmit Wi-Fi hotspot remote connection signals. Taking the ARM application processor system as the server side and the mobile phone or PC as the client side, it realizes data interaction in the form of 2.4GHz wireless communication;

[0025] The web control unit is used to realize the information interaction between the web end and the ARM application processor. Through the Wi-Fi hotspot signal and the USART data interaction method, users can remotely send requests for modifying the system's function parameters or file management to the central processing unit at the web end of the human-machine interaction interface. The central processing unit can also transmit the received real-time data to the web end of the human-machine interaction interface. The function parameters of the system include the setting of the total system loop count, the setting of the number of single-loop data acquisitions, the setting of the file management password, the setting of the Wi-Fi hotspot name and connection password, and the setting of the infinite loop mode. The file management requests include the export, deletion of data files, and the query of real-time data;

[0026] The file management unit is used to realize the functions of storing, searching, exporting, and deleting data files through the Linux system integrated on the ARM application processor. When the monitoring system inserts an external USB storage medium, the file management unit first recognizes the access signal of the external storage medium and feeds back the recognized access signal to the central processing unit through USART data interaction. The central processing unit sends an instruction to control the USB detection light to turn on according to the received access signal. When the user inputs a request signal for file copying / downloading through the human-machine interaction interface, the file management unit feeds back the request signal to the central processing unit through USART data interaction. The central processing unit sends an instruction to control the data transmission light to turn on according to the received request signal and reflects the file transmission rate by the flashing frequency;

[0027] The storage unit is used to store and back up the real-time data in the Linux system, the real-time data collected by sensors, the calculated flux data, parameter setting information, geographical location information, system time information, system operation status information, indicator light status information, as well as the temporary data information during the data processing of the MCU single-chip microcomputer and the temporary data information during the data processing of the ARM application processor. The indicator light status information includes the status indicator light indicating the system operation status, the error status light indicating the system error information, the USB detection light indicating the USB detection status, and the data transmission light indicating the data transmission status. The storage unit consists of two types of storage media, namely RAM and eMMC chips.

[0028] The gate control unit is used to control the stepping motor to lift the airtight partition, and the specific description is as follows: After the central processing unit sends an air chamber opening instruction to the gate control unit, the gate control unit controls the stepping motor to start. The central processing unit records the motor running state as 1, and the stepping motor drives the airtight partition to start lifting. When the airtight partition triggers the upper limit switch, or when the stepping motor has walked the preset number of steps without triggering the upper limit switch, the gate control unit feeds back a signal to the central processing unit. The central processing unit records the motor running state as 0 and sends an instruction to the gate control unit to cut off the motor power supply through the gate control unit. The lifting operation of the airtight partition ends, and the air chamber is in a fully open state. The gate control unit outputs a signal indicating the end of the gate lifting operation and feeds it back to the central processing unit.

[0029] The gate control unit is used to control the exhaust fan to ventilate the air chamber, and the specific description is as follows: After the central processing unit receives the signal indicating the end of the gate lifting operation, it sends an instruction to control the exhaust fan to start working. The central processing unit records the running state of the exhaust fan as 1 and starts timing the working duration of the exhaust fan through the gate control unit. When the working duration of the exhaust fan reaches the preset working duration, the gate control unit outputs a signal indicating the end of ventilation and feeds it back to the central processing unit. The central processing unit records the running state of the exhaust fan as 0 and sends an instruction to cut off the power supply of the exhaust fan, and the ventilation work ends.

[0030] The gate control unit is used to control the stepping motor to lower the airtight partition, and the specific description is as follows: After the central processing unit sends an air chamber closing instruction to the gate control unit, the gate control unit controls the stepping motor to start. The central processing unit records the motor running state as 1, and the stepping motor drives the airtight partition to start lowering. When the airtight partition triggers the lower limit switch, or when the stepping motor has walked the preset number of steps without triggering the lower limit switch, the gate control unit feeds back a signal to the central processing unit. The central processing unit records the motor running state as 0 and sends an instruction to the gate control unit to cut off the motor power supply through the gate control unit. The lowering operation of the airtight partition ends, and the air chamber is in a fully airtight state. The gate control unit outputs a signal indicating the end of the gate lowering operation and feeds it back to the central processing unit.

[0031] The gate control unit is used to control the monitoring static duration of the air chamber, and the specific description is as follows: After the central processing unit receives the signal indicating the end of ventilation, it starts timing the static duration of the air chamber through the gate control unit. When the static duration of the system reaches the preset static duration, the control operation of the monitoring static duration of the air chamber ends. The gate control unit outputs a signal indicating the end of the monitoring static and feeds it back to the central processing unit.

[0032] The described central processing unit processes the collected real-time data, which is specifically described as follows: The gas sensor unit transmits the collected gas data to the central processing unit through the RS485 communication unit. The gas data includes, but is not limited to, CO2 concentration data, O2 concentration data, CO concentration data, and CH4 concentration data. The temperature sensor transmits the collected gas chamber temperature data to the central processing unit through the RS485 communication unit. The soil moisture sensor transmits the collected soil temperature and soil moisture data to the central processing unit through the RS485 communication unit. The barometric pressure sensor transmits the collected barometric pressure data to the central processing unit through the IIC communication unit. The central processing unit performs analog-to-digital conversion processing on the analog signals received from each sensor to obtain digital quantity signals corresponding to each analog signal. The analog signals include gas data, gas chamber temperature data, barometric pressure data, soil temperature, and soil moisture data. The central processing unit applies the least squares method to perform calculation processing on the time and concentration relationship of the digital quantity signals to obtain the gas concentration rising slope value and the goodness-of-fit value. Substitute the concentration rising slope value into the flux calculation formula to obtain the flux values of each collected gas data, and store the calculated flux values and each gas data, gas chamber temperature data, barometric pressure data, soil temperature, and soil moisture data in the storage unit. The goodness-of-fit value is used to evaluate the reliability of the flux value calculation.

[0033] A monitoring method using a multi-channel acquisition and control integrated soil gas flux monitoring system includes the following steps:

[0034] Step 1: Gate lifting stage: After the start of the operation cycle, start the stepper motor to drive the lifting of the sealed partition until the upper limit switch is triggered and then cut off the power supply of the stepper motor. The circular cover on the sealed partition is lifted to the upper edge of the ventilation port, and the gas chamber is in a fully open state. Before each cycle of the system, first detect the state of the gate. If the gas chamber is not in a fully open state due to foreign object blockage or an incomplete previous cycle, it is necessary to control the stepper motor to drive the sealed partition to operate until the gas chamber is in a fully open state. If the gas chamber is already in a fully open state before the start of the first cycle, the system defaults to waiting for the stepper motor to complete the preset number of steps and then directly enters the ventilation stage;

[0035] Step 2: Ventilation stage: When the gas chamber is in a fully open state, control the ventilation fan to start working and start timing the working duration of the ventilation fan. When the working duration of the ventilation fan reaches the preset working duration, the ventilation ends;

[0036] Step 3: Monitoring static stage: After the ventilation ends, to reduce the impact of ventilation disturbance on the gas monitoring in the gas chamber, set the static duration of the gas chamber through the monitoring system. The gas in the gas chamber is in a natural gushing state. When the static duration of the gas chamber reaches the preset static duration, the monitoring static stage ends;

[0037] Step 4: Diaphragm lowering stage: When the static monitoring ends, control the stepping motor to drive the sealed partition to lower until the lower limit switch is triggered, then cut off the power supply of the stepping motor. The lower edge of the circular cover plate is closely attached to the upper edge of the inner cylinder wall of the cylinder, and the air chamber is in a fully closed state;

[0038] Step 5: Measurement stage: When the air chamber is in a fully closed state, control each sensor to start real-time data acquisition work according to the preset sampling time interval. The real-time data collected by each sensor is stored in the storage unit after being processed by the central processing unit. When the real-time data stored within each cycle reaches the preset total number of samples, the system stops recording data, and one cycle of monitoring ends. The monitoring system enters the next cycle of diaphragm lifting stage.

[0039] The beneficial effects of the present invention are:

[0040] 1) Increase in monitoring channels: Through the self-developed application program control and hardware function expansion, the present invention can realize synchronous online monitoring of multiple gases. In addition to the common CO2, temperature, and humidity sensors in soil gas flux, multiple monitoring channels such as CO, CH4, O2, and air pressure are added, and support the arbitrary addition, change, and combination of multiple gases, plug-and-play, convenient and fast. For example, in the assessment of soil greenhouse gas respiration, the concentration and flux changes of CO2 and O2 gases can be simultaneously investigated, the coupling effects of soil respiration and surface vegetation photosynthesis can be comprehensively considered, and the synergistic effect between the two can be evaluated, enhancing the credibility and persuasiveness of the data; in the monitoring and early warning of coal spontaneous combustion in coal seams or goafs, the concentration and flux data of multiple index gases such as CO2, CO, CH4, and sulfides are collected synchronously at the same point, improving the reliability and accuracy of the assessment of the combustion state of underground coal fires, the delineation of the fire area, and the prediction of the moving direction and speed.

[0041] 2) Integration of control and acquisition: Different from the split design of traditional measurement and acquisition systems, the present invention integrates the control system and the acquisition system into one, fully improving the portability and field adaptability.

[0042] 3) Upgrade of the operating system: Replace the industrial control module with high cost and large volume, and adopt the self-developed control system of low-power MCU + ARM, running the Linux operating system, with stable operation, fast operation, high fault tolerance, and low cost.

[0043] 4) Client operation permissions: Different from traditional monitoring systems where users cannot arbitrarily set and change monitoring parameters, and parameter changes can only be achieved through external computer program debugging. The present invention sets a display screen and operation buttons, and functions such as setting the number of monitoring cycle periods, time and password settings, real-time display of monitoring data, viewing and detecting operating status, and file transmission and management can be realized through the system's human-computer interaction interface.

[0044] 5) Wireless operation can be performed remotely: The present invention realizes Wi-Fi hotspot access, and mobile phones or PCs can communicate with the system via Wi-Fi. The web-based control interface is developed, and the same display functions, parameter settings and system controls as the physical operation interface can be easily realized on the web-based side. There is no need for manual field observation of the system operation status and file transfer management operations, and the monitoring efficiency has been greatly improved, which is suitable for unmanned long-term continuous monitoring work in the field.

[0045] 6) Detailed modification of hardware: The present invention centrally arranges all gas sensors in the air chamber, optimizes the spatial layout of the sensors, simplifies the function of the soil ring, cancels the sensors and their fixing rings in the soil ring, and eliminates the need for manual installation and removal of sensors, thereby avoiding vibration interference to the precision electronic components on the upper part of the air chamber. A rainproof cap is added to the air exchange port to improve the monitoring adaptability to extreme weather such as rain, snow, wind and sand. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a functional schematic diagram of the multi-channel integrated soil gas flux monitoring system of the present invention;

[0047] Figure 2 It is a schematic diagram of the structure of the multi-channel integrated soil gas flux monitoring system of the present invention;

[0048] Figure 3 It is a cross-sectional view of the structure AA in the present invention; (a) is the air chamber closed state, (b) is the air chamber open state;

[0049] Figure 4 It is a cross-sectional view of the structure BB in the present invention; (a) is the air chamber closed state, (b) is the air chamber open state;

[0050] Figure 5 It is a schematic diagram of the human-computer interaction interface of the multi-channel integrated soil gas flux monitoring system of the present invention;

[0051] Figure 6 This is a control timing diagram of the multi-channel integrated soil gas flux monitoring system of the present invention;

[0052] Figure 7 It is the electrical wiring diagram of the multi-channel integrated soil gas flux monitoring system of the present invention;

[0053] In the figure, 1 - Controller, 1 - 1 - Power interface, 1 - 2 - Soil moisture sensor interface, 1 - 3 - USB interface, 2 - Cylinder, 2 - 1 - Ventilation opening, 2 - 2 - Filter opening, 2 - 3 - Cable trough, 2 - 4 - Guide groove, 2 - 5 - Limit card slot, 2 - 6 - 1 - Front sensor fixing plate, 2 - 6 - 2 - Rear sensor fixing plate, 2 - 7 - 1 - Front sensor socket plate, 2 - 7 - 2 - Rear sensor socket plate, 2 - 8 - Rainproof cap for ventilation opening, 3 - Soil ring, 3 - 1 - Limit support ring, 3 - 2 - Ventilation hole, 4 - 1 - CO2 sensor, 4 - 2 - O2 sensor, 4 - 3 - CO sensor, 4 - 4 - CH4 sensor, 4 - 5 - Temperature sensor, 4 - 6 - Air pressure sensor, 4 - 7 - Soil moisture sensor, 5 - Gate plate, 5 - 1 - Circular cover plate, 5 - 2 - Flow guide partition, 5 - 3 - Lifting shaft, 5 - 4 - Flexible connector, 5 - 5 - Stepper motor, 5 - 6 - Dust cover, 6 - 1 - MCU single - chip microcomputer, 6 - 2 - ARM application processor, 7 - 1 - Exhaust fan, 7 - 2 - Exhaust fan fixing plate, 8 - 1 - Upper limit switch, 8 - 2 - Lower limit switch, 9 - Human - machine interface, 9 - 1 - Display screen, 9 - 2 - Indicator lights, 9 - 2 - 1 - Status indicator light, 9 - 2 - 2 - Error status light, 9 - 2 - 3 - USB detection light, 9 - 2 - 4 - Data transmission light, 9 - 3 - Operation buttons, 9 - 3 - 1 - Power on / off button, 9 - 3 - 2 - Confirmation button, 9 - 3 - 3 - Return button, 9 - 3 - 4 - Direction selection button, 9 - 4 - Web - based terminal; 10 - External power supply device; Detailed implementation mode

[0054] The following further describes the invention in conjunction with the accompanying drawings and specific implementation examples. The following preferred implementation modes are merely exemplary, and the present invention includes but is not limited to the following implementation modes.

[0055] As Figure 1-2 shown, a multi - channel acquisition - control integrated soil gas flux monitoring system includes a controller 1, a sensor unit, a gas chamber unit, and a human - machine interface 9;

[0056] The controller 1 includes an MCU single - chip microcomputer 6 - 1 and an ARM application processor 6 - 2. The MCU single - chip microcomputer 6 - 1 performs data interaction with the ARM application processor 6 - 2 through the USART method;

[0057] The sensor unit includes a gas sensor unit, a temperature sensor 4 - 5, an air pressure sensor 4 - 6, and a soil moisture sensor 4 - 7. The gas sensor unit includes but is not limited to a CO2 sensor 4 - 1, an O2 sensor 4 - 2, a CO sensor 4 - 3, and a CH4 sensor 4 - 4. Each sensor is installed in a symmetric installation manner;

[0058] The air chamber unit includes a cylinder body 2 equipped with a shutter 5, a ventilation fan 7-1, an upper limit switch 8-1, a lower limit switch 8-2, and a soil ring 3. The shutter 5 is composed of a sealed partition board, a stepping motor 5-5, a lifting shaft 5-3, a flexible connecting piece 5-4, and a dust cover 5-6;

[0059] The human-machine interaction interface 9 includes a display screen 9-1, an indicator light 9-2, operation buttons 9-3, and a web terminal 9-4;

[0060] The CO2 sensor 4-1, O2 sensor 4-2, CO sensor 4-3, CH4 sensor 4-4, temperature sensor 4-5, and soil moisture sensor 4-7 respectively perform data transmission with the MCU single-chip microcomputer 6-1 through RS485 communication. The air pressure sensor 4-6 performs data transmission with the MCU single-chip microcomputer 6-1 through IIC communication. The stepping motor 5-5 is connected to the MCU single-chip microcomputer 6-1 through a wire. The ventilation fan 7-1, upper limit switch 8-1, and lower limit switch 8-2 are respectively connected to the MCU single-chip microcomputer 6-1 through wires. The display screen 9-1, indicator light 9-2, and operation buttons 9-3 are respectively connected to the MCU single-chip microcomputer 6-1 through wires. The web terminal 9-4 performs data interaction with the ARM application processor 6-2 through a Wi-Fi hotspot signal;

[0061] The CO2 sensor 4-1 is used to collect CO2 concentration data in the air chamber in real time. The O2 sensor 4-2 is used to collect O2 concentration data in the air chamber in real time. The CO sensor 4-3 is used to collect CO concentration data in the air chamber in real time. The CH4 sensor 4-4 is used to collect CH4 concentration data in the air chamber in real time;

[0062] The temperature sensor 4-5 is used to collect air chamber temperature data in the air chamber in real time;

[0063] The air pressure sensor 4-6 is used to collect air pressure data in the air chamber in real time;

[0064] The soil moisture sensor 4-7 is used to collect soil temperature and soil moisture data of the surface around the air chamber in real time;

[0065] The MCU single-chip microcomputer 6-1 includes a central processing unit, an RS485 communication unit, an IIC communication unit, a shutter control unit, an I / O control unit, and a GPS timing and positioning unit;

[0066] After the system is powered on, the user sets each function parameter through the human-machine interface 9 and issues a cyclic operation start command. The central processing unit controls the gas sensor unit, temperature sensor 4-5, and soil moisture sensor 4-7 to start data acquisition work through the RS485 communication unit, and controls the air pressure sensor 4-6 to start data acquisition work through the IIC communication unit. The cyclic operation starts. The central processing unit automatically issues a gas chamber opening command, and controls the stepping motor 5-5 through the gate control unit to lift the sealed partition. When the lifting of the sealed partition is completed, the gate control unit outputs a signal indicating the end of the lifting operation of the gate 5 and feeds it back to the central processing unit. The central processing unit records the gas chamber status as 1, indicating that the gas chamber is in a fully open state. After receiving the signal indicating the end of the lifting operation of the gate 5, the central processing unit instructs the gate control unit to control the operation of the ventilation fan 7-1. When the preset working duration of the ventilation fan 7-1 is reached, the ventilation ends. The gate control unit outputs a signal indicating the end of the ventilation and feeds it back to the central processing unit. When the central processing unit receives the signal indicating the end of the ventilation, it instructs the gate control unit to control the monitoring and static duration of the gas chamber, meeting the requirement of allowing the gas in the gas chamber to stand still for a certain time to eliminate the disturbance effect on the soil gas gushing during the ventilation process. When the preset static duration is reached, the monitoring and static ends. The gate control unit outputs a signal indicating the end of the monitoring and static and feeds it back to the central processing unit. After receiving the signal indicating the end of the monitoring and static, the central processing unit controls the stepping motor 5-5 through the gate control unit to lower the sealed partition. When the lowering of the sealed partition is completed, the gate control unit outputs a signal indicating the end of the lowering operation of the gate 5 and feeds it back to the central processing unit. The central processing unit records the gas chamber status as 0, indicating that the gas chamber is in a fully closed state. After receiving the signal indicating the end of the lowering operation of the gate 5, the central processing unit controls the status indicator light 9-2-1 to turn on through the I / O control unit. The central processing unit starts to record the data collected by the gas sensor unit, temperature sensor 4-5, air pressure sensor 4-6, and soil moisture sensor 4-7, and stores them in the storage unit on the ARM application processor 6-2 through the USART method. When the real-time data stored in each cycle reaches the preset total number of samples, the central processing unit stops recording the data collected by each sensor. Thus, a cycle monitoring period ends. After a cycle period ends, the monitoring system enters the gas chamber opening stage of the next cycle. The control timing diagram is as Figure 6 shown, and the programming software used is keil uVision5, and the programming languages are C and C++ languages;

[0067] The central processing unit is used to implement the operation control of the gate control unit and the I / O control unit, and the central processing unit is also used to process the real-time data collected by each sensor;

[0068] The RS485 communication unit is used to implement the issuance of acquisition instructions and data reading by the central processing unit for the gas sensor unit, temperature sensor 4-5, and soil moisture sensor 4-7, and realizes that the monitoring system does not limit the types and numbers of sensors connected by means of the modbus protocol and polling reading of each sensor;

[0069] The IIC communication unit is used to implement the issuance of acquisition instructions and data reading by the central processing unit for the barometric pressure sensor 4-6;

[0070] The gate control unit is used to control the stepping motor 5-5 to lift or lower the airtight partition, control the ventilation fan 7-1 to ventilate the air chamber, and is also used to control the static time of the air chamber for monitoring;

[0071] The I / O control unit is used to implement the control of the central processing unit over the display screen 9-1, indicator light 9-2, and operation button 9-3;

[0072] The GPS timing and positioning unit includes a GPS receiver. The GPS receiver transmits data to the MCU single-chip microcomputer 6-1 through a wire, obtains the standard clock signal and geographical location information from the satellite through the GPS receiver, and transmits the standard clock signal and standard geographical location information to the central processing unit to realize the calibration of the time of the monitoring system and the positioning of the real-time location;

[0073] The ARM application processor 6-2 includes a Wi-Fi hotspot unit, a web control unit, a file management unit, and a storage unit. The ARM application processor 6-2 integrates web control functions and file management functions;

[0074] The web end 9-4 of the human-computer interaction interface 9 realizes the information interaction between the web end 9-4 and the ARM application processor 6-2 through the Wi-Fi hotspot unit and the web control unit, realizes the functional operations of storing, searching, exporting, and deleting data in the storage unit through the file management unit, and can also realize the data interaction function with the external USB storage medium through the file management unit;

[0075] The Wi-Fi hotspot unit is used to transmit Wi-Fi hotspot remote connection signals. Taking the ARM application processor 6-2 system as the server side and the mobile phone or PC as the client side, it realizes data interaction in the form of 2.4GHz wireless communication;

[0076] The web page control unit is used to realize the information interaction between the web page end 9-4 and the ARM application processor 6-2. Through the Wi-Fi hotspot signal and the USART data interaction method, users can remotely send requests for modifying the system's function parameters or file management to the central processing unit at the web page end 9-4 of the human-machine interaction interface 9. The central processing unit can also transmit the received real-time data to the web page end 9-4 of the human-machine interaction interface 9. The function parameters of the system include the setting of the total system loop count, the setting of the number of data acquisitions per single loop, the setting of the file management password, the setting of the Wi-Fi hotspot name and connection password, and the setting of the infinite loop mode. The file management requests include the export, deletion of data files, and the query of real-time data;

[0077] The file management unit is used to realize the functions of storing, searching, exporting, and deleting data files through the Linux system integrated on the ARM application processor 6-2. When the monitoring system inserts an external USB storage medium, the file management unit first recognizes the access signal of the external storage medium and feeds back the recognized access signal to the central processing unit through USART data interaction. The central processing unit sends an instruction to control the USB detection light 9-2-3 to turn on according to the received access signal. When the user inputs a request signal for file copying / downloading through the human-machine interaction interface 9, the file management unit feeds back the request signal to the central processing unit through USART data interaction. The central processing unit sends an instruction to control the data transmission light 9-2-4 to turn on according to the received request signal, and uses the flashing frequency to reflect the file transmission rate;

[0078] The storage unit consists of two types of storage media, RAM + eMMC chips, and is used to store and back up the real-time data in the Linux system, the real-time data collected by sensors, the calculated flux data, the parameter setting information, the geographical location information, the system time information, the system operation status information, the status information of the indicator light 9-2, as well as the temporary data information during the data processing of the MCU microcontroller 6-1 and the temporary data information during the data processing of the ARM application processor 6-2. The status information of the indicator light 9-2 includes the status indicator light 9-2-1 indicating the system operation status, the error status light 9-2-2 indicating the system error information, the USB detection light 9-2-3 indicating the USB detection status, and the data transmission light 9-2-4 indicating the data transmission status.

[0079] The gate control unit is used to control the stepping motor 5-5 to lift the airtight partition, and the specific description is as follows: After the central processing unit sends an air chamber opening instruction to the gate control unit, the gate control unit controls the stepping motor 5-5 to start. The central processing unit records the motor running state as 1, and the stepping motor 5-5 drives the airtight partition to start lifting. When the airtight partition triggers the upper limit switch 8-1, or when the stepping motor 5-5 has walked the preset number of steps without triggering the upper limit switch 8-1, the gate control unit feeds back a signal to the central processing unit. The central processing unit records the motor running state as 0, and sends an instruction to the gate control unit to cut off the motor power supply through the gate control unit. The lifting operation of the airtight partition ends, and the air chamber is in a fully open state. The gate control unit outputs a signal indicating the end of the lifting operation of the gate 5 and feeds it back to the central processing unit.

[0080] The gate control unit is used to control the ventilation fan 7-1 to ventilate the air chamber, and the specific description is as follows: After the central processing unit receives the signal indicating the end of the lifting operation of the gate 5, it sends an instruction to control the ventilation fan 7-1 to start working. The central processing unit records the running state of the ventilation fan 7-1 as 1, and starts timing the working duration of the ventilation fan 7-1 through the gate control unit. When the working duration of the ventilation fan 7-1 reaches the preset working duration, the gate control unit outputs a signal indicating the end of ventilation and feeds it back to the central processing unit. The central processing unit records the running state of the ventilation fan 7-1 as 0, and sends an instruction to cut off the power supply of the ventilation fan 7-1, and the ventilation work ends.

[0081] The gate control unit is used to control the stepping motor 5-5 to lower the airtight partition, and the specific description is as follows: After the central processing unit sends an air chamber closing instruction to the gate control unit, the gate control unit controls the stepping motor 5-5 to start. The central processing unit records the motor running state as 1, and the stepping motor 5-5 drives the airtight partition to start lowering. When the airtight partition triggers the lower limit switch 8-2, or when the stepping motor 5-5 has walked the preset number of steps without triggering the lower limit switch 8-2, the gate control unit feeds back a signal to the central processing unit. The central processing unit records the motor running state as 0, and sends an instruction to the gate control unit to cut off the motor power supply through the gate control unit. The lowering operation of the airtight partition ends, and the air chamber is in a fully airtight state. The gate control unit outputs a signal indicating the end of the lowering operation of the gate 5 and feeds it back to the central processing unit.

[0082] The gate control unit is used to control the static time of the gas chamber monitoring, and the specific description is as follows: After the central processing unit receives the signal indicating the end of air exchange, it starts timing the static time of the gas chamber through the gate control unit. When the static time of the system reaches the preset static time, the control operation of the static time of the gas chamber monitoring ends. A signal indicating the end of static monitoring is output through the gate control unit and fed back to the central processing unit.

[0083] The central processing unit processes the collected real-time data, and the specific description is as follows: The gas sensor unit transmits the collected gas data to the central processing unit through the RS485 communication unit. The gas data includes but is not limited to CO2 concentration data, O2 concentration data, CO concentration data, CH4 concentration data. The temperature sensor 4-5 transmits the collected gas chamber temperature data to the central processing unit through the RS485 communication unit. The soil moisture sensor 4-7 transmits the collected soil temperature and soil moisture data to the central processing unit through the RS485 communication unit. The barometric pressure sensor 4-6 transmits the collected barometric pressure data to the central processing unit through the IIC communication unit. The central processing unit performs analog-to-digital conversion processing on the analog signals received from each sensor to obtain digital quantity signals corresponding to each analog signal. The analog signals include gas data, gas chamber temperature data, barometric pressure data, soil temperature and soil moisture data. The central processing unit applies the least squares method to perform calculation processing on the time and concentration relationship of the digital quantity signals to obtain the gas concentration rising slope value and the goodness-of-fit value. The concentration rising slope value is substituted into the flux calculation formula to obtain the flux values of each collected gas data, and the calculated flux values and each gas data, gas chamber temperature data, barometric pressure data, soil temperature and soil moisture data are stored in the storage unit. The goodness-of-fit value is used to evaluate the reliability of the flux value calculation.

[0084] The system structure diagram in this embodiment is as Figure 2 shown, and the electrical wiring Figure 7 is shown, mainly including a controller 1, a cylinder 2, a soil ring 3 and sensors; the cylinder 2 and the soil ring 3 form a gas chamber together; the cylinder 2 and the controller 1 are of an integrated structure and are integrally installed on the upper part of the soil ring 3; the sensors include a CO2 sensor 4-1, an O2 sensor 4-2, a CO sensor 4-3, a CH4 sensor 4-4, a temperature sensor 4-5, a barometric pressure sensor 4-6 and a soil moisture sensor 4-7, etc.

[0085] In this embodiment, the models of the main electrical components involved are as follows: the MCU single-chip microcomputer is STM32F103ZE, the ARM application processor is RaspberryPi 3b+, the RAM is W9825G6KH, the eMMC chip is SDIN7DP2-32G, the CO2 sensor is HL-1S001, the O2 sensor is HL-1S007, the CO sensor is HL-1S006, the CH4 sensor is HL-1S005, the temperature sensor is HL-1S002, the barometric pressure sensor is HL-1S004, and the soil moisture sensor is HL-1S003.

[0086] The controller 1 and the cylinder 2 of the monitoring system are integrally installed on the soil ring 3. The upper diameter of the soil ring 3 is slightly smaller than that of the cylinder 2. During installation, it is embedded in the lower part of the cylinder 2, and the sealing connection with the cylinder 2 is realized through the limit card slot 2-5 of the cylinder 2. The cylinder 2 and the soil ring 3 are assembled into an air chamber; the soil moisture sensor 4-7 is inserted into the surface soil around the air chamber and is connected to the soil moisture sensor interface 1-2 of the controller 1 through an aviation plug, which is used to measure the temperature and moisture of the soil; on both sides of the upper cylinder wall of the cylinder 2, ventilation openings 2-1 are opened for gas exchange in the air chamber; a detachable rain cap 2-8 is provided outside the ventilation opening 2-1; a filter opening 2-2 is opened on the cylinder wall of the cylinder 2 to filter out the sand and gravel particles that may be involved under field working conditions; a wire groove 2-3 is opened on the cylinder wall of the cylinder 2 as the connection channel for each wiring and the controller 1; a limit support ring 3-1 is provided on the outer wall of the soil ring 3 to limit the pressing depth of the soil ring 3 and assist in supporting the upper structure; several ventilation holes 3-2 are opened on the limit support ring 3-1 to ensure the free diffusion state of soil gas at the soil-atmosphere two-phase interface; the monitoring system supports wireless control and data transmission of mobile phones and PC web pages 9-4.

[0087] As Figure 3 As shown in (a) below, a power supply interface 1-1, a soil moisture sensor interface 1-2, and a USB interface 1-3 are opened on the outside of the controller 1. The power supply interface 1-1 is connected to an external power supply device 10 (12V DC power supply) to supply power to the whole system. The interface is waterproof, ensuring simple, safe, and reliable operation under the premise of ensuring field adaptability; the soil moisture sensor interface 1-2 uses a waterproof aviation plug to connect the soil moisture sensor 4-7 to the control system, realizing waterproof and dustproof while ensuring stable and reliable collection data transmission; the USB interface 1-3 is connected to an external USB storage medium for exporting the data collected by the system. The interface is provided with a waterproof and dustproof cap to isolate rainwater infiltration and dust erosion. Preferably, the protection level should adopt the IP67 standard.

[0088] The middle part of the cylinder 2 is a double-layer structure of an inner cylinder and an outer cylinder. A guide groove 2-4 is opened on the inner cylinder wall surface; a limit card slot 2-5 is formed at the connection of the inner and outer cylinder walls, and a limit card slot sealing rubber ring is attached to the limit card slot 2-5 to realize the sealing connection with the soil ring 3.

[0089] Inside the cylinder body 2, a gate plate 5 is installed. The gate plate 5 includes a sealed partition plate, a lifting shaft 5-3, a flexible connecting piece 5-4, a stepping motor 5-5, and a dust-proof cover 5-6. The sealed partition plate is an integrally formed component consisting of a circular cover plate 5-1 and a rectangular diversion partition plate 5-2. The diameter of the circular cover plate 5-1 is between the inner and outer cylinder diameters. A groove is provided at the lower edge of the circular cover plate 5-1, and a sealing rubber ring is installed in the groove to achieve sealing with the inner cylinder. The lifting shaft 5-3 is embedded in the center of the sealed partition plate, and the other end of the lifting shaft 5-3 is connected to the stepping motor 5-5 through the flexible connecting piece 5-4. The stepping motor 5-5 drives the lifting shaft 5-3 to rotate, causing the sealed partition plate to slowly move axially up and down along the guide groove 2-4 on the inner cylinder wall to achieve the opening and closing of the air chamber. The dust-proof cover 5-6 is installed outside the lifting shaft 5-3, with the upper part fixed to the lower surface of the controller 1 and the lower part fixed to the upper surface of the circular cover plate 5-1, which is used to prevent dust, fine sand, etc. from adhering inside the lifting shaft 5-3 and affecting its smooth operation. The dust-proof cover 5-6 is made of a flexible, thin, and transparent material, which can clearly observe the connection stability and operation of the lifting shaft 5-3.

[0090] As Figure 3 Shown in (b) in the figure, inside the controller 1, there are an MCU single-chip microcomputer 6-1 and an ARM application processor 6-2, and the two perform data interaction through the USART method. The air pressure sensor 4-6 is installed inside the controller 1 and is directly connected to the corresponding socket of the controller 1, which is used to measure the change of the ambient atmospheric pressure.

[0091] Two sensor fixing plates 2-6-1 and 2-6-2 are arranged at the middle partition of the inner cylinder wall of the cylinder body 2. The upper ends of the sensor fixing plates are at the same height as the ventilation fan fixing plate 7-2, and the lower ends are at the same height as the lower edge of the cylinder body 2. Two sensor socket plates 2-7-1 and 2-7-2 are respectively installed on them. The CO2 sensor 4-1, the O2 sensor 4-2, and the temperature sensor 4-5 are installed on the sensor socket plate 2-7-1.

[0092] As Figure 4As shown in (a), when the gate 5 is in the fully closed state, the lower edge of the circular cover plate 5-1 is embedded in the groove along the inner wall of the cylinder body 2; on one side of the upper part of the inner wall of the cylinder body 2, a semi-circular ventilation fan fixing plate 7-2 is provided, and the ventilation fan 7-1 is fixed on its lower surface. Through program setting, it works during the ventilation stage of each cycle and stops during the rest of the stages, which is used to promote gas exchange in the air chamber; when the sealed partition descends, the diversion partition 5-2 extends into the gap between the two sensor fixing plates 2-6-1 and 2-6-2, and cooperates with the ventilation fan 7-1 during the ventilation process to form an air flow channel, avoiding turbulence, vortex and airway "short circuit", and ensuring sufficient ventilation in the air chamber; the ventilation fan fixing plate 7-2, the sensor fixing plates 2-6-1 and 2-6-2 are all integrally formed structures with the inner wall of the cylinder body; the CO sensor 4-3 and the CH4 sensor 4-4 are installed on the sensor socket board 2-7-2.

[0093] As Figure 4 shown in (b), when the gate 5 is in the fully open state, the lower edge position of the circular cover plate 5-1 is lifted to the upper edge of the ventilation opening 2-1; upper limit switches 8-1 and lower limit switches 8-2 are respectively provided at the upper and lower limit positions of the operation of the circular cover plate 5-1. When the circular cover plate 5-1 runs to the limit position, it triggers the upper limit switch 8-1 or the lower limit switch 8-2 to act, thereby cutting off the power supply and the sealed partition stops running; the wiring of the ventilation fan 7-1, the upper limit switch 8-1 and the lower limit switch 8-2 respectively passes through the wire passing holes on the wall of the cylinder body 2 and is connected to the corresponding sockets in the controller 1 through the wire groove 2-3 provided on the wall of the cylinder body 2; each sensor in the air chamber is inserted into the sensor socket board, and after the wiring of the socket board is integrated, it passes through the wire passing holes on the wall of the cylinder body 2 and is connected to the corresponding sockets in the controller 1 through the wire groove 2-3 provided on the wall of the cylinder body.

[0094] As Figure 5 shown, the human-machine interaction interface 9 is composed of a display screen 9-1, indicator lights 9-2, operation buttons 9-3 and a web end 9-4; the display screen 9-1 is connected to the MCU single-chip microcomputer 6-1 in the controller 1 through an I / O interface, and uses a dot matrix low-temperature-resistant screen, which can meet outdoor requirements; the indicator lights 9-2 include a status indicator light (State) 9-2-1, an error status light (Error) 9-2-2, a USB detection light (USB) 9-2-3, a data transmission light (Copy) 9-2-4, etc., and are respectively connected to the MCU single-chip microcomputer 6-1 in the controller 1 through an I / O interface; the operation buttons 9-3 include a power on / off key 9-3-1, a confirmation key 9-3-2, a return key 9-3-3 and a direction selection key 9-3-4, etc., and are respectively connected to the MCU single-chip microcomputer 6-1 in the controller 1 through an I / O interface; through the human-machine interaction interface 9, functions such as monitoring parameter setting, time and password setting, real-time display of monitoring data, viewing and detection of operating status, file transmission and management can be realized.

[0095] The monitoring method using the above monitoring system includes the following steps:

[0096] Step 1: The lifting stage of the gate plate 5: After the start of the operation cycle, start the stepping motor 5-5 to drive the lifting of the airtight partition until the upper limit switch 8-1 is triggered and then cut off the power supply of the stepping motor 5-5. The circular cover plate 5-1 on the airtight partition is lifted to the upper edge of the ventilation port 2-1, and the air chamber is in a fully open state. Before each cycle of the system, first detect the state of the gate plate 5. If the air chamber is not in a fully open state due to foreign object blockage or the previous cycle not being completed, then control the stepping motor 5-5 to drive the airtight partition to operate until the air chamber is in a fully open state. If the air chamber is in a fully open state before the start of the first cycle, then the system defaults to waiting for the stepping motor 5-5 to complete the preset number of steps and then directly enters the ventilation stage;

[0097] Step 2: The ventilation stage: When the air chamber is in a fully open state, control the ventilation fan 7-1 to start working and start timing the working duration of the ventilation fan 7-1. When the working duration of the ventilation fan 7-1 reaches the preset working duration, the ventilation ends;

[0098] Step 3: The monitoring and static stage: After the ventilation ends, to reduce the impact of ventilation disturbance on the gas monitoring in the air chamber, set the static duration of the air chamber through the monitoring system. The gas in the air chamber is in a natural gushing state. When the static duration of the air chamber reaches the preset static duration, the monitoring and static stage ends;

[0099] Step 4: The lowering stage of the gate plate 5: When the monitoring and static stage ends, control the stepping motor 5-5 to drive the airtight partition to lower until the lower limit switch 8-2 is triggered and then cut off the power supply of the stepping motor 5-5. The lower edge position of the circular cover plate 5-1 is tightly attached to the upper edge of the inner cylinder wall of the cylinder body 2, and the air chamber is in a fully closed state;

[0100] Step 5: The measurement stage: When the air chamber is in a fully closed state, control each sensor to start real-time data acquisition work at the preset sampling time interval. The real-time data collected by each sensor is stored in the storage unit after being processed by the central processing unit. When the real-time data stored in each cycle reaches the preset total number of samples, the system stops recording data, and one cycle of monitoring ends. The monitoring system enters the next cycle of the lifting stage of the gate plate 5, and the control timing is as Figure 6 shown.

[0101] A) Install the soil ring 3: It is recommended to select a location with a relatively high terrain and a flat ground as the measurement point, and clean the floating stones, loose soil and sundries on the ground surface. Vertically press the soil ring 3 into the soil until the limit support ring 3-1 is tightly attached to the ground; to ensure the stability of the upper air chamber and the accuracy of gas flux calculation, the pressed soil ring 3 is required to keep the plane as horizontal as possible, and to avoid the influence of soil disturbance, it is advisable to wait for 1-2 hours after the soil ring 3 is driven in before conducting data measurement.

[0102] B) Install the controller 1 and the cylinder 2: Embed the soil ring 3 into the cylinder 2, and realize the connection and sealing with the soil ring 3 through the limit card slot 2-5. Flatten it to make the axes of the controller 1, the cylinder 2 and the soil ring 3 coincide and be perpendicular to the ground.

[0103] C) Install the soil moisture sensor 4-7: Connect the interface end of the soil moisture sensor 4-7 to the soil moisture sensor interface 1-2 through an aviation plug, and insert the measuring end into the soil around the soil ring 3 with an insertion depth of not less than 3 cm for measuring the temperature and moisture of the soil.

[0104] D) Connect the power cord: Connect the power cord to the external power supply device 10 and the power interface 1-1;

[0105] E) Turn on and run: Select the power on / off key 9-3-1 on the man-machine interface 9 to turn on the machine, and the instrument display screen 9-1 is turned on. The GPS positioning and time synchronization function automatically locates and calibrates the system time. The system starts the self-check program to detect the feedback signals of each sensor. If there is no feedback, the corresponding fault information will be displayed on the display screen 9-1 of the man-machine interface 9. After the system is turned on, the sensor is immediately turned on and preheated. During the entire monitoring process, the system collects sensor data according to the set program within the cycle to achieve the stability of the sensor working state and the accuracy of the monitoring data.

[0106] F) Wireless connection: Search for the instrument Wi-Fi on the web page 9-4 (mobile phone or PC), connect through the password, and enter the corresponding website address in the browser to enter the management interface of the system web page 9-4.

[0107] G) System settings: The function parameters can be set through the operation buttons 9-3 on the man-machine interface 9 or the management interface of the web page 9-4, including the number of data collected in a single cycle, the total number of cycles, the infinite loop mode (only measure the concentration, not calculate the flux), etc.

[0108] H) Start running: Click the Run or Start command through the operation buttons 9-3 on the man-machine interface 9 or the management interface of the web page 9-4, and the system starts the monitoring work, and the status indicator light (State) 9-2-1 starts to flash.

[0109] I) Monitoring cycle: The system starts to execute the monitoring cycle program, and the monitoring cycle begins.

[0110] J) Real-time status viewing: The monitoring status of the instrument can be viewed in real time through the display screen 9-1, indicator light 9-2 on the human-machine interface 9, or the management interface of the web page 9-4. The monitoring status that can be displayed in real time includes the monitoring data of each sensor (gas concentration, temperature, moisture, air pressure value), the flux value calculated by the adjacent cycle, the operating status (normal, faulty, data transmission in progress, etc.), the completed monitoring time, and the number of completed cycles / total number of cycles, etc.

[0111] K) End of operation:

[0112] Automatic end: If the number of cycles set by the system is completed, the operating status displayed on the display screen 9-1 of the human-machine interface 9 and the web page 9-4 is both Finish, and the system automatically stops working;

[0113] Manual end: If the number of cycles set by the system is not completed and it is necessary to end the monitoring work in advance according to the actual situation, then the operation button 9-3 of the human-machine interface 9 or the web page 9-4 can be used to click the Stop command to manually stop the system operation.

[0114] L) Data transmission:

[0115] USB transmission: Insert the USB storage medium into the USB interface 1-3. At this time, the USB detection light 9-2-3 is always on. Through the operation button 9-3 of the human-machine interface 9 in cooperation with the display screen 9-1, enter the start and end times of the data to be copied, click the Copy command, and after entering the password, start exporting the data. At this time, the data transmission light 9-2-4 flashes quickly, and when the data transmission light 9-2-4 goes out, the data transmission ends, and the data is directly stored in the USB main directory;

[0116] Wireless transmission: Enter the web page 9-4 of the human-machine interface 9, enter the start and end times of the data to be copied, click the Download command, and after entering the password, select the storage path to start exporting the data, and the data is directly stored in the mobile phone or PC.

[0117] M) Turn off the power switch 9-3-1, disconnect the external power connection, and remove the power cord.

[0118] N) Remove the soil moisture sensor 4-7.

[0119] O) Remove the gas chamber: Disassemble the controller 1, the cylinder 2, and the soil ring 3 from top to bottom in sequence, and put them into the shock-absorbing storage box, and the monitoring work ends.

[0120] The above are only specific embodiments of the present invention and are not intended to limit the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, all other embodiments obtained without creative efforts, or equivalent transformations, several improvements, changes, combinations or embellishments made without departing from the principle of this application, all fall within the scope of protection of this patent.

Claims

1. A multi-channel acquisition and control integrated soil gas flux monitoring system, characterized in that, It includes a controller, a sensor unit, a gas chamber unit, and a human-machine interaction interface; The controller includes an MCU single-chip microcomputer and an ARM application processor, and the MCU single-chip microcomputer conducts data interaction with the ARM application processor through the USART method; The sensor unit includes a gas sensor unit, a temperature sensor, a barometric pressure sensor, and a soil moisture sensor. The gas sensor unit includes, but is not limited to, a CO2 sensor, an O2 sensor, a CO sensor, and a CH4 sensor; The gas chamber unit includes a cylinder body equipped with a shutter, a ventilation fan, an upper limit switch, a lower limit switch, and a soil ring. The shutter consists of a sealed partition board, a stepping motor, a lifting shaft, a flexible connecting piece, and a dust-proof cover; The middle part of the cylinder body is a double-layer structure of an inner cylinder and an outer cylinder. Guide grooves are provided on the inner wall surface of the inner cylinder; a limit card slot is formed at the connection of the inner and outer cylinder walls, and a limit card slot sealing rubber ring is attached to the limit card slot for realizing the sealed connection with the soil ring; Two sensor fixing plates are arranged at the middle partition of the inner cylinder wall of the cylinder body. A semi-circular ventilation fan fixing plate is arranged on one side of the upper part of the inner side of the inner cylinder wall of the cylinder body, and the ventilation fan is fixed on its lower surface; among them, the upper end of the sensor fixing plate is flush with the height of the ventilation fan fixing plate, and the lower end is flush with the lower edge of the cylinder body. Two sensor socket plates are respectively installed on the sensor fixing plates; the CO2 sensor, the O2 sensor, and the temperature sensor are installed on one of the sensor socket plates; the CO sensor and the CH4 sensor are installed on the other sensor socket plate; The human-machine interaction interface includes a display screen, an indicator light, an operation button, and a web page end; The CO2 sensor, the O2 sensor, the CO sensor, the CH4 sensor, the temperature sensor, and the soil moisture sensor respectively conduct data transmission with the MCU single-chip microcomputer through RS485 communication. The barometric pressure sensor conducts data transmission with the MCU single-chip microcomputer through IIC communication. The stepping motor is connected to the MCU single-chip microcomputer through a wire. The ventilation fan, the upper limit switch, and the lower limit switch are respectively connected to the MCU single-chip microcomputer through wires. The display screen, the indicator light, and the operation button are respectively connected to the MCU single-chip microcomputer through wires. The web page end conducts data interaction with the ARM application processor through a Wi-Fi hotspot signal; The CO2 sensor is used to collect the CO2 concentration data in the gas chamber in real time. The O2 sensor is used to collect the O2 concentration data in the gas chamber in real time. The CO sensor is used to collect the CO concentration data in the gas chamber in real time. The CH4 sensor is used to collect the CH4 concentration data in the gas chamber in real time; The temperature sensor is used to collect the gas chamber temperature data in the gas chamber in real time; The barometric pressure sensor is used to collect the barometric pressure data in the gas chamber in real time; The soil moisture sensor is used to collect the soil temperature and soil moisture data of the ground surface around the gas chamber in real time; The MCU single-chip microcomputer includes a central processing unit, an RS485 communication unit, an IIC communication unit, a shutter control unit, an I / O control unit, and a GPS timing and positioning unit; The central processing unit is used to realize the operation control of the shutter control unit and the I / O control unit, and is used to process the real-time data collected by each sensor; The RS485 communication unit is used to issue acquisition instructions to the gas sensor unit, temperature sensor, and soil moisture sensor by the central processing unit and read data, and realizes that the monitoring system does not limit the types and numbers of access sensors by means of the modbus protocol and polling reading of each sensor; The IIC communication unit is used to issue acquisition instructions to the barometric pressure sensor by the central processing unit and read data; The gate control unit is used to control the stepping motor to lift or lower the airtight partition, control the ventilation fan to ventilate the air chamber, and is also used to control the static time of the air chamber monitoring; The I / O control unit is used to realize the control of the display screen, indicator light, and operation button by the central processing unit; The GPS timing and positioning unit includes a GPS receiver. The GPS receiver transmits data to the MCU single-chip microcomputer through a wire, obtains the standard clock signal and geographical location information from the satellite through the GPS receiver, and transmits the standard clock signal and standard geographical location information to the central processing unit to realize the calibration of the time of the monitoring system and the positioning of the real-time position; The ARM application processor includes a Wi-Fi hotspot unit, a web control unit, a file management unit, and a storage unit. The ARM application processor integrates web control functions and file management functions; The web end of the human-computer interaction interface realizes the information interaction between the web end and the ARM application processor through the Wi-Fi hotspot unit and the web control unit, realizes the function operations of storing, searching, exporting, and deleting data in the storage unit through the file management unit, and can also realize the data interaction function with the external USB storage medium through the file management unit; The Wi-Fi hotspot unit is used to emit a Wi-Fi hotspot remote connection signal. Taking the ARM application processor system as the server side and the mobile phone or PC as the client side, it realizes data interaction in the form of 2.4GHz wireless communication; The web control unit is used to realize the information interaction between the web end and the ARM application processor. Through the Wi-Fi hotspot signal and USART data interaction method, the user can remotely send requests for modifying the function parameters of the system or file management to the central processing unit at the web end of the human-computer interaction interface. The central processing unit can also transmit the received real-time data to the web end of the human-computer interaction interface. The function parameters of the system include the setting of the total system loop number, the setting of the number of single-loop data acquisitions, the setting of the file management password, the setting of the Wi-Fi hotspot name and connection password, and the setting of the infinite loop mode. The file management requests include the export, deletion of data files, and the query of real-time data; The file management unit is used to implement the functions of storing, searching, exporting, and deleting data files through the Linux system integrated on the ARM application processor. When the monitoring system inserts an external USB storage medium, the file management unit first identifies the access signal of the external storage medium and feeds back the identified access signal to the central processing unit through USART data interaction. The central processing unit sends an instruction to control the USB detection light to turn on according to the received access signal. When the user inputs a file copy / download request signal through the human-machine interface, the file management unit feeds back the request signal to the central processing unit through USART data interaction. The central processing unit sends an instruction to control the data transfer light to turn on according to the received request signal and reflects the file transfer rate by the flashing frequency. The storage unit is used to store and back up real-time data in the Linux system, real-time data collected by sensors, calculated flux data, parameter setting information, geographical location information, system time information, system operation status information, indicator light status information, as well as temporary data information during the data processing of the MCU single-chip microcomputer and temporary data information during the data processing of the ARM application processor. The indicator light status information includes a status indicator light indicating the system operation status, an error status light indicating system error information, a USB detection light indicating the USB detection status, and a data transfer light indicating the data transfer status. The storage unit consists of two types of storage media, namely RAM and eMMC chips.

2. The multi-channel acquisition and control integrated soil gas flux monitoring system according to claim 1, characterized in that, The shutter control unit is used to control the stepping motor to lift the airtight partition, and the specific description is as follows: After the central processing unit sends an air chamber opening instruction to the shutter control unit, the shutter control unit controls the stepping motor to start. The central processing unit records the motor operation status as 1, and the stepping motor drives the airtight partition to start lifting. When the airtight partition triggers the upper limit switch, or when the stepping motor has walked the preset number of steps without triggering the upper limit switch, the shutter control unit feeds back a signal to the central processing unit. The central processing unit records the motor operation status as 0 and sends an instruction to the shutter control unit to cut off the motor power supply through the shutter control unit. The lifting operation of the airtight partition ends, and the air chamber is in a fully open state. The shutter control unit outputs a signal indicating the end of the shutter lifting operation and feeds it back to the central processing unit.

3. The multi-channel acquisition and control integrated soil gas flux monitoring system according to claim 1, characterized in that, The shutter control unit is used to control the exhaust fan to ventilate the air chamber, and the specific description is as follows: After receiving the signal indicating the end of the shutter lifting operation, the central processing unit sends an instruction to control the exhaust fan to start working. The central processing unit records the exhaust fan operation status as 1 and starts timing the working duration of the exhaust fan through the shutter control unit. When the working duration of the exhaust fan reaches the preset working duration, the shutter control unit outputs a signal indicating the end of ventilation and feeds it back to the central processing unit. The central processing unit records the exhaust fan operation status as 0 and sends an instruction to cut off the power supply of the exhaust fan, and the ventilation work ends.

4. A multi-channel acquisition and control integrated soil gas flux monitoring system according to claim 1, characterized in that, The shutter control unit is used to control the stepping motor to lower the airtight partition, and the specific description is as follows: After the central processing unit sends the air chamber closing instruction to the ram control unit, the ram control unit controls the stepping motor to start. The central processing unit records the motor running state as 1. The stepping motor drives the sealed partition to start descending. When the sealed partition triggers the lower limit switch, or when the stepping motor has walked the preset number of steps without triggering the lower limit switch, the ram control unit feeds back a signal to the central processing unit. The central processing unit records the motor running state as 0 and sends an instruction to the ram control unit to cut off the power supply of the motor through the ram control unit. The descending operation of the sealed partition ends, and the air chamber is in a completely sealed state. The ram control unit outputs a signal indicating the end of the ram descending operation and feeds it back to the central processing unit.

5. The multi-channel acquisition and control integrated soil gas flux monitoring system according to claim 1, characterized in that, The ram control unit is used to control the static time of the air chamber for monitoring, and the specific description is as follows: After the central processing unit receives the signal indicating the end of air exchange, it starts timing the static time of the air chamber through the ram control unit. When the static time of the system reaches the preset static time, the control operation of the static time of the air chamber for monitoring ends. The ram control unit outputs a signal indicating the end of the monitoring static time and feeds it back to the central processing unit.

6. The multi-channel acquisition and control integrated soil gas flux monitoring system according to claim 1, characterized in that, The central processing unit processes the collected real-time data, and the specific description is as follows: The gas sensor unit transmits the collected gas data to the central processing unit through the RS485 communication unit. The gas data includes but is not limited to CO2 concentration data, O2 concentration data, CO concentration data, CH4 concentration data. The temperature sensor transmits the collected air chamber temperature data to the central processing unit through the RS485 communication unit. The soil moisture sensor transmits the collected soil temperature and soil moisture data to the central processing unit through the RS485 communication unit. The barometric pressure sensor transmits the collected barometric pressure data to the central processing unit through the IIC communication unit. The central processing unit performs analog-to-digital conversion processing on the analog signals received from each sensor to obtain the digital quantity signals corresponding to the respective analog signals. The analog signals include gas data, air chamber temperature data, barometric pressure data, soil temperature and soil moisture data. The central processing unit applies the least squares method to perform calculation processing on the time and concentration relationship of the digital quantity signals to obtain the gas concentration rising slope value and the goodness-of-fit value. The concentration rising slope value is substituted into the flux calculation formula to obtain the flux values of the collected gas data, and the calculated flux values, as well as the respective gas data, air chamber temperature data, barometric pressure data, soil temperature and soil moisture data, are stored in the storage unit. The goodness-of-fit value is used to evaluate the reliability of the flux value calculation.

7. A monitoring method using the multi-channel acquisition and control integrated soil gas flux monitoring system according to any one of claims 1-6, characterized in that, It includes the following steps: Step 1: Gate lifting stage: After the start of the operation cycle, start the stepper motor to drive the sealed partition to lift until the upper limit switch is triggered and then cut off the power supply of the stepper motor. The circular cover on the sealed partition is lifted to the upper edge of the ventilation port, and the air chamber is in a fully open state. Before each cycle of the system, the state of the gate is first detected. If the air chamber is not in a fully open state due to foreign object blockage or an incomplete previous cycle, the stepper motor needs to be controlled to drive the sealed partition to operate until the air chamber is in a fully open state. If the air chamber is already in a fully open state before the start of the first cycle, the system defaults to waiting for the stepper motor to complete the preset number of steps and then directly enters the ventilation stage; Step 2: Ventilation stage: When the air chamber is in a fully open state, control the ventilation fan to start working and start timing the working duration of the ventilation fan. When the working duration of the ventilation fan reaches the preset working duration, the ventilation ends; Step 3: Monitoring and static stage: After the ventilation ends, to reduce the impact of ventilation disturbance on the gas monitoring in the air chamber, by monitoring the static duration of the air chamber by the monitoring system, the gas in the air chamber is in a natural gushing state. When the static duration of the air chamber reaches the preset static duration, the monitoring and static stage ends; Step 4: Gate lowering stage: When the monitoring and static stage ends, control the stepper motor to drive the sealed partition to lower until the lower limit switch is triggered and then cut off the power supply of the stepper motor. The lower edge position of the circular cover is close to the upper edge of the inner cylinder wall of the cylinder, and the air chamber is in a fully closed state; Step 5: Measurement stage: When the air chamber is in a fully closed state, control each sensor to start real-time data acquisition work at the preset sampling time interval. The real-time data collected by each sensor is stored in the storage unit after being processed by the central processing unit. When the real-time data stored in each cycle reaches the preset total number of samples, the system stops recording data, and one cycle of monitoring ends. The monitoring system enters the next cycle of the gate lifting stage.

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