High-sensitivity CO2 concentration detection device in the field and its self-diagnosis method

Abstract

This invention discloses a high-sensitivity CO2 concentration detection device for field use and its fault self-diagnosis method. The device's internal casing is divided into an air inlet chamber, a concentration quantitative control chamber, a two-stage gas mixing chamber, and a detection chamber by a wall panel. The concentration quantitative control chamber is equipped with a CO2 concentration quantitative control component that modulates the air to the desired CO2 concentration. An electrochemical CO2 sensor detects compressed air, a temperature sensor detects the temperature of the tip of a calibration cigarette, a rechargeable lighter ignites the calibration cigarette to generate CO2, and a servo motor drives a cutter to cut off the tip of the calibration cigarette. During the calibration phase, a CO2 concentration calibration value is obtained. During self-testing, the CO2 concentration of the self-test gas is obtained, and the CO2 concentration of the self-test gas is compared with the CO2 concentration calibration value to determine if there is a fault. When the detection device is working normally, the electrochemical CO2 sensor collects the CO2 concentration of the air to be tested. This invention utilizes pressure to enhance the CO2 diffusion rate and density to improve the response current of the electrochemical sensor and increase detection sensitivity.

Description

Technical Field

[0001] This invention relates to the field of carbon metering and automatic detection of CO2 concentration in the field, and in particular to a high-sensitivity detection device and method for CO2 concentration in the field with fault self-diagnosis function. Background Technology

[0002] Field CO2 detection is an indispensable technology in carbon accounting and climate change response. With the advancement of science and technology, field CO2 detection methods will become more accurate, economical, and convenient, providing strong support for global carbon emission reduction. Electrochemical CO2 sensors have significant application value in environmental monitoring, industrial safety, and other fields; however, existing technologies generally suffer from insufficient sensitivity, limited stability, and poor field adaptability.

[0003] Traditional improvement strategies focus on electrode material optimization (such as nano-modification of noble metal catalysts) and electrolyte system innovation (such as replacing liquid systems with solid electrolytes to improve lifespan), but have failed to effectively solve the following two core problems: (1) The sensitivity-pressure coupling mechanism has not been developed. Existing technologies mainly improve sensitivity by increasing the specific surface area of ​​the electrode or introducing nanomaterials, but have not paid attention to the dynamic regulation of gas diffusion rate by external pressure. For example, Chinese Patent Publication No. CN104345080A discloses a method for preparing an electrochemical carbon monoxide gas sensor electrode, which improves the sensitivity of the CO sensor by using carbon-supported PdCl / CuCl catalyst, but its design is still limited to the optimization of the material's own activity and does not utilize the pressure-diffusion synergistic effect to enhance sensitivity. (2) The contradiction between long-term stability and maintenance cost is prominent. Traditional sensors rely on periodic calibration to maintain accuracy, but calibration in the field is difficult and costly. Chinese Patent Publication No. CN202814910U discloses an electrochemical CO gas sensor that uses solid electrolyte to reduce maintenance requirements, but its fault self-diagnosis function is missing and it cannot provide real-time feedback on the sensor status. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a high-sensitivity CO2 concentration detection device for the field and its fault self-diagnosis method. This invention considers the dynamic regulation of gas diffusion rate by external pressure, integrates a fault self-diagnosis module, and utilizes the pressure-diffusion synergistic effect to enhance detection sensitivity, providing a highly robust solution for CO2 monitoring in the field.

[0005] To achieve the above objectives, the field high-sensitivity CO2 concentration detection device proposed in this invention adopts the following technical solution: the inner shell of the device is divided into an air inlet chamber, a concentration quantitative control chamber, a two-stage gas mixing chamber and a detection chamber by a wall panel, and an air inlet control valve for the concentration quantitative control chamber is provided between the air inlet chamber and the concentration quantitative control chamber.

[0006] The concentration quantitative control chamber is equipped with a CO2 concentration quantitative control component that can modulate the air to the required CO2 concentration. The concentration quantitative control chamber is connected to the primary gas mixing chamber by an air outlet for the concentration quantitative control chamber.

[0007] The CO2 concentration detection component consists of a signal acquisition component and a compression control component. The signal acquisition component includes a cylinder liner and a piston. The top of the cylinder liner has an exhaust port and is equipped with an electrochemical CO2 sensor. The piston moves away from the top of the cylinder liner to the bottom dead center, and the air to be tested enters the detection space. When the piston moves to the top dead center, the air is compressed, and the electrochemical CO2 sensor detects the compressed air. The compression control component controls the piston to reciprocate.

[0008] The CO2 concentration quantitative control component consists of an incense feeding control component and an incense burning control component. The incense feeding control component includes an incense feeding stepper motor, an incense feeding roller, an incense placement groove, a temperature sensor, and calibration incense. The calibration incense is pressed down by the incense feeding roller and placed in the incense placement groove. The incense feeding stepper motor drives the incense feeding roller to rotate. The temperature sensor detects the temperature of the tip of the calibration incense.

[0009] The incense burning control components include a servo motor, a cutter, and a rechargeable lighter. The rechargeable lighter ignites the calibration incense to produce CO2, and the servo motor drives the cutter to cut off the tip of the calibration incense.

[0010] The technical solution for the self-diagnosis of faults in the aforementioned high-sensitivity CO2 concentration detection device in the field includes the following steps:

[0011] Step 1): The ARM processor controls the air inlet control valve of the concentration quantitative control chamber and the air outlet control valve of the detection device to close simultaneously. The incense stepper motor rotates, and under the action of the incense roller, the calibration incense approaches the temperature sensor. The incense stepper motor stops. The rechargeable lighter is controlled to ignite the incense and start the timer. The temperature sensor collects the temperature signal. When the timer reaches the predetermined time, the servo motor rotates to cut off the burning part of the calibration incense. At this time, the enclosed space is filled with the calibration gas to be tested.

[0012] Step 2): The compression stepper motor rotates, and the piston moves towards the limit switch. When the limit switch is touched, the compression stepper motor stops rotating, and the piston is at the bottom dead center. Simultaneously, the intake control solenoid valve and the exhaust control solenoid valve open, and the gas sampling pump starts, filling the cylinder liner with the calibration gas to be tested in the detection chamber. The gas sampling pump, intake control solenoid valve, and exhaust control solenoid valve are then closed. The compression stepper motor rotates, causing the piston to move upward to the top dead center. The ARM processor collects the current from the electrochemical CO2 sensor and converts it into the corresponding N2 concentration. k =hi, where h is the conversion coefficient and i is the sensor current; concentration N k Used as a CO2 concentration calibration value and saved;

[0013] Step 3): Perform a self-test of the detection device: Repeat steps 1)-2) to obtain the CO2 concentration N of the gas used for the self-test. k * The CO2 concentration N of the gas used for self-testing k * Compared with the CO2 concentration calibration value N k Make a comparison and determine whether the difference is within the set error range. If it is, the detection device is faulty; otherwise, it is working normally.

[0014] Furthermore, when the detection device is working normally, the compression stepper motor rotates, causing the piston to move towards the limit switch. When the limit switch is touched, the compression stepper motor stops rotating, the intake control solenoid valve and the exhaust control solenoid valve are opened, the air sampling pump is started, the cylinder liner is filled with the air to be tested, and the air sampling pump, the intake control solenoid valve and the exhaust control solenoid valve are closed. The compression stepper motor rotates, the piston moves to the top dead center, and the top of the piston is at the top dead center position. The electrochemical CO2 sensor collects the CO2 concentration of the air to be tested.

[0015] Compared with existing technologies, the present invention has the following advantages:

[0016] 1. For electrochemical CO2 sensors, without pressurized gas of the same concentration, the CO2 diffusion rate and density are low, resulting in a correspondingly low response current. When the CO2 concentration is low, commonly used electrochemical CO2 sensors cannot detect it at all. Increased pressure accelerates CO2 diffusion to the electrode surface, increasing the diffusion rate and density, leading to a stronger current signal. Therefore, this invention establishes a pressure-sensitivity coupling mechanism, utilizing pressure to enhance the CO2 diffusion rate and density to improve the response current of the electrochemical sensor. This overcomes the limitations of traditional material optimization, significantly reducing the detection limit of the electrochemical CO2 sensor. By utilizing the pressure effect on the electrochemical CO2 sensor to improve detection sensitivity, it effectively solves the problem of high-sensitivity detection in electrochemical CO2 sensors. This lays a solid foundation for improving the accuracy of carbon measurement in the field. Compared to existing nanomaterial modification methods (which improve sensitivity by approximately 30%), this device can improve the sensitivity coefficient by several times through pressure regulation.

[0017] 2. A major problem with CO2 concentration detection devices is that their performance deteriorates over time, requiring periodic fault diagnosis. This is particularly challenging when used for field CO2 concentration detection, especially when circuit faults significantly impact statistical carbon measurement. This invention addresses this issue by implementing a self-diagnostic function for the detection device through a quantitative CO2 concentration control component.

[0018] 3. This invention features an intelligent maintenance system that integrates a fault self-diagnosis module algorithm, solving the problem of fault self-diagnosis such as long-term sensor drift in field environments. Compared to the passive solid-state electrolyte design in patent publication number CN202814910U, the device of this invention achieves fault self-diagnosis through a CO2 concentration quantitative control component. Therefore, through multi-dimensional technological innovation, it provides a highly robust solution for field CO2 monitoring and lays a technical foundation for carbon measurement standardization and environmental big data analysis.

[0019] 4. The detection device of the present invention uses a stepper motor to control the piston stroke, which makes the gas pressure acting on the electrochemical CO2 sensor very precise, greatly improving the stability of the sensor's CO2 concentration sensitivity coefficient.

[0020] 5. The detection device of this invention uses a stepper motor to control the incense-feeding rollers and forms a closed-loop control with the temperature sensor to ensure the stability of incense-feeding control. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the field CO2 concentration detection device with fault self-diagnosis of the present invention;

[0022] Figure 2 yes Figure 1 A magnified structural schematic diagram of a high-sensitivity CO2 concentration detection component.

[0023] Figure 3 yes Figure 1 A magnified structural schematic diagram of the CO2 concentration quantitative control component.

[0024] Figure 4 yes Figure 3 Schematic diagram of the AA section structure;

[0025] Figure 5 This is the logic block diagram of the measurement and control circuit of the detection device;

[0026] Figure 6 This is a graph showing the relationship between CO2 concentration and the burning time of the calibration tobacco.

[0027] In the diagram: 1. Primary gas mixing chamber; 2. Detection device housing; 3. Partition 1; 4. Partition 2; 5. Mixing chamber wall panel; 6. Air vent between the two mixing chambers; 7. Partition 3; 8. Secondary gas mixing chamber; 9. Detection chamber wall panel; 10. Detection chamber air inlet; 11. Detection device air outlet control valve; 12. CO2 concentration detection component; 13. Detection chamber; 14. Solar cell; 15. Control circuit board; 16. Carbon dioxide concentration quantitative control chamber; 17. Concentration quantitative control chamber air inlet control valve; 18. Air intake fan; 19. Air intake chamber; 20. CO2 concentration quantitative control component; 21. Concentration quantitative control chamber air outlet; 22. Concentration quantitative control chamber; 23. Servo motor; 24. Servo motor shaft; 25. Cutter; 26. Cutter bracket; 27. Incense-burning stepper motor shaft; 8. Incense roller; 29. ​​Incense stepper motor bracket; 30. Incense holder groove; 31. Calibration incense; 32. Quantitative control component bracket; 33. Rechargeable lighter; 34. Temperature sensor; 35. Temperature sensor bracket; 36. Servo motor bracket; 37. Incense stepper motor; 38. Air intake pipe; 39. Air intake pump; 40. Air intake control solenoid valve; 41. Cylinder liner; 42. Bottom dead center; 43. Nut slider; 44. Slide groove; 45. Lead screw; 46. Compression stepper motor shaft; 47. Compression stepper motor; 48. Exhaust pipe; 49. Exhaust control solenoid valve; 50. Electrochemical CO2 sensor; 51. Top dead center; 52. Piston seal ring; 53. Piston; 54. Piston connector; 55. Base; 56. Compression stepper motor and slide groove bracket; 57. Limit switch. Detailed Implementation

[0028] See Figure 1 The high-sensitivity CO2 concentration detection device for field use proposed in this invention consists of an outer shell 2. The interior of the outer shell 2 is divided by wall panels, forming five chambers: an air inlet chamber 19, a concentration quantitative control chamber 22, a primary gas mixing chamber 1, a secondary gas mixing chamber 8, and a detection chamber 13. These five chambers are interconnected. External air enters through the air inlet chamber 19, then enters the concentration quantitative control chamber 22, and is subsequently mixed in the primary gas mixing chamber 1 and the secondary gas mixing chamber 8 before finally entering the detection chamber 13 for detection.

[0029] An air intake fan 18 is installed inside the air intake chamber 19, and an air intake control valve 17 for the concentration metering control chamber 22 is installed between the air intake chamber 19 and the concentration metering control chamber 22. When the air intake fan 18 is working, it blows the air outside the outer casing 2 into the air intake chamber 19, forming a certain air pressure in the air intake chamber 19. When the air intake control valve 17 for the concentration metering control chamber is opened, the air enters the concentration metering control chamber 22 through the air intake control valve 17.

[0030] A CO2 concentration quantitative control component 20 is installed inside the concentration quantitative control chamber 22, and a concentration quantitative control chamber outlet 21 is provided between the concentration quantitative control chamber 22 and the primary gas mixing chamber 1. When the detection device of the present invention is in the self-testing state, the CO2 concentration quantitative control component 20 operates, modulating the air entering the concentration quantitative control chamber 22 to the required CO2 concentration. Then, the concentration quantitative control chamber outlet 21 opens, and the modulated air enters the primary gas mixing chamber 1 through the concentration quantitative control chamber outlet 21. Conversely, when the detection device of the present invention is in the self-testing completed state, the CO2 concentration quantitative control component 20 does not operate, the control chamber outlet control valve 21 is in the open state, and the air entering the concentration quantitative control chamber 22 directly enters the primary gas mixing chamber 1 through the concentration quantitative control chamber outlet 21.

[0031] The primary gas mixing chamber 1 and the secondary gas mixing chamber 8 are separated by a mixing chamber wall panel 5. An air vent 6 is provided between the two mixing chambers on the mixing chamber wall panel 5. An air inlet 10 for the detection chamber is provided between the secondary gas mixing chamber 8 and the detection chamber 13. Regardless of whether the detection device of this invention is in a self-test completed state or a self-test pending state, the gas passes directly from the primary gas mixing chamber 1 to the secondary gas mixing chamber 8, and then directly to the detection chamber 13.

[0032] Within the primary gas mixing chamber 1, there are baffles 3 and 4, arranged alternately and perpendicular to the air intake direction, forming a vertically turning air passage within the primary gas mixing chamber 1. Within the secondary gas mixing chamber 8, there is baffle 7, perpendicular to baffles 3 and 4, and also perpendicular to the air intake direction.

[0033] The secondary gas mixing chamber 8 and the detection chamber 13 are separated by a detection chamber wall panel 9. An air inlet 10 is located on the detection chamber wall panel 9, connecting the two chambers. Inside the detection chamber 13 are a CO2 concentration detection component 12, a solar cell 14, and a control circuit board 15. An air outlet control valve 11 is located on the outer casing 2 of the detection chamber 13. The CO2 concentration detection component 12 faces both the air inlet 10 and the air outlet control valve 11. The CO2 concentration detection component 12 detects the CO2 concentration, which powers the entire detection device. The control circuit board 15 controls the automated operation of the entire detection device. After the CO2 concentration detection component 12 completes its detection, the air is discharged from the outer casing 2 of the detection device through the air outlet control valve 11.

[0034] See Figure 2The CO2 concentration detection component 12 shown consists of a signal acquisition component and a compression control component. The signal acquisition component includes an air intake pipe 38, an air intake pump 39, an air intake control solenoid valve 40, a cylinder liner 41, an exhaust pipe 48, an exhaust control solenoid valve 49, an electrochemical CO2 sensor 50, a piston seal ring 52, a piston 53, and a piston connector 54. The air intake pipe 38 has its intake end exposed in the detection chamber 13 and directly facing the air inlet 10 of the detection chamber to detect the gas to be tested sent from the secondary gas mixing chamber 8. The other end is connected to the air inlet of the air intake pump 39, and the air outlet of the air intake pump 39 is connected to the air intake control solenoid valve 40. The other end of the air intake control solenoid valve 40 is directly connected to the cylinder liner 41, so that the air to be tested can be sent into the cylinder liner 41 by the air intake pump 39 under the control of the air intake control solenoid valve 40. The cylinder liner 41 is fixed to the base 55. A piston 53 is provided inside the cylinder liner 41 to cooperate with it. The piston 53 is connected to the piston connector 54 located outside the cylinder liner 41. An exhaust port is opened on the top of the cylinder liner 41. The exhaust port is directly connected to the exhaust control solenoid valve 49. The other end of the exhaust control solenoid valve 49 is connected to the exhaust pipe 48. The exhaust pipe 48 is directly facing the air outlet control valve 11 of the detection device.

[0035] An electrochemical CO2 sensor 50 is installed on the top of the cylinder liner 41, located on both sides of the exhaust port. When the piston 53 moves away from the top of the cylinder liner 41 to the bottom dead center 42, a detection space is formed between the bottom dead center 42 and the top of the cylinder liner 41. The air to be measured can be supplied into this space by the intake air pump 39 when the intake air control solenoid valve 40 is open. When both the exhaust air control solenoid valve 49 and the intake air control solenoid valve 40 are closed, a sealed space is formed between the bottom dead center 42 and the top of the cylinder liner 41. When the piston 53 moves closer to the top of the cylinder liner 41 to the top dead center 51, the air to be measured is compressed, and the electrochemical CO2 sensor 50 detects the compressed air. By utilizing pressure to enhance the CO2 diffusion rate and density in the sealed detection space, the response current of the electrochemical sensor is increased, thereby improving the sensitivity of the electrochemical CO2 sensor 50. Let L1 be the distance between bottom dead center 42 and top dead center 51, L2 be the distance between top dead center 51 and the top of cylinder liner 41, T1 be the temperature of the air to be measured before compression, and T2 be the temperature after compression. Then the sensitivity coefficient k improved by the electrochemical CO2 sensor 50 is:

[0036]

[0037] The compression control component is used to control the reciprocating motion of the piston 53. It includes a compression stepper motor shaft 46, a compression stepper motor 47, a nut slider 43, a slide groove 44, a lead screw 45, a compression stepper motor and slide groove bracket 56, and a limit switch 57. The compression stepper motor 47 and the slide groove 44 are fixed to the compression stepper motor and slide groove bracket 56, which is fixed to the base 55. The nut slider 43, the slide groove 44, and the lead screw 45 form a general-purpose lead screw and nut mechanism. The compression stepper motor 47 is connected to the lead screw and nut mechanism via its compression stepper motor shaft 46, which drives the piston 53 to reciprocate. The lead screw and nut mechanism consists of a lead screw 45 and a nut slider 43. The lead screw 45 is coaxially connected, and the nut slider 43 consists of a nut assembly and a slider. The inner hole of the nut assembly is fitted onto the lead screw 45, and the nut assembly is fixed to the slider. The nut slider 43 is mounted on a slide groove 44 and can slide back and forth along the slide groove 44. The nut slider 43 is connected to the piston connector 54. The limit switch 57 is fixed on the compression stepper motor and the slide groove bracket 56. The movable contact of the limit switch 57 faces the piston connector 54. When the piston connector 54 reciprocates, it will touch the limit switch 57, sending a signal that it has reached the lower stop position 42. The compression stepper motor shaft 46 rotates in both directions, causing the lead screw 45 to rotate in both directions as well. Through the action of the nut assembly in the nut slider 43, the nut slider 43 reciprocates on the slide groove 44, and the piston connector 54 controls the reciprocating motion of the piston 53.

[0038] See Figure 3 and Figure 4 The CO2 concentration quantitative control component 20 shown is composed of an incense-feeding control component and an incense-burning control component. The incense-feeding control component includes an incense-feeding stepper motor 37, an incense-feeding stepper motor shaft 27, an incense-feeding roller 28, an incense-feeding stepper motor bracket 29, an incense-placement groove 30, calibration incense 31, a temperature sensor 34, a temperature sensor bracket 35, and a quantitative control component bracket 32. The calibration incense 31, which generates CO2, is placed in the incense-placement groove 30. See details... Figure 4A toothed incense roller 28 presses down on the calibration incense 31, and the incense roller 28 is fixed on the incense stepper motor shaft 27. The incense stepper motor 37 drives the incense roller 28 to rotate. The housing of the incense stepper motor 37 is fixed on the incense stepper motor bracket 29, and the incense placement groove 30 and the incense stepper motor bracket 29 are fixed on the quantitative control component bracket 32. The temperature sensor 34 is fixed on the temperature sensor bracket 35, and is close to but does not contact the front end of the calibration incense 31. The temperature sensor bracket 35 is fixed on the servo motor bracket 36. Driven by the incense stepper motor 37, the incense roller 28 moves the calibration incense 31 forward, gradually approaching the temperature sensor 34, completing the automatic feeding of the calibration incense 31. As the burning calibration incense 31 gets closer to the temperature sensor 34, the temperature sensed by the temperature sensor 34 increases. When the temperature reaches a certain set value H0, the incense-feeding stepper motor 37 stops rotating. As the calibration incense 31 shortens during combustion and moves further away from the temperature sensor 34, the temperature sensed by the temperature sensor 34 decreases. When the temperature drops to a certain set value L0, the incense-feeding stepper motor 37 starts rotating again. This ensures that the burning part of the calibration incense 31 does not move far from the incense-placement groove 30, facilitating subsequent incense burning control.

[0039] The incense burning control component includes a servo motor 23, a servo motor shaft 24, a cutter 25, a cutter bracket 26, a rechargeable lighter 33, and a servo motor bracket 36. The rechargeable lighter 33 is fixed between the servo motor bracket 36 and the metering control component bracket 32, located directly below the front end of the calibration incense 31. The cutter 25 is fixed on the cutter bracket 26, located directly above the front end of the calibration incense 31. The cutter bracket 26 is fixed on the servo motor shaft 24, and the servo motor 23 is fixed on the servo motor bracket 36. When the front end of the calibration incense 31 moves to a certain distance (e.g., 5mm) from the incense-holding groove 30, the rechargeable lighter 33 begins ignition under the control of the control circuit board 15. The ignition time is controlled by the control circuit board 15, causing the calibration incense 31 to ignite and burn, producing CO2. When the set time is reached, the servo motor 23, under the control of the control circuit board 15, drives the cutter 25 to cut off the front end of the calibration incense 31, thereby terminating the combustion of the calibration incense 31.

[0040] See Figure 5The diagram shows the logic block diagram of the detection device's control circuit. The control circuit board 15, installed in the detection chamber 13, is the control center of the entire detection device. The control circuit board 15 includes an ARM processor, a wireless communication module, an input interface circuit, and an output interface circuit. The entire detection device is powered by the solar cell 14. The ARM processor in the control circuit board 15 issues commands through the output interface circuit to control the detection device's air outlet control valve 11, the concentration quantitative control chamber air inlet control valve 17, the air intake fan 18, the servo motor 23, the rechargeable lighter 33, the incense stepper motor 37, the gas sampling pump 39, the air intake control solenoid valve 40, the compression stepper motor 47, and the exhaust control solenoid valve 49, respectively. The ARM processor issues commands through the input interface circuit to collect and convert signals from the electrochemical CO2 sensor 50, the temperature sensor 34, and the limit switch 57, respectively.

[0041] When the detection device of the present invention is working, it can automatically complete the fault self-diagnosis function, including a calibration stage and a self-diagnosis stage, as detailed below:

[0042] I. Calibration stage: Obtaining CO2 concentration calibration values.

[0043] Step 1: The detection device is in self-test mode. First, a CO2 concentration calibration value must be stored in the ARM processor's internal memory as a basis for determining whether the detection device has malfunctioned. In a completely sealed space, the CO2 concentration produced by burning calibration smoke 31 for the same amount of time (when the concentration is in the unsaturated region) should be exactly the same. Based on this principle, as... Figure 6 As shown, for the known model and type of electrochemical CO2 sensor 50, the relationship curve between CO2 concentration and the combustion time of the calibration tobacco 31 can be obtained through offline experiments. The CO2 concentration increases linearly from the start time to the saturation period, therefore the relationship curve has a linear region. A point T is taken from the middle of the linear region of the relationship curve. k The corresponding CO2 concentration is N k When the detection device experiences sensor malfunction, zero-point drift, or pulse failure, any of these faults will affect the accuracy of CO2 concentration detection. Therefore, the CO2 concentration N can be... k This serves as the calibration value for CO2 concentration. The detection device acquires the CO2 concentration calibration value N. k The process is as follows:

[0044] Process 1: Generate a time T within the detection device. k The corresponding CO2 concentration setpoint:

[0045] (1) The ARM processor of the control circuit board 15 sends a command through the output interface circuit to simultaneously close the air inlet control valve 17 of the concentration quantitative control chamber and the air outlet control valve 11 of the detection device, making the inside of the detection device a completely closed space. The ARM processor controls the incense stepper motor 37 to rotate forward through the output interface circuit, and under the action of the incense roller 28, the calibration incense 31 moves closer to the temperature sensor 34. When installing the calibration incense 31, the front end of the calibration incense 31 is aligned with the front end of the incense placement groove 30. During initial operation, the incense stepper motor 37 is controlled to rotate forward M steps, so that the front end of the calibration incense 31 reaches directly above the lighter 33, M = L3 / W1, where W1 is the distance moved by the incense stepper motor 37 in each step, and L3 is the distance between the front end of the incense placement groove 30 and the rechargeable lighter 33.

[0046] (2) The ARM processor controls the rechargeable lighter 33 to start ignition through the output interface circuit and starts timing at the same time. The ARM processor collects the temperature signal of the temperature sensor 34 through the input interface circuit. When the temperature is less than T0, the ARM processor controls the incense stepper motor 37 to rotate forward, so that the calibration incense 31 moves closer and closer to the temperature sensor 34, and the temperature rises until the temperature is greater than or equal to the temperature T0. Then the ARM processor controls the incense stepper motor 37 to stop. T0 is the temperature value when the head of the burning calibration incense 31 is directly above the rechargeable lighter 33.

[0047] (3) When the timer reaches the predetermined time T k At this time, the ARM processor controls the servo motor 23 to rotate 90 degrees forward through the output interface circuit, so that the cutter 25 cuts off the burning part of the calibration smoke 31. At this time, the closed space inside the detection device is filled with calibration gas, and the CO2 concentration in the calibration gas is a fixed value to be detected.

[0048] Process 2: The ARM processor on control circuit board 15 uses a high-sensitivity detection method to acquire the CO2 concentration value for calibration.

[0049] (1) The ARM processor controls the compression stepper motor 47 to reverse through the output interface circuit, causing the nut slider 43, piston connector 54 and piston 53 to move towards the limit switch 57. When the limit switch 57 is touched, the ARM processor receives the stop signal from the limit switch 57 and immediately commands the compression stepper motor 47 to stop rotating. At this time, the position of the top of the piston 53 is the bottom dead center 42.

[0050] (2) The ARM processor sends a command through the output interface circuit to open the intake control solenoid valve 40 and the exhaust control solenoid valve 49 at the same time, and then sends a command to start the air pump 39 to fill the cylinder liner 41 with the calibration gas in the test chamber 13.

[0051] (3) The ARM processor sends a command to shut down the air pump 39, and then sends a command to close the air intake control solenoid valve 40 and the exhaust control solenoid valve 49 at the same time. At this time, a sealed space is formed inside the cylinder liner 41 filled with the gas to be tested.

[0052] (4) The ARM processor sends a command to control the compression stepper motor 47 to rotate forward through the output interface circuit, causing the nut slider 43, piston connector 54, and piston 53 to move to the upper dead center 51. The distance between the lower dead center 42 and the upper dead center 51 is L1. Let the distance moved by the compression stepper motor 47 in each step be W, then the number of steps moved by the compression stepper motor 47 is G = L1 / W. That is, the ARM processor controls the compression stepper motor 47 to rotate forward G steps, and at this time the top of the piston 53 is at the upper dead center 51.

[0053] (5) The ARM processor acquires the current signal from the electrochemical CO2 sensor 50 through the input interface circuit and converts it into the corresponding concentration N. k =hi information, where h is the conversion coefficient and i is the sensor detection current value.

[0054] Process 3: Replace the ARM processor with a concentration N k The information is stored in the internal memory of the ARM processor as the CO2 concentration calibration value of the detection device.

[0055] II. Self-diagnosis phase: Obtaining results indicating whether the detection device has malfunctioned.

[0056] The ARM processor determines whether the self-test cycle (1 day, 1 week, or 1 month, which can be set by the user) has expired. If the ARM processor determines that the self-test cycle has not expired, it indicates that the detection state is normal and no self-test needs to be initiated. At this time, the CO2 concentration quantitative control component 20 does not work, while the CO2 concentration detection component 12 works normally. If the cycle has expired, the self-test program is initiated. The specific self-test process is as follows:

[0057] 1) Using the method described in process 1 of step 1, the enclosed space inside the detection device is filled with self-testing gas, generating a gas that reacts with time T within the detection device. k The corresponding CO2 concentration setting for the self-testing gas.

[0058] 2) Using the method described in step 1, process 2, the ARM processor obtains the CO2 concentration N of the self-test gas. k * information.

[0059] 3) The ARM processor will detect the CO2 concentration N of the self-test gas. k * Information and Step 1: The CO2 concentration calibration value N stored in the internal memory of the ARM processor. kThe information is compared, and it is determined whether the difference is within the set error range. Once it exceeds the error range (N... k Greater than N k * If the error signal is positive (e.g., 0), it indicates a malfunction in the detection device. The ARM processor will illuminate the fault indicator and send a fault message to the host computer via its built-in wireless communication module, awaiting further processing. Conversely, if the error does not exceed the error range, the detection device is functioning normally.

[0060] Upon completion, this indicates that the detection device has transitioned from a state awaiting self-diagnosis to a state where self-diagnosis has been completed. It can then perform highly sensitive detection of the CO2 gas to be tested, obtaining an accurate CO2 concentration in the air. Details are as follows:

[0061] When the detection device is in normal working condition, the ARM processor uses a high-sensitivity detection method to acquire the CO2 concentration value to be measured:

[0062] (1) The ARM processor controls the compression stepper motor 47 to reverse through the output interface circuit, causing the nut slider 43, piston connector 54 and piston 53 to move towards the limit switch 57. When the limit switch 57 is touched, the ARM processor receives the stop signal from the limit switch 57 and immediately commands the compression stepper motor 47 to stop rotating. At this time, the position of the top of the piston 53 is the bottom dead center 42.

[0063] (2) The ARM processor sends a command through the output interface circuit to open the intake control solenoid valve 40 and the exhaust control solenoid valve 49 at the same time, and then sends a command to start the air pump 39 to fill the cylinder liner 41 with the conventional external air to be tested in the test chamber 13.

[0064] (3) The ARM processor sends a command to shut down the air pump 39, and then sends a command to close the intake control solenoid valve 40 and the exhaust control solenoid valve 49 at the same time. At this time, a sealed space is formed inside the cylinder liner 41 filled with the air to be tested.

[0065] (4) The ARM processor sends a command to control the compression stepper motor 47 to rotate forward through the output interface circuit, causing the nut slider 43, piston connector 54, and piston 53 to move to the upper dead center 51. The distance between the lower dead center 42 and the upper dead center 51 is L1. Let the distance moved by the compression stepper motor 47 in each step be W, then the number of steps moved by the compression stepper motor 47 is G = L1 / W. That is, the ARM processor controls the compression stepper motor 47 to rotate forward G steps, and at this time the top of the piston 53 is at the upper dead center 51.

[0066] (5) The ARM processor acquires the current signal from the electrochemical CO2 sensor 50 through the input interface circuit and converts it into the corresponding concentration information C = hj, where h is the conversion coefficient and j is the sensor detection current value. The ARM processor obtains a CO2 concentration information C to be measured and sends it to the host computer through the wireless communication module built into the control circuit board 15, thereby completing the high-sensitivity measurement of CO2 concentration in the field.

Claims

1. A high-sensitivity CO2 concentration detection device for field use, characterized in that: The outer shell (2) of the device is divided into an air inlet chamber (19), a concentration quantitative control chamber (22), a primary gas mixing chamber (1), a secondary gas mixing chamber (8) and a detection chamber (13) by a wall panel. A concentration quantitative control chamber air inlet control valve (17) is provided between the air inlet chamber (19) and the concentration quantitative control chamber (22). The concentration quantitative control chamber (22) is equipped with a CO2 concentration quantitative control component (20) that can modulate the air to the required CO2 concentration. The concentration quantitative control chamber (22) and the primary gas mixing chamber (1) are provided with a concentration quantitative control chamber air outlet (21). The CO2 concentration detection component (12) consists of a signal acquisition component and a compression control component. The signal acquisition component includes a cylinder liner (41) and a piston (53). The top of the cylinder liner (41) has an exhaust port and is equipped with an electrochemical CO2 sensor (50). The piston (53) moves away from the top of the cylinder liner (41) to the bottom dead center, and air enters the detection space. The piston (53) moves to the top dead center, and the air to be tested is compressed. The electrochemical CO2 sensor (50) detects the compressed air. The compression control component controls the piston (53) to reciprocate. The CO2 concentration quantitative control component (20) consists of an incense-feeding control component and an incense-burning control component. The incense-feeding control component includes an incense-feeding stepper motor (37), an incense-feeding roller (28), an incense-placement groove (30), a temperature sensor (34), and calibration incense (31). The calibration incense (31) is pressed down by the incense-feeding roller (28) and placed in the incense-placement groove (30). The incense-feeding stepper motor (37) drives the incense-feeding roller (28) to rotate. The temperature sensor (34) detects the temperature of the front end of the calibration incense (31). The incense burning control components include a servo motor (23), a cutter (25), and a rechargeable lighter (33). The rechargeable lighter (33) can ignite the calibration incense (31) to generate CO2. The servo motor (23) drives the cutter (25) to cut off the front end of the calibration incense (31).

2. The field high-sensitivity CO2 concentration detection device according to claim 1, characterized in that: The signal acquisition components also include an air intake pipe (38), an air intake pump (39), an air intake control solenoid valve (40), an exhaust control solenoid valve (49), and a piston connector (54); a through-hole air inlet (10) is provided between the secondary gas mixing chamber (8) and the detection chamber (13). The air intake end of the air intake pipe (38) is exposed in the detection chamber (13) and faces the air inlet (10), while the other end is connected to the air inlet of the air intake pump (39). The air outlet of the air intake pump (39) is connected to the air intake control solenoid valve (54). The solenoid valve (40) is connected, the other end of the air intake control solenoid valve (40) is connected to the cylinder liner (41), the piston (53) is connected to the piston connector (54) located outside the cylinder liner (41), the exhaust port at the top of the cylinder liner (41) is connected to the exhaust control solenoid valve (49), and the other end of the exhaust control solenoid valve (49) is connected to the exhaust pipe (48); the outer shell (2) at the position of the detection chamber (13) is provided with the detection device air outlet control valve (11), and the exhaust pipe (48) is directly facing the detection device air outlet control valve (11). The compression control component includes a compression stepper motor (47), a lead screw and nut mechanism, and a limit switch (57). The compression stepper motor (47) is connected to the lead screw and nut mechanism, which is connected to the piston connector (54) to drive the piston (53) to reciprocate. The limit switch (57) is directly opposite the piston connector (54).

3. The field high-sensitivity CO2 concentration detection device according to claim 2, characterized in that: The detection chamber (13) is equipped with a control circuit board (15) and a solar cell (14). The air intake chamber (19) is equipped with an air intake fan (18). The control circuit board (15) includes an ARM processor, a wireless communication module, an input interface circuit and an output interface circuit, and is powered by the solar cell (14). The ARM processor issues commands through the output interface circuit to control the air outlet control valve (11), the air inlet control valve (17), the air intake fan (18), the servo motor (23), the rechargeable lighter (33), the incense stepper motor (37), the gas sampling pump (39), the air intake control solenoid valve (40), the compression stepper motor (47), and the exhaust control solenoid valve (49) of the detection device. The ARM processor issues commands through the input interface circuit to collect and convert the signals of the electrochemical CO2 sensor (50), the temperature sensor (34) and the limit switch (57).

4. The field high-sensitivity CO2 concentration detection device according to claim 1, characterized in that: The first-stage gas mixing chamber (1) is equipped with partitions No. 1 and No. 2 arranged perpendicularly and alternately to the air intake direction. The second-stage gas mixing chamber (8) is equipped with partition No. 3, which is perpendicular to partitions No. 1 and No. 2 and perpendicular to the air intake direction.

5. A fault self-diagnosis method for the high-sensitivity CO2 concentration detection device in the field as described in claim 3, characterized in that... Includes the following steps: Step 1): The ARM processor controls the air inlet control valve (17) of the concentration quantitative control chamber and the air outlet control valve (11) of the detection device to close simultaneously. The incense stepper motor (37) rotates, and under the action of the incense roller (28), the calibration incense (31) approaches the temperature sensor (34). The incense stepper motor (37) stops. The rechargeable lighter (33) is controlled to ignite, and the timing starts at the same time. The temperature sensor (34) collects the temperature signal. When the timing reaches the predetermined time, the servo motor (23) rotates to make the cutter (25) cut off the burning part of the calibration incense (31). At this time, the closed space is filled with the calibration gas to be tested. Step 2): The compression stepper motor (47) rotates, and the piston (53) moves towards the limit switch (57). When the limit switch (57) is touched, the compression stepper motor (47) stops rotating, and the piston (53) is at the bottom dead center. At the same time, the intake control solenoid valve (40) and the exhaust control solenoid valve (49) are opened, and the gas sampling pump (39) is started. The cylinder liner (41) is filled with the calibration gas to be tested in the detection chamber (13). The gas sampling pump (39), the intake control solenoid valve (40), and the exhaust control solenoid valve (49) are closed. The compression stepper motor (47) rotates, causing the piston (53) to move upward to the top dead center. The ARM processor collects the current of the electrochemical CO2 sensor (50) and converts it into the corresponding concentration N. k =hi, where h is the conversion coefficient and i is the sensor current; the concentration N k Used as a CO2 concentration calibration value and saved; Step 3): Perform a self-test of the detection device: Repeat steps 1)-2) to obtain the CO2 concentration N of the gas used for the self-test. k * The CO2 concentration N of the gas used for self-testing k * Compared with the CO2 concentration calibration value N k Make a comparison and determine whether the difference is within the set error range. If it is, the detection device is faulty; otherwise, it is working normally.

6. The fault self-diagnosis method according to claim 5, characterized in that: When the detection device is working properly, the compression stepper motor (47) rotates, causing the piston (53) to move toward the limit switch (57). When the limit switch (57) is touched, the compression stepper motor (47) stops rotating, opens the air intake control solenoid valve (40) and the exhaust control solenoid valve (49), starts the air sampling pump (39), fills the cylinder liner (41) with the air to be tested, and closes the air sampling pump (39), the air intake control solenoid valve (40) and the exhaust control solenoid valve (49). The compression stepper motor (47) rotates, and the piston (53) moves to the top dead center, so that the top of the piston (53) is at the top dead center position, and the electrochemical CO2 sensor (50) collects the CO2 concentration of the air to be tested.

7. The fault self-diagnosis method according to claim 5, characterized in that: In step 1), the front end of the calibration incense (31) is aligned with the front end of the incense groove (30), and the incense stepper motor (37) is controlled to rotate forward M steps so that the front end of the calibration incense (31) reaches directly above the rechargeable lighter (33). M = L3 / W1, where W1 is the distance moved by the incense stepper motor (37) per step, and L3 is the distance between the front end of the incense groove (30) and the rechargeable lighter (33).

8. The fault self-diagnosis method according to claim 5, characterized in that: In step 1), when the temperature collected by the temperature sensor (34) is less than T0, the calibration incense (31) moves closer and closer to the temperature sensor (34) until the temperature rises to greater than or equal to the temperature T0, at which point the incense stepper motor (37) stops. T0 is the temperature value of the burning calibration incense (31) head facing the charging lighter (33) above.

9. The fault self-diagnosis method according to claim 5, characterized in that: In step 3), the ARM processor determines whether the set self-test cycle has expired. If it has not expired, no self-test is required, the CO2 concentration quantitative control component (20) will not work, and the CO2 concentration detection component (12) will work normally. If it has expired, a self-test will be performed.

10. The fault self-diagnosis method according to claim 6, characterized in that: The sensitivity coefficient of the electrochemical CO2 sensor (50) for acquiring the CO2 concentration of the air to be measured. L1 is the distance between the bottom dead center and the top dead center, L2 is the distance between the top dead center and the top of the cylinder liner (41), the temperature of the air to be tested before compression is T1, and the temperature after compression is T2.

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