High-precision full-range carbon dioxide sensor

Abstract

The high-precision full-range carbon dioxide sensor comprises a sampling module, the sampling module comprises a water-gas membrane separator, a micro gear pump and an exhaust water-blocking gas-permeable membrane, the sampling module is responsible for actively extracting environment gas to be detected, the water-gas membrane separator is used for preliminarily separating vaporous water from liquid water, and the micro gear pump is used for controlling the gas flow rate; and finally, the gas is discharged through the exhaust water-blocking breathable film, so that the gas sample in the optical measurement chamber is continuously updated, and internal optical elements are protected from being damaged by water vapor and pollutants. According to the invention, humidity information in the optical cavity is directly acquired by using the infrared detection module, and in-situ measurement temperature and pressure in the cavity are combined, so that'in-situ, multi-parameter and direct measurement type 'compensation of carbon dioxide concentration is realized, a compensation model is closer to physical reality, and the precision is far higher than that of an indirect compensation mode depending on an external environment sensor.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide sensor technology, and in particular to a high-precision full-range carbon dioxide sensor. Background Technology

[0002] Carbon dioxide (CO2) is a key gaseous parameter in industrial production, environmental monitoring, agriculture, and scientific research. Accurate and rapid measurement of its concentration is crucial for process control, safety early warning, emission monitoring, and scientific research. Currently, various methods exist for detecting gas concentrations, among which non-dispersive infrared (NDIR) absorption has become one of the mainstream technologies for CO2 measurement due to its advantages such as high selectivity, high stability, and long lifespan. NDIR technology is based on Beer-Lambert's law, which states that when infrared light of a specific wavelength passes through the gas being measured, its intensity decreases due to absorption by gas molecules, and the degree of attenuation is exponentially related to the gas concentration.

[0003] Chinese Patent CN220340012U relates to the field of automotive sensor technology, specifically a carbon dioxide sensor assembly. This assembly includes a housing and a PCBA board located within the housing. The housing consists of an upper cover and a lower cover. The carbon dioxide sensor employs photoacoustic spectroscopy technology, resulting in a significantly reduced size, stable signal, and long-term stable operation. The smaller size of the carbon dioxide sensor allows for a corresponding reduction in the size of the housing. The housing is formed by the upper and lower covers being snapped together, facilitating easy connection. The upper part of the carbon dioxide sensor extends into the air inlet of the upper cover, resulting in more accurate detection. One side edge of the lower cover protrudes downwards to form a connector with conductive terminals inside. This reduces the overall length of the housing, making the structure more compact and easier to install compared to existing technologies where the connector is located at one end of the housing.

[0004] Chinese Patent CN211122771U discloses a carbon dioxide sensor, comprising: a main control MCU module, and a pulse width modulation (PWM) module and a signal output module connected to the main control MCU module. The main control MCU module modulates the read carbon dioxide concentration value through the PWM module and then sends it through the signal output module. Centered on the main control MCU module, one side is connected to the carbon dioxide sensor to read the carbon dioxide concentration value; the other side is connected to both the PWM module and the signal output module. The signal output module, such as a UART serial port, outputs the precise concentration value calculated by the main control MCU module in digital signal format, such as hexadecimal, providing a more accurate concentration value compared to conventional carbon dioxide sensors. The PWM module outputs the carbon dioxide concentration value as a PWM waveform signal, reflecting the trend of carbon dioxide concentration changes. The carbon dioxide sensor provided in this patent integrates both UART and PWM signal output methods, resulting in higher output accuracy and richer signal representation, solving the problem of limited signal output methods in existing carbon dioxide sensors and facilitating user selection.

[0005] Chinese patent CN204613189U discloses a carbon dioxide sensor. This carbon dioxide sensor includes: a solar power supply device, a carbon dioxide sensor, and a timing controller. The solar power supply device is electrically connected to both the carbon dioxide sensor and the timing controller. The timing controller is signal-connected to both the solar power supply device and the carbon dioxide sensor, periodically triggering the solar power supply device to power the carbon dioxide sensor and periodically waking the carbon dioxide sensor to detect environmental data. Powering the sensor via the solar power supply device ensures a stable power supply. Controlling the solar power supply device to power the sensor periodically and periodically waking the carbon dioxide sensor to detect environmental data achieves efficient power management, avoiding malfunctions due to battery depletion and eliminating the environmental limitations imposed by an external power cord.

[0006] Chinese Patent CN110261538B discloses an air conditioning fresh air system and a calibration method for its carbon dioxide sensor. This invention aims to solve the problem of inaccurate detection results from carbon dioxide sensors in existing air conditioning fresh air systems. To this end, the air conditioning fresh air system of this invention includes a first standard gas tank and a first control valve connected to each other. When the first control valve is open, standard gas from the first standard gas tank is blown towards the carbon dioxide sensor. The calibration method of this invention includes the following steps: switching the first control valve to the open state; after the first control valve has been switched to the open state for a first preset time, causing the carbon dioxide sensor to detect the concentration value of carbon dioxide; and replacing the detected concentration value with the first standard value. The calibration method of this invention effectively avoids severe drift of the carbon dioxide sensor over time through the above steps, thereby effectively ensuring the accuracy of the carbon dioxide sensor detection results.

[0007] Chinese patent CN114518435B discloses a carbon dioxide sensor assembly for coal mines, including a carbon dioxide sensor body, a gas-sensitive probe at the bottom of the carbon dioxide sensor body, a protective shell on the outside of the gas-sensitive probe, ventilation holes on the outside of the protective shell, an annular threaded groove at the bottom of the protective shell, a support cover on the annular threaded groove, a dustproof component for easy positioning and installation on the support cover, and a protective component with air blowing cleaning function on the outside of the protective shell. This invention, by adding multiple ventilation holes to the protective shell of the gas-sensitive probe, allows carbon dioxide from the mine to enter through multiple ventilation holes, improving the carbon dioxide sensor's concentration detection effect from multiple directions, thereby protecting the gas-sensitive probe and facilitating its use in coal mining environments, thus ensuring personal safety.

[0008] Based on the aforementioned publicly available patent documents, traditional NDIR sensors face a series of technical challenges in practical industrial applications and complex environment monitoring, limiting further performance improvements and the expansion of their application scope. The main problems are as follows: 1. The contradiction between measurement range and accuracy: For traditional sensors with fixed optical path and fixed light source intensity, the measurement dynamic range is limited. When the CO2 concentration is high, the relative absorption rate of infrared light tends to saturate, resulting in a significant decrease in measurement accuracy or even failure to measure in the high concentration range. To cover a wide range from trace concentrations to high concentrations, it is often necessary to equip multiple sensors of different specifications or complex mechanical dimming mechanisms, which increases the system cost and complexity. 2. Cross-interference and environmental factors: Actual gas samples often contain water vapor (H2O), whose infrared absorption spectrum partially overlaps with or is adjacent to that of CO2. Especially in open environments or industrial humid gases, the interference of water vapor can seriously affect the accuracy of CO2 measurement results. In addition, changes in gas pressure and ambient temperature can also change the absorption characteristics of gas molecules, introducing measurement errors. Although traditional sensors have compensation, they mostly use fixed coefficients or single sensors, which are insufficient for real-time and accurate compensation in dynamically changing environments. 3. Sampling and Response Speed ​​Limitations: For process monitoring or safety monitoring, rapid response is crucial. Traditional sampling methods rely on free gas diffusion, resulting in a slow response time (T90), especially in low-flow-rate or confined space applications, failing to reflect rapid changes in gas concentration in a timely manner. Furthermore, efficiently and continuously acquiring dry gas samples from humid industrial gas sources while avoiding damage to the sensor from liquid water is also an engineering challenge. 4. System stability and maintenance: Aging and fluctuations of infrared light sources, as well as the sensitivity of infrared detectors (such as photoconductive sensors) to ambient temperature, can lead to baseline drift and signal fluctuations, requiring frequent calibration. Traditional constant current driven light sources and simple detector temperature control methods are difficult to maintain the long-term stability of the optical path system over a wide temperature range, affecting the reliability of measurements and maintenance cycles. To address the aforementioned issues, existing technologies employ mechanical structures such as multi-optical paths, filter wheels, or adjustable apertures to broaden the measurement range or enable reference measurements. However, this often results in increased sensor size, structural complexity, power consumption, and cost. Regarding interference resistance, while dual-wavelength or multi-channel technologies are used, there is still room for improvement in the accurate dynamic compensation for water vapor and the coordinated real-time compensation for pressure and temperature. Therefore, there is an urgent need in this field for a novel NDIR carbon dioxide sensor technology that achieves wide-range, high-precision, and fast-response measurements, while possessing strong anti-cross-interference capabilities (especially for water vapor), excellent environmental adaptability, and a compact and stable system structure to meet the increasingly complex needs of industrial engineering and environmental monitoring applications. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-precision full-range carbon dioxide sensor.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A high-precision full-range carbon dioxide sensor, comprising: Sampling Module: This module includes a water vapor membrane separator, a micro gear pump, and an exhaust water-barrier and breathable membrane. It actively extracts the gas from the environment to be measured, uses the water vapor membrane separator to initially separate gaseous and liquid water, controls the gas flow rate through the micro gear pump, and finally discharges the gas through the exhaust water-barrier and breathable membrane. This continuously updates the gas sample within the optical measurement chamber and protects the internal optical components from moisture and contaminants.

[0011] Optical Measurement Chamber: Contains the gas sample to be measured after it has been processed by the sampling module, providing a gas chamber environment for infrared absorption measurement.

[0012] Infrared light source: Emits broad-spectrum infrared light into the optical measurement chamber. This broad-spectrum infrared light contains at least three characteristic wavelengths: a first wavelength for humidity compensation, a second wavelength for reference light intensity detection, and a third wavelength for carbon dioxide concentration measurement.

[0013] Infrared detection module: configured to selectively detect the light intensity of at least the first wavelength, the second wavelength and the third wavelength, and convert the optical signal into an electrical signal.

[0014] Environmental parameter detection module: Includes pressure and temperature sensors directly integrated into the optical measurement chamber or its connecting gas line, which can detect the gas pressure and ambient temperature in the measurement chamber in real time and in situ, providing accurate environmental parameters for concentration compensation.

[0015] Control and processing unit: As the core of the sensor, it is electrically connected to the infrared light source, infrared detection module, environmental parameter detection module and micro gear pump.

[0016] The control and processing unit is configured to perform the following core operations: a) Adaptive Range Measurement: First, the infrared light source is controlled to emit infrared light at a low initial intensity (or standard intensity). Based on the signal intensity detected by the infrared detection module at the third wavelength (the absorption wavelength of carbon dioxide), the current carbon dioxide concentration is initially determined to belong to a wide range (e.g., in the mol or percentage range). Then, based on this initial determination, the driving current of the infrared light source is dynamically adjusted to output a "precise measurement intensity" that matches the concentration range (e.g., for high concentrations, a lower intensity is used to avoid signal saturation; for low concentrations, a higher intensity is used to improve the signal-to-noise ratio). Finally, under this optimized intensity, the detection signal at the third wavelength is acquired again to accurately calculate the carbon dioxide concentration. This process achieves automatic switching and optimization of the measurement range.

[0017] b) Multi-parameter compensation: After obtaining the accurately measured original concentration value, comprehensive compensation is performed. The compensation parameters come from three aspects: 1) real-time gas pressure and ambient temperature values ​​provided by the environmental parameter detection module; 2) humidity information of the indoor gas sample obtained by calculating the absorbance and inverting the light intensity detected by the infrared detection module at the first wavelength. Based on the built-in compensation algorithm model, the control and processing unit uses the above parameters to perform comprehensive linear or nonlinear correction on the original carbon dioxide concentration value, and finally outputs a high-precision carbon dioxide concentration value compensated for environmental factors.

[0018] As a further improvement of the present invention, in the adaptive range measurement operation, the range interval is divided into at least three discontinuous or continuous intervals, covering the carbon dioxide concentration range from 0 to 100%. The specific interval division may include, but is not limited to, multiple or all combinations of 0-2000mol, 5000mol, 30000mol, 50000mol, 10%, 20%, 50%, 70% and 100%, so as to achieve accurate measurement from trace to pure carbon dioxide gas.

[0019] As a further improvement of the present invention, the control and processing unit precisely adjusts the light intensity of the infrared light source through a closed-loop control method. Specifically, the light intensity of the second wavelength (reference channel, not absorbed by the target gas and major interfering gases) is used as the reference light intensity. The system presets a target light intensity value that matches the current range. Based on the difference between the target light intensity and the real-time detected reference light intensity, the driving current of the infrared light source is dynamically adjusted through a PID (proportional-integral-derivative) algorithm, thereby achieving precise and stable control of the infrared light emission intensity and overcoming the effects of light source aging and temperature drift.

[0020] As a further improvement of the present invention, a constant temperature control module is also included. This module includes an ETC constant temperature cooling element and a temperature sensor disposed on the infrared detection module. Based on the actual temperature of the infrared detection module measured by the temperature sensor, the control and processing unit controls the drive current of the ETC constant temperature cooling element (heating or cooling) through a PID algorithm, maintaining the infrared detection module at a constant optimal operating temperature, greatly reducing detector temperature drift and improving signal stability.

[0021] As a preferred embodiment of the present invention, the first wavelength is 2450nm, which is sensitive to water vapor absorption and is specifically used to detect the water vapor concentration in the optical cavity to achieve humidity compensation; the second wavelength is 3910nm, which is located in the absorption valley of carbon dioxide and water vapor, and serves as a reference channel unaffected by the target gas and the main interfering gas; the third wavelength is 4260nm, which is located in the strong absorption peak range of carbon dioxide and is specifically used for carbon dioxide concentration measurement.

[0022] As a further improvement of the present invention, the sampling module adopts an optimized configuration: the air inlet of the micro gear pump is connected to the air inlet water-resistant and breathable membrane located at the bottom of the sensor via an air path, and its air outlet is connected to the air outlet water-resistant and breathable membrane located at the top of the sensor via an air path. This design forms a bottom-up air intake and exhaust path, which is beneficial for utilizing natural gas convection and preventing condensation accumulation. At the same time, the double water-resistant and breathable membrane design further ensures the protection level of the sensor.

[0023] As a further improvement of the present invention, the sensor communication interface is an industrial standard RS485 interface, which supports protocols such as Modbus RTU, making it easy to integrate. The housing is preferably made of titanium alloy, which has the advantages of high strength, corrosion resistance and lightweight, and is suitable for harsh industrial environments.

[0024] The beneficial effects of this invention are as follows: 1. By directly acquiring humidity information inside the optical cavity using an infrared detection module, and combining it with the temperature and pressure measured in situ inside the cavity, "in-situ, multi-parameter, direct measurement" compensation for carbon dioxide concentration is achieved. The compensation model is closer to physical reality and its accuracy is far higher than that of indirect compensation methods that rely on external environmental sensors.

[0025] 2. Closed-loop light intensity control stabilizes the light source output, and constant temperature control stabilizes the detector performance. This dual approach fundamentally reduces the drift of core optical components, ensuring the long-term stability of the sensor and low maintenance requirements.

[0026] 3. The titanium alloy housing enables the sensor to effectively cope with harsh working conditions such as high humidity, condensation, and dust, ensuring reliable sampling and a long service life.

[0027] 4. It integrates intelligent range judgment, closed-loop control, and comprehensive compensation algorithm, so users can obtain reliable data without manually switching ranges or performing complex calibrations, and can easily connect to various control systems through standard industrial interfaces. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the electrical principle of a high-precision full-range carbon dioxide sensor proposed in this invention. Figure 2 This is a first schematic diagram of carbon dioxide measurement using a high-precision full-range carbon dioxide sensor proposed in this invention. Figure 3 This is a second schematic diagram of carbon dioxide measurement using a high-precision full-range carbon dioxide sensor proposed in this invention. Figure 4 This is a schematic diagram of the sensor structure of a high-precision full-range carbon dioxide sensor proposed in this invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection", and "setting" should be interpreted broadly. For those skilled in the art, the specific meaning of the above terms in this patent can be understood according to the specific circumstances.

[0030] Reference Figures 1-4 The high-precision full-range carbon dioxide sensor in this embodiment has a hardware system that mainly includes a sampling module, an optical measurement chamber, an infrared light source, an infrared detection module, an environmental parameter detection module, a constant temperature control module, and a control and processing unit.

[0031] In this invention, the sampling process is as follows: When the sensor is working, the control and processing unit activates a micro gear pump. Ambient gas enters through the bottom inlet water-blocking and permeable membrane, first passing through a water-gas membrane separator where liquid water is blocked and separated. The dried gaseous sample, driven by the micro gear pump, is pumped into the optical measurement chamber. After optical detection is completed in the chamber, the gas continues to flow and exits the sensor through the top exhaust water-blocking and permeable membrane. This active, unidirectional, bottom-up airflow path effectively refreshes the gas sample and prevents the retention of contaminants and condensate.

[0032] Optical detection and signal processing: The control and processing unit drives the infrared light source to emit broad-spectrum infrared light. After the beam passes through the gas sample in the optical measurement chamber, it is received by the infrared detection module. The infrared detection module uses multi-channel filter or grating beam splitting technology to accurately extract the light intensity signals of 2450nm (water vapor channel), 3910nm (reference channel) and 4260nm (carbon dioxide channel) respectively, and convert them into voltage signals.

[0033] Adaptive range switching: The control and processing unit first controls the infrared light source to be driven by a standard current to emit an initial light intensity and reads the original voltage signal of the 4260nm channel. The system has pre-stored signal intensity thresholds corresponding to different concentration ranges. By comparing these thresholds, it can quickly determine which range the current CO2 concentration roughly belongs to. Based on the determination result, it finds the "target reference light intensity value" (corresponding to the target voltage of the 3910nm channel) that matches the range. Subsequently, the system enters the light intensity closed-loop adjustment stage: using the actual voltage of the current 3910nm channel as feedback, the PID controller calculates and outputs a new light source drive current. After the light intensity stabilizes, the system again acquires the signal of the 4260nm channel with high precision and calculates the uncompensated original carbon dioxide concentration value.

[0034] Multi-parameter compensation: The system performs the following simultaneously while calculating the original concentration: Humidity compensation calculation: Based on the light intensity signal of the 2450nm channel and combined with the Beer-Lambert law, the volumetric humidity H of the gas inside the optical cavity is calculated.

[0035] Environmental parameter reading: Read the current gas temperature T and absolute pressure P from the temperature and pressure sensors integrated on the optical measurement chamber.

[0036] Temperature control: Throughout the measurement process, the control and processing unit continuously monitors the temperature sensor on the infrared detection module. If the detector temperature deviates from the set constant operating point (e.g., 45°C), the current of the ETC thermostat is adjusted to heat or cool it, ensuring that the detector is in a thermally stable state.

[0037] Output and Communication: The compensated high-precision carbon dioxide concentration value can be output as a digital signal via an RS485 interface. All sensor parameter settings, calibration, and advanced diagnostic functions can also be performed through this interface.

[0038] The specific implementation is as follows: When the sensor measures, it first uses the minimum light intensity to measure the approximate range of the gas concentration to be measured, and then uses the corresponding light intensity to accurately measure the gas concentration according to the range. To ensure measurement accuracy, the measurement range is divided into 9 segments: 0-2000mol, 5000mol, 30000mol, 50000mol, 10%, 20%, 50%, 70%, and 100%. Among them, % is the mole percentage, 1% = 10000mol. For easy recording, if it exceeds a certain mol, it can be expressed as a percentage. When measuring the gas concentration, the appropriate infrared light intensity will be dynamically selected so that the relative absorption rate will not fall into the saturation region, thus ensuring the accuracy of the concentration measurement. The relative absorption rate of gas infrared radiation varies with pressure, temperature, and moisture. Therefore, the sensor is equipped with a high-precision gas pressure sensor, a temperature sensor, and an infrared moisture detection channel. The pressure, temperature, and moisture in the gas chamber are measured in real time, and the carbon dioxide output value is linearly compensated. Ambient temperature affects the signal output of the photoconductivity sensor. The photoconductivity sensor is protected by an ETC thermostatic cooling chip. The actual temperature of the photoconductivity sensor is measured by a temperature sensor. A PID algorithm is used to control the drive current of the ETC thermostatic cooling chip to precisely control the temperature of the photoconductivity sensor. A miniature gear pump is installed inside the sensor. The gear pump draws gas from behind the water-resistant and breathable membrane below the sensor and exhausts it through the water-resistant and breathable membrane installed on the top of the sensor. This allows for timely replenishment of the sample gas, thereby improving the sensor's response time. By exhausting the gas upwards, it does not affect environmental monitoring. In this application, the structures and connections not described in detail are all prior art, and their structures and principles are well known, so they will not be described in detail here.

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high precision full range carbon dioxide sensor characterized by, The application relates to a carbon dioxide concentration measuring device, comprising: a sampling module, which comprises a water vapor membrane separator, a micro gear pump and an exhaust water-blocking air permeable membrane, extracts, separates and updates a gas sample to be measured; an optical measuring chamber containing the gas sample to be measured; an infrared light source emitting broadband infrared light to the optical measuring chamber, wherein the broadband infrared light at least contains a first wavelength for humidity compensation, a second wavelength for reference light intensity detection and a third wavelength for carbon dioxide concentration measurement; an infrared detection module configured to detect at least the light intensity of the first wavelength, the second wavelength and the third wavelength; an environmental parameter detection module comprising a pressure sensor and a temperature sensor, which detects the gas pressure and the environmental temperature in the optical measuring chamber in real time; a control and processing unit electrically connected with the infrared light source, the infrared detection module, the environmental parameter detection module and the micro gear pump; wherein the control and processing unit is configured to perform the following operations: a) adaptive range measurement: controlling the infrared light source to emit infrared light at an initial light intensity, and preliminarily judging the range interval of the carbon dioxide concentration according to the detection signal of the infrared detection module at the third wavelength; then, based on the determined range interval, dynamically adjusting the infrared light source to a matched accurate measurement light intensity, and again performing accurate measurement of the carbon dioxide concentration according to the detection signal at the third wavelength; b) multi-parameter compensation: based on the gas pressure and the environmental temperature detected by the environmental parameter detection module, and the humidity information reflected by the light intensity at the first wavelength detected by the infrared detection module, linearly compensating the carbon dioxide concentration value obtained by accurate measurement.

2. A high accuracy full range carbon dioxide sensor according to claim 1, characterized in that In the adaptive range measurement operation, the range interval is divided into at least three discontinuous or continuous intervals, covering the carbon dioxide concentration range of 0-100%.

3. A high accuracy, full range carbon dioxide sensor according to claim 2, wherein, The range interval includes multiple or all of 0-2000mol, 5000mol, 30000mol, 50000mol, 10%, 20%, 50%, 70% and 100%.

4. The high accuracy, full range carbon dioxide sensor of claim 1, wherein, The control and processing unit adjusts the light intensity of the infrared light source in a closed-loop control mode, specifically: taking the light intensity at the second wavelength as the reference light intensity, and dynamically adjusting the driving current of the infrared light source through a PID algorithm according to the difference between the preset target light intensity and the reference light intensity, so as to realize accurate control of the infrared light intensity.

5. The high accuracy, full range carbon dioxide sensor of claim 1 wherein, Further comprising a constant temperature control module, which comprises an ETC constant temperature refrigeration sheet and a temperature sensor arranged on the infrared detection module; the control and processing unit controls the driving current of the ETC constant temperature refrigeration sheet through a PID algorithm according to the actual temperature of the infrared detection module measured by the temperature sensor, so that the infrared detection module is maintained at a constant working temperature.

6. The high accuracy, full range carbon dioxide sensor of claim 1, wherein, The first wavelength is 2450nm, the water vapor concentration detection is used for humidity compensation; the second wavelength is 3910nm, which is a reference channel not affected by carbon dioxide and water vapor absorption; and the third wavelength is 4260nm, which is located in the absorption peak range of carbon dioxide and is used for carbon dioxide concentration measurement.

7. The high accuracy, full range carbon dioxide sensor of claim 1 wherein, The configuration of the sampling module is that the air inlet of the micro gear pump is connected to the air inlet water-blocking air permeable membrane at the bottom of the sensor through an air path, and the air outlet is connected to the air outlet water-blocking air permeable membrane at the top of the sensor through an air path, thereby forming a downward air suction and exhaust path.

8. The high accuracy, full range carbon dioxide sensor of claim 1 wherein, The sensor communication interface is an RS485 interface, and the shell material is titanium alloy.

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