Research On Non-spectral Infrared CO₂ Gas Sensor With Temperature Compensation Function

The monitoring of carbon dioxide（CO₂）levels is one of the important safeguards for safety in mining industry operations.The extensive activities involved in mining release large amounts of CO₂,which inevitably increases the probability of coal mining accidents.Therefore,timely detection of CO₂concentration is crucial to ensure the safety of miners.Based on non-dispersive infrared（NDIR）differential detection technology,a high-precision,fast response,stable,large-range and adaptable CO₂gas sensor has been developed.On this basis,an experimental testing platform has been established to analyze its performance indicators through a series of experiments.The main research contents are as follows:（1）Determine the overall design scheme for CO₂gas concentration detection.Based on the research of the development of gas sensors at home and abroad,establish a non-dispersive infrared differential detection model according to the principle of infrared spectroscopy absorption and introduce a reference channel to effectively improve the detection accuracy and anti-interference ability of the sensor.（2）Preparation of dual channel pyroelectric detector sensitive elements.Lithium tantalate crystal infrared sensitive components were prepared using thinning,polishing,sputtering and other process technologies.A dual channel reverse parallel structure was designed to achieve the conversion of light signals to electrical signals.The sensitive element,filter,and preamplifier circuit were encapsulated through a TO5 tube shell,and their voltage response rate,noise,and detectivity were tested.（3）Establishment of optical system.By using electrical modulation instead of mechanical modulation,the stability of the entire system has been improved.A 3D model of the multi-reflection chamber structure was completed using Solid Works,and the internal light path was simulated using optical software Trace Pro to achieve sufficient absorption of infrared light.The chamber model was prepared using 3D printing technology and the chamber walls were plated with gold for anti-corrosion treatment.A waterproof and breathable film was placed on the upper layer for moisture and dust protection.（4）Hardware circuit and upper computer system design.The hardware part uses STM32microcontroller as the core.For the characteristics of infrared light source,the light source driving circuit is designed to achieve electrical modulation;for the working characteristics of the detector,the signal conditioning circuit is designed to amplify and filter the weak output signals of the detector;for the sensitivity of the sensor to temperature,the temperature acquisition circuit is designed to realize the real-time acquisition of the ambient temperature.The CO₂gas concentration acquisition interface is designed through Lab VIEW software to achieve information interaction between the upper computer and the microcontroller.（5）Using a laboratory testing platform,calibration experiments were conducted at different temperatures using standard CO₂gas concentrations ranging from 0%to 5%,exploring temperature compensation methods and testing the sensor’s precision,repeatability,stability,and response time indicators.Experimental data showed that the sensor designed in this project can accurately detect CO₂gas concentrations within a range of 0%to 5%by temperature compensation,with an absolute error of less than±0.1%within 0%to 3%concentration and less than±0.15%within 3%to 5%concentration.The overall relative error was less than 3%,and the response time was less than 30s,demonstrating excellent repeatability and stability.This study elaborates on the key technologies for designing a non-dispersive infrared CO₂gas sensor,achieving the expected performance indicators of the system,meeting the demand for real-time detection of CO₂gas concentration in environments such as mines,and providing practical reference value for subsequent research on high-performance gas sensors.