具有温度补偿的非分光红外CO2传感器设计

近年来，温室效应愈发明显，环境二氧化碳（CO₂）浓度增加带来的副作用严重影响了人们的生产生活。目前，商业化的CO₂传感器体积较大，便携化、高精度、模块化等方面不尽人意，设计了一种基于热释电的非分光红外法（NDIR） CO₂浓度测量系统，主要分为气室结构设计、信号电路设计、软件控制设计与数据处理四个部分。气室结构设计方面采用单通道结构设计，并对气室进行了光学仿真，最终确定了气室的尺寸，有效提高了系统的测量精度。信号电路设计方面设计了一种基于差分方式的小信号放大电路，将有效信号从噪声中提取并放大，提高分辨率。软件控制设计方面应用数字滤波算法，滤除干扰与杂波，提取数据中的有效值，提高信噪比。数据处理方面，搭建CO₂气体测试平台，通过温湿度与峰峰值补偿公式补偿温度对峰峰值产生的影响，再使用25 ℃下曲线拟合法计算气体浓度值，最终通过串口输出。经过测试，该系统测量范围为5%，相对误差值在1500 ppm以内，能够满足防火报警、矿下监测等场合的安全测试需求。

Design of non-dispersive infrared CO2 sensor with temperature compensation

In recent years, the greenhouse effect has become more and more obvious. The side effects brought by increasing of CO₂ concentration have seriously affected people's production and life, and are even closely related to everyone's healthy. In defect of the large size, portability, high precision, and modularity of CO₂ commercial sensors currently, a pyroelectric-based non-dispersive infrared (NDIR) method measuring CO₂ concentration system was designed. The system design was mainly divided into four parts: air chamber structure design, signal circuit design, software control design and data processing. The air chamber structure design adopted a single-channel structure design, which was optically simulated. Finally, the size of the air chamber was determined, which effectively improved the measurement accuracy of the system. In terms of signal circuit design, a small signal amplifying circuit based on the differential method was designed to extract and amplify the effective signal from the noise to increase resolution. The software control design employed digital filtering algorithm to filter out interference and clutter, extract the effective value in the data, and improve the signal-to-noise ratio. In view of data processing, a gas test platform was built, and the temperature and humidity and peak-to-peak compensation formulas were used to compensate for the influence of temperature on the peak-to-peak value. Then, the gas concentration value was calculated using the curve fitting method at 25 ℃, and finally output through the serial port. After testing, the measurement range of the system is 5%, and the relative error is within 1500 ppm, which can meet the safety requirements of fire alarm, underground and other occasions monitoring.