中红外二氧化碳传感器的研制及在农业中的应用

Development and Agricultural Application of a Mid-Infrared Carbon Dioxide Sensor System

利用二氧化碳气体分子在4.25μm处的基频吸收带,研制了一种差分式中红外二氧化碳检测系统.系统的光路部分由热辐射红外光源、双通道热释电探测器和球面反射镜构成,电路部分主要包括信号处理、光源驱动及主控模块.采用Tracepro软件对气室结构进行仿真和优化设计,使气体吸收光程达到30cm,改善了系统的性能.实验研究了系统对不同浓度二氧化碳气体样品的传感特性.实验结果表明,由拟合曲线得到的浓度与实际浓度误差较小,在0~5 000ppm范围内,测得二氧化碳浓度的标准差小于45ppm,而在500ppm以下,测量浓度的标准差小于5ppm;对浓度为0ppm的二氧化碳气体样品连续测量2h,测量结果的标准差约为2.8ppm;根据Allan方差分析得到系统的1σ检测下限为2.5ppm.在每个二氧化碳传感器上增加无线模块nRF24L01,构成传感器节点,在选定的日光温室大棚中构建了无线传感器网络,采集了温室大棚中的二氧化碳浓度信息,验证了所研制的传感器性能.

Using the fundamental absorption band at the wavelength of 4.25μm of carbon dioxide molecule,a differential mid-infrared carbon dioxide detection system was developed.The optical part of the system includes infrared thermal emitter,dual-channel pyroelectric detector and spherical mirror and the circuit part mainly consists of signal-processing,source-driving and main-control module.Simulating and optimizing the structure of the gas cell by using Tracepro software,eventually,the optical path of the gas absorption reaches 30 cm,and the performance of the system is improved.Preparing standard carbon dioxide gases with different concentration and investigating the sensing characteristics of system on carbon dioxide gas.Experimental results indicate that,the error between the measured concentration which are obtained by fitting curve and actual concentration is small,in the range of 0~5000ppm,the standard deviation of the measured concentration is less than 45 ppm,and that is less than 5 ppm under 500ppm;the standard deviation of 2 hours long-term measurement concentration on the 0ppm is about 2.8ppm;the 1σ theoretical limit of detection obtained from the Allan variance is 2.5ppm.Finally,each carbon dioxide sensor becomes a sensor node by adding wireless module nRF24L01 on each carbon dioxide sensor.Building a wireless sensor network in the chosen greenhouse.We have collected the carbon dioxide concentration and verified the performance of the developed sensor by filed application.