基于红外吸收光谱的设施园艺二氧化碳检测系统的研究

发布时间：2018-01-29 08:01

本文关键词： 红外吸收光谱 CO_2浓度检测无线传感器网络设施园艺　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：本论文来源于国家科技支撑计划项目“现代节能高效设施园艺装备研制与产业化示范”,项目编号:2014BAD08B00。设施园艺克服了传统种植方式的缺点,不易受地域、自然环境和气候等因素的限制,实现了高产、优质的目的,对农业的发展具有重大意义。CO_2作为植物光合作用的重要原料,其浓度的大小对温室大棚内农作物的生长具有重要的影响,因此检测温室大棚内CO_2的浓度十分必要。在众多的CO_2检测方法中,红外吸收光谱法因其独特的优势得到了人们的普遍关注和广泛应用。此外,构建无线传感器网络能多点采集温室大棚内的CO_2浓度,且克服了有线传输的弊端。本论文研究了基于红外吸收光谱法的设施园艺CO_2检测系统。分析CO_2分子的红外吸收光谱,选择4.25μm附近的强基频吸收峰作为CO_2分子的吸收波长,选择适宜的红外热光源和双通道热释电探测器,并采用球面反射镜增加光程的同时将光线汇聚至探测器,很好地优化了光路结构。设计制作了光源的恒流源驱动电路、信号处理电路和无线通信电路等硬件电路。为了适应温室中的高湿环境,密闭封装光路和电路部分,光路中气体的扩散通过膨化聚四氟乙烯薄膜实现。编写了系统的软件程序,程序包含浓度采集和无线传感器网络两部分,CO_2浓度检测节点采集数据以后加入无线传感器网络,并将采集的数据通过网络发送至汇聚节点,最后汇聚节点通过串口将数据传输给计算机,计算机显示并存储得到的数据。配置了不同浓度的CO_2气体样品进行气体实验,完成了传感器的标定和相关性能的检测。CO_2传感器的检测范围是0~5000 ppm;在150~5000 ppm范围内,测量值的相对误差在-6.0%~9.9%之间;测量了传感器在0 ppm时的长时间稳定性,浓度上下波动峰值是15 ppm,标准差为2.8ppm;计算传感器在0 ppm时输出结果的艾伦方差,得到传感器的1σ检测下限为2.5 ppm。在温室中运用该检测系统对CO_2浓度进行实际测量,得到的曲线与实际相符,从而验证了该检测系统能够较好地应用于温室大棚内CO_2浓度的检测中。本论文的创新点包含两点,一是利用自制的反射镜气室和差分中红外吸收光谱技术,研制了红外CO_2传感器,并对传感器进行防湿处理以适应温室大棚内高湿的环境;二是结合无线射频通信技术构建无线CO_2传感器网络,实现对温室大棚内CO_2浓度的多点检测,并利用研制的CO_2检测系统在日光温室大棚中开展了现场试验。
[Abstract]:This paper comes from the national science and technology support project "modern energy-saving and efficient facilities horticultural equipment development and industrialization demonstration". Project number: 2014BAD08B00. facility horticulture overcomes the shortcomings of traditional planting methods and is not easy to be restricted by such factors as region, natural environment and climate, thus achieving the goal of high yield and good quality. It is of great significance to the development of agriculture. As an important raw material of plant photosynthesis, the concentration of COS _ 2 has an important influence on the growth of crops in greenhouse. Therefore, it is very necessary to detect the concentration of CO_2 in greenhouse. Among many CO_2 detection methods, infrared absorption spectrometry has been widely concerned and widely used because of its unique advantages. The wireless sensor network can collect the concentration of CO_2 in greenhouse. And overcome the shortcomings of cable transmission. This paper studied the facility horticultural CO_2 detection system based on infrared absorption spectrometry. The infrared absorption spectra of CO_2 molecules were analyzed. The strong fundamental frequency absorption peak near 4.25 渭 m is chosen as the absorption wavelength of CO_2 molecule, and the suitable infrared pyroelectric source and two-channel pyroelectric detector are selected. The spherical mirror is used to increase the optical path and the light is converged to the detector, which optimizes the structure of the optical path. The constant current source driving circuit of the light source is designed and fabricated. Hardware circuits such as signal processing circuits and wireless communication circuits. In order to adapt to the high humidity environment in the greenhouse, the optical circuit and circuit parts are sealed. The diffusion of gas in the optical path is realized through expanded PTFE thin film. The software program of the system consists of two parts: concentration acquisition and wireless sensor network. The data collected by the CO_2 concentration detection node is added to the wireless sensor network, and the collected data is sent to the convergence node through the network. Finally, the data is transmitted to the computer through the serial port. The computer displays and stores the obtained data. Different concentrations of CO_2 gas samples are configured to carry out gas experiments. The calibration of the sensor and the detection of the related performance. The detection range of the CO2 sensor is 0 ~ 5000 ppm; In the range of 150 ~ 5000 ppm, the relative error of the measured value is -6.0% or 9.9%. The stability of the sensor for a long time at 0 ppm was measured. The peak value of concentration fluctuation was 15 ppmand the standard deviation was 2.8 ppm. By calculating the Allen variance of the sensor output at 0 ppm, the 1 蟽 detection limit of the sensor is 2. 5 ppm. The system is used to measure the concentration of CO_2 in greenhouse. The obtained curves are in good agreement with the practice, which proves that the system can be applied to the detection of CO_2 concentration in greenhouse. The innovation of this paper includes two points. First, the infrared CO_2 sensor is developed by using self-made reflector chamber and differential mid-infrared absorption spectrum technology, and the sensor is moisturized in order to adapt to the high humidity environment in greenhouse. The other is to construct wireless CO_2 sensor network with radio frequency communication technology to realize the multi-point detection of CO_2 concentration in greenhouse. The field test was carried out in the greenhouse by using the developed CO_2 detection system.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP274

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