应用于水质监测的气相色谱流量控制器的研发

发布时间：2018-05-04 16:16

本文选题：挥发性有机物 + 流量控制　；参考：《湖南师范大学》2015年硕士论文

【摘要】：挥发性有机物(VOCs)是一类常见的有机污染物,广泛存在于大气与水环境中。气相色谱作为一种分离混合物各组分的高效方法,在有机污染物检测领域得到了广泛的应用。气相色谱的流量控制技术是实现水环境中挥发性有机物自动化监测设备小型化的关键技术之一。目前,气相色谱-质谱联用法是我国有机物检测的主要手段,水环境中的挥发性有机物监测对实验室检测依赖比较严重,因此,能够现场监测挥发性有机物的自动化监测设备亟需得到研究和开发。论文在流体力学的基础上对管路内以及色谱柱中的气流流量的测量原理和方法进行了分析,推导了气相色谱中的流量计算公式,对模拟输出和数字输出的差压传感器性能进行测试,为选型提供了理论指导。基于TM4C1233H6PM微处理器和节流差压法设计制作了具有过流、过压、防反接以及防雷保护的流量控制硬件,编写了流量控制器的测控软件。结合传感器和被控对象以及控制器件比例阀特性,研究了基于改进型PID控制的流量控制策略,并确定了参数整定的步骤和方法。流量控制器采用RS-485总线通信,使用ModBus通信协议作为控制器与仪器控制单元的通信协议。该气体流量控制器能在0-600mL/min范围内对气流具有较好的控制效果,其控制响应时间小于2s,过冲小于0.5%,在控制精度上小流量时优于0.7%,中高流量时优于0.5%;在针对控制器通信功能干扰测试中,能够排除错误帧的干扰,提取并应答正确的数据帧。
[Abstract]:Volatile organic compounds (VOCs) are a kind of common organic pollutants, which widely exist in the atmosphere and water environment. Gas chromatography, as an efficient method for separating components of mixtures, has been widely used in the field of detection of organic pollutants. The flow control technology of gas chromatography is one of the key technologies to realize the miniaturization of volatile organic compounds (VOCs) automatic monitoring equipment in water environment. At present, gas chromatography-mass spectrometry (GC-MS) is the main method for the detection of organic compounds in China. The monitoring of volatile organic compounds in water environment depends heavily on laboratory detection. The automatic monitoring equipment which can monitor volatile organic compounds on site needs to be researched and developed. On the basis of hydrodynamics, the measuring principle and method of flow rate in pipeline and chromatographic column are analyzed, and the calculation formula of flow rate in gas chromatography is deduced. The performance of differential pressure sensor with analog output and digital output is tested, which provides theoretical guidance for selection. Based on TM4C1233H6PM microprocessor and throttle differential pressure method, the flow control hardware with overcurrent, overvoltage, anti-backconnect and lightning protection is designed and manufactured. The measurement and control software of flow controller is programmed. Based on the characteristics of sensor, controlled object and proportional valve of controller, the flow control strategy based on improved PID control is studied, and the steps and methods of parameter setting are determined. The flow controller uses RS-485 bus to communicate, and ModBus protocol is used as the communication protocol between the controller and the instrument control unit. The gas flow controller can control the airflow in the range of 0-600mL/min. The control response time is less than 2 s, the overshoot is less than 0.5, the control precision is better than 0.7 when the flow is small, and the middle and high flow is better than 0.5. In the test of interference of the communication function of the controller, the interference of error frame can be eliminated, and the correct data frame can be extracted and answered.
【学位授予单位】：湖南师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X853

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