基于拉曼光谱的亚硝酸盐监测系统的设计与研究

发布时间：2018-08-06 12:17

【摘要】：亚硝酸盐是一种剧毒物质,同时也可以作为食品添加剂使用,过度摄入亚硝酸盐将会引起中毒,后果严重。在摄入过量的亚硝酸盐后,血液中的亚铁血红蛋白氧化成高铁血红蛋白,使其携氧的能力减弱进而引起组织缺氧,造成机体损坏。亚硝酸盐除了会对人体产生危害,还会导致水生物中毒,严重影响水产养殖的经济效益。因此,研究一种快速、实时在线的亚硝酸盐检测系统对于食品安全和水产养殖业均具有极为重要的意义。本系统的硬件部分主要包括光学系统和电子学系统。其中光学系统是基于共振拉曼技术设计的,同时联合液芯光纤技术可以大大提升拉曼光谱的强度。重点从光源的选取、液芯光纤的制备、滤光片的选取、分光单色器的选取以及检测器的选取五个方面对光学系统进行了设计,通过测试分析确定各模块符合本论文设计要求。经过光路调理,实现光信号到电信号的转变。信号转变过程中,CCD的驱动脉冲是由STM32产生并控制的,在CCD输出端和STM32输入端之间加入信号调理电路进行信号整定,将电流转换放大成合适的电压值,然后滤波,使其电压幅度在STM32内部ADC输入电压允许范围内。STM32与上位机的通信使用RS232进行串行通信,STM32将转换后的数字值一方面传入上位机显示用,另一方面存入SD卡中备份。本系统的软件部分实现的功能有CCD驱动、ADC驱动、存储、通讯和LabVIEW图形显示。CCD驱动程序使STM32芯片提供一定占空比的时钟脉冲信号,让CCD每个像元里产生的信号电荷转移出去转变为最终对应光强的电信号。ADC驱动程序采集信号调理模块处理过的被激发的拉曼散射光强度信息。存储程序实现检测系统数据以及时间信息的保存,方便用户以后对历史数据进行查询和处理。通讯程序是与上位机进行通讯的代码,采用标准RS232协议。基于LabVIEW设计光谱仪应用程序,显示采集到的光谱图像以及亚硝酸盐浓度曲线,同时也可以控制光谱仪参数及光谱数据的存储。实验结果表明,该系统可以实现对水溶液中亚硝酸根离子浓度的监测功能。系统成功完成了对光谱数据的采集、处理及显示,可以适用于多种水样中的亚硝酸盐检测,重现性较好,准确性较高。
[Abstract]:After ingesting excessive nitrite, ferrous hemoglobin in blood is oxidized to methemoglobin, which weakens its ability to carry oxygen and then causes hypoxia in tissues and damages the body. Nitrite will not only harm human body, but also lead to aquatic poisoning, which seriously affects the economic benefits of aquaculture. Therefore, it is of great significance for food safety and aquaculture to study a fast and online nitrite detection system. The hardware of this system mainly includes optical system and electronic system. The optical system is designed on the basis of resonance Raman technique, and the intensity of Raman spectrum can be greatly enhanced by the combination of liquid-core fiber technology. The optical system is designed from five aspects: the selection of light source, the preparation of liquid-core optical fiber, the selection of filter, the selection of optical monochromator and the selection of detector. Through testing and analysis, it is determined that each module meets the design requirements of this paper. After the light path conditioning, to achieve the light signal to electrical signal transformation. In the process of signal transformation, the driving pulse of STM32 is generated and controlled by STM32. A signal conditioning circuit is added between the output of CCD and the input of STM32 to adjust the signal and amplify the current to the appropriate voltage value, then filter it. The voltage amplitude is within the range of ADC input voltage in STM32. STM32 communicates with the host computer using RS232 serial communication. STM32 transmits the converted digital value to the host computer for display on the one hand and stores it in the SD card for backup on the other hand. The functions of the software part of the system include CCD driver, storage, communication and LabVIEW graphics display. CCD driver makes the STM32 chip provide the clock pulse signal with certain duty cycle. The signal charge transfer generated in each pixel of CCD is transformed into an electric signal corresponding to the light intensity. ADCs driver acquires the stimulated Raman scattering intensity information processed by the signal conditioning module. The stored program can save the system data and time information, which is convenient for users to query and process the historical data. The communication program is the code of communication with the host computer, and adopts the standard RS232 protocol. A spectrometer application program based on LabVIEW is designed to display the collected spectral images and nitrite concentration curves, and to control the storage of spectrometer parameters and spectral data. The experimental results show that the system can monitor the concentration of nitrite ion in aqueous solution. The system has successfully completed the collection, processing and display of spectral data, which can be applied to the detection of nitrite in many kinds of water samples, with good reproducibility and high accuracy.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP274

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