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1、 毕业论文基于PSD浓度检测系统设计与分析 学 院： 专 业： 学生姓名： 学 号： 指导教师： 摘 要摘 要目前，实时液体浓度检测技术相对来说还比较落后，因此研究新型的液体浓度检测系统具有十分重要的意义。工业生产中检测液体浓度的方法有比重法、化学分析法、超声波法及光学法等。但这些方法既费时又需繁琐的人工取采样，滞后性大，无法实现实时在线检测液体浓度，鉴于以上问题，本文设计了一种基于PSD的浓度检测系统。浓度的变化会引起液体折射率的变化，对于固定的入射光线，折射率的变化会导致出射光线发生偏移，利用光电位置敏感器件检测出光线偏移量的大小，进而得到液体的折射率，从而计算出液体浓度，再由LED显示出
2、来。本系统主要由半导体激光器、双隔离窗光学系统、PSD信号处理电路、基于8051单片机的A/D采集运算控制电路和显示电路等组成。双隔离窗光学系统采用两个隔离窗使光线在待测液体中两次折射，测量结果更精确；PSD信号调理电路主要由前置放大、加法器、减法器和除法器等部分构成，将对信号进行I/V变换和放大处理；基于8051单片机的A/D采集运算控制电路主要对PSD调理后的模拟量信号转变为数字量，并将信号输入至单片机进行分析处理，从而得到浓度值，最后由显示系统显示出来。通过实验发现，光源强度和温度漂移对本系统的影响非常小，该系统具有结构简单、稳定性好、灵敏度高、响应时间快以及自动化程度高等优点，能够方便
3、、准确地实现液体浓度的实时在线检测。本浓度检测系统可广泛应用在化工、制糖、食品、制药等诸多行业，是一种具有广阔发展前景的浓度检测系统。关键词：位置敏感器件（PSD），半导体激光器，液体浓度，8051单片机- I -ABSTRACTABSTRACTAt present, real-time on-line liquid concentration detection technology is still relatively backward. Research of a new type of liquid concentration detection system is of great
4、 significance. The proportion of liquid concentration detected in the industrial production method, chemical analysis, optical method. However, these methods are time-consuming and tedious manual to take sampling lag, can not achieve real-time online detection of the liquid concentration, in view of
5、 the above problems, this paper designs a new type of concentration detection system based on position sensitive detector. In the chemical and pharmaceutical, light industry and beverage and environmental protection departments and the various fields of scientific research and national defense are t
6、o detect and control the parameters of the liquid concentration. At present, the proportion of liquid concentration detected in the industrial production method, chemical analysis, ultrasonic and optical method. However, these methods are time-consuming and tedious manual to take sampling lag, can n
7、ot achieve real-time online detection of the liquid concentration, in view of the above problems, the designs a new type of concentration detection system based on position sensitive detector.Concentration change can cause the change of liquid refractive index, the fixed incident light, the refracti
8、ve index change will cause a shift of the emergent light, using photoelectric position sensitive device detect the size of the deviation of the light, the refractive index liquid is obtained, to calculate the liquid concentration, displayed by LED. This system is mainly composed of semiconductor las
9、er window, double isolation optical system, PSD signal processing circuit, based on 51 single chip microcomputer A/D acquisition operation control circuit and display circuit, etc. Double isolation optical system consists of two separate window bends light after two, make more accurate measurement r
10、esults; PSD signal disposal circuit is mainly composed of preamplifier, summator, subtracter and divider and other parts, will be the signal I/V transform and processing to enlarge; Based on 51 single chip microcomputer A/D sampling operation control circuit mainly of PSD after analog signals into d
11、igital quantity, and will be treated as signal input to the MCU is analyzed, the density is obtained, finally displayed by the display system.Experiments found that light intensity and temperature drift of this system is a very small effect, the system has simple structure, good stability, high sens
12、itivity, fast response time and high degree of automation, etc. The liquid can be realized conveniently and precisely, and real-time on-line detection of concentration. The concentration detection system can be widely used in chemical industry, sugar, food, pharmaceutical and other industries, is a
13、kind of concentration detecting system has the broad prospects for development.Key words: PSD, semiconductor laser diode， liquid concentration, MCU8051II目录- 3 - -目 录目 录摘 要IABSTRACTII目 录IV第一章 绪论11.1 课题设计的目的意义11.2 国内外研究现状11.2.1 位置敏感探测器(PSD)国内外发展状况11.2.2 液体浓度测量的国内外研究现状21.3 课题设计的主要内容3第二章 总体方案42.1 系统总体方案
14、设计42.2 系统性能指标5第三章 光学系统的设计63.1 光源的选择63. 2 光学系统设计7第四章 基于8051单片机的PSD信号处理电路的设计104.1 半导体位置敏感器件PSD104.1.1 PSD的工作原理104.1.2 PSD的主要性能参数124.1.3 影响PSD性能的因素134.1.4 PSD的选取144.2 PSD信号调理电路的设计154.2.1 前置滤波器、主放大电路、模拟除法器154.2.2 背景干扰及暗电流消除194.2.3 陷波电路224.3 8051单片机硬件系统234.3.1 单片机系统概述234.3.2 电源电路设计244.3.3 AD574芯片及其接口254.
15、3.4 MCS-8051单片机274.3.5 AD574A与单片机的接口电路284.3.6 基于MAX232的通讯模块28第五章 LED显示电路设计305.1 LED的结构305.2 显示器接口31第六章 系统的软件设计326.1 系统软件设计流程326.2 A/D转换子程序设计336.3 LED显示子程序设计336.4 十进制编码与BCD编码的相互变换34第七章 浓度检测系统35第八章 系统误差分析368.1 光强波动的影响368.2 位置敏感器件对系统的影响368.3 温度对系统测量的影响37结 论39参考文献40致 谢42第一章 绪论第一章 绪论液体浓度测量在工业中占有非常重要的地位。对溶液浓度的测量与控制在化工、制糖、乳制品等行业中有着广泛的作用,它是提高产品质量的重要技术手段。1.1
