电导率的设计.doc

毕业设计、毕业论文 题目: 电导率仪的设计 学院: 电气与电子工程学院 专业班级: 生物医学工程 指导教师: 2010年 6月 10日 摘要 电解质电导率是电解质溶液的一个基本物理量。它是电化学分析的重要参数，也是衡量水质的一个重要指标。本文介绍一种基于51系列单片机的电导率仪的研制，仪器通过单片机控制光耦的选通产生12V的交流方波，再经稳压管转化成10V电压。通过4052电子开关进行量程切换。被测信号经放大、精密整流后转化为直流电压，并送入4052电子开关，同时温度信号送入该电子开关，然后经A/D分别转换为数字信号。A/D转换器选用LM331，该芯片采用压频转换的方式实现A/D转换。其具有转换精度高、能更好的实现数字电路与模拟电路的隔离。最后由单片机进行计算，显示出温度值及溶液电导率值。 经试验测试，仪器误差在1%以内，该仪器除了完成温度值及溶液电导率值的显示还具有标准电流、电压信号输出；大屏幕LCD汉字液晶显示；232串行通信及历史数据保持，便于数据的保存与管理，对不同工业现场具有较强的适应能力。 压频转换Conductivity Instrument ABSTRACT Electrolyte solution, electrolyte conductivity is a fundamental physical quantity. It is an important electrochemical parameter, is also an important indicator to measure water quality. This paper presents a conductivity of 51 computers based instrument, apparatus, controlled by microcontroller strobe op to coupler produces 12V AC square wave, and then converted to 10V by the voltage regulator. Range of electronic switches by 4052 switch. The measured signal by the amplification, precision rectified into DC voltage, and electronic switches into 4052, while the temperature signal into the electronic switch, and then by the A/D converted into digital signals, respectively. A/D converter used LM331, which chip voltage-frequency conversion means to achieve the A/D conversion. With the conversion of its high accuracy, can better realize digital circuits with analog circuit isolation. Finally calculated by the MCU, indicating that temperature and solution conductivity.  After that, test equipment error within 1% of the equipment in addition to the completion of temperature and solution conductivity values show also has the standard current, voltage signal output; large-screen liquid crystal display LCD character; 232 serial communication and maintaining historical data, to facilitate data preservation and management of various industrial field has strong adaptability. Key words: conductivity Square Wave Precision rectifier VFC  目 录 第一章 绪论 1 1.1 题目背景与意义 1 1.2 国内外研究概况与发展