pH值监测仪设计

电气自动化论文编号:ZD325  论文字数:8403,页数:24

目　　录

一　引言 1
 1.1 课题来源及意义 1
 1.2 国内外发展现状 1
 1.3 课题主要工作 1
二　系统功能及原理图 2
 2.1 系统实现目标 2
 2.2 系统工作原理结构图 2
三　系统硬件设计 3
 3.1 PH复合电极测量电路 3
 3.2 pH复合电极工作原理 4
 3.3 pH值温度补偿 5
 3.4 A/D转换 5
 3.4.1 转换电路设计 5
 3.4.2 AD转换电路图 6
 3.5输出显示 7
 3.6串行通讯 8
 3.6.1 RS-232串口通信 8
 3.6.2 单片机及PC机串行通信电路 8
四　系统软件设计 10
 4.1 系统初始化 10
 4.2 数据采集 10
 4.3 数据处理 11
 4.4 串行通讯模块 11
五　整机调试及结果分析 14
 5.1 硬件电路调试 14
 5.2 软件程序调试 14
 5.3 pH传感器的校正 14
 5.4 pH传感器的标定 14
 5.5 系统测量数据及分析 15
六　结束语 16
谢    辞 17
参考文献 18
附    录 19

摘　　要

 在环保、化工、食品、医学等行业经常需要监测pH值，因此，设计了基于单片机控制的pH值监测仪。硬件设计以AT89S52单片机为控制核心；传感器采用pH复合电极；为了与传感器的高内阻匹配，信号调理采用CA3140、UA741等运放构成三级放大电路；利用ADC0809模数转换器实现A/D转换；通过单片机与RS232串行通信口完成数据通信；使用1602液晶器实时显示pH值。软件设计采用C语言编制控制程序，用Visual C++软件编制了计算机监测界面，以便实现远程数据监测。针对实际中电路设计遇到的问题，给出了相应的调试方法。根据pH值复合电极的测量原理、电极的结构，引出了pH值的温度补偿方法；为了提高测量精度，对pH传感器进行了校正和标定。经过实验测试，仪器检测精度达到0.1%，设计的电路具有元件少、体积小、易维修以及成本低等特点。
 
 
关键词： pH复合电极    AT89S52    CA3140    串行通信        
 

A Design of pH Value Monitor
ABSTRACT

 The pH value is monitored in many industries,such as protection,chemicals,food,medicine, environmental and so on.So a pH value monitor was designed based on MCU control.AT89S52 SCM is the main control in the design of hardware;the pH complex electrode is adopted as the sensor;in order to match the high internal resistance of the sensor, third class amplifier circuit is composed of CA3140,UA741 in the signal conditioning.A/D converter is implemented through ADC0809.The data traffic is accomplished through the SCM and RS232 serial communication interface;the LCD1602 screen is used to display the pH value in real time. The C language is adopted to prepare control procedure in the software design,and the Visual C++ software is used to prepare the computer monitoring interface,so that the teledata monitoring can be finished easily. The corresponding debugging methods are given. to against the problem in the design of actual circuit. According to the measurement principle of pH value composite electrode and electrode structure, the pH value of temperature compensation is carried on.In order to increase the measuring accuracy the pH sensor.has been carried on to the calibration and correction After experimental testing, equipment testing can reach 0.1 percent.This design has many featuers,such as fewer components,small size,easy maintenance and low cost.
 
Key words：pH Composite Electrode    AT89S52    CA3140    Serial Communication