pH测试仪的设计本科生设计

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长 春 工 业 大 学

毕业设计、毕业论文

题 目: pH测试仪的设计

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毕业设计（论文）原创性声明和使用授权说明

原创性声明

使用授权说明

摘要

本文设计的pH测试仪采用电化学原理及单片微型计算机技术完成对各种溶液中氢离子浓度的测定。本论文详细地论述了pH测试仪的设计，包括氢离子浓度的测量原理、标定方法、传感器设计，测量电路原理图和系统软件的设计。

pH测试仪配用适当的参比电极和指示电极能够对氢离子的浓度进行测定。采用的三电极测量系统可大大降低外界干扰的影响。输入电路采用高阻差分放大电路，输入电阻可高达1012。传感器的独特设计可以降低参比电极内溶液的离子干扰。仪器电路以MCS-51单片机系统为核心，使本仪器的智能化程度高。这样，使其具有校准记忆，能自动调节斜率，温度自动补偿的能力及检测时间定时等功能。采用人机对话方式，可实现自动测量、标定、存储、显示数据等功能。仪器的标定采用两点标定法对仪器进行校准。

关键词：三电极；两点标定；高阻；温度补偿

TITLE：The Design of the pH Instrument Abstract

On the basis of electrochemical principle and single-chip microcomputer techniques, this system can measure activity in solution. The paper details the research and design of inligent versatile ion meter, including the measuring principle, the calibration way, the design of transducer, measuring circuit software scheme .

The pH tester is equipped with the appropriate reference electrode and indicator electrode to the concentration of ions was determined. We used three-electrode measurement system can greatly reduce the impact of outside interference. The unique sensor design can reduce the reference electrode and ionic interference. Instrument circuit system to MCS-51 microcontroller core, is the instrument of memory, can automatically adjust the slope, automatic temperature compensation capability and the detection time timer functions. The use of man-machine dialogue, enabling automatic measurement, calibration, storage, display data functions. We use two points of calibration to calibrate the instrument.

Key words: pH value; Temperature Compensation; The correct calibration of

pH Meter

目 录

第一章 绪论 ....................................................... - 1 - 1.1 课题背景 ..................................................... - 1 - 1.2 PH测试仪研究的必要性 ........................................ - 2 - 1.3 PH测试仪的发展概况 ........................................... - 3 - 1.4主要内容 ...................................................... - 4 - 第二章 PH测试仪的整体设计......................................... - 5 - 2.1 PH测试仪的测量原理 ........................................... - 5 - 2.1.1 三电极测量系统 .......................................... - 6 - 2.1.2 两点标定法 .............................................. - 6 - 2.2 PH测试仪的测量方法 ........................................... - 7 - 2.2.1指示电极 ................................................. - 8 - 2.2.2 参比电极 ................................................ - 9 - 2.2.3 测量电池的电动势........................................ - 10 - 2.3 温度对测量的影响 ............................................ - 10 - 2.4 检测下限与测量范围 .......................................... - 11 - 2.5 方案论证 .................................................... - 11 - 2.6 本章小结 .................................................... - 13 - 第三章 PH测试仪的硬件设计........................................ - 13 - 3.1 PH测试仪的电路原理图 ........................................ - 13 - 3.2 输入电路 .................................................... - 14 - 3.2.1温度采集电路 ............................................ - 14 - 3.2.2 pH信号采集电路 ......................................... - 15 - 3.3 模拟转换开关 ................................................ - 17 - 3.4 AD转换器 .................................................... - 18 - 3.5 DA转换器 .................................................... - 19 - 3.6 标准信号输出电路 ............................................ - 20 - 3.7电源模块的设计 ............................................... - 21 - 3.8键盘和显示的设计 ............................................. - 21 - 3.9 总线扩展电路 ................................................ - 22 - 3.10 本章小结 ................................................... - 24 -