pH值監測儀設計

電氣自動化論文編號:ZD325  論文字數:8403,頁數:24

目　　錄

一　引言 1
 1.1 課題來源及意義 1
 1.2 國內外發展現狀 1
 1.3 課題主要工作 1
二　系統功能及原理圖 2
 2.1 系統實現目標 2
 2.2 系統工作原理結構圖 2
三　系統硬件設計 3
 3.1 PH復合電極測量電路 3
 3.2 pH復合電極工作原理 4
 3.3 pH值溫度補償 5
 3.4 A/D轉換 5
 3.4.1 轉換電路設計 5
 3.4.2 AD轉換電路圖 6
 3.5輸出顯示 7
 3.6串行通訊 8
 3.6.1 RS-232串口通信 8
 3.6.2 單片機及PC機串行通信電路 8
四　系統軟件設計 10
 4.1 系統初始化 10
 4.2 數據采集 10
 4.3 數據處理 11
 4.4 串行通訊模塊 11
五　整機調試及結果分析 14
 5.1 硬件電路調試 14
 5.2 軟件程序調試 14
 5.3 pH傳感器的校正 14
 5.4 pH傳感器的標定 14
 5.5 系統測量數據及分析 15
六　結束語 16
謝    辭 17
參考文獻 18
附    錄 19

摘　　要

 在環保、化工、食品、醫學等行業經常需要監測pH值，因此，設計了基于單片機控制的pH值監測儀。硬件設計以AT89S52單片機為控制核心；傳感器采用pH復合電極；為了與傳感器的高內阻匹配，信號調理采用CA3140、UA741等運放構成三級放大電路；利用ADC0809模數轉換器實現A/D轉換；通過單片機與RS232串行通信口完成數據通信；使用1602液晶器實時顯示pH值。軟件設計采用C語言編制控制程序，用Visual C++軟件編制了計算機監測界面，以便實現遠程數據監測。針對實際中電路設計遇到的問題，給出了相應的調試方法。根據pH值復合電極的測量原理、電極的結構，引出了pH值的溫度補償方法；為了提高測量精度，對pH傳感器進行了校正和標定。經過實驗測試，儀器檢測精度達到0.1%，設計的電路具有元件少、體積小、易維修以及成本低等特點。
 
 
關鍵詞： pH復合電極    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