基于單片機的數字直流電位差計的設計

測控論文編號:CK042   論文字數:17221,頁數:37

目錄
摘要 I
1  緒論 1
2 我國直流電位差計的發展和產品現狀 2
3 軟硬件設計 4
3.1 P89C58單片機控制和顯示電路設計 4
3.1.1 HT1621LCD驅動器主要特點 4
3.1.2 監視定時器(WDT) 4
3.1.3 系統時鐘 5
3.1.4 LCD驅動／偏置電路 6
3.1.5 HT1621LCD驅動器應用實例 6
3.2 外部存儲器設計 7
3.3 AD轉換芯片的電路設計 9
3.3.1 AD7714的基本情況 10
3.3.2 AD7714的應用介紹 11
3.4 模數轉換AD7714電路原理 15
4 可調式mV信號源的總體設計原理 18
4.1 TL431的使用 19
4.2 儀器內部電路電源設計方案 19
4.2.1 固定三端穩壓器7809的運用 20
4.2.2 +5V恒壓電路設計 21
5 溫度值直讀的軟件查表技術 23
6 零點與滿幅值校準 25
7 整機低功耗設計 26
8  儀器的使用說明 27
8.1 主要技術指標 27
8.2 儀器面板功能說明 27
8.3 儀器使用方法 28
9  電位差計誤差分析 30
9.1 溫度電動勢產生的誤差 30
9.2 工作電源電壓不穩產生的誤差 30
10  總結 31
致謝 32
參考文獻 33

摘要

 本文介紹了智能型直流電位差計的各組成單元的軟硬件設計。用PHILIPS的P89C58大存儲容量單片機（32K Flash），以滿足5種熱電偶的電勢/溫度表格的存儲量；24位的Σ—△型A／D轉換器AD7714的應用保證了測量單元的高精度和高分辨率；軟件中的對分搜索查表法，使5種熱電偶分度值所對應的溫度值得以快速直讀；用軟件方法進行零點和滿幅的調準，消除了儀器的系統誤差；運用8段數碼型液晶器，方便了電位差計的讀數；可調式mV信號源的指標可滿足校驗多種工業儀表的需要；整機的低功耗設計，改良了儀器的供電形式，可使用市電供電和普通干電池供電兩用，消除了不同場所因儀器供電原因所造成的不方便因素。傳統的直流電位差計使用步驟較多，還易受工作電源不穩定、檢流計靈敏度、標準電池與環境溫度等有關因數影響。因此，用現代電子技術研制一種mV信號校準儀是很有意義的。
關鍵字 直流電位差計；mV信號源；AD轉換；低功耗

Abstract

 This paper introduces a kind of intelligent dc potentiometer unit of the design of the software and hardware. P89C58 of PHILIPS is a large capacity single-chip (32K Flash);it met the five kinds of thermocouple EMF / temperature form of storage needs; the application of 24 bits Σ—△A/D converter AD7714 make the measurement unit to have high resolution and precision; the check form method in the software can directly read the value of the temperature corresponding potential of 5 thermocouples. It eliminates the system errors of the meter that adjusting the zero and the full scale with the software method; The use of a digital liquid crystal 8, and to facilitate the potential difference of readings; the target of the adjustable mV signal source can satisfy the needs of verifying some industry meters; the whole instrument designs low-power, improved the form of equipment supply, use city electricity supply and the general power of dual-use dry-cell batteries, eliminating the supply of different places due to equipment caused by the inconvenient factors. DC potentiometer traditional use of these steps is not only more, but also vulnerable to instability in the work of power, sensitivity galvanometer, standard cell and the environment impact of temperature and other relevant factors. Therefore, the use of modern electronic technology to develop a mV signal calibrator is of great significance.
Keywords DC potentiometer；mV Signal Generator；AD conversion；Low Consume