基于单片机的数字直流电位差计的设计

论文编号:CK042论文字数:17221,页数:37

摘要

本文介绍了智能型直流电位差计的各组成单元的软硬件设计。用PHILIPS的P89C58大存储容量单片机（32K Flash），以满足5种热电偶的电势/温度表格的存储量；24位的Σ—△型A／D转换器AD7714的应用保证了测量单元的高精度和高分辨率；软件中的对分搜索查表法，使5种热电偶分度值所对应的温度值得以快速直读；用软件方法进行零点和满幅的调准，消除了仪器的系统误差；运用8段数码型液晶器，方便了电位差计的读数；可调式mV信号源的指标可满足校验多种工业仪表的需要；整机的低功耗设计，改良了仪器的供电形式，可使用市电供电和普通干电池供电两用，消除了不同场所因仪器供电原因所造成的不方便因素。传统的直流电位差计使用步骤较多，还易受工作电源不稳定、检流计灵敏度、标准电池与环境温度等有关因数影响。因此，用现代电子技术研制一种mV信号校准仪是很有意义的。

关键字 直流电位差计；mV信号源；AD转换；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

目录

摘要I

1 绪论1

2我国直流电位差计的发展和产品现状2

3软硬件设计4

3.1 P89C58单片机控制和显示电路设计4

3.1.1 HT1621LCD驱动器主要特点4

3.1.2 监视定时器(WDT)4

3.1.3 系统时钟5

3.1.4 LCD驱动／偏置电路6

3.1.5 HT1621LCD驱动器应用实例6

3.2 外部存储器设计7

3.3 AD转换芯片的电路设计9

3.3.1 AD7714的基本情况10

3.3.2 AD7714的应用介绍11

3.4 模数转换AD7714电路原理15

4可调式mV信号源的总体设计原理18

4.1 TL431的使用19

4.2 仪器内部电路电源设计方案19

4.2.1 固定三端稳压器7809的运用20

4.2.2 +5V恒压电路设计21

5温度值直读的软件查表技术23

6零点与满幅值校准25

7整机低功耗设计26

8 仪器的使用说明27

8.1 主要技术指标27

8.2 仪器面板功能说明27

8.3 仪器使用方法28

9 电位差计误差分析30

9.1 温度电动势产生的误差30

9.2 工作电源电压不稳产生的误差30

10 总结31

致谢32

参考文献33