二线制无源数字显示表的设计与实现

二线制无源数字显示表是指在不外接直流电源的前提下,实现二线制变送器检测到的工业参数的LED显示。在4～20mA闭环回路中分别串接一个取样电阻和一个三端可编程并联稳压二极管(TL431),取样电阻提取检测到的物理量的信息,TL431为系统提供电源。显示范围由键盘键入并存入EEPROM(AT24C01)中,显示表在系统上电后读入数据并进入工作状态。采用4位低功耗高亮度LED作为显示器。本显示表采用低功耗器件。

On the basis of no outer direct flow power source, tow-wire passive digital indicator realizes LED displaying of industry parameter which tow-wire transmitter inspects. In 4-20mA close circuit,it serially connects a sample resistance and a 3-terminal adjustable shut voltage regulator. Sample resistance abstracted information of physical quantity. TL431 provided power source for system. The scale of display was saved into EEPROM （AT24C01） by typing keyboard. Digital indicator reading data and entering work state as long as the system is powered on. We took four bit low function lost and high light degree LED as displayer. This paper all took low function lost instruments.