二线无源LED现场显示单元设计

Design and realization of two-wire passive LED local displaying unit

二线无源LED现场显示单元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LED现场显示。在4～20mA闭环回路中分别串接一个取样电阻和一个稳压二极管，取样电阻提取检测到的物理量的信息，稳压二极管与倍压电路配合为系统提供电源。显示范围由键盘键人并存如EEPROM（X25043）中，显示单元在掉电后自动读人数据并进人工作状态。采用4位低功耗高亮度LED作为显示器。本单元全部采用低功耗器件。

On the basis of no outer direct flow power source, tow-wire passive LED local displaying unit realizes LED local displaying of industry parameter which tow-wire transmitter inspects. In 4～20mA close circuit, it serially connects a sample resistance and a steady voltage two polar tube. Sample resistance abstracted information of physical quantity. Steady voltage two polar tube connecting with twice voltage circuit provided power source for system. The scale of display was saved into EEPROM （X25043） by typing keyboard. Displaying unit automated reading data and entering work state, take four bits low function lost and high light degree LED as displayer. This paper all took low function lost instruments.