【正文】 field bus DS18B20 temperature acquisition,then the temperature data into the microcontroller for data processing, with the inspection speed, scalability and low cost characteristics. The design of the temperature acquisition system fully plays the characteristics of the AT89C51 microcontroller, bined with existing technology, greatly reduces the circuit plexity, the system has accurate temperature control, good control interface, high stability, strong antiinterference advantages . Using the RS485 bus, a pair of twisted pair can achieve multistation work, the distributed system, simple equipment, low cost, can municate over long distances to get the advantages of a wide range of applications. The 4way system can detect temperature, test temperature range is 55 ℃ ~ +125 ℃ . This design uses eight AT89C51 MCU, MCU software programming large degree of freedom can be achieved by programming a variety of arithmetic and logic control algorithm. Small volume and hardware implementation is relatively simple, easy to install. Temperature acquisition system based on microcontroller is widely used by puter, auto test, a number of microelectronics and automatic control technology, signal acquisition is not only convenient, simple and great advantages of flexibility, but also can greatly improve the technical indicators measured temperature . Key words: RS485 bus； Singlechip microputer； Temperature measurement system － II－ 蘭州交通大學畢業(yè)設計（論文） 目 錄 摘 要 ..................................................................................................................................... I Abstract ..................................................................................................................................... II 目 錄 .................................................................................................................................. III 1 緒論 ........................................................................................................................................ 4 課 題 背 景 與 意義 ......................................................................................................... 4 課題研究現(xiàn)狀 ............................................................................................................. 3 本 課 題 的 研 究 內(nèi) 容 與 目標 ......................................................................................... 3 2 基本方案比較 ........................................................................................................................ 4 設 計 方 案一 ................................................................................................................. 4 設 計 方 案二 ................................................................................................................. 5 設 計 方 案三 ................................................................................................................. 5 3 RS485 接口標準 .................................................................................................................... 7 接 口 標 準 的 選擇 ......................................................................................................... 7 RS485 的 應 用 原則 .................................................................................................... 8 4 單元模塊設計 ...................................................................................................................... 10 溫度傳感器的選擇方案 ........................................................................................... 10 DS18B20 的介紹 ...................................................................................................... 12 DS18B20簡介 ............................................................................................... 12 DS18B20的特性 ........................................................................................... 12 DS18B20的結構 ........................................................................................... 13 DS18B20在溫度測量方面的應用 ............................................................... 15 電源模塊設計 ............