[工学]采用EM235的多路温度信号采集装置论文.doc

摘　要 在科学研究和生产实践的诸多领域中，温度控制占有极为重要的地位，特别是在食品、大棚温室、冶金、化工、建材、机械、石油等工农业生产中具有举足轻重的作用。随着电子及计算机技术的发展，由原来的简单逻辑量控制，逐步具备了计算机控制系统的功能，由于在计算能力、抗干扰能力、响应速度、通信联网能力、灵活性及可维护性等方面的诸多优点，PLC在温度控制系统中得到了大量运用，本文设计了基于PLC的多路温度采集系统。 在以PLC控制为核心的多路温度采集装置中，EM235将温度电压信号模拟量转化为数字量，PLC将AD转化的数字量进行数据处理，然后通过RS485通信发给有单片机组成的显示模块进行温度值的显示。 关键词：PLC，EM235，温度传感器，RS485通信 Abstract In the scientific research and production practice in many fields, Temperature control has very important position.Especially in food, awning greenhouse, metallurgy, chemical industry, building materials, machinery, petroleum and other industrial and agricultural production that plays an important role. Along with the development of electronic and computer technology, by original simple logic quantity control, and gradually has the computer control system of the function, because in the computing power, anti-interference ability , response speed, communication networking ability, flexibility and maintainability, and other aspects of the many other advantages, PLC in temperature control system got a lot of use, this paper introduces the design of multi-channel based on PLC temperature gathering system. In PLC control as the core of multi-channel temperature gathering device, temperature voltage signal analogue into the digital quantity through the EM235. PLC is carries on the data processing for the transformation of the digital by AD. And then by RS485 communication to a single chip microcomputer temperature display modules of the display. Key words：PLC，EM235，Temperature sensorRS485 communications 目 录 前　言 1 1 系统方案设计 3 1.1 系统原理 3 1.2 系统总体框图 3 1.3 系统器件选择 3 2 系统硬件设计 5 2.1 概述 5 2.2 PLC主机S7-226CPU 5 2.2.1 CPU结构 5 2.2.2 CPU供电方式 6 2.2.3 CPU226的性能参数 6 2.3 EM235扩展模块 8 2.3.1 EM235的技术参数 8 2.3.2 EM235模块接线 8 2.3.3 EM235模块设置 9 2.3.4 EM235模块的寻址 11 2.4 温度信号的采集 13 2.4.1 Pt100铂电阻 13 2.4.2铂热电阻测温原理 13 2.4.3 恒流源式测温电路 14 2.5 信号预处理 16 2.5.1 三种干扰的定义 16 2.5.2 常用的抑制干扰措施 16 2.5.3 抑制自身干扰 17 2.5.4 抑制辐射干扰 19 2.5.5 抑制电源干扰 19 2.6 温度显示模块 19 2.6.1 Atmega16单片机 19 2.6.2