文档介绍：吉林化工学院毕业设计说明书
基于现场总线的温度采集器的设计
Design of Temperature Collecting Module Based on Field-Bus
学生学号: 05510128
学生姓名: 相阳
专业班级: 自动0501
指导教师: 翟玉文
职称: 教授
起止日期: ~
吉林化工学院
Jilin Institute of Chemical Technology
摘要
温度是现代工业生产过程中的一个重要参数, 在生产过程中常需对温度进行检测和监控,特别是在电力、化工等大型自动化企业的生产过程中往往需要监视和测量几十个温度参数。在某些特殊的生产场合(比如印染和炼油),温度参数测量和控制的精度直接影响后续产品的质量。
本文介绍一种基于RS485现场总线的温度采集模块的设计方法。热电阻随温度的变化而产生不同的电阻信号,电阻信号经过恒定电流变成模拟电压信号,单片机内部多路模拟开关电路对模拟信号进行采集,A/D转换模块对采集到的信号进行模数转换,把转换得到的数字信号按照顺序分别送入单片机,单片机通过RS485现场总线实现与PC机的挂接。
由于电阻值与温度值之间是非线性关系,为了提高测量精度克服非线性误差,减少分度表的存储量,采用二次插值算法计算温度数值,℃,℃。单片机通过现场总线能够把温度值以MODBUS协议的形式发送给PC机,实现了工控计算机的现场总线集中管理。
关键词:温度采集;PT100热敏电阻;RS485总线
Abstract
Temperature is the process of modern industrial production as an important parameter, in the production process often required to detect and monitor the temperature, especially in the electricity, chemical industry and other large enterprises, automation of production processes often require dozens of monitoring and measuring the temperature parameters. Production in some special occasions (such as printing and dyeing and refining), temperature measurement and control parameters directly affect the accuracy of follow-up to the quality of the product.
In this paper, based on the temperature RS485 fieldbus module design method of collection. Thermal resistance with temperature changes in the resistance of different signals, resistance constant current signal into the analog voltage signal, single-chip multi-channel analog switches internal circuitry of the analog signal acquisition, A / D converter module of the signal collected analog-to-digital conversion, to convert digital signals received, respectively, in accordance with the sequence into single-chip, single-chip RS485 fieldbus through with PC-articulated.
As the resistance value and temperature is non-linear relationship between, in order to improve the measurement accuracy to e the non-linear error, reducing the index storag