基于PLC的简易数字电压表的设计(数控论文)

I江苏城市职业学院毕业设计（论文）（2014届）设计（论文）题目基于PLC的简易数字电压表的设计办学点（系）张家港办学点（工程系）专业机械设计与制造班级11机械（普）学号学生姓名指导教师杜维娜职称讲师II目录摘要·········································································································II一概述···································································································11数字电压表的发展现状············································································12用PCL设计数字电压表的意义···································································1二可编程控制器（PLC）的选型···································································21PLC选型的考虑因素···············································································21.1控制对象和范围的确定····································································21.2PLC机型选择的考虑因素·································································22PLC的选择···························································································32.1PLC结构的合理性··········································································32.2PLC功能的相当性··········································································32.3PLC机型的统一性··········································································3三对PLC控制系统软件进行编制和设计·······················································41PLC控制系统软件的编制程序··································································42PLC控制系统软件设计的主要内容····························································53PLC控制系统软件的编程分类··································································53.1离线编程的PLC···············································································53.2在线编程的PLC···············································································6四对PLC控制系统硬件进行设计·································································81FX-4AD的模拟量输入模块······································································82PLC的中央处理单元（CPU）···································································113PLC的存储器和常用类型·········································································114电源····································································································125FX2N-32MR型PLC················································································126人机界面—FXGOT930··········································································12五总结···································································································14致谢·········································································································15参考文献···································································································16III基于PLC的简易数字电压表的设计摘要本课题是《基于PLC的简易数字电压表的设计》的开发性论文。随着智能化微机测量和控制技术的迅猛发展，以PLC为核心的数字电压表开始以迅雷不及掩耳之势火速占领电子测量领域。本文首先介绍数字电压表的发展现状；其次，着重论述PLC设计数字电压表的意义；接着，深度分析对PLC的选型，并对FX系列的PLC做总结性的概述。同时，在本文的硬件部分，将主要对课题模拟量输入输出模块FX-4AD,FX2N-32MR型PLC及人机界面F930做出详细的介绍。从而，确保所设计出来的简易数字电压表能够实现精度高、测量准确可靠、性价比高、运行可靠的优点。关键词：数字电压表，PLC，FX系列，方案设计1基于PLC的简易数字电压表的设计一概述1数字电压表的发展现状众所周知，在电量的测量过程中，电压、电流以及频率是其中最为基础的三个被测量，然而又以电压量的测量最为普遍。同时，随着电子技术的不断发展，电压测量的准度变得愈发要求精准，于是数字电压表就成为了工业以及生活中必不可少的一种测量仪器。数字电压表，一般简称为DVM，它的工作原理是采用数字化的测量技术，把连续的模拟量转变成为不连续的数字形式，同时加以显示。由于数字电压表具有读数准确方便、精度高、误差小、测量速度快等优势，于是迅速得到了广泛的应用。【1】近几十年以来，随着半导体技术、集成电路以及微型处理器技术的不断发展，数字电路和数字化测量技术也取得了巨大的进步，从而促使了数字电压表的迅猛发展，并不断出现越来越契合需要的新的电压表类型，例如今天我们将要深度探讨的基于PLC的简易数字电压表。目前来看，数字电压表的内部核心部件其实就是A/D转化器，而其转化的精准度在很大程度上影响着数字电压表的精准度，因而，我们在设计数字电压表的时候就必须着眼于高精度和低成本这两个重要侧重点。2用PCL设计数字电压表的意义PCL就是可编程逻辑控制器，也被称作可编程控制器，是一种经过特殊设计的工业计算机，整个设计原则就是围绕简单和实用进行展开的。PLC的发展与计算机技术、控制技术和通信网络技术等高新技术的发展有着息息相关的因素，正式这些高新技术的发展才推动了可编程控制器的发展。传统的电压表大多采用的是指针式面板，它的精度低，可视距离近，已经越来越不适应社会的发展需要。而随着智能化微机测量和控制技术的飞速发展，以PLC为核心的数字电压表越来越凸显出自己不可替代的优势。本课题介绍的基于PLC为核心的数字电压表设计，就具有性价比高、使用方便、精度高的特点，在2工业生产等电子测量领域有着非比寻常的广泛应用。传统的数字电压表其实各有特点，它们适合于现场做简单的手工测量，但是如果需要完成远程测量并要对测量数据做更进一步的分析处理时，传统数字电压表就显现出自己的劣势——无法完成了。然而，基于PLC的数字电压表，一方面可以完成测量数据的传递，另一方面又可以借助PLC做测量数据的处理。因此，这种类型的数字电压表在功能和实际应用上，都有着无可比拟的优势，于是基于PLC数字电压表的设计无论是开发还是在应用上都具有良好的发展前景。二可编程控制器（PLC）的选型基于PLC的简易数字电压表的设计,最基本的就是PLC的选型。电气技术人员必须要与工艺技术人员和机械技术人员进行合作，详细的了解设备生产工艺的实际具体要求与机械设备的技术性能，结合实际选用合适的PLC，才能满足生产设备的工艺要求。在选用的过程中，要选择那些既能满足生产设备工艺要求，又具有高性价比的PLC产品。1PLC选型的考虑因素（1）控制对象和范围的确定我们在应用PLC的时候，首先应该要详细地分析被控对象、控制过程以及控制要求，了解工艺流程之后再列出控制系统的所有功能和它的指标要求，与其他工业控制计算机加以比较之后再进行最后的选择。如果要控制的对象所在的工业环境比较恶劣，而安全性和可靠性的要求特别的严格，系统工艺又比较复杂而用常规的继电——接触器控制很难实现，同时工艺流程又需要经常性的对象和现场变动的话，用PLC数字电压表进行控制是最恰当的选择。（2）PLC机型选择的考虑因素一般而言，PLC机型的选择主要讲的就是其功能上如何实现我们的需要，并不会浪费机器的容量。在选择机型之前，我们首先要对控制对象进行下面一系列的考虑：（a）有多少个开关量需要输入，其电压分别是多少；（b）有多少个开关量需要输出，其输出的功率是多少；（c）是否存在特殊的控制要求；3(d)现场对PLC的扫描速度有什么要求等。【2】2PLC的选择随着可编程控制器（PLC）的不断推广和应用，PLC产品在市面上的种类堪称是淋漓满目，数量繁多，而且其功能也是日渐完善。近年来，美国、日本、德国等国引进的PLC产品加上我国自主开发的产品在结构型式、性能、容量以及价格等方面都各有不同，适用的场合也是各有侧重点，因此，合理的在各有千秋的PLC产品群里面选择满足自己需求的产品，对于提高PLC控制系统的技术和经济指标都有着十分重要的作用和意义。可编程控制器的机型选择基本原则应该在其功能满足要求的前提下，要能够保证操作可靠、维护方便、使用简单以及最佳的性价比。具体来说，就是要能够满足以下几点：(1)PLC结构的合理性对于工艺过程比较固定、环境条件较好的使用场合，可以选择整体式结构的PLC。(2）PLC功能的相当性对于开关量控制的工程项目，对其的控制速度如果不需要进行考虑，一般选择低档PLC就可以了；当然，对于那些以开关量控制为主，并且带有少量的模拟量控制的工程项目，要选用带A/D转换、D/A转化和数据传送功能的低档PLC；如果是控制要求比较高的工程项目，例如要实现闭环控制、PID运算和通信联网的话，就要选用中档或者是高档PLC了。其中高档PLC主