开题报告(基于单片机的流量检测系统).doc

本科毕业设计(论文)开题报告题目： 基于单片机的流量检测系统的设计 课 题 类 型： 设计 实验研究 论文 学 生 姓 名： 学 号： 专 业 班 级： 电子信息工程082班 学 院： 电气工程学院 指 导 教 师： 开 题 时 间： 2012/03/18 2012 年 03月10日基于单片机的流量检测系统的设计1、 选题依据1、数字流量计的现状分析、分类及发展趋势流量是现代工业测量过程中的一个重要参数，人类对流体的测量具有悠久的历史。流量检测的发展可追溯到古代的水利工程和城市供水系统，古罗马凯撒时代已采用孔板测量居民的饮用水水量；公元前1000年左右古埃及用堰法测量古尼罗河的流量；我国著名的都江堰水利工程应用宝瓶口的水位观察水量大小等等。流量仪表应用范围很广，在工业生产、能源计量、环境保护工程、交通运输、生物技术、科学实验领域都有涉及。我国近代流量测量技术发展比较晚，早起所需的流量仪表均从国外进口。中国流量仪表制造业从上世纪30年代中期以仪表修配开始，到解放前后在上海、天津等沿海地区形成了现代流量仪表的民族工业。到改革开放前，经历了仿制、统一设计、自行研究开发过程，目前已近初具规模，基本上能满足中等水平流量仪表的需要。改革开放以来又经历了技术引进，与国际先进技术企业合资、合作，仪表性能和水平有了很大提高。近年国际主流企业纷纷在中国建立生产基地，既增强了研发能力也增添了竞争因素，现在我国流量计产品已很全面，基本覆盖所有行业，满足各行业产生需要，技术革新较快，但在产品生产工艺上仍然有很大提高的空间。为了适应各种用途，各种类型的流量计相继问世，投入使用的类型有上百种。根据其测量方法和结构原理大致分为差压式流量计、浮子流量计、容积式流量计、电磁流量计、涡街流量计、科里奥利质量流量计、超声流量计、插入式流量计等。20世纪随着各领域对流量测量需求的牵引，使得流量计得到快速发展，尤其是微电子技术的迅速发展，为流量计的制造技术提供各种新型的元器件，进一步推动了流量计从机械式向智能化、模块化发展。新技术、新器件、新材料和新工艺及新软件的开发应用，使得流量计的测量准确度越来越高，流量的测量范围越来越广。同时流量计对测量介质的要求在降低，适用范围也越来越宽，智能化程度及可靠性得到了很大的提高。2、意义与生产需求流量就是在单位时间内流体通过一定截面积的量。这个量用流体的体积来表示，称为瞬时体积流量，简称体积流量；用流量的质量来表示称为瞬时质量流量，简称质量流量。这一段时间内流体体积流量或质量流量的累积值称为累积流量。对在一定通道内流动的流体的流量进行测量统称为流量计量。流量测量的流体是多样化的，如测量对象有气体、液体、混合流体；流体的温度、压力、流量均有较大的差异，要求的测量准确度也各不相同。因此，流量测量的任务就是根据测量目的，被测流体的种类、流动状态、测量场所等测量条件，研究各种相应的测量方法，并保证流量量值的正确传递。流量的测量在热电生产、石油化工、食品卫生等工业领域具有广泛的应用。随着传感器技术，微电子技术、单片机技术的发展，为气体流量的精确测量提供了新的手段。充分利用单片机丰富的硬件资源，配以适当的检测接口电路，可精确测量由涡街流量传感器或电磁流量传感器输出的代表流量大小的脉冲信号，以及气体在当地状态下的压力、温度等模拟电压信号。由软件计算出流量，以简单的硬件结构实现了一个高可靠性、高精度、多功能的气体流量检测系统。工业生产中过程控制是流量测量与仪表应用的一大领域，流量与温度、压力和物位一起统称为过程控制中的四大参数，人们通过这些参数对生产过程进行监视。3、选题的目的以及研究的意义训练综合运用已学课程的基本知识，独立进行单片机应用技术和开发工作，掌握单片机程序设计、调试和应用电路设计、分析及调试检测。对流体流量进行正确测量和调节是保证生产过程安全经济运行、提高产品质量、降低物质消耗、提高经济效益、实现科学管理的基础。流量的检测和控制在化工、能源电力、冶金、石油等领域应用广泛。人们为了控制大气污染，必须对污染大气的烟气以及其他温室气体排放量进行监测；废液和污水的排放，使地表水源和地下水源受到污染，人们必须对废液和污水进行处理，对排放量进行控制。于是数以百万计的烟气排放点和污水排放口都成了流量测量对象。同时在科学试验领域，需要大量的流量控制系统进行仿真与试验。2、 研究方案1、数字流量计设计具体思路如下：要对流量进行检测，首先主要由流量传感器采集流量信息，然后经过AD转换器将连续的模拟信号离散化后传给单片机，用电源给单片机供电，单片机软件系统根据事先的设定值对采集的信息进行处理，输出离散的数字信号。数字信号通过数码管显示，从而实现对流量信息的实时显示；另外还可设置最低和最高警戒流量值，当流量不在正常范围内时，报警电路便会识别同时发出报警声，提醒流量超出正常范围，需及时采取措施。此设计采用AT89C51八位单片机为核心，是因为单片机软件编程的自由度大，可通过编程实现各种各样的算术算法和逻辑控制。而且体积小，硬件实现简单，安装方便。既可以单独对液位传感器控制工作，还可以与PC机通信。另外AT89C51在工业控制上也有着广泛的应用，编程技术及外围功能电路的配合使用都很成熟。流量传感器选用涡轮传感器，在测量范围内，传感器输出的脉冲总数与流过传感器的流体体积成正比，其比值为仪表常数。A/D转换器采用的是AD0809型号，它是8位逐次逼近型A/D转换器。报警元件采用蜂鸣器和发光二极管，实现声光报警。2、基于单片机的流量检测系统的硬件结构框图如下：数码管显示 单片机 AT89C51 A/D转换器流量传感器复位电路报警电路晶振电路电源电路 系统硬件结构框图3、 重点和难点：本次设计的重点和难点是流量信息经模数转换后的电压信号在送入单片机后作怎样的处理才能在LED显示器上转换显示成水位数据，以及各模块的软件编程，并将各硬件电路合理搭接。在今后的毕业设计过程中必将努力想出解决办法。3、 进度计划阶 段起始日期终止日期 进 度第一阶段2012.02.182008.02.28完成选题和资料收集，论证设计可行性第二阶段2012.03.012012.03.10学习相关参考文献和资料第三阶段2012.03.112008.03.18确定方案和技术关键，完成开题报告第四阶段2012.03.192012.04.08完成硬件电路的设计第五阶段2012.04.092008.04.29完成软件程序的设计第六阶段2012.05.012012.05.31进行调试与仿真，撰写毕业论文第七阶段2012.06.012012.06.15修改论文，准备答辩四、参考文献1 谢维成、杨加国.单片机原理与应用及C51程序设计M.北京：清华大学出版社，2006.2 童诗白、华成英.模拟电子技术基础M.北京：高等教育出版社，2006.3 阎石.数字电子技术基础M.北京：高等教育出版社，2006.4 彭为.单片机典型系统设计实例精讲M.北京：电子工业出版社，2006.5 梁国伟、蔡武昌.流量测量技术及仪表M.北京：机械工业出版社，2002.6 王玉巧、蔡晓艳.基于单片机的流量控制J.科技信息，2010,9X. 7 徐晓光、潘伟;、徐康.基于单片机的涡轮流量检测仪设计J.工业控制计算机，2008,08.8 孙昌权.基于AT89C52单片机的智能流量积算仪设计J.广西轻工业，2010,12.9 魏颖.基于单片机的流量检测表设计J.太原科技，2007,10.10 于文辉.基于单片机的智能流量控制系统J.微计算机信息杂志，2009,26 .11 苏贝、周常柱、胡松.单片机在流量测量中的应用J.微计算机信息杂志，2005,5.12 Keith Lambert.Flow Measurement and Instrumentation:A time of change for the journalJ.Flow Measurement and Instrumentation，2010,21(2):79-80.五、外文文献 Microcomputer SystemsElectronic systems are used for handing information in the most general sense; this information may be telephone conversation, instrument read or a companys accounts, but in each case the same main type of operation are involved: the processing, storage and transmission of information. in conventional electronic design these operations are combined at the function level; for example a counter, whether electronic or mechanical, stores the current and increments it by one as required. A system such as an electronic clock which employs counters has its storage and processing capabilities spread throughout the system because each counter is able to store and process numbers. Present day microprocessor based systems depart from this conventional approach by separating the three functions of processing, storage, and transmission into different section of the system. This partitioning into three main functions was devised by Von Neumann during the 1940s, and was not conceived especially for microcomputers. Almost every computer ever made has been designed with this structure, and despite the enormous range in their physical forms, they have all been of essentially the same basic design. In a microprocessor based system the processing will be performed in the microprocessor itself. The storage will be by means of memory circuits and the communication of information into and out of the system will be by means of special input/output(I/O) circuits. It would be impossible to identify a particular piece of hardware which performed the counting in a microprocessor based clock because the time would be stored in the memory and incremented at regular intervals but the microprocessor. However, the software which defined the systems behavior would contain sections that performed as counters. The apparently rather abstract approach to the architecture of the microprocessor and its associated circuits allows it to be very flexible in use, since the system is defined almost entirely software. The design process is largely one of software engineering, and the similar problems of construction and maintenance which occur in conventional engineering are encountered when producing software. The figure1.1 illustrates how these three sections within a microcomputer are connected in terms of the communication of information within the machine. The system is controlled by the microprocessor which supervises the transfer of information between itself and the memory and input/output sections. The external connections relate to the rest (that is, the non-computer part) of the engineering system. Fig.1.1 Three Sections of a Typical MicrocomputerAlthough only one storage section has been shown in the diagram, in practice two distinct types of memory RAM and ROM are used. In each case, the word memory is rather inappropriate since a computers memory is more like a filing cabinet in concept; information is stored in a set of numbered boxes and it is referenced by the serial number of the box in question. Microcomputers use RAM (Random Access Memory) into which data can be written and from which data can be read again when needed. This data can be read back from the memory in any sequence desired, and not necessarily the same order in which it was written, hence the expression random access memory. Another type of ROM (Read Only Memory) is used to hold fixed patterns of information which cannot be affected by the microprocessor; these patterns are not lost when power is removed and are normally used to hold the program which defines the behavior of a microprocessor based system. ROMs can be read like RAMs, but unlike RAMs they cannot be used to store variable information. Some ROMs have their data patterns put in during manufacture, while others are programmable by the user by means of special equipment and are called programmable ROMs. The widely used programmable ROMs are erasable by means of special ultraviolet lamps and are referred to as EPROMs, short for Erasable Programmable Read Only Memories. Other new types of device can be erased electrically without the need for ultraviolet light, which are called Electrically Erasable Programmable Read Only Memories, EEPROMs. The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while others are designed for controlling special hardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor. The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while others are designed for controlling special hardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor. The microprocessor , memory and input/output circuit may all be contained on the same integrated circuit provided that the application does not require too much program or data storage . This is usually the case in low-cost application such as the controllers used in microwave ovens and automatic washing machines . The use of single package allows considerable cost savings to e made when articles are manufactured in large quantities . As technology develops , more and more powerful processors and larger and larger amounts of memory are being incorporated into single chip microcomputers with resulting saving in assembly costs in the final products . For the foreseeable future , however , it will continue to be necessary to interconnect a number of integrated circuits to make a microcomputer whenever larger amounts of storage or input/output are required.Another major engineering application of microcomputers is in process control. Here the presence of the microcomputer is usually more apparent to the user because provision is normally made for programming the microcomputer for the particular application. In process control applications the benefits lf fitting the entire system on to single chip are usually outweighed by the high design cost involved, because this sort lf equipment is produced in smaller quantities. Moreover, process controllers are usually more complicated so that it is more difficult to make them as single integrated circuits. Two approaches are possible; the controller can be implemented as a general-purpose microcomputer rather like a more robust version lf a hobby computer, or as a packaged system, signed for replacing controllers based on older technologies such as electromagnetic relays. In the former case the system would probably be programmed in conventional programming languages such as the ones to9 be introduced later, while in the other case a special-purpose language might be used, for example one which allowed the function of the controller to be described in terms of relay interconnections, In either case programs can be stored in RAM, which allows them to be altered to suit changes in application, but this makes the overall system vulnerable to loss lf power unless batteries are used to ensure continuity of supply. Alternatively programs can be stored in ROM, in which case they virtually become part of the electronic hardware and are often referred to as firmware. More sophisticated process controllers require minicomputers for their implementation, although the use lf large scale integrated circuits the distinction between mini and microcomputers, Products and process controllers of various kinds represent the majority of present-day microcomputer applications, the exact figures depending on ones interpretation of the word product. Virtually all engineering and scientific uses of microcomputers can be assigned to one or other of these categories. But in the system we most study Pressure and Pressure Transmitters. Pressure arises when a force is applied over an area. Provided the force is one Newton and uniformly over the area of one square meters, the pressure has been designated one Pascal. Pressure is a universal processing condition. It is also a condition of life on the planet: we live at the bottom of an atmospheric ocean that extends upward for many miles. This mass of air has weight, and this weight pressing downward causes atmospheric pressure. Water, a fundamental necessity of life, is supplied to most of us under pressure. In the typical process plant, pressure influences boiling point temperatures, condensing point temperatures, process efficiency, costs, and other important factors. The measurement and control of pressure or lack of it-vacuum-in the typical process plant is critical.The working instruments in the plant usually include simple pressure gauges, precision recorders and indicators, and pneumatic and electronic pressure transmitters. A pressure transmitter makes a pressure measurement and generates either a pneumatic or electrical signal output that is proportional to the pressure being sensed.In the process plant, it is impractical to locate the control instruments out in the place near the process. It is also true that most measurements are not easily transmitted from some remote location. Pressure measurement is an exception, but if a high pressure of some dangerous chemical is to be indicated or recorded several hundred feet from the point of measurement, a hazard may be from the pressure or from the chemical carried.To eliminate this problem, a signal transmission system was developed. This system is usually either pneumatic or electrical. And control instruments in one location. This makes it practical for a minimum number of operators to run the plant efficiently.When a pneumatic transmission system is employed, the measurement signal is converted into pneumatic signal by the transmitter scaled from 0 to 100 percent of the measurement value. This transmitter is mounted close to the point of measurement in the process. The transmitter output-air pressure for a pneumatic transmitter-is piped to the recording or control instrument. The standard output range for a pneumatic transmitter is 20 to 100kPa, which is almost universally used.When an electronic pressure transmitter is used, the pressure is converted to electrical signal that may be current or voltage. Its standard range is from 4 to 20mA DC for current signal or from 1 to 5V DC for voltage signal. Nowadays, another type of electrical signal, which is becoming common, is the digital or discrete signal. The use of instruments and control systems based on computer or forcing increased use of this type of signal.Sometimes it is important for analysis to obtain the parameters that describe the sensor/transmitter behavior. The gain is fairly simple to obtain once the span is known. Consider an electronic pressure transmitter with a range of 0600kPa.The gain is defined as the change in output divided by the change in input. In this case, the output is electrical signal (420mA DC) and the input is process pressure (0600kPa). Thus the gain. Beside we must measure Temperature Temperature measurement is important in industrial control, as direct indications of system or product state and as indirect indications of such factors as reaction rates, energy flow, turbine efficiency, and lubricant quality. Present temperature scales have been in use for about 200 years, the earliest instruments were based on the thermal expansion of gases and liquids. Such filled systems are still employed, although many other types of instruments are available. Representative temperature sensors include: filled thermal systems, liquid-in-glass thermometers, thermocouples, resistance temperature detectors, thermostats, bimetallic devices, optical and radiation pyrometers and temperature-sensitive paints.Advantages of electrical systems include high accuracy and sensitivity, practicality of switching or scanning several measurements points, larger distances possible between measuring elements and controllers, replacement of components(rather than complete system), fast response, and ability to measure higher temperature. Among the electrical temperature sensors, thermocouples and resistance temperature detectors are most widely used.单片机系统广义地说，微处理系统是用于处理信息的，这种信息可以是电话交谈，仪器读数或企业帐户，但是各种情况下都涉及相同的主要操作：信息处理、存储和传递。在常规的电子设计中，这些操作都是以功能平台方式组合起来的，例如计数器，无论是电子还是机械的，都要存储当前值，并按要求将该值增1。诸如采用计数器的电子钟之类的任一系统要使其存储和处理能力遍布整个系统，因为每个计数器都能存储和处理一些数字。当前微处理化系统与上述的常规方法不同，它将处理，存储和传输三个功能分离形成不同的系统单元。这种形成三个主要单元的分离方法是冯-诺依曼在20世纪40年代所设想出来的，并且是针对微计算机的设想。从此几乎所有制成的计算机都是用这种结构设计的，尽管包含宽广的物理形式，从根本上来说他们均是具有相同的基本设计。在微处理器系统中，处理是由微处理器本身完成的。存储是利用存储器电路，而进入和出自系统的信息传输则是利用特定的输入/输出（I/O）电路。要在一个微处理器化时钟中找出执行计数功能的一个特殊硬件是不可能的，因为时间存储在存储器中，而在固定的时间间隔下由微处理器控制增值。但是，规定系统运转过程的软件包含实现计数器功能的单元。由于系统几乎完全由软件所定义，所以对微处理器结构和其辅助电路这种看起来非常抽象的处理方法使其在应用时非常灵活。这种设计过程主要是软件工程，而且在生产软件时，就会遇到产生于常规工程中相似的构造和维护问题。 图1.1 微型计算机的三个组成部分图1.1显示出了微型计算机中这三个单元是如何按照机器中的信息通信方式而联接起来的。该系统由微处理器控制，它管理自己与存储器和输入/输出单元的信息传输。外部的连接与工程系统的其余部分（即非计算机部分）有关。尽管图中显示的只有一个存储单元，实际中有RAM和ROM两种不同的存储器被使用。由于概念上的计算机存储器更像一个公文柜，上述的“存储器”一词是非常不恰当的；信息存放在一系列已标号的“箱子”中，而且可按问题由“箱子”的序列号进行信息的参考定位。微计算机常使用RAM（随机存取存储器），在RAM中数据可被写入，并且在需要时可被再次读出。这种数据能以任一所希望的次序从存储器中读出，不必按写入时的相同次序，所以有“随机”存取存储器。另一类型ROM（只读存储器）用来保持不受微处理器影响的固定的信息标本；这些标本在电源切断后不会丢失，并通常用来保存规定微处理器化系统运转过程的程序。ROM可像RAM一样被读取，但与RAM不一样的是不能用来存储可变的信息。有些ROM在制造时将其数据标本放入，而另外的则可通过特殊的设备由用户编程，所以称为可编程ROM。被广泛使用的可编程ROM可利用特殊紫外线灯察除，并被成为EPROM，即可察除可编程只读存储器的缩写。另有新类型的期器件不必用紫外线灯而用电察除，所以称为电可察除可编程只读存储器EEPROM。 微处理器在程序控制下处理数据，并控制流向和来自存储器和输入/输出装置的信息流。有些输入/输出装置是通用型的，而另外一些则是设计来控制如磁盘驱动器的特殊硬件，或控制传给其他计算机的信息传输。大多数类型的I/O装置在某种程度下可编程，允许不同形式的操作，而有些则包含特殊用途微处理器的I/O装置