SHANDONGＵＮＩＶＥＲＳＩＴＹ ＯＦ ＴＥＣＨＮＯＬＯＧＹ
毕业论文
粮食水分在线测量系统设计
学 院： 电气与电子工程学院 专 业： 电子信息工程 学生姓名： 李先栋 学 号： 0712103860 指导教师： 申晋
2011 年 6 月
摘要
摘要
粮食问题是涉及到每一个国家国计民生的重大课题，解决这一问题的方法除去扩大耕地面积、提高单位面积产量外，粮食的安全储藏显得尤为重要。
粮食干燥是粮食安全储藏的重要环节，它是一个连续的生产过程。其流程是首先将原粮经处理后送入干燥塔，再经过预热、干燥、缓苏，待冷却至常温，达到安全水分14%左右后排出干燥塔。在此过程中，粮食水分在线测量是制约粮食干燥系统的核心技术。
在本次毕业设计中，确定了一种用于颗粒状的粮食水分在线测量系统。该系统将圆筒型结构的粮食水分测量传感器置于干燥机的出口和入口处，粮食的水分变化导致传感器电容量的变化,经过精密的信号采集、转换与处理,完成粮食水分在线实时测量。本文的主要内容可归纳如下:
(1)分析了粮食的介质特性，扼要介绍了现代水分检测技术的基本原理。指出了粮食水分检测技术尤其是快速检测技术的现实意义。
(2)进行了电容测量电路的硬件设计，主要包括:传感器结构设计，各种电容检测电路的对比分析，电容电压转换电路设计，模数转换电路设计，温度检测电路设计以及存储电路设计，并对电路进行了调试和实际检测。
(3)对粮食水分测量的软件部分设计，包括主程序和若干子程序，主要有巡回子程序、频率设置子程序、温度设置子程序、传感器选择子程序和暂停子程序等。
(4)粮食水分检测样本的制备，数据采集方案的设计及具体实施，最后通过对影响水分检测各因素之间的理论分析，指出了水分与电压、温度、重量之间的关系。
关键词：粮食水分、在线测量、电容传感器、多元分析
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Abstract
Abstract
Grain counts for much for the national economy and people?s livelihood. To solve the problem of lack of grain, sage storage of grain is an effective measure besides enlarging area of plantation and increasing its output by unit acreage.
During the process of grain storage grain dryness is a critical procedure, which in fact is a continuous process. The flow of grain dryness is as follows: put the grain being treated into drying tower, after process of warm-up, drying and cooling to normal temperature, when the moisture of grain is 14%,which is sage moisture, it is time to be expelled from the drying tower. During the above drying course, the core technique is the online test technology, which can restrict performance of the drying system.
In this paper, an online moisture test system for grain is identified. In this system, cylindrical moisture sensors are put at the entry and outlet of the drying device. When the capacitance of moisture sensor changes aroused by grain moisture change, and the changing signals are collected, transformed and conditioned, the system accomplishes its online real-time task of measurement. The main content is as follows: (1) Medium characteristic of grain is analyzed and principle of modern moisture measurement technology, especially the realistic meaning of celerity measurement is introduced.
(2) Capacitive measurement hardware circuit designs, including: sensor design, Capacitor voltage conversion circuit design, Analog -digital conversion circuit design, the temperature detection circuit design and circuit design store. Circuit and the Commissioning and the actual detection
(3) Moisture meter on the part of software design, including the main program and several subroutines, there are roving Subroutine, temperature settings Subroutine, Subroutine pressure settings, sensor selection, such as subroutines and suspended subprogram.
(4) Preparation of sample of grain moisture measurement, design and implement of project, analysis of theory which affect moisture measurement. The relationship of moisture, voltage temperature and weight is pointed out.
Key Words: Grain moisture, online test, Capacitance sensor, Multivariate Analysis
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目录
目录
摘要 ............................................................................................................................................... I Abstract ......................................................................................................................................... II 目录 ............................................................................................................................................ III 第一章 绪论 ............................................................................................................................ - 1 - 1.1 课题的背景、目的和意义 ........................................................................................... - 1 -
1.1.1 课题的背景 ........................................................................................................... - 1 - 1.1.2 课题的目的和意义 ............................................................................................... - 1 - 1.2 粮食水分在线测量技术发展方向 ............................................................................... - 2 - 1.3 粮食中的水分及粮食介电特性分析 ........................................................................... - 3 - 1.3.1 粮食水分 ............................................................................................................... - 3 - 1.3.2 粮食介电特性分析 ............................................................................................... - 4 - 1.4 粮食水分测量方法列举 ............................................................................................... - 4 - 1.4.1 电阻法在线测量粮食水分 ................................................................................... - 4 - 1.4.2 电容法在线测量粮食水分 ................................................................................... - 5 - 1.4.3 微波吸收法在线测量粮食水分 ........................................................................... - 6 - 1.4.4 中子法在线测量粮食水分 ................................................................................... - 8 - 1.4.5 红外线法在线测量粮食水分 ............................................................................... - 9 - 1.4.6 其他在线粮食水分测量方法 ............................................................................. - 10 - 第二章 总体方案设计 .......................................................................................................... - 12 - 第三章 粮食水分在线测量硬件系统设计 .......................................................................... - 14 - 3.1 粮食水分在线测量传感器设计 ................................................................................. - 14 -
3.1.1 电容式传感器结构设计 ..................................................................................... - 14 - 3.1.2 电容式水分传感器的构成及结构优化 ............................................................. - 16 - 3.2 电容检测电路设计 ..................................................................................................... - 17 - 3.2.1 几种常用电容式水分测量电路的比较 ............................................................. - 17 - 3.2.2 电容电压转换电路设计 ..................................................................................... - 18 - 3.3 模数转换电路设计 ..................................................................................................... - 21 - 3.3.1 AD7714各引脚功能 ............................................................................................ - 22 - 3.3.2 AD7714性能特点 ................................................................................................ - 23 - 3.3.3 AD7714片内寄存器及其功能 ............................................................................ - 23 - 3.3.4 AD7714与单片机接口 ........................................................................................ - 25 - 3.4 温度传感器的设计 ..................................................................................................... - 26 - 3.4.1 DS18B20数字温度传感器工作方式.................................................................. - 26 - 3.4.2 DS18B20与单片机接口 ..................................................................................... - 27 - 3.5 测量参数存储电路设计 ............................................................................................. - 28 - 3.5.1 I2C总线简介 ........................................................................................................ - 28 - 3.5.2 用AT89C52单片机模拟I2C总线工作方式 .................................................... - 29 - 3.5.3 E2PROM存储芯片24WC02的工作方式 .......................................................... - 29 - 3.5.4 24WC02与单片机接口 ....................................................................................... - 30 -
III
目录
3.6 单片机系统与PC机的通讯 ...................................................................................... - 31 - 第四章 粮食水分在线测量软件系统设计 .......................................................................... - 32 - 4.1 单片机系统软件设计 ................................................................................................. - 32 -
4.1.1 主程序 ................................................................................................................. - 32 - 4.1.2 电容值测量程序设计 ......................................................................................... - 33 - 4.1.3 温度测量程序设计 ............................................................................................. - 33 - 4.1.4 E2PROM与单片机接口程序设计 ...................................................................... - 35 - 4.1.5 通讯中断服务程序 ............................................................................................. - 37 - 4.2 上位机软件设计 ......................................................................................................... - 38 - 4.2.1 上位机编程语言及软件功能介绍 ..................................................................... - 38 - 4.2.2 上位机与单片机通讯功能的实现 ..................................................................... - 39 - 第五章 测量数据的采集和处理 .......................................................................................... - 41 - 5.1 样品数据的采集 ......................................................................................................... - 41 - 5.2 采样数据处理 ............................................................................................................. - 41 -
5.2.1 粗大误差的剔除 ................................................................................................. - 41 - 5.2.2 有效数字与数字修约 ......................................................................................... - 42 - 5.2.3 水分测量数据的处理 ......................................................................................... - 42 - 5.3 水分测量数据分析 ..................................................................................................... - 42 - 5.3.1 水分-电压关系 .................................................................................................... - 42 - 5.3.2 水分-温度关系 .................................................................................................... - 43 - 5.3.3 水分-重量关系 .................................................................................................... - 44 - 总结 ........................................................................................................................................ - 45 - 参考书目 ................................................................................................................................ - 46 - 致谢 ........................................................................................................................................ - 48 - 附件 ........................................................................................................................................ - 49 -
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