【作者】 林丽兰；

【导师】 何勇；

【作者基本信息】 浙江大学 ， 农业电气化与自动化， 2005， 硕士

【摘要】 21世纪以来,计算机技术及微电子技术的发展渗透到测量和仪器仪表技术领域,已极大的影响了检测和控制领域的发展,诞生了一些新的检测思想和检测手段,其中虚拟仪器正成为测控领域新的发展方向。另一方面,精细农业是21世纪农业发展的一个重要方向,将推动粗放型农业向知识型、技术型的现代农业转变,中国作为农业大国,实施精细农业的前提和难点是农田信息的采集。本文针对现阶段的情况,重点研究了应用虚拟仪器技术、传感器技术、数据库技术实现农田信息的快速采集和处理,拓展了现有的农田信息测量手段,也大大拓展了虚拟仪器的应用领域。主要研究内容如下: (1)分析了虚拟仪器与传统仪器相比的优越性,开发和维护费用低,技术更新周期短,软件在仪器中起着关键作用;在开放性、灵活性方面与计算机同步。在此基础上,针对当前农田信息测量中存在的问题,提出将虚拟仪器作为农田信息统一测量平台的方案。 (2)研究了农田信息的快速测量方法及测量原理,结合传感器技术、信号处理技术和虚拟仪器技术,研制了农田信息的虚拟仪器测量系统。该系统集成度高,由一块数据采集卡、一套软件和若干传感器便可实现多个参数的同时测量,避免了目前农田信息的全面测量需要多台仪器的局面。 (3)分析了虚拟仪器系统的设计思想,根据虚拟仪器“软件就是仪器”的核心,针对本文农田信息的测量项目,采用模块化的设计思想。整个测量系统分为五大模块:pH值测量模块、电导率测量模块、温度测量模块、GPS测量模块和数据库操作模块。软件结构清晰,可读性强,可扩展性好;简化系统的调试工作。 (4)使用pH电极测量土壤溶液的pH值,选择电位分析法和两点校正法对测量值进行校正。使用热电偶测量土壤温度,采用集成温度传感器AD590进行冷端温度补偿,对热电偶的输出电势与温度之间的关系进行曲线拟合,以提高温度的测量精度。使用电导电极测量土壤配比溶液的电导率,利用温度校正原理自动对测试结果进行温度校正。 (5)在分析GPS卫星定位原理及输出语句数据格式的基础上,设计了OEM型GPS接收机与计算机的软件接口程序,实现了GPS数据的计算机采集。给出了GPS数据的处理方法,包括大地坐标与直角坐标转换、不同坐标系转换、高斯投影等,并编程实现了GPS农田定位信息的投影变换。 (6)分析了数据库与农田信息测量系统结合的优越性,数据库强大的数据存储、查询、调用等功能将给测量系统以强大的技术支持;并且,可通过和通用数据库的连接,实现与其它应用平台或者管理信息系统的连接,为决策分析和变量更多还原

【Abstract】 Since 21st century, the development of computer technology and micro-electronics technology has penetrated the fields of measurement and instrument technology, and greatly stimulated them to further progresses. Virtual instrument (VI), as a new developing technology, is attracting more and more attentions in measurement and control field. On the other hand, precision agriculture (PA) is a very important aspect for agriculture development. PA would promote the change from extensive agriculture to knowledge and technology-based agriculture. According to the condition of China, the acquisition of field information is the premise and difficulty for PA practice. This paper mainly studied the technology of field information acquisition and process based on techniques of GPS, sensors, database and virtual instrument. The studies have expanded current field information measurement methods and strengthen the application of virtual instrument. The main contents of this paper include:(1) Virtual instrument is beyond c ompared w ith traditional instrument, which includes lower cost of exploitation and maintenance, shorter period of technology update, flexibility and so on. Therefore, aimed at drawbacks in field information acquisition, a new project of VI-based system for real-time measuring field information was put forward.(2) The method and principle for fast measurement field information were studied. A VI measurement system for measuring field information was developed using sensor technique, signal conditioning technique, database technique etc. This system composed of several sensors, a DAQ card and computer system, in addition, this VI application was designed using Graphical language LabVIEW. It could measure multi-variable at the same time, which avoiding using many different instruments to measure whole file information at present.(3) Based on the analysis of the principle of GPS location and output-sentence format, the software interface were designed for OEM GPS receiver and computer to realize GPS data acquisition by computer. The methods of processing GPS data was given, and the gauss transform of GPS data was achieved by application program.(4) A pH electrode was used to acquire soil pH, and the methods of electric-potential analysis and two-point correction were selected to improve the measurement precision. A thermocouple was used to acquire soil temperature,更多还原