LabVIEW实践之路14-15

LabVIEW入门讲义背景介绍LabVIEW是实验室虚拟仪器集成环境（Laboratory Virtual Instrument Engineering Workbench）的简称，是美国国家仪器公司（NATIONAL INSTRUMENTS，简称NI）的创新软件产品，也是目前应用最广、发展最快、功能最强的图形化软件集成开发环境。

目前它广泛地被工业界、学术界和研究实验室所接受，视为一个标准的数据采集和仪器控制软件。

LabVIEW集成了与满足GPIB、VXI、RS-232和RS-485协议的硬件及数据采集卡通讯的全部功能。

它还内置了便于应用TCP/IP、ActiveX等软件标准的库函数。

这是一个功能强大且灵活的软件。

利用它可以方便地建立自己的虚拟仪器，其图形化的界面使得编程及使用过程都生动有趣。

图形化的程序语言，又称为“Ｇ”语言。

其编写的程序称为虚拟仪器VI（Virtual Instrument），以.VI后缀。

使用这种语言编程时，基本上不写程序代码，取而代之的是流程图或流程图。

它尽可能利用了技术人员、科学家、工程师所熟悉的术语、图标和概念，因此，LabVIEW 是一个面向最终用户的工具。

它可以增强你构建自己的科学和工程系统的能力，提供了实现仪器编程和数据采集系统的便捷途径。

使用它进行原理研究、设计、测试并实现仪器系统时，可以大大提高工作效率。

以下的课程内容可以在wiki上找到：/doku.php?id=home:whyx:labview第一课 LabVIEW概述第一节虚拟仪器（VI）的概念使用LabVIEW开发平台编制的程序称为虚拟仪器程序，简称为VI。

VI包括三个部分：程序前面板、框图程序和图标/连接器。

程序前面板用于设置输入数值和观察输出量，用于模拟真实仪表的前面板。

在程序前面板上，输入量被称为控制（Controls），输出量被称为显示（Indicators）。

控制和显示是以各种图标形式出现在前面板上，如旋钮、开关、按钮、图表、图形等，这使这得前面板直观易懂。

第8章 波形运算 155
的；线性方式会给出最佳的峰值与均值比。

¾ 信号输出：产生的波形信号。

¾ 峰值因数：输出信号的峰值电压与平均值电压的比。

¾ 实际单频信号频率：
如果强制频率转换为TRUE ，则输出强制转换频率后单频的频率。

8.1.7 课堂练习——生成混合信号
本小节演示使用基本混合单频VI 产生不同形式的信号波形。

操作提示： 本实例利用基本混合单频VI 对混合单频的各种参数进行调节，并输出必要信息。

前面板及程序框图如图8-10和图8-11所示。

图
8-10 前面板
图8-11 程序框图
8.1.8 仿真信号
Express VI 可模拟正弦波、方波、三角波、锯齿波和噪声。

该VI
还存在于【函数】选板 生成混合信号。

虚拟仪器技术实验指导书信息电子技术学院赵化启注意：在试验之前，首先创建一个以自己名字命名的目录，所有的练习程序都保存到该目录中。

补充练习所生成的VI，以“EX＋练习序号.vi”命名，如EX01.vi等。

实验一 Labview软件VI的创建实验1.实验目的：（1）创建一个VI程序。

（2）创建一个VI程序模拟温度测量。

2.实验要求：（1）学会使用工具模板、控件模板、函数模板。

（2）了解控件的快捷菜单、属性。

学会如何使用帮助。

（3）理解不同的数据类型是通过颜色和线形来区分的。

3.实验器材：虚拟仪器综合实验平台（PC机等）4.实验内容及原理：虚拟仪器 (VI: Virtual Instrument) 是在以通用计算机为核心的硬件平台上，由用户设计定义，具有虚拟面板，测试功能由测试软件实现的一种计算机仪器系统。

虚拟仪器是以特定的软件支持取代相应功能的电子线路，用计算机完成传统仪器硬件的一部分乃至全部功能，它是以具备控制、处理分析能力的软件为核心的软仪器。

使用者在操作这台计算机时，就象在操作一台他自己设计的仪器一样。

利用Labview软件可以实现VI的设计。

创建一个VI程序模拟温度测量。

假设传感器输出电压与温度成正比。

例如，当温度为70°F时，传感器输出电压为0.7V。

本程序也可以用摄氏温度来代替华氏温度显示。

本程序用软件代替了DAQ数据采集卡。

在程序面板使用编程→数值→随机数（0到1)来仿真电压测量，然后把所测得的电压值转换成摄氏或华氏温度读数。

5.实验步骤：●选择文件 >> 新建VI，打开一个新的前面板。

假如已关闭了所有的VI，则在LabVIEW的对话框中选择新建VI。

注意：若控件面板不可见，可选择菜单察看 >> 控件选板，使控件面板可见。

也可以在前面板的空白区域内单击鼠标右键的方法弹出快捷菜单，使控件面板可见。

●在菜单新式 >> 数值中选择温度计（或Express >> 数值显示控件 >> 温度计），并置于前面板上。

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本文部分内容来自网络整理，本司不为其真实性负责，如有异议或侵权请及时联系，本司将立即删除！== 本文为word格式，下载后可方便编辑和修改！ ==labview,实习报告篇一：labviEW虚拟仪器实习报告实验一：实验步骤（1）启动LabVIEW，创建一个VI并命名为test1。

（2）在前面板中放置一个温度计控件，并修改控件标签名为发动机温度和设置最大值为100。

该控件从“控件—经典—经典数值”子选项板中获得。

（3）按同样的方法在前面板中放置一个仪表控件，并修改仪表控件的标签名为汽车速度，标尺刻度范围为0～150。

（4）按同样的方法在前面板中放置一个数值输入控件，并修改控件标签名为发动机转速。

（5）从“窗口”下拉菜单中选择“显示程序窗口”切换到程序框图窗口。

（6）在程序窗口中创建乘法函数，该函数中函数选项板中的“函数—编程—数值”子选项板中选择，并和发动机转速输入控件连线，为乘法函数创建一个常量，修改为图中所示值。

（7）按同样的方法创建加法函数、平方根函数和除法函数，并按图中所示修改常量值和连好线。

（8）切换至前面板，在发动机转速控件中输入数值，点击运行按钮，运行VI程序。

（9）修改图标为T/V以表示该子VI输出量为发动机温度和汽车速度，并保存。

前面板：程序框图：实验二：实验步骤：（1）启动LabVIEW，创建一个vi并保存为test2。

（2）在前面板中创建一个旋钮控件，修改标签名为发动机转速，设置数值范围为0～5000，从旋钮控件中调出一个数字显示控件来同步显示旋钮控件当前值。

（3）在前面板创建两个数值显示控件，并修改标签名为汽车速度和发动机温度。

（4）切换至程序框图窗口。

（5）在程序框图中创建一个大于或等于函数。

（6）在程序框图中调用实验一的子函数，从函数选板中的“函数—选择VI”选在实验一创建的子vi.vi。

（7）在程序框图中创建一个蜂鸣器函数，并按图示连线情况连线。

（8）切换至前面板，在发动机转速中输入数值，点击运行按钮运行。

实验一虚拟仪器及LabVIEW入门实验一要求：运行National Instruments LabVIEW ，完成下列实验讲义中的所给出的练习题1-1和1-2。

并完成实验报告。

１．1虚拟仪器概述虚拟仪器（virtual instrumention）是基于计算机的仪器。

计算机和仪器的密切结合是目前仪器发展的一个重要方向。

粗略地说这种结合有两种方式，一种是将计算机装入仪器，其典型的例子就是所谓智能化的仪器。

随着计算机功能的日益强大以及其体积的日趋缩小，这类仪器功能也越来越强大，目前已经出现含嵌入式系统的仪器。

另一种方式是将仪器装入计算机。

以通用的计算机硬件及操作系统为依托，实现各种仪器功能。

虚拟仪器主要是指这种方式。

下面的框图反映了常见的虚拟仪器方案。

虚拟仪器的主要特点有：⏹尽可能采用了通用的硬件，各种仪器的差异主要是软件。

⏹可充分发挥计算机的能力，有强大的数据处理功能，可以创造出功能更强的仪器。

⏹用户可以根据自己的需要定义和制造各种仪器。

虚拟仪器实际上是一个按照仪器需求组织的数据采集系统。

虚拟仪器的研究中涉及的基础理论主要有计算机数据采集和数字信号处理。

目前在这一领域内，使用较为广泛的计算机语言是美国NI公司的LabVIEW。

虚拟仪器的起源可以追朔到20世纪70年代，那时计算机测控系统在国防、航天等领域已经有了相当的发展。

PC机出现以后，仪器级的计算机化成为可能，甚至在Microsoft公司的Windows诞生之前，NI公司已经在Macintosh 计算机上推出了以前的版本。

对虚拟仪器和LabVIEW长期、系统、有效的研究开发使得该公司成为业界公认的权威。

普通的PC有一些不可避免的弱点。

用它构建的虚拟仪器或计算机测试系统性能不可能太高。

目前作为计算机化仪器的一个重要发展方向是制定了VXI标准，这是一种插卡式的仪器。

每一种仪器是一个插卡，为了保证仪器的性能，又采用了较多的硬件，但这些卡式仪器本身都没有面板，其面板仍然用虚拟的方式在计算机屏幕上出现。

《虚拟仪器》实验指导书适用专业:机械电子、自动化等课程代码: 8300091 总学时: 32 总学分: 2编写单位:机械学院编写人:车畅审核人:审批人:批准时间:年月日实验1 LabVIEW入门1 实验目的（1）初步学会使用LabVIEW；（2）掌握创建自己的VI。

2 实验任务（1）建立一个测量温度和容积的VI；（2）为 VI创建图标和联接器；（3）使用LabvIEW图表模式。

3 实验步骤练习 1-1 使用三种图表模式目的：查看 VI 分别在三种模式下执行时图表的显示。

1．建立前面板及流程图如下该程序中利用一个循环产生连续的sin(i)函数值，并及时地在chart图表上显示出来，现在前面板上的chart是一个strip，这是一个坐标式显示器，与纸带式图表记录器相似。

每接受一个新数据，新数据就将显示在右侧，而原有数据移动到左侧图１－1 图表的例子2．用鼠标选中chart,点击右键，可在快速菜单中选择Advanced»Update Mode子菜单。

可以选择更换其他两种更新模式。

示波器模式是一个返回式的显示器，与示波器类似。

每接受一个新数据时，它就把新数据绘制在原有数据的右侧。

当数据曲线到达显示区的右边缘时，VI 会删除全部图形，从左边缘重新开始绘制曲线。

示波器模式显然要快于条状图模式，因为它不会因为滚动产生溢出。

扫描模式更接近于示波器模式，但是当数据曲线到达显示区的右边时，不会变成空白，而是会出现一个移动的垂线，标记新数据的开始，并当VI添加新数据时穿过整个显示区。

练习 1-1 结束。

4 实验报告写出练习 1-1的中的步骤要点，附上运行时的前后面版图形。

实验2 程序结构1 实验目的（1）学会使用LabVIEW中的While循环；（2）学会使用LabVIEW中的移位寄存器；（3）学会使用LabVIEW中的For循环；（4）学会使用LabVIEW中的CASE结构；（5）学会使用LabVIEW中的顺序结构；（6）学会使用LabVIEW中的公式节点。