基于LabVIEW的虚拟频率计设计

摘要I摘要虚拟仪器是在计算机基础上通过增加相关硬件和软件构建而成的、具有可视化界面的仪器，它融合了测试理论、仪器原理和技术、计算机接口技术、高速总线技术以及图形软件编程技术等于一体，利用计算机强大的数字的处理能力来实现仪器的诸多功能，打破了传统仪器的框架，形成了一种新的仪器模式。文章分析了虚拟仪器技术的现状及今后的发展趋势，介绍了虚拟仪器、LabVIEW的相关知识。叙述了虚拟频率计的理论基础，阐述了过零计数法测频原理和线性插值法原理。设计了过零计数法测频的程序框图，介绍了DAQmx驱动软件的编程方法，创建仿真设备，排除波形过零点附近的波动干扰。用仿真设备产生模拟波形并验证过零计数法测频的程序框图的正确性。介绍了数据采集理论，设计了USB2832数据采集卡驱动层程序，完成了频率测量和误差分析，验证了奈奎斯特定理。关键词：虚拟仪器，LabVIEW，过零计数法，线性插值法，数据采集卡ABSTRACTIIAbstractVirtualInstrumentisbasedoncomputerrelatedhardwareandsoftwarebyincreasingthebuildingmadewithavisualinterfaceoftheinstrument,whichcombinesthetesttheory,theoryandtechnologyequipment,computerinterfacetechnology,high-speedbustechnologyandgraphicssoftwareprogrammingtechnology.Theuseofpowerfuldigitalcomputerprocessingpowertoachievetheinstrument'smanyfeatures,thetraditionalinstrumentsoftheframeworkisbroken,theformationofanewinstrumentmodelisestablished.TheVirtualInstrumenttechnologypresentconditionandandfuturedevelopmenttrendarefirstlyanalyzedinthispaper,theknowledgeofrelatedvirtualinstrumentandLabVIEWaredescribed.Thetheoreticalbasisofvirtualfrequencymeterareelaborated,theworkingprinciplesofzero-crossingcountingmethodandlinearinterpolationmethodareelaborated.Theflowdiagramofvirtualfrequencymeterisdesigned.TheprogrammingmethodofthedriversoftwarerelatedDAQmxaredescribed,thesimulationequipmentisestablished,thefluctuationsofwaveformareexcluded.analogwaveformisgeneratedbysimulationequipment,Theflowdiagramofvirtualfrequencymeterisverified.Thetheoreticaldatacollectionisdescribed，thedriverdiagramofUSB2832dataacquisitioncardisdesigned.Frequencymeasurementanderroranalysisarecompleted,Nyquisttheoremisverified.KeyWords:VirtualInstrument,LabVIEW,zero-crossingcountingmethod,linearinterpolation,dataacquisitioncard目录III目录第1章引言.....................................................................................................................11.1测控技术的发展现状........................................................................................11.2虚拟仪器的概述................................................................................................21.2.1虚拟仪器的概念......................................................................................21.2.2虚拟仪器的特点及优势..........................................................................31.2.3虚拟仪器技术的发展趋势......................................................................41.2.4虚拟仪器技术在教学实验中的应用前景..............................................41.3论文主要内容....................................................................................................5第2章过零计数法测频原理与系统设计.....................................................................62.1过零计数法测频原理.........................................................................................62.2线性插值法........................................................................................................82.3虚拟频率计系统设计......................................................................................102.4小结....................................................................................................................11第3章应用层程序设计与仿真...................................................................................123.1程序模块化设计概述......................................................................................123.1.1程序设计的模块化原则........................................................................123.1.2软件系统的模块化设计原则................................................................133.2虚拟频率计应用层程序设计..........................................................................143.2.1LabVIEW编程语言的组成部分...........................................................143.2.2程序设计流程图....................................................................................153.2.3应用层程序设计....................................................................................163.2.3.1LabVIEW名词和函数.................................................................163.2.3.1应用层程序设计..........................................................................183.3DAQmx仿真....................................................................................................193.3.1NI数据采集卡的驱动软件....................................................................193.3.2DAQmx驱动函数..................................................................................213.3.2.1DAQmx驱动函数介绍................................................................213.2.3.2DAQmx驱动函数设计................................................................243.3.2过零点附近的波动处理........................................................................26目录IV3.4仿真结果...........................................................................................................283.5本章小结..........................................................................................................29第4章数据采集...........................................................................................................304.1数据采集理论..................................................................................................304.1.1数据采集技术概论................