外文翻译---LabVIEW的测量和数据分析.docx

外文翻译---LabVIEW的测量和数据分析.docx

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LabVIEWforMeasurementandDataAnalysis

LabVIEWisthetoolofchoiceduetoitsunparalleledconnectivitytoinstruments,powerfuldataacquisitioncapabilities,naturaldataflow-basedgraphicalprogramminginterface,scalability,andoverallfunctioncompleteness.

Introduction

Usersgenerallystarttheirworkbyacquiringdataintoanapplicationorprogram,becausetheirtaskstypicallyrequireinteractionwithphysicalprocesses.Inordertoextractvaluableinformationfromthatdata,makedecisionsontheprocess,andobtainresults,thedataneedstobemanipulatedandanalyzed.Unfortunately,combininganalysiswithdataacquisitionanddatapresentationisnotalwaysastraightforwardprocess.Applicationsoftwarepackagestypicallyaddressonecomponentoftheapplication,butseldomaddressallaspectsandneedstogettoacompletesolution.LabVIEWwasdesignedtoaddresstherequirementsforastart-to-finish,fully-integratedsolution,sothatcustomerscanseamlesslyintegrateallphasesoftheirapplicationinasingleenvironment.

Figure1.LabVIEWVirtualInstrumentBlockDiagram

Whiletherearemanytoolsthatindependentlyaddresseachoftherequirements,only

LabVIEWcombinesallofthemwiththepowerofgraphicalprogrammingandstate-of-the-artdataacquisitionhardware,usingthepowerofyourPC.Itisthecombinationofdataacquisition,dataanalysis,andpresentationofresults,thattrulymaximizesthepowerofVirtualInstrumentation.Avirtualinstrumentconsistsofanindustry-standardcomputerorworkstationequippedwithpowerfulapplicationsoftware,cost-effectivehardwaresuchasplug-inboards,anddriversoftware,whichtogetherperformthefunctionsoftraditionalinstruments.ThisiswhyapplicationsandprogramsbuiltwithLabVIEWarereferredtoasVI（virtualinstruments）.

Asanengineering-focusedtool,LabVIEWmakeshundredsofanalysisfunctionsavailableforresearchers,scientists,andengineers,aswellasstudentsandprofessors.Theycanbuildthesefunctionsrightintotheirapplicationstomakeintelligentmeasurementsandobtainresultsfaster.

ChoosingtheCorrectMethodforAnalysis

Usersincorporateanalysisintotheirapplicationsandprogramsindifferentways.Therearecertainconsiderationsthathelpdeterminethewayinwhichanalysisshouldbeperformed.

Inlinevs.Offlineanalysis

Inlineanalysisimpliesthatthedataisanalyzedwithinthesameapplicationwhereitisacquired.Thisisgenerallythecasewhendealingwithapplicationswheredecisionshavetobemadeduringruntimeandtheresultshavedirectconsequencesontheprocess,typicallythroughthechangingofparametersorexecutingofactions.Thisistypicallythecaseincontrolapplications.Whendealingwithinlineanalysis,itisimportanttoconsidertheamountofdataacquiredandtheparticularanalysisroutinesthatareperformedonthatdata.Aproperbalancemustbefoundbecausetheycouldeasilybecomecomputationallyintensiveandhaveanadverseeffectontheperformanceoftheapplication.

Otherexamplesforinlineanalysisareapplicationswheretheparametersofthemeasurementneedtobeadaptedtothecharacteristicsofthemeasuredsignal.Onecaseiswhereoneormoresignalsneedtobelogged,butthesechangeveryslowlyexceptforsuddenburstsofhigh-speedactivity.Inordertoreducetheamountofdata

logged,theapplicationwouldhavetoquicklyrecognizetheneedforahighersamplingrate,andreduceitwhentheburstisover.Bymeasuringandanalyzingcertainaspectsofthesignalstheapplicationcanadapttothecircumstancesandenabletheappropriateexecutionparameters.Althoughthisisonlyoneexample,therearethousandsofapplicationswhereacertaindegreeofintelligence-theabilitytomakedecisionsbasedonvariousconditions-andadaptabilityarerequired,whichcanonlybeprovidedbyaddinganalysisalgorithmstotheapplication.

Decisionsbasedonacquireddataarenotalwaysmadeinanautomatedmanner.Veryfrequently,thoseinvolvedwiththeprocessneedtomonitortheexecutionanddeterminewhetheritisperformingasexpectedorifoneormorevariablesneedtobeadjusted.Althoughitisnotuncommonforuserstologdata,extractitfromafileordatabaseandthenanalyzeitofflineto modifytheprocess,manytimesthechangesneedtohappenduringruntime.Inthesecases,theapplicationmusthandlethedatacomingfromtheprocess,andthenmanipulate,simplify,format,andpresentthedatainawaythatitismostusefultotheuser.LabVIEWuserscanthentakeadvantageofthemanyvisualizationobjectstopresentthatdatainthemostconciseandusefulmanner.

LabVIEWoffersanalysisandmathematicalroutinesthatnativelyworktogetherwithdataacquisitionfunctionsanddisplaycapabilities,sothattheycanbeeasilybuiltintoany application. In addition, Lab VIEW offers analysisroutines forpoint-by-pointexecution;theseroutinesaredesignedspecificallytomeettheneedsofinlineanalysisinreal-timeapplications.Usersshouldconsidercertainaspectswhendecidingwhetherpoint-by-pointroutinesareappropriate.

Point-by-pointanalysisisessentialwhendealingwithcontrolprocesseswherehigh-speed,deterministic,point-by-pointdataacquisitionispresent.Anytimeresourcesarededicatedtoreal-timedataacquisition,point-by-pointanalysisbecomesanecessityasacquisitionratesandcontrolloopsareincreasedbyordersofmagnitude.Thepoint-by-pointapproachsimplifiesthedesign,implementation,andtestingprocess,becausetheflowoftheapplicationcloselymatchesthenaturalflowofthereal-world processes that the application is monitoring and controlling.

Figure2.Array-basedAnalysisvs.Point-by-PointAnalysis

Real-timedataacquisitionandanalysiscontinuetodemandmorestreamlinedandstableapplications.Point-by-pointanalysisisstreamlinedandstable,becauseittiesdirectlyintothe acquisitionandanalysisprocess.Withstreamlined,stablepoint-by-pointanalysis,theacquisitionandanalysisprocesscanmoveclosertothepointofcontrolinFPGA（fieldprogrammablegatearray）chips,DSPchips,embeddedcontrollers,dedicatedCPUs,andAsics.

Tobetterunderstandtheadvantagesofpoint-by-pointanalysisroutines,NationalInstrumentssuggestsreadingthedocumenttitled"GettingStartedwithLabVIEWPoint-By-PointVIs."

ThisdocumentdescribeshowtousetheVIandincludesacasestudythat showsacompleteapplicationbuiltinLabVIEW.Theapplicationdemonstratesthesimplicityandflexibilityofpoint-by-pointanalysis.

Byaddingthesepowerfulalgorithmsandroutinesintoapplications,userseliminatetheguessworkandcreateintelligentprocessesthatcananalyzeresultsduringruntime,improvingefficiencyanditerativelycorrelatinginputvariablestoexperimentorprocessperformance.

Offlineapplicationsdon’ttypicallyhavethedemandforresultstobeobtainedinreal-timefashioninordertomakedecisionsontheprocess.Offlineanalysisapplicationsrequireonlythatsufficientcomputationalresourcesareavailable.Themainintentofsuchapplicationsistoidentifycauseandeffectofvariablesaffectingaprocessbycorrelatingmultipledatasets.Theseapplicationsgenerallyrequire

importingdatafromcustombinaryorASCIIfilesandcommercialdatabasessuchasOracle,Access,andotherQL/ODBC-enableddatabases.OncethedataisimportedintoLabVIEW,usersperformseveralorhundredsofavailableanalysisroutines,manipulatethedata,andarrangeitin aspecificformatforreportingpurposes.LabVIEWprovidesfunctionstoaccessanytypeoffileformatanddatabase,seamlesslyconnecttopowerfulreportingtoolssuchasNIDiademandtheReportGenerationToolkitforMicrosoftOffice,andexecutethelatestdata-sharingtechnologiessuchasXML,Web-enableddatapresentation,andActiveX.

Programmaticvs.InteractiveAnalysis

AsLabVIEWusers,scientistsandengineersareveryfamiliarwiththemanywaysinwhichtheycanacquiredatafromhundredsofdevices.Theybuildintelligenceintotheirapplicationstoperforminlineanalysisandpresentresultswhiletheapplicationsarerunning.Inaddition,theyareawarethatacquiringdataandprocessingitforthesakeofonlinevisualizationisnotenough.Userstypicallystorehundredsorthousandsofmegabytesofdatainharddrivesanddatabases.Afteranywherefromonetohundredsofrunsoftheapplication,usersproceedtoextractinformationinordertomakedecisions,compareresults,andmakeappropriatechangestotheprocess,untilthedesiredresultsareachieved.。

Itisrelativelyeasytoacquireamountsofdatasolargethatitrapidlybecomes

unmanageable.Infact,withafastDAQboardandenoughchannels,itmayonlytakeafewmillisecondstocompilethousandsofvalues.Itisnotatrivialtasktomakesenseoutofallthatdata.Engineers andscientistsaretypicallyexpectedto presentreports,creategraphs,andultimatelycorroborateanyassessmentsandconclusionswithempiricaldata.Withouttherighttools,thiscaneasilybecomeadauntingtask,resultinginlostproductivity.

Inordertosimplifytheprocessofanalyzingmeasurements,LabVIEWprogrammerscreateapplicationsthatprovidedialogsandinterfacesthatotherscanusesothatdependingontheirinput,specificanalysisroutinesareperformedonanygivendataset.Bybuildingthistypeofapplication,usersbuildacertaindegreeofinteractivityintotheirapplications.Forthistobeefficient,theprogrammermusthaveextensive

knowledgeabouttheinformationandthetypesofanalysisinwhichtheuserisinterested.

Figure3.TimeDomainReflectionVIBasedonJointTime-FrequencyAnalysisF