基于LabVIEW的英文文獻

中北大學2013屆畢業(yè)設計說明書英文文獻及中文翻譯第5頁共10頁ElectricMeasurementswithLabVIEWDambovitaAbstract:ThepaperpresentsadataacquisitionsystemwhichconsistsinHalleffectsensors,aPCI6023(NationalInstruments)dataacquisitionboard,LabVIEWgraphicalprogrammingenvironmentandtheexperimentalresultsachievedbytheauthorsconcerningthebehaviorofacelectricalcircuits.Theinstrumentsusedinthemeasurementtechniqueweredevelopedascomputerdatabaseequipments,usingwelldeterminedfunctions(theacquisitionofparameters,signalprocessing/adapting)withthecommunicationpossibilityonaserialinterfaceoronaparallelport.Today,dataacquisitionboardsareusedandcanbeassembleddirectlyintothecomputer,havingtheoperationpossibilityofanoscilloscope.TheappearanceoftheLabVIEWenvironmentwasmotivatedbytheresearchautomationactivityandbytheapplicationdevelopment,basedonahierarchicalinstrumentstructure,whichiscomposedbytheuser'sinterfaceandthevisualprogrammingelements.Keywords：dataacquisition,graphicalprogramming,Halleffect,electricpower1IntroductionTheuseoftheLabVIEWgraphicalprogrammingenvironmentensurestheanalysisandstudyofpowermeasurementmethodsinsingle-phaseandthree-phasealternativecurrentcircuits[3,6,7].Theevolutioninbothelectricmeasurementtechnique,intheelectronicfieldandintheareaofdataacquisitionsystems,argumentstheopportunityandjustificationofdesigningnewinstrumentsinordertoimprovetheresearchactivityinthisarea[2,3].Themodernappliedmetrologyisintegrallylinkedwithotherfast-growingdomains,suchascomputertechnology,dataprocessingandtelecommunications.Adaptationoftheinformationsystems’techniquesfortheneedsofmeasurementsystemscreatedanewinterdisciplinaryfielddealingwithDistributedMeasurement-ControlSystems(DMCS).ElementsofDMCS(nodes)aredistributedterritorially,connectedviawiredorwirelessnetworkandabletoexchangeinformationbetweeneachother.CurrentlytheresearchintheareaofDMCSisfocusedontheapplicabilityissuesandadaptingofnewinformationandcommunicationtechnologiesforsuchsystems[8].Nowadays,averyimportantissueinDMCStechnologyensuresthesafetyofcommunication.Inmanycases,thesuccessofoftencostlyexperimentsormissionsandalsothebiologicalandeconomicalsecuritydependsontheproperfunctioningofsuchsystems.Duetothestillgrowingintegrationwithtelecommunicationsandgeneralpubliccomputernetworks,thesecurityofdistributedmeasurementsystemshasbeendramaticallyreduced.InmanyDMCStheinformationsecurityofthenetworkbecomesoneofthemajordevelopmentproblems.Informationsecurityissuesarealsoveryimportant(becauseofthespecificopennessofsuchsystems,andeaseofattack)inthewirelessandmobileDMCSsystems.SincethenodesofDMCScanbebothsocalledMeasuringServers,usuallybasedonPCswithhugeprocessorpower,aswellasmobilewirelesssensorspoweredfrombattery,theexistingdisparityofcalculationpowermakesanotherimportantissueforthedevelopmentofcommonmethods,ensuringthesafetyofDMCS.Thereforethereisanurgentneedtodeveloppropermethodsandtoolstoensurethesafetyandsecurityofthesesystems[1,8].Thesoftwareplaysnowadaysahugeroleinmeasurementsystemsandveryoftendeterminestheirquality.Thegrowingprocessors’computingpowerandmemorycapacityallowsforthedevelopmentofmorecomplexsoftware.Animportantissuebecomesthecreationofnewmethodsandsoftwaretoolsfordesigningdistributedmeasurementsystems,andinparticularlow-costandeasyto-uselibrariesandtoolsfordesigningsoftwarethatprovidessecureexchangeofinformationindependentlyofusedinformationandcommunicationinfrastructure.ExistingsoftwaredesigntoolsdedicatedforDMCS,integratedsoftwareenvironmentssuchasLabVIEW,LabWindows/CVI,HPVEE,enablesimpleandflexibledevelopmentprocessofapplications,butamongothersdonotincludelibrariesforsecuredataexchange.Thesecurityproblemwasonlyslightlyconsideredwhichhasresultedintheintroductionofcertainaccesscontrolmechanismstocertainpartsofanapplication(frontpanelsandtheircomponents)basedonloginandpasswordidentificationsystem.Butthereisnouseofcryptographicmethods,andtheinformationbetweennodesissentexplicitly,mostlyasaplaintext.Therefore,itseemsnecessarytodevelopacompletelibraryoffunctions,programsand(current-voltageconverter)orcurrentmeasurementtransformerscanbeusedforcurrents.Theuseofbothvoltagedividersandshuntsmustbedonebytakingintoaccountthecurrentthroughthevoltagedivider,thevoltagedropontheshunt,thepowerdissipation,parasiteresistances,self-heatingeffects,dynamiceffects.Fig.2.DataacquisitionsystemFig.3.ExperimentalresultsTheuseofvoltage-currentmeasurementtransformersensurestheenergeticsystem’sgalvanicisolationofthemeasuringsystem,butitintroducesratioandangleerrorsandrealizesaninadequateperturbationtransfer.TheadoptedsolutionwastousecurrentandvoltagetransducersbasedontheHalleffect.Theblockdiagramoftheacquisitionsystemispresentedinfig.2andfig.3presentstheexperimentalresults.Remark:Thevoltagevaluesandtheparametersoftheconsumersinfig.3a,wereintroducedintotheapplicationrealizedforsimulation(fig.1).3.PowerMeasurementinThree-PhaseACCircuitsForarandomreceiver(Z),consistinginlinearimpedances,formingasystemwithnnodeswhichisalimentedthroughacircuitwithnconductors[1],thetotalcomplexapparentpower(S)transmittedtothereceiveris:ByexpressingthepotentialsofthenodesusingthepotentialdifferencesreportedtoapointNhavingarandompotential,theexpression(3.1)becomes:(14)Thedefinitionsofactiveandreactivepowergivethefollowingresults:ThetotalactivepowerP(respectivelythereactivepower–Q)consumedbyarandomreceiverwithnphasesandalimentedthroughalineofnconductors,isequaltothesumofnactivesingle-phasepowers(orreactivesingle-phasepowers)whicharegivenbytheIklinecurrents,withtheUkNvoltagesbetweenthenconductorsandtheNpoint.Thealternativethree-phasecircuitshavethefollowingvoltagesystem:Ifthevoltagesystemsuppliesathree-phasebalancedreceiver,thecurrentsystemwillbe:Ifthephaseimpedancesaredifferent,thereceiverisnotbalancedandtheabsorbedcurrentsfromthesourcecanbecalculatedwithmethodsthatarerelatedtostarconnectedthree-phasebalancedreceivers,itresults:Regardingtheimpedancevalueoftheneutralconductor(Z0),thevoltagevaluewillbe:Fig.4.DataAcquisitionSystem–blockdiagramTheblockdiagramofthedataacquisitionsystemispresentedinfig.4.Themeasuringmethodsforactive/reactivepowerinthree-phaseaccircuits,dependonthetypeoftheconsumerandthenumberofconductorsintheelectricenergysupplysystem.Forthree-phasecircuitswithneutralconductor(n=4),thegeneralizedtheorembecomes:Thetotalactivepowerinthiscasecanbemeasuredbyusingthe4wattmetermethod(ifarandomvalueisgiventothepotentialoftheNpoint)orusingthe3wattmetermethod(ifthepotentialoftheNpointisequaltotheoneoftheneutralconductor).Fig.5.DataAcquisitionSystem–experimentalresults4ConclusionTheimplementationoftheapplications(simulatinganddataacquisition)intotheLabVIEWgraphicalprogrammingenvironmenthasbeenrealizedbasingontheoreticalaspectsandexperimentaldeterminationsinthelaboratory,usingaccuratedevices.Theseapplicationscanbeusedbothforstudyingthemeasurementmethodsofpower(student/personneltrainingbecauseoftheabilityofmodifyingtheparametersofthecircuitsandoftheeffectdisplay)andforperforminghighaccuracymeasurements.Theuseofthepresentedsignalconditioningsystemenlargesthedataacquisitionabilitiesintheelectricsystem,inordertostudythe