基于LabVIEW的英文文献.docx

基于LabVIEW的英文文献.docx

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基于LabVIEW的英文文献

ElectricMeasurementswithLabVIEW

Dambovita

Abstract:

ThepaperpresentsadataacquisitionsystemwhichconsistsinHalleffectsensors,aPCI6023（NationalInstruments）dataacquisitionboard,LabVIEWgraphicalprogrammingenvironmentandtheexperimentalresultsachievedbytheauthorsconcerningthebehaviorofacelectricalcircuits.Theinstrumentsusedinthemeasurementtechniqueweredevelopedascomputerdatabaseequipments,usingwelldeterminedfunctions（theacquisitionofparameters,signalprocessing/adapting）withthecommunicationpossibilityonaserialinterfaceoronaparallelport.Today,dataacquisitionboardsareusedandcanbeassembleddirectlyintothecomputer,havingtheoperationpossibilityofanoscilloscope.TheappearanceoftheLabVIEWenvironmentwasmotivatedbytheresearchautomationactivityandbytheapplicationdevelopment,basedonahierarchicalinstrumentstructure,whichiscomposedbytheuser'sinterfaceandthevisualprogrammingelements.

Keywords：

dataacquisition,graphicalprogramming,Halleffect,electricpower

1Introduction

TheuseoftheLabVIEWgraphicalprogrammingenvironmentensurestheanalysisandstudyofpowermeasurementmethodsinsingle-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,programsandtoolstailoredtospecificprogrammingenvironments,whichwouldgivetheapplicationorsystemdevelopertheopportunitytodesignandsimulatesecureandsafedistributedmeasurementsysteminaneasyandintuitiveway.Theseadditivesshouldhelptoensuresafetransmissionofdatainanycommunicationinfrastructureandthecreationofmechanismsforauthenticationandintegrityofbothmeasurementandcontroldata.

Inthepreviouswork,theauthorshaveanalyzedtheLabVIEWenvironmentcapabilitiesforefficientimplementationofcryptographicalgorithms[1].Thenextphaseofthework,describedinthispaper,istodevelopnewmathematicaltoolforLabVIEWenvironment-aLargeNumberlibrary（alsoknownasBigIntegerorarbitrarylengthintegerlibrary）.Thislibraryallowsforthecomputationonnumberswitharbitrary（withinthelimitsofavailablememory）numberofdecimaldigits,farexceedingthetypicalrepresentationincomputersystems（32or64bit）.Largenumbersarewidelyusedinmanypopularcryptographicalgorithms,includingRSA,RabinorElGamalpublic-keyencryptionsystems,usedforboth,dataencryptionandthegenerationofsecuredigitalsignatures[2,3].TheLNlibraryinadditiontobasicarithmeticoperationincludesoperationmoduloNinthesuitableringsorfinitebodies,functionsforcalculatingtheoppositeelementinsuchalgebrasandprimalitytestalgorithms.

2.PowerMeasurementinSingle-PhaseACCircuits

Theinstantaneouspower[1,2,3,4]toanelectricdipoleisdefinedastheproductoftheinstantaneousvaluesofthevoltage（u）totheterminalofthedipoleandthecurrent（i）thatflowsthroughthedipole:

P=ui

（1）

Theinstantaneouspowercanbeclassifiedintoinputandoutputpower,dependingontheassociationofthevoltage（u）andthecurrent（i）,whichrespectstheruleofreceiversandgenerators.Inasine-wavesteady-statewiththeTperiod,theactivepower（P）canbedefinedastheaveragevalueoftheinstantaneouspower,consideringanaturalnumberofperiods:

Forasingle-phasecircuitwhichfunctionsunderasine-wavepermanentrate,inwhichthevoltageandcurrenthavethefollowingexpressions:

itresults:

-theactivepower:

P=UIcosϕ

-thereactivepower:

Q=UIsinϕ（5）

-theapparentpower:

S=UI

Thecomplexapparentpower（S）isdefinedintothesimplifiedcomplexrepresentationastheproductbetweenthecomplexvoltage（U）andtheconjugatecomplexcurrent（I*）:

Therealpartofthecomplexpower（S）istheactivepower（P）,theimaginarypartisthereactivepower（Q）,themoduleistheapparentpower（S）andtheargumentisequaltothephasedisplacement（ϕ）ofthecircuit:

Forasingle-phasecircuitwhichdoesnotfunctioninsine-waverate[4]andhastheterminalvoltageu（t）:

therecanbedefined:

theactivepower:

thereactivepower:

theapparentpower:

S=UI（11）

Bytakingintoaccounttherelationsabove,wecannoticethatS²≠P²+Q²andthereforethenotionofdeformingpowercanbeintroduced:

Theapplicationbelow（fig.1）whichisrealizedbyusingtheLabVIEWgraphicalprogrammingenvironment,basingonthepresentedtheoreticalconsiderations[2,5,6,7],allowsthegraphicaldisplayofthetimevariationofthevoltage,thecurrent,theinstantaneousandactivepower.Controlelementsareusedinordertomodifythevoltageandthechargeimpedanceparameters,andalsootherelementsareusedforindicatingthevoltage,thecurrent,thepowerfactor,theactive,reactiveandapparentpower（inordertoobtainanaccurateviewofthecurrent,itispossibletomultiplytheamplitude1,10,20,50or100times）.

Fig.1.Single-PhaseACCircuitsOperationandPowerMeasurement–simulation

2.2SignalConditioning

Theacquisitiondataboardisacomplexsystemwhichallowsparametermeasurementandmonitoringfromatechnologicalprocess,usingtransducerswhichcantransformstudiedphysicalmeasuresintoelectricalvoltage[1,3,4,6,7].Forsingle-phaseaccircuits,itisnecessarytoobtainsignalswithvoltage-rangeamplitude,tobeappliedattheinputoftheboard.Forphase/linevoltages,resistivevoltagedividers（donotensuregalvanicisolation）orvoltagemeasurementtransformers（ensuregalvanicseparation）canbeused.Shunts（current-voltageconverter）orcurrentmeasurementtransformerscanbeusedforcurrents.Theuseofbothvoltagedividersandshuntsmustbedonebytakingintoaccountthecurrentthroughthevoltagedivider,thevoltagedropontheshunt,thepowerdissipation,parasiteresistances,self-heatingeffects,dynamiceffects.

Fig.2.Dataacquisitionsystem

Fig.3.Experimentalresults

Theuseofvoltage-currentmeasurementtransformersensurestheenergeticsystem’sgalvanicisolationofthemeasuringsystem,butitintroducesratioandangleerrorsandrealizesaninadequateperturbationtransfer.TheadoptedsolutionwastousecurrentandvoltagetransducersbasedontheHalleffect.Theblockdiagramoftheacquisitionsystemispresentedinfig.2andfig.3presentstheexperimentalresults.

Remark:

Thevoltagevaluesandtheparametersoftheconsumersinfig.3a,wereintroducedintotheapplicationrealizedforsimulation（fig.1）.

3.PowerMeasurementinThree-PhaseACCircuits

Forarandom