冷库温度控制系统的设计-外文翻译

大连交通高校信息工程学院毕业设计(论文)外文翻译学生姓名1111专业班级自动化0111班指导老师1111职称11111所在单位电气工程系教研室主任完成日期1111年4月13日DateAcquisitionDateacquisitionsystemsareusedtoacquireprocessoperatingdataandstoreitonsecondarystoragedevicesforlateranalysis.Manyofthedataacquisitionsystemsacquirethisdataatveryhighspeedsandverylittlecomputertimeislefttocarryoutanynecessary,ordesirable,datamanipulationsorreduction.Allthedataarestoredonsecondarystoragedevicesandmanipulatedsubsequentlytoderivethevariablesofinterest.Itisveryoftennecessarytodesignspecialpurposedataacquisitionsystemsandinterfacestoacquirethehighspeedprocessdata.Thisspecialpurposedesigncanbeanexpensiveproposition.Powerfulmini-andmainframecomputersareusedtocombinethedataacquisitionwithotherfunctionssuchascomparisonsbetweentheactualoutputandthedesirableoutputvalues,andtothendecideonthecontrolactionwhichmustbetakentoensurethattheoutputvariablesliewithinpre-setlimits.Thecomputingpowerrequiredwilldependuponthetypeofprocesscontrolsystemimplemented.Softwarerequirementsforcarryingoutproportional,ratioorthreetermcontrolofprocessvariablesarerelativelytrivial,andmicrocomputerscanbeusedtoimplementsuchprocesscontrolsystems.Itwouldnotbepossibletousemanyofthecurrentlyavailablemicrocomputersfortheimplementationofhighspeedadaptivecontrolsystemswhichrequiretheuseofsuitableprocessmodelsandconsiderableon-linemanipulationofdata.Microcomputerbaseddataloggersareusedtocarryoutintermediatefunctionssuchasdataacquisitionatcomparativelylowspeeds,simplemathematicalmanipulationsofrawdataandsomeformsofdatareduction.Thefirstgenerationofdataloggers,withoutanyprogrammablecomputingfacilities,wereusedsimplyforslowspeeddataacquisitionfromuptoonehundredchannels.Alltheacquireddatacouldbepunchedoutonpapertapeorprintedforsubsequentanalysis.Suchhardwireddataloggersarebeingreplacedbythenewgenerationofdataloggerswhichincorporatemicrocomputersandcanbeprogrammedbytheuser.Theyofferanextremelygoodmethodofcollectingtheprocessdata,usingstandardizedinterfaces,andsubsequentlyperformingthenecessarymanipulationstoprovidetheinformationofinteresttotheprocessoperator.Thedataacquiredcanbeanalyzedtoestablishcorrelations,ifany,betweenprocessvariablesandtodevelopmathematicalmodelsnecessaryforadaptiveandoptimalprocesscontrol.Thedataacquisitionfunctioncarriedoutbydataloggersvariesfromoneloggingsystemtoanother.Simpledataloggingsystemsacquiredatafromafewchannelswhilecomplexsystemscanreceivedatafromhundreds,oreventhousands,ofinputchannelsdistributedaroundoneormoreprocesses.Therudimentarydataloggersscanselectnumberofchannels,connectedtosensorsortransducers,inasequentialmannerandthedataarerecordedindigitalformat.Adataloggercanbededicatedinthesensethatitcanonlycollectdatafromparticulartypesofsensorsandtransducers.Itisbesttouseanon-dedicateddataloggersinceanytransducerorsensorcanbeconnectedtotheuseofappropriatesignalconditioningmodules.Microcomputercontrolleddataacquisitionfacilitatesthescanningofalargenumberofsensors.Thescanningratedependsuponthesignaldynamicswhichmeansthatsomechannelsmustbescannedatveryhighspeedsinordertoavoidaliasingerrorswhilehereisverylittlelossofinformationbyscanningothercannelsatslowerspeeds.Insomedataloggingapplicationsthefasterchannelsrequiresamplingatspeedsofupto100timespersecondwhileslowchannelscanbesampledonceeveryfiveminutes.Theconventionalhardwired,non-programmabledataloggerssampleallthechannelsinasequentialmannerandthesamplingfrequencyofallthechannelsmustbethesame.Thisprocedureresultsintheaccumulationofverylargeamountsofdata,someofwhichisunnecessary,andalsoslowsdowntheoveralleffectivesamplingfrequency.Microcomputerbaseddataloggerscanbeusedtoscansomefastchannelsatahigherfrequencythanotherslowspeedchannels.Thevastmajorityoftheuserprogrammabledataloggerscanbeusedtoscanupto1000analogand1000digitalinputchannels.Asmallnumberofdataloggers,withahigherdegreeofsophistication,aresuitableforacquiringdatafromupto15,000analoganddigitalchannels.ThedatafromdigitalchannelscanbeintheformofTransistor-TransistorLogicorcontactclosuresignals.Analogdatamustbeconvertedintodigitalformatbeforeitisrecordedandrequirestheuseofsuitableanalogtodigitalconverters(ADC).ThecharacteristicsoftheADCwilldefinetheresolutionthatcanbeachievedandtherateatwhichthevariouschannelscanbesampled.AnincreaseinthenumberofbitsusedintheADCimprovestheresolutioncapability.SuccessiveapproximationADC’sarefasterthanintegratingADC’s.Manymicrocomputercontrolleddataloggersincludeafacilitytoprogramthechannelscanningrates.Typicalscanningratesvaryfrom2channelspersecondto10,000channelspersecond.Mostdataloggershavearesolutioncapabilityof±0.001%orbetter.Itisalsopossibletoachievearesolutionof1micro-volt.Theresolutioncapability,inabsoluteterms,alsodependsupontherangeofinputsignals,Standardinputsignalrangesare0-1-volt,0-50voltand0-100volt.Thelowestmeasurablesignalvariesform1uvoltto50uvolt.Ahigherdegreeofrecordingaccuracycanbeachievedbyusingmoduleswhichacceptdatainsmall,selectablerages.Analternativeistheautorangingfacilityavailableonsomedataloggers.Theaccuracywithwhichthedataareacquiredandloggedontheappropriatestoragedeviceisextremelyimportant.Itisthereforenecessarythatthedataacquisitionmoduleshouldbeabletorejectcommonmodenoiseandcommonmodevoltage.Typicalcommonmodenoiserejectioncapabilitieslieintherange110dBto150dB.Adecibel(dB)isatermwhichdefinestheratioofthepowerlevelsoftwosignals.ThusifthereferenceandactualsignalshavepowerlevelsofNrandNarespectively,theywillhavearatioofndecibels,where

n=10Log10(Na/Nr)Protectionagainstmaximumcommonmodevoltagesof200to500voltisavailableontypicalmicrocomputerbaseddataloggers.Thevoltageinputtoanindividualdataloggerchannelismeasured,scaledandlinearisedbeforeanyfurtherdatamanipulationsorcomparisonsarecarriedout.Inmanysituations,itbecomesnecessarytoalterthefrequencyatwhichparticularchannelsaresampleddependinguponthevaluesofdatasignalsreceivedfromaparticularinputsensor.Thusachannelmightnormalbesampledonceevery10minutes.If,however,thesensorsignalsapproachthealarmlimit,thenitisobviouslydesirabletosamplethatchannelonceeveryminuteorevenfastersothattheoperatorscanbeinformed,therebyavoidinganycatastrophes.Microcomputercontrolledintelligentdataloggersmaybeprogrammedtoalterthesamplingfrequenciesdependinguponthevaluesofprocesssignals.Otherdataloggersincludeself-scanningmoduleswhichcaninitiatesampling.Theconventionalhardwireddataloggers,withoutanyprogrammingfacilities,simplyrecordtheinstantaneousvaluesoftransduceroutputsataregularsamplinginterval.Thisrawdataoftenmeansverylittletothetypicaluser.Tobemeaningful,thisdatamustbelinearisedandscaled,usingacalibrationcurve,inordertodeterminetherealvalueofthevariableinappropriateengineeringunits.Priortotheavailabilityofprogrammabledataloggers,thisfunctionwasusuallycarriedoutintheoff-linemodeonamini-ormainframecomputer.Therawdatavalueshadtobepunchedoutonpapertape,inbinaryoroctalcode,tobeinputsubsequentlytothecomputerusedforanalysispurposesandconvertedtotheengineeringunits.Papertapepunchesareslowspeedmechanicaldeviceswhichreducethespeedatwhichchannelscanbescanned.Analternativewastoprintouttherawdatavalueswhichfurtherreducedthedatascanningrate.Itwasnotpossibletocarryoutanylimitcomparisonsorprovideanyalarminformation.Everysinglevalueacquiredbythedataloggerhadtoberecordedeventhoughitmightnitserveanyusefulpurposeduringsubsequentanalysis;manydatavaluesonlyneedrecordingwhentheylieoutsidethepre-setlowandhighlimits.1.ABSTRACTThefeaturesofthedataacquisitionandcontrolsystemsoftheNASALangleyResearchCentersJetNoiseLaboratoryarepresented.TheJetNoiseLaboratoryisafacilitythatsimulatesrealisticmixedowturbofanjetenginenozzleexhaustsystemsinsimulatedight.Thesystemscapableofacquiringdataforacompletetake-o_assessmentofnoiseandnozzleperformance.Thispaperdescribesthedevelopmentofanintegratedsystemtocontrolandmeasurethebehaviorofmodeljetnozzlesfeaturingdualindependenthighpressurecombustingairstreamswithwindtunnelow.Theacquisitionandcontrolsystemiscapableofsimultaneousmeasurementofforces,moments,staticanddynamicmodelpressuresandtemperatures,andjetnoise.Thedesignconceptsforthecoordinationofthecontrolcomputersandmultipledataacquisitioncomputersandinstrumentsarediscussed.Thecontrolsystemdesignandimplementationareexplained,describingthefeatures,equipment,andtheexperiencesofusingaprimarilyPersonalComputerbasedsystem.Areasforfuturedevelopmentareexamined.2.INTRODUCTIONTheproblemofjetnoisehasbeenstudiedformanyyears.Sincesoundfromjetsisgeneratedbyavarietyofuidmechanicalmechanismsincludingturbulence,reducingjetnoiseischallenging.TheparticularpartofjetnoisestudiedintheJetNoiseLaboratory(JNL)oftheNASALangleyResearchCenter(LaRC)isthenoisegeneratedbythejetexhaust,orplume.Fluidmechanicphenomenonthatgenerateplumenoiseareturbulentmixing,supersoniceddyMachwaveradiation,noisegeneratedbyturbulenteddiespassingthroughshocksdenotedasbroadbandshocknoise,andresonantshockoscillationknownasscreech.Inordertomakeprogressinthe_eldofjetnoisereduction,scienti_cresearchhasbeenrequiredtotrytounderstandthephysicsbehindthedierentnoisegenerationmechanisms.Thesimulation3.DATAACQUISITIONSYSTEMSTheDynamicDataAcquisitionSystem(DDAS)isdesignedtorecordtimedatawithfrequenceupto100KHz.TheJNLDDASisbasedonaSUNSPARC10VMEbuscomputerwithrecordingcapacityof30dynamicchannels.AVMEarrayprocessingcardisincludedforperformingdataanalysis(primarilyfastFouriertransforms)inconjunctionwithdataacquisition.TheJNLhasa28microphonelineararrayforrecordingthefareldjetacoustics.Bruel&Kj_r(B&K)InstrumentsType41361/4"free_eldresponsemicrophonesandType2811MultiplexerPowerSuppliesareused.Themicrophonebandwidthextendstoabout100KHz.Dependingonthenozzlemodel,dynamicpressuresensorsmaybeushmountedtoaninternalpartofthenozzletomeasurethesurfacepressureuctuations.TheusualsensorisKuliteSemiconductorProductsModelXCE-093,witha3/32"diameterandacustomdesignedwatercoolingjacketisusedtoprotectthesensor.ThedirectoutputoftheB&K2811arebuered,ltered,andampliedbyPrecisionFilters,Inc.TheseGPIBprogrammablebandpassampliersprovidelowandhighpasscornerfrequencyselectionupto102.3KHz,pre-_ltergainofupto40dBin10dBsteps,andpost-_ltergainfrom-9.9to30.0dBbystepsof0.1dB.Eachmicrophonesignalisthensplitintothreepaths:twodirentanalogtodigital(A/D)convertertypesandacustom32channelvoltmeter.AfterdataisrecordedintotheTDRmemory,thehostcomputerdownloadstheinformationoveraGPIBIEEE-488businterfaceorovertheTDR16bitparallelbusthroughacustominterfacecircuitintothehostcomputer.Theparallelbustransferrateisabout170KB/secversusabout30KB/secfortheGPIBinterface.Anotherdatasetisacquiredatalowersamplerate,usually62.5KHzwitha16bitICS-110AVMEcardfromIntegratedCircuitsandSystemsLimited.ThemicrophonesignalsrecordedbytheICS-110Acardarelow-passedthrougha32channelVMEampli_ercardwith25KHz_xedcornerfrequencyfromFrequencyDevicesIncorporated.Figure3.1NoiseDynamicDataAcquisitionSystemcard)controlstheICSA/DcardovertheVSBbusthewritesthedatatotheSUNharddisks.Figure3Ashowsablockdiagramofthecompletedynamicdatasystem.AnotherimportantpartoftheDDASisacustom32channelRoot-Mean-Square(RMS)voltmeterwithaLiquidCrystalDisplay(LCD)display.TheRMSvoltmeterusesanembeddedZ80basedsingleboardcomputerbyZ-Worldthathasa12bitA/DconvertertomeasuretheoutputofthemultiplexedRMStoDCconvertercircuits.TheZ80computerdisplaystheoverallSoundPressureLevel(SPL)ofthemicrophonearrayona7"x4"LCDscreeninabargraphformat(Figure3B).TheDDASreadsthevoltagesontheRMSvoltmetertoselectampli_ergainsofthemicrophonesignalsbeforedigitizationbytheTDR.TheDDAScomputer,whilethecentralcontroller,isnottheonlycomputerinthesystem.TheStaticDataAcquisitionSystem(SDAS)isdesignedtorecordslowlyvaryingsignalsandcomputetheaveragevaluesofthesesignalsoversometimespan.TheJNLSDASisaModcompOpenArchitecturecomputer.TheModcompisa6-UVMEbussystemusingdualMotorola88KCPUsandtheREAL/IXreal-timeUNIXoperatingsystem.ThedataacquisitionsoftwareusedontheModcompwasdevelopedbyWyleLaboratoriesundercontracttoNASA.Itfeaturesagraphicaluserinterface(GUI),realtimegraphicsdisplays,userprogrammableequationsandcalibrationsforchannels,andadjustabledatapointdurationandsamplingrate.Bothindividualsamplesandtheaveragevaluesoverthepointdurationcanbesavedtodisk.TheanaloginputsystemisaNe_InstrumentCorporationSystem620Series600whichhasa100KHzsamplerate16bitA/Dconverterandcanscanupto512channelspersystem.TheJNLNe_has64channelsinone7"rackmountunit.TheNe_620alsosuppliesampli_cationandlowpass_lters.TheforcebalanceloadcellsarepoweredthroughaNe_System620Series300signalconditioner.Theloadcellsarefullbridgewithbuilt-intemperaturecompensation.ThermocouplesareconnectedtotheNe_Series600throughaKayeInstrumentsUniformTemperatureReferenceplate(UTR).Thisisothermalterminalstriphasa100Ohmplatinumresistancetemperaturedetector(RTD)tomeasurethecoldjunctiontemperatureoftheplatewherethespeci_cthermocouplewirechangestotwistedpaircopperwiring.TheModcompsoftwareisprogrammedtocorrectforthecoldjunctiontemperatureandperformsamulti-zonepolynomial_tofthethermocouplevoltagetoderivetemperature.AnothermajorpartoftheSDASisthemeasurementofstaticpressures.Criticaltosettingthejetoperatingconditionsarethetotalpressuresjustupstreamofthenozzleexit(termedthechargingstation)Thenozzlemodelsmightalsohavepressuretapsalongthewallsothatinternalvelocitycanbecalculatedforcomparisontocomputationaluidmechanicssolutions.Otherpressuresaremeasuredusingprobesremotelypositionedintheactualjetexhaustplume.TheJNLusestheElectronicallyScannedPressure(ESP)SystemfromPressureSystemsIncorporated(PSI).Thisproductconsistsofsensormodulesof16,32,48,or64individualstraingaugepressuresensors(overallsizeofamoduleisabout2.5"x1.5"x1.5").Thesensorsaremultiplexedineachmoduleandatotherexternaljunctionsbeforebeingmeasuredbya16bitA/Dconvertercapableofsamplingat50KHz.Eachmodulehasabuiltinvalvesothatcalibrationpressuresmaybeappliedtotheprocesssideofthesensors.Thesystemincludesworkingstandardpressuresources4.INTEGRATIONOFSYSTEMSTheentireJNLDDASiscomprisedofavarietyofdi_erentinstrumentsandcomputers.ThemaincomputeroriginallywasaDECMicro-VAXcomputerbuthasbeenchangedtoaSUNUNIXsystem.InstrumentationconnectstothishostthroughtheGeneralPurposeInterfaceBus(GPIB)orRS-232serialcommunications.MostoftheoriginaldataacquisitionsoftwarewascodedinFORTRAN.Themaine_ectofswitchingfromDECtoUNIXwasthatthesoftwareforaccessingRS-232serialportsandGPIBadapterwerenowthroughtheClanguage.MostoftheengineerssupportingtheJNLhadonlyFORTRANprogrammingexperience,soasetofCfunctionswerecreatedtosimplifyaccesstotheCserialandGPIBfeaturesfromtheFORTRANlanguage.AlmosteveryprogramfortheJNLusesacombinationofCandFORTRANroutines.ThenewestinstrumentadditionstothesystemareVMEbuscardswhichareaccessedthroughClanguagebasedoperatingsystemfunctionsanddrivers.Anoperatingsystemfeaturethatimprovesthedataacquisitionprogramsissharedmemory.Sharedmemoryallowsmultipleindependentprogramstocommunicatewitheachotherveryrapidly.OnUNIXcomputers,thesharedmemoryregioniscreatedbyCfunctions.TheaddressoftheregionispassedasanargumenttoaFORTRANsubroutineandtheFORTRANcodeusesastructurede_nitiontode_nevariablesrelativetomemorylocations.ThissharingfeaturewasalsoavailableundertheDECVMSoperatingsystem.AnotherimportantmechanismforconnectingcomputersisbyusingtheEthernetnetwork.TheSDASdevelopedbyWyleLabsincludedaserverprogramthatwasbasedonBerkeleyStandardDistribution(BSD)Sockets.Theservercansendoutrealtimeoraverageddata,betriggeredtotakeadatapoint,acceptvaluesintothesysteminrealtime,andprovideSDASstatusinformation.TwoprogramsdevelopedfortheDDAScombineallofthesefeaturesandserveasthefoundationfortestingwiththeDSPM.ArealtimeprogramcalledBackgroundisdesignedtoprovideinformationformonitoringtheconditionsofthefacilityandmodel.Backgroundestablishesthesharedmemoryregion,initializescommunicationwithvariousinstruments,connectstotheSDASbysocketsandthecontrolsystembyRS-232.Itthenentersanendlessloopinwhichitreadstheinstruments,SDAS,andcontrolsystemvalues,calculatesderivedvaluessuchasaveragepressureandtemperatureatthechargingstation,thensendsvaluestotheSDASandthecontrolsystem.TheothermainprogramoftheDDASthatacquiresthemicrophonesignalsisnamedlsawtafterthefacility.ThisistheprogramthatcoordinatesthedataacquisitionprocessesoftheSDAS(forperformanceandmodelaerodynamicdata),thecontrolsystem,andtheDDAS(dynamicmicrophoneandpressuredata).Aseriesofmenusprovidetheusertheopportunitytochangedefaultsettingsforsuchthingsasnumberofsensorstorecord,samplerate,sizeofthedataset,and_ltercuto_frequencies.OncetheoperatorshaveadjustedtheDSPMtotherequiredtestconditions,thedataacquisitionoperatorproceedstothesectionoftheprogramthatcommunicateswiththeRMS-DCmeterandadjuststhePrecisionFiltergainstoreachthetargetRMSvalue.Whenthedataacquisitionoperatorissatis_edthattheDSPMisatthecorrectconditionsandthatthegainsareacceptable,thelsawtprogramtriggerstheSDAS(whichissettoaveragefrom10to30seconds)theICS-110Acardwhichsamplesat62.5KHzfor8seconds,andthePaci_cTDRswhichsampleat250KHzfor2seconds.Thecurrentvaluesinthebackgroundprogramarewrittentoalog_leatboththestartandtheendoftheaveragingperiod.5.FUTUREIMPROVEMENTSAsresearchrequirementschange,sodothetoolsnecessarytomeetthoserequirements.EveryaspectoftheJNLdataacquisitionandcontrolsystemshavebeenmodi_edinsomewayafterenteringservice.Thecontrolsystemiscurrentlyinadequateforclosedloopcontrolofbothburnerssimultaneously.ReplacingsomeoftheOptomuxI/Owithahigherspeedtypeisbeingexaminedasawayofimprovingthesystemforclosedloopcontrol.InstallingPCI/OcardsthatwouldstillbecontrolledbytheParagonTNTsoftwareisoneoption.AddingaProgrammableLogicController(PLC)orotherbrandofcontrolsystem/softwarepackagethatcanbeinterfacedtoParagonTNTisbeingconsideredaswell.TheOptomuxanaloginputisa12bitA/Dconverterandforcertainparametersmoreresolutionisdesired.TheDDASislimitedcurrentlybythe12bitresolutionandthedatadownloadspeedofthePaci_cInstrumentsTDRs.Becauseofthe12bitresolutionthegainsmustbesetcarefullytopreventclippingbutachievethehighestsignaltonoiseratio(SNR)anddynamicrange.Futureplansincludethepurchaseof16bitA/Dconverters,providinga_nerresolutionwhichinturngivesagreaterdynamicrangeforagivengainsetting.Thegainsmustbesetjusthighenoughtogetabovethe_lternoiseoorforgoodrecording.meterforallchannels,computingthegainrequiredtogetabout1voltRMS,settingthosegains,thenrecheckingtheRMSvaluesbeforetakingdata.Jetnoisetendstohavecrestfactorsnear3(non-sinusoidal)andthereforeusingRMSisnotareliablewaytopreventclipping.Thegainsettingprocesscantakefrom2to5minutes.TheotherlimitationoftheTDRsystemistheslowdownloadspeed.Ittakesapproximately4.5minutestoreadoutthedataandwriteittodiskontheDDAScomputer.ThegoalforsettingthegainsandhavingthedatawrittenouttotheDDASdisksisatotalof2minutes.OnetypeofproductthatisbeingexaminedtomeetthisrequirementisaVMEbusbasedA/Dcardwith16bitA/Dconvertersthatcansampleat250KHz,withahighspeeddataportconnectedtoanauxiliaryprocessor(AP)liketheSKYBoltcurrentlyused.For32channels,theaggregatedataratewouldbe8millionsamples/secondorabout15.26MB/second.6.ACKNOWLEDGMENTSTheauthorwouldliketothanktheJetNoiseGroupoftheAeroacousticBranchfortheirsupportandcommentsduringthedevelopmentofthesystemsdescribedinthispaper.Aswithanyprojectofthisscope,manypeoplewereinvolvedinbuildingthisentiresystem.Inparticular,IwouldliketorecognizeNASAengineersJackSeiner,MichaelPonton,MarthaBrown,HenryHaskin,andRobertGrandle,NASAoperationssupportpersonnelCli_ordWilliford,GregoryHogg,BeverlyJonesAnderson,RichardWhite,JohnSwartzbaugh,andFernandusRattli_,andsupportcontractorsJerryLyle,CharlesSmith,andCarlDavis.数据采集数据采集​​系统，用于采集运行中的数据，并存储在协助存储器上，以供日后分析。很多数据采集系统以很高的速度获得这些数据，并且留给电脑很少的时间进行任何必要的或可取的数据操作或削减。全部数据都存储在协助存储设备上，随后获得感爱好的变量。设计专用的数据采集系统和接口来获得高速过程数据是特别必要的。这种特殊目的的设计可能是个昂贵的主见。强大的迷你和主机计算机被用来将数据采集与其他功能,如比较实际输出和期望的输出值,然后确定限制行为,在预先设定的限制内实行措施保证产出变量。其计算实力须要将取决于类型的过程限制系统的实现。针对执行比例、比率或过程变量三项限制的软件需求相对琐碎,但微型计算机可用于实现这样的过程限制系统。它将不行能运用很多现有的微机的实施高速自适应限制系统必需运用合适的过程模型和可观的在线操作数据。微机数据采集器是用来进行中间数据采集等功能于一体,在相对较低的速度,简洁的数学操作的原始数据和一些形式的数据归算的。第一代数据采集器没有任何可编程计算机设备,采纳慢速从一百个频道采集了数据。全部获得的数据可以在纸带上穿孔或打印之后的分析。这种硬件连线数据采集器被与微机结合、并可由用户编程的新一代数据采集器所取代。他们供应了一个极好的过程数据收集方法,采纳标准化的接口,随后执行必要的操纵向过程操作员供应这有用的信息。获得的数据可用于分析在过程变量与开发自适应和优化过程限制必需的数学模型之间是否具有差异性。数据采集器执行的数据采集功能在不同系统之间变更。简洁的数据日志系统获得数据从几个通道而困难系统接收数据从数百,甚至数千输入通道的分布在一个或多个过程。初步的数据采集器用扫描数来选择,用一个依次的方式连接到传感器或转换器,数据记录用数字格式。一个数据监测器在某个意义上说,它只能收集数据从特定类型的传感器及转换器。最好是运用非专用数据采集器因为任何传感器或转换器能被连接到运用适当的信号处理模块。微型计算机限制的数据采集便于大量的传感器扫描。扫描速率取决于信号动态，这意味着为了避开错误一些通道必需在特别高速扫描,而在较慢的速度扫描其他通道信息会有特别小的损失。在一些数据采集应用中，快速通道须要可达每秒100次的采样速度，而慢速通道可以每隔五分钟采样一次。传统的硬件接线、不行编程的数据采集器以一种连续的方式采样全部的通道，并且全部通道的采样频率都必需是相同。本程序的结果在积累了大量的数据,其中一些是不必要的,也减缓了全面有效的采样频率。和其它慢速通道相比，基于微机的数据采集器可用在较高频率下扫描快速通道。绝大多数的用户可编程的数据采集器可以用来扫描1000个模拟和1000个数字输入通道。少量的数据采集器,具有较高的先进性,适合从15000模拟和数字通道获得数据。数字通道的数据可以有以下几种形式:晶体管-晶体管逻辑或节点闭合信号。模拟数据必需被转换成数字形式记录并且必需运用合适的模拟/数字转换器(ADC)。ADC的特性能定义可实现的辨别率，以及不同通道都可以采样分析的速率。越来越多的用于提高位辨别率的A/D转换器。逐次靠近型ADC的辨别率比积分型ADC快。很多微型计算机限制的数据采集器一起运用包括设施规划通道扫描率。典型的扫描速率变更从每秒2频道到每秒10000个通道。大多数数据采集器具有±0.01%或更好的辨别实力。也有可能达到1微伏的辨别率。从肯定意义上来说，辨别实力也取决于输入信号的范围,标准输入信号范围为0-10伏特、0-50伏特和0-100伏特。最低的可测量从1到50伏特的信号变更，运用在较小、可选范围内接收数据的模块可获得较高的采集精度。另一种是从数据采集器里得到的自动测距装置。精确的数据获得、登陆合适的存储设备是特别重要的，因此对数据采集模块来说抑制共模噪声和共模电压是必要的。典型的共模噪声抑制实力在110dB-150dB范围之间，分贝(dB)即为定义为两种信号功率电平比值，因此,假如参考信号和实际信号的功率电平分别为Nr、Na,它们的比值为n分贝，其中n=10Log10（Na/Nr)防止最大一般模式电压200至500伏特的典型可在微机数据采集器一起运用。电压输入到一个单独的数据樵夫通道量测、规模化和线性化任何进一步的数据操作前或比较执行。在很多状况下,有必要变更从某一特定输入传感器收到的数据信号所确定的特定通道的采样频率，因此，某种通道可能每隔10分钟采样一次，但是假如传感器信号靠近报警门限，很明显就须要每分钟、甚至更快的采样，这样就能使操作员能够刚好获知信息,避开任何灾难的来临。微型计算机限制的智能数据采集器可编程用于变更基于过程信号值的采样频率，包含自扫描模块的其他数据采集器可以主动采样。没有任何编程设施的传统硬件接线数据采集器,能简洁地在固定采样间隔内记录传感元件输出的瞬时值，这个原始数据通常很少与典型用户相关。为了使其有意义,该数据必需运用校准曲线进行线化和调整,这样就能以适当的工程单位确定变量的真实值。在可编程数据采集器可用之前,该函数通常是在微型或大型计算机的离线模式上执行。原始数据值必需以二进制或八进制代码在纸带上打孔,用于输入计算机进行随后的分析目的,并转换为工程单位，纸带打孔是能降低通道扫描速度的低速机械装置，另一种是打印出原始数据值,并进一步降低数据扫描速率的装置，它不行能进行任何限制比较或供应任何报警信息。由数据采集器获得的每一个单值都必需进行记录,即使它可能在以后的分析中不起到任何有用的目的；另外很多数据值只需当他们处在预设低限和高限之外时进行记录。1.摘要美国国家航空和宇宙航行局兰利探讨中心喷气机噪音试验室介绍了数据采集和限制系统的特点。喷气机噪声试验室模拟现实的混合设备,建立拥有喷嘴喷气发动机排气系统。该系统能够获得一个完整的噪声和喷嘴性能评估数据。本文阐述了开发于一体的限制和测量喷气机喷嘴具有双重独立模型高压燃烧空气流与风隧道的综合性系统。数据采集、限制系统能够同时测量力气、时刻、静态和动态限制模型的压力和温度,和喷气机的噪声。为协调限制计算机和多种数据采集计算机和仪器的设计概念进行了探讨。对限制系统的设计与实现进行说明,指出描述的特点,设备和阅历的个人电脑运用主要基于系统。检查将来的发展领域。2.引言喷气机噪声的问题已经被探讨了很多年。自从喷气机噪声产生于多种机械机制包括湍流,削减喷气机噪声是有挑战性的。美国国家航空和宇宙航行局兰利探讨中心(LaRC)喷气机噪声试验室(JNL)探讨喷气机噪声是由喷射排气噪声,或羽毛产生。流体力学现象产生的羽流噪声是紊流混合、超音速艾迪马赫波辐射、噪声产生的旋涡通过湍流冲击噪声宽带冲击作为属性,共振冲击振动称为尖叫。为了取得新进展的喷气机降噪，探讨须要试着去了解背后的物理噪声产生的机理。仿真模型在射流规模上取得了巨大的成果。真正喷气机的一个重要特征是高温尾气燃烧过程和行为温度对噪声产生的机理。在一个不能供热的环境下导致喷气机的噪音削减,并不总是喷气机降噪热的解决方案。喷气机噪音大大降低,须要从一个探讨机构,可以制作出逼真的温度、压力。一个正常的涡扇发动机，一般用于亚音速运输喷气机，有一个热燃烧机制（核心流）包围一个冷却的压缩机制（旁路或风扇流）。3.数字采集系统动态数据采集系统(DDAS)是用来记录时间数据,高达100千赫兹的频率。JNLDDAS是基于SUNSPARC10VME计算记录实力为30个动态通道。一个VME阵列处理卡是包括了执行数据分析(主要是快速傅里叶变换)和结合数据采集。JNL拥有28个传音器线性数组记录喷气机噪音的状况。Br_uel和Kj_r(B&K)仪器41361/4型自由响应传音器和2811型多路复用器电源运用。传音器带宽延长到大约100千赫兹。依据喷嘴模型、动态压力传感器安装可以推一个内部的部分测量表面压力喷嘴。通常的传感器产品模型XCE-093,直径3/32英寸，常规设计水冷夹是用来爱护传感器。精密过滤器B&K2811的干脆输出是变更的。通过这些GPIB可编程的器件供应低通和高通过拐角频率选择102.3KHz,压力以10分贝为阶梯增加到40分贝为止,以0.1分贝为阶梯从-9.9分贝增加到30.0分贝。每一个话筒信号分成了三个部分:两个模拟到数字(A/D)类型转换器和一个定制的32路的电压表。数据记录到TDR存储器,主机通过一个定制的主计算机在GPIBIEEE-488总线接口或者在TDR16位并行总线接口电路中下载信息。并行总线传输速率约为170KB/秒GPIB接口速率约30KB/秒。从集成电路与系统有限公司的16位62.5千赫兹ICS-110AVME卡上，以低采样率获得另一个数据集。从频率设备股份有限公司通过32路拐角频率25K