数据采集系统文献翻译

SelectingtheRightDataAcquisitionSystemEngineersoftenmustmonitorahandfulofsignalsoverextendedperiodsoftime,andthengraphandanalyzetheresultingdata.Theneedtomonitor,recordandanalyzedataarisesinawiderangeofapplications,includingthedesign-verificationstageofproductdevelopment,environmentalchambermonitoring,componentinspection,benchtoptestingandprocesstrouble-shooting.Thisapplicationnotedescribesthevariousmethodsanddevicesyoucanusetoacquire,recordandanalyzedata,fromthesimplepen-and-papermethodtousingtoday'ssophisticateddataacquisitionsystems.Itdiscussestheadvantagesanddisadvantagesofeachmethodandprovidesalistofquestionsthatwillguideyouinselectingtheapproachthatbestsuitsyourneeds.IntroductionIngeotechnicalengineering,wesometimeencountersomedifficultiessuchasmonitoringinstrumentsdistributedinalargearea,dangerousenvironmentofworkingsitethatcausesomedifficultyforeasyaccess.Inthiscase,operatorsmayadoptremotecontrol,bywhichalargeamountofmeasureddatawillbetransmittedtoaobservationroomwherethedataaretobecollected,storedandprocessed.Theautomaticdataacquisitioncontrolsystemisabletocompletethetasksasregularautomaticdatamonitoring,acquisitionandstore,featuringhighautomation,largedatastorecapacityandreliableperformance.Thesystemiscomposedofacquisitioncontrolsystemanddisplaysystem,withthefollowingfeatures:1.No.ofChannels:32(canbeincreasedordecreasedaccordingtouser'srealneeds.)2.Scanningduration:decidedbyuser,fastest32points/second3.Storecapacity:20G(maybeincreasedordecreased)4.Display:(a)Tableofparameter(b)Historytendency(c)Columngraphics.5.Function:realtimemonitoringcontrol,warning6.Overalldimension:50cm×50cm×72cmDataacquisitionsystems,asthenameimplies,areproductsand/orprocessesusedtocollectinformationtodocumentoranalyzesomephenomenon.Inthesimplestform,atechnicianloggingthetemperatureofanovenonapieceofpaperisperformingdataacquisition.Astechnologyhasprogressed,thistypeofprocesshasbeensimplifiedandmademoreaccurate,versatile,andreliablethroughelectronicequipment.Equipmentrangesfromsimplerecorderstosophisticatedcomputersystems.Dataacquisitionproductsserveasafocalpointinasystem,tyingtogetherawidevarietyofproducts,suchassensorsthatindicatetemperature,flow,level,orpressure.Somecommondataacquistiontermsareshownbelow:Dataacquisitiontechnologyhastakengiantleapsforwardoverthelast30to40years.Forexample,40yearsago,inatypicalcollegelab,apparatusfortrackingthetemperatureriseinacrucibleofsodiumtungsten-bronzeconsistedofathermocouple,abridge,alookuptable,apadofpaperandapencil.Today'scollegestudentsaremuchmorelikelytouseanautomatedprocessandanalyzethedataonaPCToday,numerousoptionsareavailableforgatheringdata.Theoptimalchoicedependsonseveralfactors,includingthecomplexityofthetask,thespeedandaccuracyyourequire,andthedocumentationyouwant.Dataacquisitionsystemsrangefromthesimpletothecomplex,witharangeofperformanceandfunctionality.PencilandpaperTheoldpencilandpaperapproachisstillviableforsomesituations,anditisinexpensive,readilyavailable,quickandeasytogetstarted.Allyouneedtodoishookupadigitalmultimeter(DMM)andbeginrecordingdatabyhand.Unfortunately,thismethodiserror-prone,tendstobeslowandrequiresextensivemanualanalysis.Inaddition,itworksonlyforasinglechannelofdata;whileyoucanusemultipleDMMs,thesystemwillquicklybecomesbulkyandawkward.Accuracyisdependentonthetranscriber'sleveloffastidiousnessandyoumayneedtoscaleinputmanually.Forexample,iftheDMMisnotsetuptohandletemperaturesensors,manualscalingwillberequired.Takingtheselimitationsintoaccount,thisisoftenanacceptablemethodwhenyouneedtoperformaquickexperiment.StripchartrecorderModernversionsofthevenerablestripchartrecorderallowyoutocapturedatafromseveralinputs.Theyprovideapermanentpaperrecordofthedata,andbecausethisdataisingraphicalformat,theyallowyoutoeasilyspottrends.Oncesetup,mostrecordershavesufficientinternalintelligencetorununattended—withouttheaidofeitheranoperatororacomputer.Drawbacksincludealackofflexibilityandrelativelylowaccuracy,whichisoftenconstrainedtoafewpercentagepoints.Youcantypicallyperceiveonlysmallchangesinthepenplots.Whilerecordersperformwellwhenmonitoringafewchannelsoveralongperiodoftime,theirvaluecanbelimited.Forexample,theyareunabletoturnanotherdeviceonoroff.Otherconcernsincludepenandpapermaintenance,papersupplyanddatastorage,allofwhichtranslateintopaperoveruseandwaste.Still,recordersarefairlyeasytosetupandoperate,andofferapermanentrecordofthedataforquickandsimpleanalysis.ScanningdigitalmultimeterSomebenchtopDMMsofferanoptionalscanningcapability.Aslotintherearoftheinstrumentacceptsascannercardthatcanmultiplexbetweenmultipleinputs,with8to10channelsofmuxbeingfairlycommon.DMMaccuracyandthefunctionalityinherentintheinstrument'sfrontpanelareretained.Flexibilityislimitedinthatitisnotpossibletoexpandbeyondthenumberofchannelsavailableintheexpansionslot.AnexternalPCusuallyhandlesdataacquisitionandanalysis.PCplug-incardsPCplug-incardsaresingle-boardmeasurementsystemsthattakeadvantageoftheISAorPCI-busexpansionslotsinaPC.Theyoftenhavereadingratesashighas100,000readingspersecond.Countsof8to16ch