DAQAssistantHelpJanuary2008,370467L-01ThishelpfiledescribeshowtousetheDAQAssistanttointeractivelyconfigurecommonmeasurementtasks,globalvirtualchannels,orscales.InNILabVIEW7.xandlater,NILabWindows™/CVI™7.xandlater,orNIMeasurementStudio7.xandlater,youalsocanusetheDAQAssistanttogenerateNI-DAQmxcodefromyourtasksandglobalvirtualchannels.YoucanalsousetheDAQAssistantwithNILabVIEWSignalExpress2.xandlater.Tonavigatethishelpfile,usetheContents,Index,andSearchtabstotheleftofthiswindow.Formoreinformationaboutthishelpfile,refertothefollowingtopics:Conventions—formattingandtypographicalconventionsusedinthishelpfileRelatedDocumentationGlossaryImportantInformationTechnicalSupportandProfessionalServicesTocommentonNationalInstrumentsdocumentation,refertotheNationalInstrumentsWebsite.©Copyright2003–2008NationalInstrumentsCorporation.Allrightsreserved.
RelatedDocumentationThefollowingdocumentscontaininformationthatyoumightfindhelpfulasyouusethishelpfile:
DAQGettingStartedGuide—ThisguidedescribeshowtoinstalltheNI-DAQmxdriversoftware,yourdataacquisition(DAQ)device,andhowtoconfirmthatyourdeviceisoperatingproperly.LabVIEWHelp—ThishelpfilecontainsinformationaboutLabVIEWpalettes,menus,tools,VIs,andfunctions.Thishelpfilealsoincludesstep-by-stepinstructionsforusingLabVIEWfeatures.InLabVIEW,selectHelp.LabWindows/CVIHelp—TheLabWindows/CVIHelpincludesthefollowingsections:
UsingLabWindows/CVI—Informationaboutwindows,menus,commands,dialogboxes,andoptionsforcustomizingconfigurationdefaults.LibraryReference—ReferenceinformationforallLabWindows/CVIlibraryfunctions.ProgrammerReference—InformationaboutdevelopingprogramsinLabWindows/CVI.ExamplePrograms—DescriptionsofeachoftheexampleprogramsincludedwithLabWindows/CVI.ToolsLibrary—DescriptionsoftheadditionalinstrumentdriversincludedwithLabWindows/CVI.
InLabWindows/CVI,selectHelp»Contents.Measurement&AutomationExplorerHelpforNI-DAQmx—ThishelpfilecontainsinformationonconfiguringandtestingDAQdevices,SCXIdevices,PXIsystems,SCCdevices,serialandparallelports,andRTSIcablesusingMeasurement&AutomationExplorer(MAX)forNI-DAQmx,andinformationonspecialconsiderationsforoperatingsystems.InMAX,selectHelp»HelpTopics»NI-DAQmx.NIMeasurementStudioHelp—ThishelpfilecontainsinformationaboutusingMeasurementStudioforMicrosoftVisualC++,Visual
Basic,andthe.NETplatform.InVisualStudio.NET,selectHelp»Contents.NI-DAQmxHelp—ThishelpfiledescribeshowtouseNI-DAQmxtoprogramyourNationalInstrumentsdevice.NI-DAQmxisthesoftwareyouusetocommunicatewithandcontrolyourNIdevice.SelectStart»AllPrograms»NationalInstruments»NI-DAQ.TakinganNI-DAQmxMeasurementinLabVIEW—ThistutorialteachesyouhowtotakeanNI-DAQmxmeasurementinLabVIEW7.xorlaterusingtheDAQAssistant.TheDAQAssistantisagraphicalinterfaceforconfiguringmeasurementtasks,globalvirtualchannels,andscales.YoualsocanusetheDAQAssistanttogenerateNI-DAQmxcodefromthetask.RefertoTakinganNI-DAQmxMeasurementinLabVIEWintheLabVIEWHelp.
UsingHelpConventionsNavigatingHelpSearchingHelpPrintingThisHelpFile
ConventionsThishelpfileusesthefollowingconventions:<> Anglebracketsthatcontainnumbersseparatedbyanellipsisrepresentarangeofvalues
associatedwithabitorsignalname—forexample,DIO<3..0>.
» The»symbolleadsyouthroughnestedmenuitemsanddialogboxoptionstoafinalaction.ThesequenceFile»PageSetup»OptionsdirectsyoutopulldowntheFilemenu,selectthePageSetupitem,andselectOptionsfromthelastdialogbox.Thisicondenotesanote,whichalertsyoutoimportantinformation.
Thisicondenotesacaution,whichadvisesyouofprecautionstotaketoavoidinjury,dataloss,orasystemcrash.
bold Boldtextdenotesitemsthatyoumustselectorclickoninthesoftware,suchasmenuitemsanddialogboxoptions.Boldtextalsodenotesparameternames,emphasis,oranintroductiontoakeyconcept.
darkred Textinthiscolordenotesacaution.
green Underlinedtextinthiscolordenotesalinktoahelptopic,helpfile,orWebaddress.
italic Italictextdenotesvariables,emphasis,crossreferences,oranintroductiontoakeyconcept.Italictextalsodenotestextthatisaplaceholderforawordorvaluethatyoumustsupply.
monospace Textinthisfontdenotestextorcharactersthatyoushouldenterfromthekeyboard,sectionsofcode,programmingexamples,andsyntaxexamples.Thisfontisalsousedforthepropernamesofdiskdrives,paths,directories,programs,subprograms,subroutines,devicenames,functions,operations,variables,filenames,andextensions.
NavigatingHelp(WindowsOnly)Tonavigatethishelpfile,usetheContents,Index,andSearchtabstotheleftofthiswindoworusethefollowingtoolbarbuttonslocatedabovethetabs:
Hide—Hidesthenavigationpanefromview.Locate—LocatesthecurrentlydisplayedtopicintheContentstab,allowingyoutoviewrelatedtopics.Back—Displaysthepreviouslyviewedtopic.Forward—DisplaysthetopicyouviewedbeforeclickingtheBackbutton.Options—Displaysalistofcommandsandviewingoptionsforthehelpfile.
SearchingHelp(WindowsOnly)UsetheSearchtabtotheleftofthiswindowtolocatecontentinthishelpfile.Ifyouwanttosearchforwordsinacertainorder,suchas"relateddocumentation,"addquotationmarksaroundthesearchwordsasshownintheexample.SearchingfortermsontheSearchtaballowsyoutoquicklylocatespecificinformationandinformationintopicsthatarenotincludedontheContentstab.
WildcardsYoualsocansearchusingasterisk(*)orquestionmark(?)wildcards.Usetheasteriskwildcardtoreturntopicsthatcontainacertainstring.Forexample,asearchfor"prog*"liststopicsthatcontainthewords"program,""programmatically,""progress,"andsoon.Usethequestionmarkwildcardasasubstituteforasinglecharacterinasearchterm.Forexample,"?ext"liststopicsthatcontainthewords"next,""text,"andsoon.
NestedExpressionsUsenestedexpressionstocombinesearchestofurtherrefineasearch.YoucanuseBooleanexpressionsandwildcardsinanestedexpression.Forexample,"exampleAND(programORVI)"liststopicsthatcontain"exampleprogram"or"exampleVI."Youcannotnestexpressionsmorethanfivelevels.
BooleanExpressionsClickthe buttontoaddBooleanexpressionstoasearch.ThefollowingBooleanoperatorsareavailable:
AND(default)—Returnstopicsthatcontainbothsearchterms.Youdonotneedtospecifythisoperatorunlessyouareusingnestedexpressions.OR—Returnstopicsthatcontaineitherthefirstorsecondterm.NOT—Returnstopicsthatcontainthefirsttermwithoutthesecondterm.NEAR—Returnstopicsthatcontainbothtermswithineightwordsofeachother.
SearchOptionsUsethefollowingcheckboxesontheSearchtabtocustomizeasearch:
Searchpreviousresults—Narrowstheresultsfromasearchthatreturnedtoomanytopics.Youmustremovethecheckmarkfromthischeckboxtosearchalltopics.Matchsimilarwords—Broadensasearchtoreturntopicsthatcontainwordssimilartothesearchterms.Forexample,asearchfor"program"liststopicsthatincludethewords"programs,""programming,"andsoon.Searchtitlesonly—Searchesonlyinthetitlesoftopics.
PrintingHelpFileTopics(WindowsOnly)CompletethefollowingstepstoprintanentirebookfromtheContentstab:
1. Right-clickthebook.2. SelectPrintfromtheshortcutmenutodisplaythePrintTopics
dialogbox.3. SelectthePrinttheselectedheadingandallsubtopicsoption.
NoteSelectPrinttheselectedtopicifyouwanttoprintthesingletopicyouhaveselectedintheContentstab.
4. ClicktheOKbutton.
PrintingPDFDocumentsThishelpfilemaycontainlinkstoPDFdocuments.ToprintPDFdocuments,clicktheprintbuttonlocatedontheAdobeAcrobatViewertoolbar.
GettingStartedTheDAQAssistanthelpsyouconfiguretasks,virtualchannels,andscalesusingagraphicalinterface.YoucanlaunchtheDAQAssistantfromyourNationalInstrumentsapplicationsoftwaresuchasLabVIEW,LabVIEWSignalExpress,LabWindows/CVI,orMeasurementStudio.YoualsocanlaunchtheDAQAssistantfromMAX.UsingtheDAQAssistant,youcandothefollowingthings:
CreateandedittasksandvirtualchannelsAddvirtualchannelstotasksCreateandeditscalesTestyourconfigurationSaveyourconfigurationGeneratecodeinyourNIapplicationsoftwareforuseinyourapplicationViewconnectiondiagramsforyoursensors
NoteYoumustuseversion7.xorlaterofLabVIEW,LabWindows/CVI,orMeasurementStudioorversion2.xorlaterofLabVIEWSignalExpresstousetheDAQAssistant.
ChannelsandTasksPhysicalChannelsandVirtualChannelsAphysicalchannelisaterminalorpinatwhichyoucanmeasureorgenerateananalogordigitalsignal.Avirtualchannelisacollectionofsettingssuchasaname,aphysicalchannel,inputterminalconnections,thetypeofmeasurementorgeneration,andcanincludescalinginformation.InNI-DAQmx,virtualchannelsareintegraltoeverymeasurement.InNI-DAQmx,usetheDAQAssistant,accessiblefromMAXorNIapplicationsoftwaretoconfigurechannelsandmeasurementtasks.RefertotheDAQAssistantHelpandMeasurement&AutomationExplorerHelpforNI-DAQmx.YoucanalsoconfigurevirtualchannelswiththeNI-DAQmxAPIinyourapplicationprogram.InTraditionalNI-DAQ(Legacy)andearlierversions,youcanuseMAXtoconfigurevirtualchannels,anoptionalwaytorecordwhichchannelsarebeingusedfordifferentmeasurements.
TasksAtask,animportantconceptforNI-DAQmx,isacollectionofoneormorevirtualchannelswithtiming,triggering,andotherproperties.Conceptually,ataskrepresentsameasurementorgenerationyouwanttoperform.Youcansetupandsavealloftheconfigurationinformationinataskandusethetaskinanapplication.
GlobalVirtualChannelsandLocalVirtualChannelsInNI-DAQmx,youcanconfigurevirtualchannelsaspartofataskorseparatefromatask.Virtualchannelscreatedinsideataskarelocalvirtualchannels.Virtualchannelsdefinedoutsideataskareglobalvirtualchannels.YoucancreateglobalvirtualchannelsinMAXorinyourapplicationsoftwareandsavetheminMAX.Youcanuseglobalvirtualchannelsinanyapplicationoraddthemtoanumberofdifferenttasks.Ifyoumodifyaglobalvirtualchannel,thechangeaffectsalltasksinwhichyoureferencethatglobalvirtualchannel.Inmostcases,itissimplertouselocalvirtualchannels.
NoteIfyouareusingLabVIEW8.0andlater,youcanalsocreatetasksandchannelslocaltoaLabVIEWProject.
UsingtheDAQAssistantinYourApplicationUsingtheDAQAssistant,youcancreate,configure,andsavevirtualchannelsortasksforuseinyourapplications.IfyouareusingNIapplicationsoftware,youalsocangeneratecodebasedonataskorvirtualchannel.RefertoLabVIEWHelp,LabWindows/CVIHelp,MeasurementStudioHelp,orNI-DAQmxKeyConceptsformoreinformationaboutprogrammingwithyourtaskorglobalchannel.
OpeningtheDAQAssistantYoucanopentheDAQAssistantfromyourNIapplicationsoftwareorfromMAX.WhenyouopentheDAQAssistant,awizardpromptsyoufortheinformationneededtocreateyournewtask.Whenthewizardisdone,theDAQAssistantopens,andyoucanconfiguretiming,triggering,measurement-specificsettings,andscaling.YoucanalsousetheDAQAssistanttocreateaglobalvirtualchannel.YoucanopentheDAQAssistanttocreateataskin:
LabVIEWLabWindows/CVIMeasurementStudioMAX
YoucanalsousetheDAQAssistantinLabVIEWSignalExpresstocreateDAQstepsortouseglobalvirtualchannelsinyourproject.
OpeningtheDAQAssistantinLabVIEWYoucanopentheDAQAssistanttocreateataskinoneofthefollowingways:
PlacetheDAQmxTaskNamecontrolonthefrontpanel.Right-clickthecontrol,andselectNewDAQmxTask.IfyouareusingLabVIEW8.0andlater,youcancreateatasklocaltotheProject,oryoucancreateataskinMAX.TocreateataskinaProject,right-clickMyComputerintheProjectExplorerwindow.Then,selectNew»Task.InLabVIEW7.x,clicktheConfigurepull-downmenuonthemainLabVIEWlaunchscreenandselectCreateNewTask(DAQAssistant).PlacetheDAQAssistantExpressVIontheblockdiagram.ThisVIcreatestasksthatarefullycontainedinasingleVI.
NoteIfyouconfigureataskusingtheDAQAssistantExpressVI,thetaskislocaltotheapplicationandcannotbesavedtoMAXforuseinotherapplications.YoumustconverttheDAQAssistantExpressVItoanNI-DAQmxTasktousethetaskinotherapplications.YoucanalsogeneratecodefromtheDAQAssistantExpressVI.Right-clicktheDAQAssistantExpressVIonthefrontpanelinLabVIEWandselectGenerateNI-DAQmxCode.
InLabVIEW7.xorlater,selectFile»NewandbrowsetheFromTemplatesfoldertoDataAcquisitionwithNI-DAQmx.
RefertoTakinganNI-DAQmxMeasurementinLabVIEWintheLabVIEWHelpforstep-by-stepinstructionsforcreatingataskinLabVIEWandgeneratingcodebasedonthetask.FormoreinformationaboutcreatingtasksandchannelswithProjectinLabVIEW,refertotheLabVIEWHelp.AfteropeningtheDAQAssistant,createthenewtask.
OpeningtheDAQAssistantinLabWindows/CVIToopentheDAQAssistant,selectTools»Create/EditDAQmxTasks.IntheCreate/EditDAQmxTasksdialogbox,youcanchoosetocreateataskinMAXorintheLabWindows/CVIproject.YoumustuseMAXtocreateglobalvirtualchannelsforuseinLabWindows/CVI.ForinformationaboutthedifferencesbetweencreatingataskintheprojectorinMAX,refertotheLabWindows/CVIHelp.YoualsocancreateaMAX-basedtaskinLabWindows/CVIwhenyouselectNewTaskfromtheTaskNamecontrolintheDAQmxLoadTaskfunctionpanel.AfteropeningtheDAQAssistant,createthenewtask.
OpeningtheDAQAssistantinMAXToopentheDAQAssistant,completethefollowingsteps:
1. Right-clickDataNeighborhood,andselectCreateNewfromtheshortcutmenu.IfyouareusingaremotesystemrunningLabVIEWReal-Time,expandRemoteSystems,findandexpandyourtarget,thenright-clickDataNeighborhoodandselectCreateNew.
2. SelectNI-DAQmxTaskintheCreateNewwindow.3. ClickNext.TheDAQAssistantopens.4. Createyourtask.5. ClickSaveTasktosavethetasktoMAX.
TipYoucanalsoright-clickyourdeviceunderDevicesandInterfacesandselectCreateNewtolaunchtheDAQAssistantfromMAX.
OpeningtheDAQAssistantinMeasurementStudioTouseaDAQmxtaskclassinaMeasurementStudioapplication,youmustfirstcreatetheDAQmxtaskclasswithintheapplication.YoumustuseMAXtocreateglobalvirtualchannelsforuseinMeasurementStudio.CompletethefollowingstepstocreateaDAQmxtaskclass:
1. OpentheprojectinwhichyouwanttocreateaDAQmxtaskclass.2. SelectProject»AddNewItemtoopentheAddNewItemdialog
box.3. IntheCategoriespane,selectMeasurementStudio»Assistants.4. IntheTemplatespane,selectDAQmxTask.5. SpecifyanamefortheDAQmxtaskfileandclickOpen.The
nameyouchooseforthefilebecomestheclassname.6. IntheNewDAQmxTaskdialogbox,specifywhethertocreatea
newtaskortomakeaprojectcopyofaglobaltaskthatyoucreateinMAX.
NoteIfyouchooseaglobaltaskandmakechangestothetask,thosechangesarenotsavedtotheglobaltaskstoredinMAX.
7. ClickFinish.TheDAQAssistantopensforyoutocreatethenewtask.
Afteryoucompletethesesteps,theDAQAssistantaddsa.mxbfiletotheproject.The.mxbfilestorestheDAQmxtaskclassconfigurationinformation.TheDAQAssistantaddsreferencestoappropriateNIclasslibrariestotheproject.
GlobalVirtualChannelsToopentheDAQAssistanttocreateglobalvirtualchannels,completethefollowingsteps:
NoteIfyouareusingLabWindows/CVIorMeasurementStudio,youmustcreateyourglobalvirtualchannelsinMAX.
1. InMAX,right-clickDataNeighborhoodandselectCreateNew.IfyouareusingaremotesystemrunningLabVIEWReal-Time,expandRemoteSystems,findandexpandyourtarget,thenright-clickDataNeighborhoodandselectCreateNew.
2. IntheCreateNewwindow,selectNI-DAQmxGlobalVirtualChannelandclickNext.TheDAQAssistantopens.YoualsocanopentheDAQAssistantdirectlywithinLabVIEW,LabWindows/CVI,orMeasurementStudioversion7.xorlater:
InLabVIEWandLabVIEWReal-Time,usetheDAQmxGlobalChannelcontroltoopentheDAQAssistant.Right-clickthecontrolandselectNewChannel(DAQAssistant).IfyouareusingLabVIEW8.0orlater,youcancreatechannelslocaltoaLabVIEWProject,oryoucancreatechannelsinMAX.TocreatechannelsinaProject,right-clickMyComputerintheProjectExplorerwindow.Then,selectNew»Channel.
3. InLabVIEW7.x,clicktheConfigurepull-downmenuandselectCreateDAQmxChannel(DAQAssistant).
4. InLabWindows/CVIorMeasurementStudio,firstyoumustcreateataskaspreviouslydescribed.IntheDAQAssistant,clickAddExistingDAQmxGlobalChannelstoaddglobalvirtualchannelstoyourtask.YoumustuseMAXtocreateglobalvirtualchannels.
5. Configuretheglobalvirtualchannel.6. Saveyourconfiguration.
IfyouopenedtheDAQAssistantfromLabVIEWorLabWindows/CVI,clickOK.IfyouopenedtheDAQAssistantfromMeasurementStudio,selectFile»Save.
IfyouopenedtheDAQAssistantfromMAX,clickSaveChannel.
Younowcanusetheglobalvirtualchannelinanapplicationoraddtheglobalvirtualchanneltoatask.Refertotheapplicationsoftwaredocumentationformoreinformationaboutusingaglobalvirtualchannelorgeneratingcode.
UsingtheDAQAssistantinLabVIEWSignalExpressYoucanusetheDAQAssistantwithLabVIEWSignalExpresstocreateDAQsteps.ToopentheDAQAssistantinLabVIEWSignalExpress,completethefollowingsteps:
1. ClickAddStep.2. SelecteitherAcquireSignals»DAQmxAcquireorGenerate
Signals»DAQmxGenerate.3. SelecttheI/Otype,suchasanaloginput,foryourmeasurement.4. Selectthemeasurementtype,suchasvoltage.5. TheDAQAssistantopens,beginningwiththeConfigurationtab.
Youcanconfiguresettingsandtestyourstep.
CreatingaTaskorGlobalVirtualChannelAftertheDAQAssistantopens,completethefollowingstepstocreateanewtaskorglobalvirtualchannel:
1. SelectanI/Otype,suchasanaloginput.2. Selectthemeasurementorgenerationtoperform.Youcanlater
addmultiplemeasurementtypestoatask,butyoumustfirstcreatethetaskwithonemeasurementtype.
3. Selectthesensortouse,ifapplicableforthatmeasurement.4. Adialogboxforthetaskyouspecifiedpromptsyoutoselectthe
physicalchannelsfromwhichtocreatelocalvirtualchannelsinthetask.Alternatively,youcanaddglobalvirtualchannelstothetask,orcopyinformationfromanexistingglobalvirtualchanneltolocalvirtualchannels.IfyoursystemisconfiguredwithaTEDSsensor,clicktheTEDStab.Selectthephysicalchannel(s).TheDAQAssistantimportsthesettingfromthesensor,andusestheinformationtocreatethetask.ClickNext.
NoteForhardwarethatsupportsmultiplechannelsinatask,youcanselectmultiplechannelstoaddtoyourtaskatthesametime.
5. Typethenewtaskorglobalvirtualchannelname.ClickFinish.6. Configuremeasurement-specificsettings,timing,triggering,and
scaling,ifnecessary.IfoneormorechannelsareconfiguredforTEDSsensors,somesettingsloadedfromTEDSarenoteditable.
7. Saveyourconfiguration.NoteInatask,youcanaddchannelsofthesameordifferentmeasurementtypes.
AddingMultipleChannelstoTasksForhardwarethatsupportsmultiplephysicalchannelsinatask,youcanselectmultiplechannelstoaddtothetaskatthesametime.Toselectparticularphysicalchannels,holdthe<Ctrl>keywhileselectingthechannels.Toselectarangeofphysicalchannels,clickthefirstphysicalchannel,thenpressandholdthe<Shift>key,andselectthelastphysicalchannelintherange.Allphysicalchannelsbetweenthetwoselectionsarehighlighted.YoucanalsoselectmultipleglobalvirtualchannelsandanyTEDSchannelsyouhaveconfigured.WhenyouclicktheAddChannelsbutton,alistofallchannelsofthesameI/Otypeasyourtaskappears.Thislistincludeschannelsfromalldevicesinyoursystem.Unlessyourhardwaresupportsmultidevicetasks,youcanaddonlychannelsfromthesamedevicetothetask.Youcanalsocreateataskwithmultiplechannelsofdifferentmeasurementtypes.
DuplicatingNI-DAQmxGlobalVirtualChannelsTocopyaglobalvirtualchannel,completethefollowingsteps:
1. ExpandDataNeighborhood.2. ExpandNI-DAQmxGlobalVirtualChannels.3. Right-clicktheglobalvirtualchannelyouwanttocopy.4. SelectDuplicate.5. Adialogboxpromptsyoutoselectphysicalchannelsfromalistof
validchannelsforthemeasurementtype.Selectthephysicalchannelstouseinthenewglobalvirtualchannels.TheDAQAssistantgeneratesanIDforeachnewglobalchannel,consistingoftheoriginalIDwithanincrementednumberappendedtotheend.
6. ClickOK.
CreatingaTaskwithMultipleMeasurementTypesTocreateataskwithmultiplemeasurementtypes,firstcreateataskwithaninitialmeasurementtype.Then,clicktheAddChannelsbuttontoaddthenextchannel(s).
NoteYoucanhavemultiplemeasurementtypes,suchasvoltage,temperature,andpressure,inthesametask.However,yourtaskmustcontainonlyonemeasurementclass,suchasanaloginputoranalogoutput.
WhenyouclicktheAddChannelsbutton,alistofallchannelsofthesameI/Otypeasyourtaskappears.Thislistincludeschannelsfromalldevicesinyoursystem.Unlessyourhardwaresupportsmultidevicetasks,youcanaddonlychannelsfromthesamedevicetothetask.
NamingChannels,Tasks,andScalesUsethefollowingguidelinestonameyourchannels,tasks,andscales:
Useanyalphanumericcharacters.Donotusenon-alphanumericcharacterswiththefollowingexceptions:
InNI-DAQmx7.4orlater,dashesareallowedinchannel,task,andscalenames.Spacesareallowed.Youcanuseunderscoreswithinthechannel,task,orscalename,butyoucannotuseleadingunderscores,suchas_Dev1.
Youmustusenomorethan256characters.
SpecialConsiderationswithLabVIEWProjectIntheDAQAssistant,youreceiveawarningdialogifyouattempttonameaLabVIEWProjectchannelthesamenameasanexistingMAXglobalvirtualchannel.TheDAQAssistantforcesyoutochooseauniquename.However,inLabVIEWProject,youcanright-clickachannelandrenameittothesamenameasaMAXglobalvirtualchannel.IfyoudorenamethechanneltothesamenameasaMAXchannel,thenexttimeyouusetheDAQAssistant,oranI/OControl,theMAXchannelwillbegrayedoutandyoucannotselectit.
EditingaTaskorGlobalVirtualChannelYoucanusetasksandglobalvirtualchannelsinyourNIapplicationsoftwareorinMAX.
LabVIEWCompletethefollowingstepstoeditataskorglobalvirtualchannelsavedinMAX:
1. PlaceeitheraDAQmxTaskNamecontroloraDAQmxGlobalChannelcontrolonthefrontpanel.
2. Selectthetaskorglobalvirtualchannelfromthepull-downlist.3. Right-clickthecontrolandselectEditDAQmxTaskorEdit
DAQmxChannel.Then,selectthedestination.4. ModifythetaskorglobalvirtualchannelwhentheDAQAssistant
launches.5. ClickOKtosavethechanges.
LabVIEWSignalExpressWithLabVIEWSignalExpress2.5andlater,youcanimporttasksfromMAXandcopyglobalvirtualchannelsfromMAXintoDAQsteps.IfyouimportataskfromMAX,thetaskbecomeslocaltothatLabVIEWSignalExpressproject,andyoucannotsaveitbacktoMAX.Also,anyglobalvirtualchannelscontainedinthetaskbecomelocalvirtualchannels.Then,youcanusethechannelsinyourLabVIEWSignalExpressapplication.
LabWindows/CVIYoumustuseMAXtoeditglobalvirtualchannels.Toeditatask,selectTools»Create/EditDAQmxTasksandchoosethetaskyouwanttoedit.YoualsocaneditMAX-basedtaskswithinMAXbyselectingDataNeighborhood»NI-DAQmxTasksandchoosingthetaskyouwanttoedit.
MeasurementStudioYoumustuseMAXtoeditglobalvirtualchannelsorMAX-basedtasks.
Toeditaproject-basedtask,gototheprojectanddouble-clickthe.mxbfiletolaunchtheDAQAssistant.
MAXToeditataskorglobalvirtualchannelusingtheDAQAssistantfromwithinMAX,completethefollowingsteps:
1. ExpandDataNeighborhood.2. ExpandNI-DAQmxTasksorNI-DAQmxGlobalVirtual
Channels.3. Clickthetaskorglobalvirtualchannelyouwanttoedit.4. ModifythetaskorglobalvirtualchannelintheDAQAssistant.5. ClickSavewhenyouarefinished.
NoteIfanasteriskappearsnexttoaglobalvirtualchannel,thechannelhasunsavedchanges.
AddingVirtualChannelstoTasksYoucanaddvirtualchannelstoyourtask.Additionalvirtualchannelsmustbeofthesameclass,suchasanaloginputoranalogoutput,asthetask.Toaddvirtualchannelstoyourtask,completethefollowingsteps:
1. ClicktheAddbutton.2. Fromthedrop-downlist,selectthemeasurementtypetoadd.3. Adialogboxpromptsyoutoselectaphysicalchannelfromalist
ofvalidphysicalchannel(s)forthatmeasurementtype.Selectthephysicalchannelstoaddtoyourtask.Alternatively,youcanaddexistingglobalvirtualchannelsorcopyinformationfromanexistingglobalvirtualchanneltoalocalvirtualchannel.
4. ClickOK.5. Repeatthesestepstoaddmorevirtualchannels.
CreatingandEditingScalesYoucanusetheDAQAssistanttocreateandeditscalesforyourtasksandglobalvirtualchannels.YoucanuseanNI-DAQmxScaletospecifyaconversionfromtheprescaledunitsmeasuredbyaphysicalchanneltothescaledunitsassociatedwithyourtransduceroractuator.Youcanthenassociatethisscalewithoneormorevirtualchannels.Often,youdonotneedtocreateanNI-DAQmxScale,becauseNI-DAQmxhasexplicitsupportforthemostcommontransducersandactuators.Forexample,whencreatingananaloginputtemperaturevirtualchannel,youcanspecifywhichtypeoftransducer(suchasathermistor,RTD,orthermocouple)isusedtomakethemeasurement.However,ifNI-DAQmxdoesnotexplicitlysupportyourtransduceroractuator,youcancreateanNI-DAQmxScalethatspecifieshowtoconvertfromtheprescaledunitstothescaledunits.NoticethatthesameNI-DAQmxScalecanbeassociatedwithmultiplevirtualchannels.YoudonotneedtocreateanNI-DAQmxScaleforeachvirtualchannelifthescaleisthesame.
CreatingScalesFollowthesestepstocreatenewscales:
1. Youcancreateanewscaleinthefollowingways:DAQAssistant—ClicktheScaleiconandselectCreateNew.MAX—Right-clickScalesintheconfigurationtree,andselectNewScale.IntheCreateNewwindow,selectNI-DAQmxScale.LabVIEW—PlacetheDAQmxScaleNamecontrolonthefrontpanel.Right-clickthecontrolandselectNewScale(DAQAssistant).
2. WhentheCreateScalewizardlaunches,selectthescaletypeandclickNext.
3. Enteranameforyourscale.4. ClickFinishtocontinueconfiguringyourscaleintheDAQ
Assistant.5. ClickOKorSaveScaletosaveyourscaletoMAX.
EditingScalesLabVIEW—Completethefollowingstepstoeditapreviouslysavedcustomscale:
1. PlaceaDAQmxScaleNamecontrolontheblockdiagram.2. Selectacustomscaleyoupreviouslycreatedandsaved.3. Right-clickthecontrolandchooseEditScale(DAQAssistant).4. ModifythescaleintheDAQAssistant.5. ClickOKtosavethechanges.
MAX—Completethefollowingstepstoeditapreviouslysavedcustomscale:
1. ExpandScales.2. Clickthescaleyouwanttoedit.3. ModifythescaleintheDAQAssistant.4. ClickSaveScalewhenyouarefinished.
TestingYourConfigurationClickRuntotestyourconfigurationandmakesureyoursensorsandsignalsareconnectedproperly.Dataacquiredappearsinthepreviewview.Verifythatyouareacquiringtheexpecteddataandthatyouconnectedthesignalproperly.Ifnecessary,modifyanysettingsandclickRuntotestyourconfigurationagain.
SavingYourConfigurationYoucansaveyourtaskorglobalvirtualchannelconfigurationtoMAXinseveralways,dependingonhowyoulaunchedtheDAQAssistant.Tosaveyourconfiguration,dothefollowing:
MAX—ClickSaveonthetoolbar.YoualsocancheckforerrorsinyourtaskbyclickingSave.Ifyourtaskhasanerror,adialogboxappears.ClickNointhedialogboxtocancelthesaveandshowtheerror(s).LabVIEW—ClickOK.
NoteIfyouconfigureataskusingtheDAQAssistantExpressVI,thetaskislocaltotheapplicationandcannotbesavedtoMAXforuseinotherapplications.YoumustconverttheDAQAssistantExpressVItoanNI-DAQmxTasktosavethetasktoMAXforuseinotherapplicationsortogeneratecode.
LabWindows/CVI—ClickOK.MeasurementStudio—SelectFile»Save.
YoucanaccesssavedglobalvirtualchannelsandtasksinDataNeighborhoodinMAXorinyourNIapplicationsoftware.
NoteYoucannotsaveaglobalvirtualchanneloratasktoMAXwithLabVIEWSignalExpress.
UsingYourTaskorGlobalVirtualChannelinYourApplicationSoftwareYoucanusetasksorglobalvirtualchannelssavedinMAXwhenprogrammingyourapplications.IfyouareusingLabVIEW7.xorlater,LabWindows/CVI7.xorlater,orMeasurementStudio7.xorlater,youcangeneratecodefromyourtaskorglobalvirtualchannelforuseinyourapplication.RefertoLabVIEWHelp,LabWindows/CVIHelp,MeasurementStudioHelp,orNI-DAQmxHelpformoreinformationaboutprogrammingwithyourtaskorglobalvirtualchannel.RefertoLabVIEWSignalExpressHelpforinformationaboutusingtheDAQAssistantinLabVIEWSignalExpress.
NoteYoucanaccessglobalvirtualchannelsinLabWindows/CVIandMeasurementStudioonlyifyouareaddingthemtoatask.
LabVIEWCompletethefollowingstepstoaccessyourtaskorglobalvirtualchannel:
1. PlaceeithertheDAQmxTaskNamecontrolortheDAQmxGlobalChannelcontrolonthefrontpanel.
2. Clickthepull-downmenuandselectthetaskorglobalvirtualchannel(s)youwanttouseinyourapplication.Youcanselectmultipleglobalvirtualchannels,butnotmultipletasks.YoualsocanselectBrowsetofindtasksandglobalvirtualchannels.
LabVIEWSignalExpressToaccessataskyoucreatedinMAX,selectTools»ImportTaskfromMAXinLabVIEWSignalExpress2.5andlater.
NoteAnyglobalvirtualchannelsinthetaskyouimportbecomelocalvirtualchannelsinLabVIEWSignalExpress.
YoualsocancopyglobalvirtualchannelsintoyourDAQstepsinLabVIEWSignalExpresswhenyouareaddingchannelstothestep.
1. SelecttheVirtualtab.TheVirtualtabappearsonlyifyouhavealreadycreatedaglobalvirtualchannelofthesamemeasurementtypeasyourstep.
2. Selecttheglobalvirtualchannelyouwanttocopytothestep.Whenyoucopytheglobalvirtualchanneltoyourstep,itbecomesalocalvirtualchannel.
LabWindows/CVICompletethefollowingstepstoaccessyourtask:
1. OpentheDAQmxLoadTaskfunctionpanel.2. Press<Enter>intheTaskNamecontrol.Alistoftasknamesyou
canuseappearsinthecontextmenu.3. Selectthetaskyouwanttousefromthecontextmenu.
MeasurementStudioLaunchoneofthefollowingwizardsfromtheProject»AddNewItemmenu:
TouseataskstoredinMAXtocreateanewproject-basedtask,usetheDAQmxTaskAddNewItemwizard.ToreferenceataskstoredinMAXwhencreatingaVisualC++DAQmxUserCode,usetheDAQmxUserCodeAddNewItemwizard.ToreferenceataskstoredinMAXwhencreatinga.NETDAQmxUserControl,usetheDAQmxUserControlAddNewItemwizard.
EachofthesewizardsopensadialogboxyoucanusetoselectatasksavedinMAX.
ConvertingtheDAQAssistantExpressVItoanNI-DAQmxTaskWhenyouconfigureataskusingtheDAQAssistantExpressVI,thetaskislocaltotheapplicationandcannotbeusedinotherapplications.YoucanconvertaDAQAssistantExpressVItoanNI-DAQmxTaskifyouwanttosavethetasktoMAXforuseinotherapplicationsortogeneratecode.
NoteIfyouareworkingwithinaprojectinLabVIEW,convertingtheDAQAssistantExpressVItoatasksavesthetasktotheproject.
CompletethefollowingstepstoconverttheDAQAssistantExpressVItoanNI-DAQmxTask.
1. Right-clicktheDAQAssistantExpressVIandselectConverttoNI-DAQmxTaskfromtheshortcutmenu.
2. TheDAQAssistantlaunches,andyoucanmodifythetask,ifnecessary.
3. ClicktheOKbutton.4. AnNI-DAQmxTaskreplacestheDAQAssistantExpressVI.
CalibratingChannelsUsetheChannelCalibrationWizardtoaddsoftwarechannelcalibrationtoavirtualchannel.Channelcalibrationtakessensors,hardware,andmeasurementsoftwareintoaccountandappliescompensationtothemeasurementinadditiontoallscalingandhardwarecalibration,thusimprovingmeasurementaccuracy.CompletethefollowingstepstolaunchtheChannelCalibrationWizardfromtheDAQAssistantandcalibrateanaloginputvirtualchannels.
1. Selectanexistingtaskorglobalchannelorcreateanewtaskorglobalchannel.
2. ClicktheCalibrationtabintheDAQAssistant.3. SelectoneormorevirtualchannelsfromtheChannelList.You
mustselectonlyonetypeofvirtualchannel.Ifyouselectvirtualchannelsofdifferentmeasurementtypes,theCalibratebuttonisdisabled.
4. ClickCalibrate.TheChannelCalibrationWizardlaunches.Completethescreenstocalibratetheselectedvirtualchannel.Youcancalibrateasmanydatapointsasneededtoproduceacalibrationtable.TheChannelCalibrationWizardstoresasetofcalibrationpropertiesforeachvirtualchannelyoucalibrate.SelectPropertiesintheCalibrationtaboftheDAQAssistanttoviewcalibrationhistory,verifythecalibration,recalibratetheselectedvirtualchannel(s),andgenerateacalibrationreport.Ifyouselectvirtualchannelsofdifferentmeasurementtypes,thePropertiesbuttonisdisabled.Aftercalibratingthevirtualchannel,clickEnableCalibrationtoenableordisablethecalibration.IfEnableCalibrationisdisabled,thecalibrationissavedbutnotappliedtotheselectedvirtualchannels.Todeleteacalibration,selectoneormorevirtualchannelsintheChannelListandclickDeleteCalibration.IntheCalibrationtab,theCalibrationDateandExpirationDateshowwhenthelastcalibrationoccurredandwhenthecalibrationexpires.Iftheseindicatorsaredisabled,youhaveselectedvirtualchannelsthathavedifferentcalibrationand/orexpirationdatesorarenotcalibrated.
GeneratingCodeIfyouareusingNIapplicationsoftwareversion7.xorlater,youcangeneratecodeforuseinyourapplications.YoucangeneratecodeinLabVIEW7.xorlater,LabVIEWSignalExpress2.xorlater,LabWindows/CVI7.xorlater,andMeasurementStudio7.xorlaterfromanytasksavedinMAX.YoualsocangeneratecodefromaglobalvirtualchannelinLabVIEW7.xorlater.AnychangesyoumaketothegeneratedcodeapplyonlytothetaskintheapplicationandarenotsavedbackintothetaskorglobalvirtualchannelintheDAQAssistant.
TypesofCodeGenerationTherearethreeoptionsforgeneratingcodeinyourNIapplicationsoftwarefromataskorglobalvirtualchannel:
Example—Generatesallthecodenecessarytorunthetaskorglobalvirtualchannel,suchasVIsneededtoreadorwritesamples,VIstostartandstopthetask,loops,andgraphs.Choosethisoptionifyouwanttorunthetaskorglobalvirtualchannelyoucreatedtoverifythatitworksortouseyourconfigurationinasimpleapplication.ThegeneratedcodeisasimpleNI-DAQmxexamplethatyoucanthenmodifyforyourapplication.Configuration—Generatesthecodethatreplicatestheconfigurationofthetasksandglobalvirtualchannels.Choosethisoptionifyouwanttodeployyourapplicationtoanothersystem.RefertoDeploymentintheNI-DAQmxHelplocatedatStart»AllPrograms»NationalInstrumentsformoreinformation.
WhenyougenerateConfigurationcode,thelinkbetweentheapplicationandtheDAQAssistantislost.AnychangesyoumaketotheconfigurationcodearenotreflectedintheDAQAssistant.YoucanregenerateConfigurationcodefromtheDAQAssistant,buttheregeneratedcodedoesnotmaintainpreviouschangesthatyoumadetothecode.
CautionAlthoughgeneratedconfigurationcodeincludescodetocreateglobalvirtualchannelsandtasks,itdoesnotincludecodetocreatescales.Ifyougenerateconfigurationcodefordeploymentofapplicationsthatincludescales,youmustensurethatthescalesareconfiguredinthetargetcomputer.RefertoDeploymentintheNI-DAQmxHelpfordeploymentoptions.
ConfigurationandExample—YoumustuseLabVIEWtogeneratethistypeofcode.Choosethisoptionifyouwanttocreateaportable,completeapplicationthatcanrunonothersystems.NoteIfyouright-clicktheDAQAssistantExpressVIandselectGenerateNI-DAQmxCode,yougeneratebothconfigurationandexamplecode.
GeneratingCodeinYourApplicationSoftwareSelectyourNIapplicationsoftwareformoreinformationonthetypesofcodeyoucangenerateandhowtousetheDAQAssistanttogeneratecode.
LabVIEWLabVIEWSignalExpressLabWindows/CVIMeasurementStudio
GeneratingCodeinLabVIEWThissectiondescribeswhathappensduringcodegenerationinLabVIEWandhowtogeneratecodeusingtheDAQAssistant.
TypesofCodeGenerationYoucangenerateallthreetypesofcodeinLabVIEW.Forgeneralinformationaboutthetypesofcodeandspecialconsiderations,refertoGeneratingCode.
Example—ThisoptionaddstotheVIyouareworkingin.Configuration—TheI/Oconstant/controlisreplacedwithasubVIthatcontainsVIsandpropertynodesusedforphysicalchannelcreationandconfiguration,timingconfiguration,andtriggeringconfigurationusedinthetaskorglobalvirtualchannel.
CautionAlthoughgeneratedconfigurationcodeincludescodetocreateglobalvirtualchannelsandtasks,itdoesnotincludecodetocreatescales.Ifyougenerateconfigurationcodefordeploymentofapplicationsthatincludescales,youmustensurethatthescalesareconfiguredinthetargetcomputer.RefertoDeploymentintheNI-DAQmxHelpfordeploymentoptions.
ConfigurationandExample—ThisoptiongeneratesbothConfigurationcodeandExamplecodeforthetaskorglobalvirtualchannelinonestep.
GeneratingCodeinLabVIEWCompletethefollowingstepstogeneratecode:
1. PlaceeithertheDAQmxTaskNamecontrolorDAQmxGlobalChannelcontrolonthefrontpanel.
2. Clickthepull-downmenuandselectthetaskorglobalvirtualchannelfromthelist.
3. Right-clickthecontrolandselectGenerateCode»Example,Configuration,orConfigurationandExample.
GeneratingCodeinLabVIEWUsingtheDAQAssistantExpressVIIfyouconfigureataskusingtheDAQAssistantExpressVI,youcanright-clicktheVIandselectGenerateNI-DAQmxCodetogenerateconfigurationandexamplecode.ThecodereplacestheDAQAssistantExpressVI.
NoteWhenyouconfigureataskusingtheDAQAssistantExpressVI,thetaskislocaltotheapplicationandcannotbesavedtoMAXforuseinotherapplications.YoucanconverttheDAQAssistantExpressVItoanNI-DAQmxTasktosavethetasktoMAXforuseinotherapplications.
GeneratingCodeinLabVIEWSignalExpressAfteryoucreateandsaveaprojectinLabVIEWSignalExpress,youcangenerateLabVIEWcodefromLabVIEWSignalExpress.RefertotheLabVIEWSignalExpressHelpforinstructionsonhowtogenerateVIsfromaLabVIEWSignalExpressproject.IfyouhaveDAQstepsinyourLabVIEWSignalExpressproject,thosestepsareconvertedtoDAQAssistantExpressVIsinLabVIEW.However,inthefollowingsituations,LabVIEWSignalExpresscreatesatop-levelExpressVIforyourentireproject:
YouhavesynchronizedDAQstepsbysharingtriggeringortimingsignalsbetweentheminoneproject.AnyDAQstepcontainsmorethanonemeasurementtype,suchasvoltageandtemperature.DAQstepsareanalogoutputordigitaloutput.YouhaveconfiguredexecutiondelaysbetweenyourDAQsteps.
Inthesecases,youmustdouble-clickthetop-levelexpressVItoopenLabVIEWSignalExpresstochangetheprojectsettings.
GeneratingCodeinLabWindows/CVIThissectiondescribeswhathappensduringcodegenerationinLabWindows/CVIandhowtogeneratecodeusingtheDAQAssistant.
TypesofCodeGenerationYoucangeneratetwotypesofcodeinLabWindows/CVI.Forgeneralinformationaboutthetypesofcodeandspecialconsiderations,refertoGeneratingCode.
Example—Thisoptioncreatesafunctionthathasthetaskandaddsthesourcefilestotheproject.Configuration—TheDAQmxLoadTaskfunctionisreplacedwithacalltoaDAQAssistant-generatedfunctionthatbuildsthetaskprogrammatically.
CautionAlthoughgeneratedconfigurationcodeincludescodetocreateglobalvirtualchannelsandtasks,itdoesnotincludecodetocreatescales.Ifyougenerateconfigurationcodefordeploymentofapplicationsthatincludescales,youmustensurethatthescalesareconfiguredinthetargetcomputer.RefertoDeploymentintheNI-DAQmxHelpfordeploymentoptions.
GeneratingCodeinLabWindows/CVITogenerateexamplecodeinLabWindows/CVI,completethefollowingsteps:
1. Right-clickacalltoDAQmxLoadTaskinasourcefile.2. SelectGenerateDAQExampleCode.3. Specifythenameofthefunctionthatrunsyourtaskandthefileto
containthegeneratedexamplecode.4. ClickOK.
Thegeneratedcodeincludessourceandheaderfilesthatdefinetheruntaskfunction.LabWindows/CVIautomaticallyaddsthesefilestotheprojectandmodifiesthecurrentsourcefiletocalltheruntaskfunction.Whencalled,theruntaskfunctionprogrammaticallycreatesauserinterfacepanelthatallowsyoutostartthetaskanddisplaythedata.Togenerateconfigurationcode,youcanstoreataskinyourproject,whichcausestheDAQAssistanttogeneratesourcecodetocreatethespecifiedtaskprogrammatically.Thegeneratedsourceandheaderfiledefineanentrypointfunctionthatconfiguresthetaskandreturnsataskhandle.Ageneratedbinaryfile(.mxb)containsabinarydescriptionofthetaskthatisusedwheneditingthetaskintheDAQAssistant.TheDAQAssistantaddsallthreefilestotheprojectwhenyoucreateaproject-basedtask.YoucanconvertaMAX-basedtasktoaproject-basedtaskbyright-clickingDAQmxLoadTaskinasourcefileandselectingCopyDAQTaskToProjectfromthecontextmenu.Thisoptionperformsthefollowingactions:
GeneratesandaddsfilestotheprojectReplacesDAQmxLoadTaskwithacalltothegeneratedentrypointfunctionAddsanincludestatementforthegeneratedheaderfile
GeneratingCodeinMeasurementStudioThissectiondescribeswhathappensduringcodegenerationinMeasurementStudioandhowtogeneratecodeusingtheDAQAssistant.
TypesofCodeGenerationYoucangeneratetwotypesofcodeinMeasurementStudio.Forgeneralinformationaboutthetypesofcodeandspecialconsiderations,refertoGeneratingCode.
Example—Thisoptioncreatesafunctionthathasthetaskandaddsthesourcefilestotheproject.Configuration—TheDAQmxLoadTaskfunctionisreplacedwithacalltoaDAQAssistant-generatedfunctionthatbuildsthetaskprogrammatically.
CautionAlthoughgeneratedconfigurationcodeincludescodetocreateglobalvirtualchannelsandtasks,itdoesnotincludecodetocreatescales.Ifyougenerateconfigurationcodefordeploymentofapplicationsthatincludescales,youmustensurethatthescalesareconfiguredinthetargetcomputer.RefertoDeploymentintheNI-DAQmxHelpfordeploymentoptions.
GeneratingCodeinMeasurementStudioAfteryouconfigureandsaveatask,aclassisgeneratedandaddedtotheproject.Theclasscontainsthesourcecodethatcorrespondstotheconfigurationinformationthatisstoredinthe.mxbfile.
NoteWhenyouusetheDAQAssistantconfigurationeditortomakechangestotheDAQmxtaskclass,the.mxbfileissavedandthetaskcodeisregenerated.Ifyoumakechangesdirectlytothegeneratedsourcecodefile,thosechangesarelostwhenthesourcecodeforthe.mxbfileisregenerated.ToenhanceorextendthecodethattheDAQAssistantgenerates,youcancopythesourcecodefile,changethenameoftheDAQmxtaskclass,andaddthecopiedfiletotheproject.Thecopiedfileisnotassociatedwitha.mxbfile.Asaresult,theDAQAssistantdoesnotoverwritethesourcecodefile.
GeneratingCodefora.NETDAQmxTaskClassTheDAQmxtaskclasscodeiscontainedinahidden.csor.vbsourcecodefileintheproject.Thissourcecodefilehasthesamebasenameasthe.mxbfile,buthasanextensionthatcorrespondstothelanguageofthesourcecode.Completethefollowingstepstoviewthehidden.csor.vbfile:
1. SelectShowAllFilesintheSolutionExplorertoolbar.2. IntheSolutionExplorer,expandthe.mxbfilenode.3. Right-clickthe.csor.vbfileandselectViewCodetoviewthe
code.
Togeneratethesourcecode,the.mxbfilehasaCustomToolpropertythatassociatestheDAQAssistantwiththe.mxbfile.
TipYoucanviewthepropertysettingsforthe.mxbfile.SelectthefileintheSolutionExplorerandviewitspropertiesinthePropertiesWindow(View»PropertiesWindow).
GeneratingCodeforaVisualC++DAQmxTaskClassTheDAQmxtaskclasscodeiscontainedina.hand.cppfileintheproject.Thesefileshavethesamebasenameasthe.mxbfile,buthavedifferentextensionsfortheheaderandsourcefiles.
TheMeasurementStudioAdd-Inmonitorsallchangestothe.mxbfile.Whenan.mxbfilethatiscontainedinaVisualC++projectissaved,theadd-incausestheDAQAssistanttogeneratethesourcecodefortheconfigurationthatisstoredinthe.mxbfile.
RefertotheNIMeasurementStudioHelpformoreinformationaboutgeneratingcodeandusingataskinMeasurementStudio.
GeneratingDiagramsandReportsIntheDAQAssistant,youcanusetheConnectionDiagramtooltodisplayeitheratextoranHTMLfileoftheconnectionsfromeachsensortotheconnectorblocks.YoucanalsousetheMAXReportWizardtogenerateareportoftheNI-DAQmxhardwareandsoftwareconfigurationofthesystem.
ConnectionDiagramsTheConnectionDiagramtoolintheDAQAssistantcancreateeithertextorHTMLreportsoftheconnectionsfromeachsensortotheconnectorblock.
ViewingConnectionDiagramsToviewaconnectiondiagramfromwithintheDAQAssistant,clickConnectionDiagram.Selecteachvirtualchannelinthetasktoviewconnectionsfromsensortoconnectorblock.Theconnectionslistdisplayseachoftheconnectionsintextformat,specifyingterminalnamesandnumbers.UsetheSaveasHTMLoptionintheConnectionDiagramtooltogenerateanHTMLreportofyourtask.Thereportcontainsthefollowingitems:
ListofvirtualchannelsinthetaskPhysicalchannelsDevicetypesMeasurementtypesConnectiondiagrams
Tosaveaconnectiondiagram,clickSaveasHTMLandenteranamefortheHTMLfile.Animagessubdirectoryiscreatedthatcontainsalloftheconnectiondiagramimages.UseawebbrowsersuchasMicrosoftInternetExplorertodisplayandprinttheHTMLreport.
ConnectionDiagramSupportThetoolcurrentlysupportsanaloginputmeasurementtypesandthefollowingMIOandSCXIscrewterminalblocks:
CB-11CB-27CB-37FHCB-37FVCB-50CB-68LPCB-68LPRCB-C68DAQPad-6015/6016PXI-4204PXI-4220SCB-100SCB-68SCXI-1300,1303,1304,1308,1313,1314,1314T,1315,1317,1320,1321,1322,1327,1328,1338TB-2705TB-2706TB-2725TBX-68
MAXReportGenerationInadditiontotheConnectionDiagramtoolintheDAQAssistant,youcanusetheMAXReportWizardtogenerateareportoftheNI-DAQmxhardwareandsoftwareconfigurationofthesystem.Thereportincludesthefollowing:
Realandsimulateddeviceinformation,includingdevicename,devicetype,serialnumber,connectedaccessory,andothersettingsTaskinformation,includingchannels,timing,triggering,andotherpropertysettingsGlobalchannelpropertysettingsCustomscalepropertysettings
TheMAXReportWizardsupportsbothlocalandremotesystems.
GeneratingCurrentorVoltageYoucangeneratetwomainkindsofsignalsforchannels:
Singlesamples,includingDCsignals—Whengeneratingsinglesamples,youcanusesoftwareorhardwaretiming(ifavailable)tocontrolwhenyourdevicegeneratesasignal.Multiplesamples—UsemultiplesamplestogenerateanACsignal,suchasasinewave.Alsocalledbufferedanalogoutput,generatingmultiplesamplesinvolvesthefollowingsteps:
1. Yourapplicationwritesmultiplesamplesintoabuffer.2. Allthesamplesinthebufferarethensenttoyourdevice
accordingtothetimingyouspecify.Youcanusesoftwareorhardwaretiming(ifyourdevicesupportshardwaretiming)tocontrolwhenyourdevicegeneratesasignal.
NoteSomecurrentgenerationdevices,suchastheSCXI-1124,allowyoutouseeitheraninternalorexternalcurrentsupply.Thechoiceofsupplyisdeterminedbytheterminalconnectionsusedtoconnecttheloadtothedevice.Ifyouplantouseaninternalsupply,connecttheloadtotheterminalsSUPPLYandISINK.Ifyouplantouseanexternalsupply,jointhesupplyandloadtoISINKandGND.Itisimportanttoverifythattheterminalconnectionsarecorrect.Inadditiontoproperconnections,verifythattheattachedloaddoesnotexceedthecapabilitiesofthedevice.Refertoyourdevicedocumentationformoreinformation.
Clickhereformoreinformationaboutgeneratingvoltage.Clickhereformoreinformationaboutgeneratingcurrent.
MeasuringAccelerationwithanAccelerometerAccelerationisachangeinvelocitywithrespecttotime.Accelerometersaretransducersthatrepresentaccelerationasavoltage.Theyarespecifiedbytherange,frequencyresponse,andthesensitivityofthedevice.Accelerometerscomeintwoaxialtypes.Themostcommonaccelerometermeasuresaccelerationalongonlyasingleaxis.Thesecondtypeisatri-axialaccelerometer,whichcancreatea3Dvectorofacceleration.Bothtypesofaccelerometercanbeeitherpassiveoractivesensors.Bothtypesalsocomewitheitherbothleadsinsulatedfromthecase(isolated)orwithoneleadgroundedtothecase.Tomeasureaccelerationwithapassivesensor,thesensormustbeconnectedtoacharge-sensitiveamplifier.Theactiveaccelerometerisnearlyidenticaltothepassiveaccelerometer,withtheadditionofacharge-sensitiveamplifierbuiltinsidetheaccelerometer.Thecurrentsourceprovidestheexcitationforthebuilt-inamplifierofthesensor,whiletheinstrumentationamplifiermeasuresthevoltagepotentialacrosstheleadsofthesensor.SomeanaloginputdevicessupportprogrammableACorDCcoupling.Ifyourdevicesupportsthisfeature,youraccelerationmeasurementtaskiscreatedusingACcoupling.Ifyoudesireadifferentcouplingbehavior,youcanchangethispropertyprogrammatically.
MeasuringAnalogFrequencyTomeasurethefrequencyofanACsignal,youneedcircuitrythatproducestriggersofthesamefrequencyasthemeasuredsignal.TheparametersthatdeterminewhentotriggerareThresholdLevelandHysteresis.Everytimethesignalpassesfrom(ThresholdLevel–Hysteresis)toThresholdLevel,atriggeroccurs.
Note(ThresholdLevel–Hysteresis)mustbebetween–0.5and4.48fortheSCXI-1126module.
Apulsegeneratorusesthesetriggersandproducesapulseonceeveryfrequencycycle.Thewidthofthispulseissetbytheinputfrequencyrange.Astheinputfrequencyrangeincreases,thepulsewidthgrowssmaller.ThispulsetrainisthenconvertedtoaDCsignalthathasalevelproportionaltothedutycycleofthepulsetrain.Thedutycycleisthefractionofaperiodofthepulsetrainwhenthepulseisoccurring.TheDCsignalhasavoltagethatisproportionaltotheinputfrequencyandcanthereforebescaledtothatfrequencyvalue.
MeasuringAngularDisplacementwithanRVDTAngulardisplacementismovementaboutanaxis,suchastheangularmotionoftheshaftofamotor.Anangulardisplacementsensorisadevicewhoseoutputsignalrepresentstherotationoftheshaft;itcannotmeasurethephysicaldisplacementofthewholeshaft.Onetypeofsensorthatmeasuresangulardisplacementisarotaryvariabledifferentialtransformer(RVDT).RVDTsaretherotationalversionofLVDTsandgenerallyoperateoverarangeof±30°–70°.Theyareavailableinservo-mountandcanrotatethrough360°withoutencounteringastop.RVDTsrequirespecialelectronicsdesignedforthesensor.RVDTstypicallyhaveadelayof10mscausedbyrequiredfilteringinthesignalconditioner.Theyareextremelyruggedandoperateoverwidetemperatureranges.Inenvironmentscharacterizedbyextremesintemperatureandshock,anRVDTistheclearchoiceforrotationalapplicationswhenyouneedmorethan70°ofmeasurementrange.
MeasuringCurrentMostmeasurementdevicescanmeasurevoltageswithinacertainrange.Witharesistor,youalsocanmeasurethecurrentthroughananaloginputconnector.Todoso,youmustplaceaknownresistanceinparallelwiththeinputconnectorandcurrentsource.YoucanmeasurevoltagedroppedacrosstheresistorandconvertittocurrentusingOhm'sLaw:I(A)=V(V)/R(Ω)
whereIisthecurrent,Visthevoltage,andRistheresistance.Measuringcurrentiscommonbecausemanydevicesgeneratea4–20mAcurrenttorepresentaphysicalquantity.Forinstance,youcanusecurrenttomeasurethelevelinatank.Usingalevelsensor,4mAcouldrepresentanemptytank,and20mAcouldrepresentafulltank.
MeasuringCustomVoltagewithExcitationThismeasurementtypeallowsyoutousesensorsthatarenotexplicitlysupportedbyNI-DAQmxandrequirevoltageexcitation,suchasbridgesensors,loadcells,andpressuretransducers.Typically,youusethismeasurementtypewithSCXImodulesthatincludeanexcitationsourceandconfigureacustomscaletoconvertthevoltagethesensorreturnstotheunitsyouwanttomeasure.ForsensorsthatarenotexplicitlysupportedbyNI-DAQmxanddonotrequireanyexcitation,usethevoltagemeasurementtypewithacustomscale.ForsensorsthatarenotsupportedbyNI-DAQmxandrequirecurrentexcitation,usethevoltagemeasurementtypewithacustomscale,andusetheAIexcitationDAQmxChannelpropertiestoconfiguretheexcitation.
MeasuringLinearDisplacementwithanLVDTLineardisplacementismovementinonedirectionalongasingleaxis.Thelinearvariabledifferentialtransformer(LVDT)isasensorthatmeasureslineardisplacement.LVDTsoperateontheprincipleofatransformerandconsistofastationarycoilassemblyandmoveablecore.AnLVDTmeasuresdisplacementbyassociatingaspecificsignalvalueforanygivenpositionofthecore.LVDTsignalconditionersgenerateasinewavefortheprimaryoutputsignalandsynchronouslydemodulatethesecondaryoutputsignal.Thedemodulatedoutputispassedthroughalowpassfiltertoremovehigh-frequencyripple.TheresultingoutputisaDCvoltageproportionaltocoredisplacement.ThesignoftheDCvoltageindicateswhetherthedisplacementistotheleftorright.LVDTstypicallycomein4-wire(openwire)and5-wire(ratiometricwire)configurations.WiresfromthesensorconnecttoasignalconditioningcircuitthattranslatestheoutputoftheLVDTtoameasurablevoltage.Themethodofsignalconditioninguseddifferentiatesthe4-wireand5-wireconfigurations.
MeasuringResistanceResistanceistheoppositiontopassageofanelectriccurrent.Oneohmistheresistancethroughwhich1Vofelectricforcecausesoneamperetoflow.Twocommonmethodsformeasuringresistancearethe2-wiremethodandthe4-wiremethod.Forbothmethods,acurrentissentthrougharesistorwithameasurementdevicemeasuringthevoltagedropfromthesignalacrosstheresistor.The2-wiremethodiseasiertoimplement,butisnotasaccurateforresistancesbelow100Ω.Tocalculateresistance,usethefollowingformula:R=V/I
whereR=resistance,V=voltage,andI=current.
MeasuringSoundPressureSoundpressureisthedynamicvariationofthestaticpressureofairandismeasuredinforceperunitarea(Pa).Theinstantaneoussoundpressureistypicallyaveragedoveracertaindurationtogivesoundpressurelevel.Soundpressurelevelisnormallyrepresentedonalogarithmicamplitudescale,whichissimilartothehumanperceptionofhearing.Typicalvaluesonthislogarithmicscaleareasoundlevelof0dB,whichistheaveragethresholdofhumanhearing,60to70dBfornormalconversation,110dBatanextremelyloudconcert,and150dBforthenoiseofarockettakeofforajetengineatcloserange.TheSoundPressureLevel(SPLorLP)indecibelsisdefinedasthefollowing:SPL=20log10(p/pref)wherepistheinstantaneoussoundpressureinPaandprefis20µPa,theinternationallyacceptedreferenceforsoundpressuremeasurements,whichroughlycorrespondstothethresholdofhumanhearing.Youcanuseamicrophonetomeasuresoundpressure.Themicrophoneactsasatransducer,creatingavoltagesignalthatisproportionaltotheinstantaneoussoundpressure.SomeanaloginputdevicessupportprogrammableACorDCcoupling.Ifyourdevicesupportsthisfeature,yoursoundpressuremeasurementtaskdefaultstoACcoupling.Ifyouwantadifferentcouplingbehavior,youcanchangethispropertyprogrammatically.
MeasuringStrainwithaStrainGageStrainistheamountofdeformationofabodyduetoanappliedforce.Specifically,strainisdefinedasthefractionalchangeinlength.Straincanbepositive(tensile)ornegative(compressive).Inpractice,themagnitudeofmeasuredstrainisverysmall.Therefore,strainisoftenexpressedasmicrostrain(µε).Whenabarisstrainedwithauniaxialforce,PoissonStraincausesthegirthofthebartocontractinthetransverse,orperpendicular,direction.ThemagnitudeofthistransversecontractionisamaterialpropertyindicatedbyitsPoisson'sRatio.Tomeasurestrain,youtypicallyuseoneormorestraingagesinaWheatstonebridgeinoneofseveralbridgeconfigurations.
UsingtheStrainGageCalibrationWizardWhenyouconfigureastrainmeasurementtask,youcanusetheStrainGageCalibrationWizardtocalibrateyourstraingage.Completethefollowingstepstocalibratethestraingage:
1. ClickCalibratetolaunchtheStrainGageCalibrationWizard.2. FollowthestepsontheSetupHardwarewindow.Youcan
configurethefollowingsettings:EnableOffsetNullingEnableShuntCalibration
3. ClickNext.4. UsetheMeasureandCalibratewindowtomeasureandcalibrate
yourstraingage.Thesoftwareautomaticallytakesthefirstmeasurement,andthetabledisplaystheresults.Thetableshowsthefollowinginformation:ChannelInformationOffsetAdjustment—Thissectionshowsinformationabouttheoffseterrortohelpyoudetermineifyoushouldperformanoffsetnullcalibration.Performanoffsetnullcalibrationifyouperformashuntcalibration.GainAdjustment—Thissectionshowsvaluesrelatedtogainerrorandtheshuntcalibrationprocedure:
5. Performyourmeasurementandcalibrationwiththefollowingbuttons:
ClickMeasuretomakeapreliminarymeasurementusingtheoffsetandshuntcalibrationdatafromapreviouslyrunstraingageprocedure.ClickResetDatatoresettheoffsetandshuntcalibrationdataandmakeameasurementusingtheirdefaultvalues.ClickCalibratetoperformtheoffsetand/orshuntcalibration.Thetableshowstheresultingmeasurements.
6. ClickFinishwhenyouaredone.Thecalibrationdataissavedaspartofyourvirtualchannel.Onsuccessfulcompletion,thesoftwareautomaticallyusesthecalibrationdatawhenscaling
voltagetostrainsonthisvirtualchannel.NoteIfyouareusinganSCXI-1520withanSCXI-1314terminalblock,PXI-4220,SCXI-1121withanSCXI-1321terminalblock,oranSCXI-1122withanSCXI-1322terminalblock,refertoDevice-SpecificStrainGageInformationformoreinformationaboutdevice-specificsettings.
RelatedTopicsOverviewofStrainGagesSignalConditioningRequirementsforStrainGagesTroubleshootingYourStrainGageCalibrationHighAccuracyConsiderations
Device-SpecificStrainGageCalibrationInformationThefollowingdeviceshaveadditionalissuesrelatedtostraingagecalibration.SCXI-1520(withSCXI-1314terminalblock),PXI-4220OffsetNulling—Thesedevicesusehardwarenullingcircuitry.TheresultingcalibrationvaluesarestoredintheAI.Bridge.Balance.CoarsePotandAI.Bridge.Balance.FinePotattributesofyourstrainvirtualchannel.AnyresidualoffsetvalueisstoredintheAI.Bridge.InitialVoltageattributeofyourstrainvirtualchannelforadditionalsoftwarecompensation.SCXI-1121(withSCXI-1321terminalblock)OffsetNulling—UsetheoffsetnullingpotentiometercircuitontheSCXI-1321toreduceinitialoffsetbeforeperformingthecalibration.ClickMeasureasyouadjustthepotentiometertoreadthenewoffsetvalue.AnyresidualoffsetvalueisstoredintheAI.Bridge.InitialVoltageattributeofyourstrainvirtualchannelforadditionalsoftwarenullingcompensation.SCXI-1122(withSCXI-1322terminalblock)OffsetNulling—Thehardwarecannotperformoffsetnulling,sotheoffsetvalueisstoredintheAI.Bridge.InitialVoltageattributeofyourstrainvirtualchannelforsoftwarenullingcompensation.
TroubleshootingYourStrainGageCalibrationRefertothefollowinglistifyoureceiveanerrorwhilecalibratingyourstraingage:
Makesureyouhaveanactualstraingageconnectedtoyourphysicalchannel,whichisatrest(nostrain).Checkyourstrainattributesandmakesuretheyreflectthecapabilityofyourmeasurementhardwareandyourstraingagesetup.Makesureyouhavecorrectlyconnectedyourstraingage.Half-bridgeandquarter-bridgesetupsrequirecompletionnetworks.Ifyourmeasurementhardwarehasabuilt-incompletionnetwork,makesureyouprogramitinsoftwareorsetthecompletionjumpersinhardware.Additionally,quarter-bridgestraingagesetuprequiresyoutoconnectanexternalquarter-bridgecompletionresistor.Alwaysuseaprecisioncompletion-resistorwhosevalueisequaltothenominalgageresistanceofyourquarter-bridgestraingage.Refertoyourdevicedocumentationfordetails.Makesureyouhavespecifiedthecorrectlocationofyourshuntresistor.Onsomedevices,theshuntresistorlocationisfixed.Onotherdevices,youcanchoosetheshuntresistorlocation.Refertoyourdevicedocumentationtoseewheretheshuntresistorislocatedbydefault.Ifyouaredrawingalotofcurrentthroughoneormorestraingages,connecttheremotesenseinputstoyourhardware(ifsupported).Ifyouhavelongleadwireswithlargeleadresistance,connecttheremotesensetocompensateforthevoltagedropacrosstheleads.Makesureyourstraingageisproperlybondedtothestrainspecimen.Makesureyourstraingagedoesnothaveanyshortoropencircuits.
HighAccuracyConsiderationsYourstraingagemeasurementscanbeinaccurateduetooneormorefactors.Thefollowingtableliststheseerrorsandwaystominimizeeachtypeoferror.
ErrorType HowtoMinimizetheErrorGain Performfrequentshuntcalibration.
Usearemotesensortoaccountforexcitationvoltagedropacrossleadwires.Useastraingagewithahigherprecisiongagefactor.Accuratelyspecifyshuntresistancebymanuallymeasuringit.
Offset Performfrequentoffsetnulling.Useprecisioncompletionresistors(forquarter-bridgeandhalf-bridgesetup).Checkthegageresistanceofyourstraingage.Usearemotesensortoaccountforvoltagedropacrossleadwires.Checktheaccuracylimitationoftheoffsetnullingcircuit.
Noise Over-sampleyourdata.Useahardwarelowpassfilter.Useasoftwarelowpassfilter.
TemperatureDrift Performfrequentcalibration.Useatemperature-compensatedbridgetype(allexceptquarter-bridgeI).
MeasuringTemperaturewithaCurrentExcitationThermistorAthermistorisasemiconductormadefrommetaloxides,pressedintoasmallbead,disk,orothershapeathightemperatures,andcoatedwithepoxyorglass.AswithanRTD,bypassingacurrentthroughathermistor,youcanreadthevoltageacrossthethermistorandthusdetermineitstemperature.UnlikeRTDs,thermistorshaveahigherresistance(anywherefrom2,000to10,000Ω)andamuchhighersensitivity(~200Ω/°C).However,thermistorsaregenerallyusedtomeasuretemperatureonlyuptothe300°Ctemperaturerange.Becausethermistorshavehighresistance,lead-wireresistancedoesnotaffecttheaccuracyofthemeasurements.UnlikeRTDs,2-wiremeasurementsareadequate.NI-DAQmxscalestheresistanceofathermistortoatemperatureusingtheSteinhart-Hartthermistorequation:
whereTisthetemperatureinKelvins,Risthemeasuredresistance,andA,B,andCareconstantsprovidedbythethermistormanufacturer.
MeasuringTemperaturewithaThermocoupleAthermocoupleiscreatedwhentwodissimilarmetalstouch,andthecontactpointproducesasmallopen-circuitvoltagethatcorrespondstotemperature.Thermocouplemeasurementsrequiresensingofthecold-junctiontemperaturewherethethermocouplewireisconnectedtothemeasurementsystem.Therefore,signalconnectionaccessoriesshouldincludeanaccuratecold-junctionsensor,andshouldbedesignedtominimizeanytemperaturegradientsbetweenthecold-junctionsensorandthermocouplewireconnections.Othersignalconditioningrequirementsincludeamplificationandfiltering,becausethermocouplesgeneratelow-voltagesignalsandaresusceptibletonoise.Yoursystemmustalsoperformlinearizationthroughhardwareorsoftwarebecausetheoutputvoltageisnotlinearwithtemperature.
MeasuringTemperaturewithaVoltageExcitationThermistorAthermistorisasemiconductormadefrommetaloxides,pressedintoasmallbead,disk,orothershapeathightemperatures,andcoatedwithepoxyorglass.AswithanRTD,bypassingavoltagethroughathermistor,youcanreadthevoltageacrossthethermistorandthusdetermineitstemperature.UnlikeRTDs,thermistorshaveahigherresistance(anywherefrom2,000to10,000Ω)andamuchhighersensitivity(~200Ω/°C).However,thermistorsaregenerallyusedtomeasuretemperatureonlyuptothe300°Ctemperaturerange.Becausethermistorshavehighresistance,lead-wireresistancedoesnotaffecttheaccuracyofthemeasurements.UnlikeRTDs,2-wiremeasurementsareadequate.NI-DAQmxscalestheresistanceofathermistortoatemperatureusingtheSteinhart-Hartthermistorequation:
whereTisthetemperatureinKelvins,Risthemeasuredresistance,andA,B,andCareconstantsprovidedbythethermistormanufacturer.
MeasuringTemperaturewithanRTDAnRTDisatemperaturesensingdevicewithresistancethatincreaseswithtemperature.SignalconditioningisgenerallyrequiredtomeasuretemperatureusinganRTD.BecauseanRTDisapassiveresistivedevice,youmustpassacurrentthroughthedevicetoproduceameasurablevoltage.Providingcurrenttotakearesistivemeasurementisaformofsignalconditioningcalledcurrentexcitation.InadditiontoproducingcurrentexcitationfortheRTD,signalconditioningamplifiestheoutputvoltagesignal,andfiltersthesignaltoremoveunwantednoise.YoualsocanusesignalconditioningtoelectricallyisolatetheRTDandthemonitoredsystemfromtheDAQsystemandthehostcomputer.
MeasuringVoltageMostmeasurementdevicesaredesignedformeasuring,orreading,voltage.TwocommonvoltagemeasurementsareDCandAC.DCvoltagesareusefulformeasuringphenomenathatchangeslowlywithtime,suchastemperature,pressure,orstrain.ACvoltages,ontheotherhand,arewaveformsthatconstantlyincrease,decrease,andreversepolarity.MostpowerlinesdeliverACvoltage.
DigitalYoucanusethedigitalportsandlinesinyourDAQdevicestoacquireorgeneratedigitalsamples.Refertothefollowingsectionsformoreinformation:AcquiringaDigitalSample(Line)AcquiringaDigitalSample(Port)GeneratingaDigitalSample(Line)GeneratingaDigitalSample(Port)
AcquiringaDigitalSample(Line)YoucanusethedigitallinesinyourDAQdevicetoacquireadigitalvalue.Thisacquisitionisbasedonsoftwaretiming.Eachlinecorrespondstoavirtualchannelinyourtask.RefertotheNI-DAQmxHelpforinformationaboutsampletimingtypesandchangedetection.AllEandMSeriesdevicessupportTTL(transistor-transistorlogic)-compatibledigitalsignals.ATTLsignalhasthefollowingtwostates:
LogicLow=0Vto+0.8VLogicHigh=+2Vto+5V
Commonapplicationsforimmediatedigitalmeasurementsincludecontrollingrelaysandsensingexternaldevicestates,suchasthestateofaswitch.
AcquiringaDigitalSample(Port)Youcanusethedigitalport(s)inyourDAQdevicetoacquireadigitalvalue.Thisacquisitionisbasedonsoftwaretiming.Youcanconfiguretheportsindividuallytoeithermeasureorgeneratedigitalsamples.Eachportcorrespondstoavirtualchannelinyourtask.RefertotheNI-DAQmxHelpforinformationaboutsampletimingtypesandchangedetection.AllEandMSeriesdevicessupportTTL(transistor-transistorlogic)-compatibledigitalsignals.ATTLsignalhasthefollowingtwostates:
LogicLow=0Vto+0.8VLogicHigh=+2Vto+5V
Commonapplicationsforimmediatedigitalmeasurementsincludecontrollingrelaysandsensingexternaldevicestates,suchasthestateofaswitch.
GeneratingaDigitalSample(Line)YoucanusethedigitallinesinyourDAQdevicetogenerateadigitalsample.Thisoperationisbasedonsoftwaretiming.Eachlinecorrespondstoavirtualchannelinyourtask.AllEandMSeriesdevicessupportTTL(transistor-transistorlogic)-compatibledigitalsignals.ATTLsignalhastwostates,logiclowandlogichigh:LogicLow=0Vto+0.8VLogicHigh=+2Vto+5V
Commondigitalgenerationapplicationsincludecontrollingrelaysanddrivingexternaldevices,suchasanLED.
GeneratingaDigitalSample(Port)Youcanusethedigitalport(s)inyourDAQdevicetogenerateadigitalsample.Thisoperationisbasedonsoftwaretiming.Onsomedevices,youcanconfiguretheportsindividuallytoeithermeasureorgeneratedigitalsamples.Eachportcorrespondstoavirtualchannelinyourtask.AllEandMSeriesdevicessupportTTL(transistor-transistorlogic)-compatibledigitalsignals.ATTLsignalhasthefollowingtwostates:
LogicLow=0Vto+0.8VLogicHigh=+2Vto+5V
Commondigitalgenerationapplicationsincludecontrollingrelaysanddrivingexternaldevices,suchasanLED.
CountingEdgesInedgecounting,yourdevicecountsrisingorfallingedgesusingacounter.Youcanchoosetodoeithersingle-point(on-demandorhardwaretimed)edgecountingorbuffered(sampleclock)edgecounting.Whendoingon-demandedgecounting,eachsubsequentreadreturnsthenumberofedgescountedsincethecounterwasstarted.Ifyouperformmultiplereadswithoutfirststartingthecounter,thecounterimplicitlystartsandstopswitheachReadfunction/VIcall,andthenumberofcountededgesisnotcumulativebetweenreadcalls.Whendoinghardware-timededgecounting,thereadreturnsavalueoneachactiveedgeofthesampleclock.Inthismode,youcannotspecifyabuffer.Youmustsupplyanexternalsampleclockforhardware-timededgecounting.Whendoingbufferededgecounting,thenumberofedgescountedislatchedoneachactiveedgeofthesampleclockandstoredinthebuffer.Youmustsupplyanexternalsampleclockforbufferededgecounting.Thefollowingfigureshowsanexampleofedgecountinginwhichthecounterinadevicecountsfiveedgesontheinputterminal.
Whendoingbufferededgecounting,thenumberofedgescountedislatchedoneachactiveedgeofthesampleclockandstoredinthebuffer.Thereisnobuilt-inclockforbufferededgecounting,soyoumustsupplyanexternalsampleclock.
GeneratingaPulseUsingacountertooutputpulsesiscalledpulsegeneration.SomemeasurementdevicescangenerateTTLpulsesfromthecounter/timerofthedevice.Thepulseiseitherlow(startshigh,pulseslow,andreturnshigh)orhigh(startslow,pulseshigh,andreturnslow).Apulsecanbeusedasaclocksignal,agate,oratriggerforothermeasurementsandgenerations.Eachpulseorpulsetrainconsistsofthreeparts:
InitialDelay—TheamountoftimetheoutputremainsattheidlestatebeforegeneratingthepulseHighTime—Theamountoftimethepulseisatahighlevel(5V)LowTime—Theamountoftimethepulseisatalowlevel(0V)
UsingtheDAQAssistant,youcanconfigurehowlongapulsegeneratedwithinataskremainsathighlevelorlowlevel.ThepolarityofthepulsegenerationiscontrolledbyIdleState.WithIdleStatesettoLow,thepulsegenerationstartslowfortheInitialDelay,transitionshighforthehightime,andthentransitionslowforthelowtime.Thehighandlowtimesarethenrepeatedforthedesirednumberofpulses.WithIdleStatesettoHigh,thepulsegenerationstartshighfortheInitialDelay,transitionslowforthelowtime,andthentransitionshighforthehightime.Thelowandhightimesarethenrepeatedforthedesirednumberofpulses.Inbothcases,theoutputrestsatIdleStateafterthegenerationcompletes.Clickhereformoreinformationaboutgeneratingpulses.
MeasuringDigitalFrequencyYoucanusethecountersofyourdevicetomeasurefrequency.Tomeasurethefrequencyofasignalusingthecountersofyourdevice,usethetimebaserateofyourcounterasareferencefrequency.Toconfigureyourmeasurement,specifytheexpectedrangeoftheinputsignal,sothatNI-DAQmxcanchooseitstimebasetoprovidethehighestresolutionforthemeasurement.Youcancalculatethefrequencyofyoursignalbasedonthetimebaserateandthenumberofcountsusingthefollowingformula:Frequency(inHz)=CounterTimebaseRate/Count
Togettheperiodofthesignal,takeinverseofthefrequency.If,forexample,thetimebaserateofyourmeasurementdeviceis100MHzandyouarecounting500counts,thefrequencyoftheinputsignalis200kHz.TheCounterTimebaseRateisaknownfrequency(20MHzor100kHz)andallowsyoutomakefrequencyandtimemeasurements.Toconfigureameasurement,youspecifytheexpectedrangeoftheinputsignal.Basedonthisrange,NI-DAQmxautomaticallypickstheinternaltimebasethatprovidesthehighestresolutionforyourmeasurementandusesitasthecountertimebase.Dependingonthephaseoftheinputsignalinrelationtothestartofthemeasurement,thefirstsampleofcontinuousmeasurementsisofteninvalid.Forinstance,ifyouareperformingacontinuousperiodmeasurement,andyoustartthemeasurementwhentheinputsignalishalfwaythroughitscurrentcycle,themeasuredperiodforthefirstsampleishalfofitsexpectedvalue.Subsequentsamplesindicatethecorrectvaluesbecausetheyareguaranteedtohaveseenafullperiodoftheinputsignal.Forthisreason,thefirstsampleofcontinuousperiod,pulse-width,andsemiperiodmeasurementsoftenindicatesasmallervaluethantheactualvalue.Forcontinuousfrequencymeasurements,thefirstsampleoftenindicatesahigherfrequencythantheactualfrequency.Forfrequencymeasurements,youalsocanperformmeasurementswithoneortwocounters.Formostapplications,settingMeasurementMethodto1Counter(LowFrequency)issufficientanddesirablebecauseitusesfewerresources.However,ifyouhaveahigh-frequencyorwidelyvaryingsignal,youmaywishtouseoneofthetwocounter
measurementmethods—2Counters(HighFrequency)or2Counters(LargeRange).Dependingontherateofyourinputsignalandmeasurementmethodused,yourmeasurementissubjecttodifferentquantizationerror.NI-DAQmxautomaticallyinternallyroutesasneededtoperformthemeasurementacrosspairedcounters.
MeasuringPeriodYoucanusethecountersonyourmeasurementdevicetomeasureperiod.Periodmeasurementsmeasurethetimebetweenconsecutiverisingorfallingedges.
Theformulaforperiodisasfollows:Period(inseconds)=Count/CounterTimebaseRate
whereCountisthenumberofticksofthecountertimebasethatelapsedduringoneperiodoftheinputsignalbeingmeasured.TheCounterTimebaseRateisaknownfrequency(20MHzor100kHz)andallowsyoutomakefrequencyandtimemeasurements.Toconfigureameasurement,specifytheexpectedrangeoftheinputsignal.Basedonthisrange,NI-DAQmxautomaticallychoosestheinternaltimebasethatprovidesthehighestresolutionforyourmeasurementandusesitasthecountertimebase.Dependingonthephaseoftheinputsignalinrelationtothestartofthemeasurement,thefirstsampleofcontinuousmeasurementsisofteninvalid.Forinstance,ifyouareperformingacontinuousperiodmeasurement,andyoustartthemeasurementwhentheinputsignalishalfwaythroughitscurrentcycle,themeasuredperiodforthefirstsampleishalfofitsexpectedvalue.Subsequentsamplesindicatethecorrectvaluessincetheyareguaranteedtohaveseenafullperiodoftheinputsignal.Forthisreason,thefirstsampleofcontinuousperiod,pulse-width,andsemiperiodmeasurementsoftenindicatesasmallervaluethantheactualvalue.Forcontinuousfrequencymeasurements,thefirstsampleoftenindicatesahigherfrequencythantheactualfrequency.Forperiodmeasurements,youalsocanperformmeasurementswithoneortwocounters.Formostapplications,settingMeasurementMethodto1Counter(LowFrequency)issufficientanddesirablebecauseitusesfewerresources.However,ifyouhaveahigh-frequencyorwidelyvaryingsignal,youmaywishtouseoneofthetwocountermeasurementmethods—2Counters(HighFrequency)or2Counters(LargeRange).
Dependingontherateofyourinputsignalandmeasurementmethodused,yourmeasurementissubjecttodifferentquantizationerror.NI-DAQmxautomaticallyinternallyroutesasneededtoperformthemeasurementacrosspairedcounters.
MeasuringPositionwithaLinearEncoderOndevicesthatusetheNI-TIOtimingchip,youcanusethecounterstoperformpositionmeasurementswithencoders.Anencoderisadevicethatconvertslinearorrotarydisplacementintodigitalorpulsesignals.Linearpositioncanbemeasuredwithtwo-pulseencoders.Youcanchoosetodoeithersingle-point(on-demand)positionmeasurementorbuffered(sampleclock)positionmeasurement.ThecountermeasuresthepositionoftheencoderusingtheAandBsignals,whichareoffsetby90°.TheNI-TIOcountersalsosupporttheZindex,whichprovidesaprecisereferencepointandisavailableonsomequadratureencoders.Toconfigureameasurement,youspecifytheinitialsensorpositionthroughtheInitialPositionattribute/property,dependingonyourencodertype.YoucanalsospecifyiftheZInputTerminalisusedwiththeZIndexEnableattribute/property.ThereloadpositionuponaZindexsignal,aswellaswhenaZindexpositionshouldcauseareloadtooccurinrelationtotheAandBsignalsarealsoconfigurablethroughtheZIndexPhaseandZIndexValueattributes/properties,respectively.Whenperforminganon-demandpositionmeasurement,youfirstcalltheStartVI/functiontoarmthecounter.Eachsubsequentreadreturnsthecurrentpositionoftheencoder.Ifyouperformmultiplereadswithoutfirststartingthecounter,thecounterimplicitlystartsandstopswitheachReadfunction/VIcall,andthepositionisnotrecordedproperlybetweenreadcalls.Whendoingbufferedpositionmeasurement,thecurrentpositionislatchedoneachactiveedgeofthesampleclockandstoredinthebuffer.Thereisnoonboardclockforbufferedpositionmeasurement,soyoumustsupplyanexternalsampleclock.
MeasuringPositionwithanAngularEncoderOndevicesthatusetheNI-TIOtimingchip,youcanusethecounterstoperformpositionmeasurementswithencoders.Anencoderisadevicethatconvertslinearorrotarydisplacementintodigitalorpulsesignals.AngularpositioncanbemeasuredwithX1,X2,andX4quadratureencoders.Youcanchoosetodoeithersingle-point(on-demand)positionmeasurementorbuffered(sampleclock)positionmeasurement.ThecountermeasuresthepositionoftheencoderusingtheAandBsignals,whichareoffsetby90°.TheNI-TIOcountersalsosupporttheZindex,whichprovidesaprecisereferencepointandisavailableonsomequadratureencoders.Toconfigureameasurement,youspecifytheinitialsensorpositionthroughtheInitialAngleattribute/property,dependingonyourencodertype.YoualsocanspecifyiftheZInputTerminalisusedwiththeZIndexEnableattribute/property.ThereloadpositionuponaZindexsignal,aswellaswhenaZindexpositionshouldcauseareloadtooccurinrelationtotheAandBsignalsarealsoconfigurablethroughtheZIndexPhaseandZIndexValueattributes/properties,respectively.Whenperforminganon-demandpositionmeasurement,youfirstcalltheStartVI/functiontoarmthecounter.Eachsubsequentreadreturnsthecurrentpositionoftheencoder.Ifyouperformmultiplereadswithoutfirststartingthecounter,thecounterimplicitlystartsandstopswitheachReadfunction/VIcall,andthepositionisnotrecordedproperlybetweenreadcalls.Whendoingbufferedpositionmeasurement,thecurrentpositionislatchedoneachactiveedgeofthesampleclockandstoredinthebuffer.Thereisnoonboardclockforbufferedpositionmeasurement,soyoumustsupplyanexternalsampleclock.
MeasuringPulseWidthYoucanusethecountersonyourmeasurementdevicetomeasurepulsewidth.Pulse-widthmeasurementsmeasurethetimebetweeneitherarisingandafallingedge,orafallingandarisingedge.
Theformulaforpulsewidthisasfollows:Pulsewidth(inseconds)=Count/CounterTimebaseRate
whereCountisthenumberofticksofthecountertimebasethatelapsedduringonepulsewidthoftheinputsignalbeingmeasured.TheCounterTimebaseRateisaknownfrequency(20MHzor100kHz)andallowsyoutomakefrequencyandtimemeasurements.Toconfigureameasurement,youspecifytheexpectedrangeoftheinputsignal.Basedonthisrange,NI-DAQmxautomaticallypickstheinternaltimebasethatprovidesthehighestresolutionforyourmeasurementandusesitasthecountertimebase.Dependingonthephaseoftheinputsignalinrelationtothestartofthemeasurement,thefirstsampleofcontinuousmeasurementsisofteninvalid.Forinstance,ifyouareperformingacontinuousperiodmeasurement,andyoustartthemeasurementwhentheinputsignalishalfwaythroughitscurrentcycle,themeasuredperiodforthefirstsampleishalfofitsexpectedvalue.Subsequentsamplesindicatethecorrectvaluessincetheyareguaranteedtohaveseenafullperiodoftheinputsignal.Forthisreason,thefirstsampleofcontinuousperiod,pulse-width,andsemiperiodmeasurementsoftenindicatesasmallervaluethantheactualvalue.Forcontinuousfrequencymeasurements,thefirstsampleoftenindicatesahigherfrequencythantheactualfrequency.
MeasuringSemiperiodYoucanusethecountersonyourmeasurementdevicetomeasuresemiperiod.Semiperiodmeasurementsmeasurethetimebetweenconsecutiveedges,alternatingbetweenhightimeandlowtime.
Theformulaforsemiperiodisasfollows:Semiperiod(inseconds)=Count/CounterTimebaseRate(inHz)
whereCountisthenumberofticksofthecountertimebasethatelapsedduringthehighorlowtimeofthesignaltomeasure.TheCounterTimebaseisaclockwithaknownfrequency(20MHzor100kHz)andallowsyoutomakefrequencyandtimemeasurements.Toconfigureameasurement,specifytheexpectedrangeoftheinputsignal.Basedonthisrange,NI-DAQmxautomaticallychoosestheinternaltimebasethatprovidesthehighestresolutionforyourmeasurementandusesitasthecountertimebase.Dependingonthephaseoftheinputsignalinrelationtothestartofthemeasurement,thefirstsampleofcontinuousmeasurementsisofteninvalid.Forinstance,ifyouareperformingacontinuousperiodmeasurement,andyoustartthemeasurementwhentheinputsignalishalfwaythroughitscurrentcycle,themeasuredperiodforthefirstsampleishalfofitsexpectedvalue.Subsequentsamplesindicatethecorrectvaluessincetheyareguaranteedtohaveseenafullperiodoftheinputsignal.Forthisreason,thefirstsampleofcontinuousperiod,pulse-width,andsemiperiodmeasurementsoftenindicatesasmallervaluethantheactualvalue.Forcontinuousfrequencymeasurements,thefirstsampleoftenindicatesahigherfrequencythantheactualfrequency.
MeasuringTwo-EdgeSeparationYoucanusethecountersonyourmeasurementdevicetomeasuretwo-edgeseparation.Two-edgeseparationisthetimebetweentherisingorfallingedgeofonedigitalsignal(SignalAinthefollowingfigure)andtherisingorfallingedgeofanotherdigitalsignal(SignalBinfigure).
Theformulafortwo-edgeseparationisasfollows:Two-EdgeSeparation(inseconds)=Count/CounterTimebaseRate(inhertz)
whereCountisthenumberofcountertimebaseticksbetweenthespecifiededgeofthefirstsignalandthespecifiededgeofthesecondsignal.TheCounterTimebaseRateisaknownfrequencyformakingfrequencyandtimemeasurements.Toconfigureameasurement,specifytheexpectedrangeoftheinputsignal.Basedonthisrange,NI-DAQmxautomaticallyselectstheinternaltimebasethatprovidesthehighestresolutionforyourmeasurementandusesthattimebaseasthecountertimebase.
MeasurementsUsingTwoCountersYoucanmeasuredigitalfrequencyortheperiodofaTTLsignalusingtwocounters.Twomethodsarethehigh-frequencymeasurementmethodandthelargerangemeasurementmethod.
High-FrequencyMeasurementMethodIfyoumeasurethedigitalfrequencyortheperiodofaTTLsignalwithhigherfrequency,youcanusethehigh-frequencymethod.Toperformmeasurementsusingthismethod,NI-DAQmxusesthepairedcountertogenerateapulsetrainwithaperiodspecifiedusingthemeasurementtimeattribute/property.Themeasurementtimeisgenerallymuchlargerthantheperiodoftheinputsignalbeingmeasuredtoreducequantizationerror.However,themeasurementtimemustbesmallenoughtokeepthecounterfromrollingover.Themeasurementcountercountsthenumberofperiodsoftheinputsignalthatoccurduringthemeasurementtime,averagestheresults,andreturnstheaveragedvalueintheReadfunction/VI.Thevaluereturnediscalculatedasfollows:Period(inseconds)=MeasurementTime/NumberofPeriodsCountedFrequency(inHertz)=NumberofPeriodsCounted/MeasurementTime
TipAsyouincreasetime,theaccuracyofthereadingalsoincreases.However,ifyouspecifytoolargeatime,thecountermayrollover,leadingtoaninaccuratefrequencyorperiodmeasurement.
LargeRangeMeasurementMethodIfyoumeasurethedigitalfrequencyortheperiodofaTTLsignal,youcanusethistwo-countermethodtomeasuresignalswithlargeranges.Thismethodisusefulwhenyouhaveawidelyvaryingsignaltomeasureandwouldlikeincreasedaccuracythroughouttheentirerange.Refertothequantizationerrorsectionformoreinformationonincreasingmeasurementaccuracywiththelarge-rangemeasurementmethod.Youcanalsousethismethodtomeasuresignalfrequenciesthatarefasterthanyourcountertimebaserateaslongastheinputsignaldoesnotexceedthemaximuminputfrequencysupportedbythecounter.Toperformmeasurementsusingthismethod,NI-DAQmxusesthepairedcountertodividetheinputsignalbyavaluespecifiedbyDivisor.However,youneedtobecarefultheDivisoryouchoosedoesnotcausethecountertorollover.ThisDivisorhastheeffectofshiftingthemeasurablefrequencyrangeupward.Forexample,ifyouareusinga24-bitcounterandyourCounterTimebaseRateis100kHz,themeasurablefrequencyrangeisapproximately0.006Hzto50kHz.However,withaDivisorof4,themeasurablefrequencyrangebecomes0.024Hzto200kHz.Thedividedinputsignalisthenmeasuredusingthelowfrequencyonecountermeasurementmethod.ThemeasuredperiodisthenscaledusingtheDivisor,andreturnedaccordingtothefollowingformula:Period=MeasuredPeriod/DivisorFrequency=Divisor/MeasuredPeriod
TipAsyouincreasethedivisor,theaccuracyofthereadingalsoincreases.However,ifyouspecifytoolargeadivisor,thecountermayrollover,leadingtoaninaccuratefrequencyorperiodmeasurement.
GlossaryPrefixes Numbers/Symbols A B C D E F G H I
J L M N O P R S T U V W
Symbol Prefix Valuen nano 10-9
µ micro 10-6
m milli 10-3
k kilo 103
M mega 106
Symbol Meaning% percent+ positiveof,orplus– negativeof,orminusΩ ohmº degree
Aacceleration Achangeinvelocitywithrespecttotime.accelerometer Asensorthatrepresentsaccelerationasavoltage.ADC Analog-to-digitalconverter—anelectronicdevice,often
anintegratedcircuit,thatconvertsananalogsignaltoadigitalvalue.
address Acharactercodethatidentifiesaspecificlocation(orseriesoflocations)inmemory.
ADE Applicationdevelopmentenvironment—someexamplesincludeLabVIEWandLabWindows/CVI.
advancedterminal
AterminalnotaccessiblefromtheI/Oconnectororaterminalnotcommonlyusedinmeasurementapplications.
AI Analoginput—acquisitionofdata.amplification Atypeofsignalconditioningthatimprovesaccuracyin
theresultingdigitizedsignalbyincreasingsignalamplituderelativetonoise.
analog Datarepresentedbycontinuouslyvariablephysicalquantities.
AO Analogoutput—generationofdata.angulardisplacement
Movementaboutanaxis,suchastheangularmotionoftheshaftofamotor.
angulardisplacementsensor
Adevicewhoseoutputsignalrepresentstherotationoftheshaft,suchasarotaryvariabledifferentialtransformer(RVDT).
API Applicationprogramminginterface—Alibraryoffunctions,classesorVIs,attributes,andpropertiesforcreatingapplicationsforyourdevice.
asynchronous 1. Hardware—asignalthatoccursorisacteduponatanarbitrarytime,withoutsynchronizationtoanothersignal,suchasareferenceclock.
2. Software—aVIorfunctionthatbeginsanoperationandreturnspriortothecompletionorterminationoftheoperation.
attenuation Thereductionofavoltageoracousticalpressure.Measuredreferencedtotheoriginalvoltage.
Bbandwidth Therangeoffrequenciespresentinasignal,ortherangeof
frequenciestowhichameasuringdevicecanrespond.baseaddress
Amemoryaddressthatservesasthestartingaddressforprogrammableregisters.Allotheraddressesarelocatedbyaddingtothebaseaddress.
bipolar Asignalrangethatincludesbothpositiveandnegativevalues(forexample,5Vto+5V).
BIOS BasicInput/OutputSystem—BIOSfunctionsarethefundamentallevelofanyPCorcompatiblecomputer.BIOSfunctionsembodythebasicoperationsneededforsuccessfuluseofthecomputerhardwareresources.
bit Thesmallestunitofdatausedinadigitaloperation.Bitsarebinary,sotheycanbeeithera1ora0.
buffer Insoftware,temporarystorageforacquiredorto-be-generatedsamples.
bus Thegroupofconductorsthatinterconnectindividualcircuitryinacomputer.Typically,abusistheexpansionvehicletowhichI/Oorotherdevicesareconnected.ExamplesofPCbusesaretheISAbusandPCIbus.
CCSeries Afamilyofdevicesormodulesusedforanaloginput,
analogoutput,digitalinput/output,andcounter/timerapplications.CSeriesdevicesworkwithchassisbasedontheCompactDAQ,CompactRIO,andotherarchitectures,andarecomponentsoftheNIUSB-9XXXdevices.
cDAQ TheprefixoftheproductmodelnameofaCompactDAQdevice,suchasNIcDAQ-9172.
CH Channel.channel 1. Physical—aterminalorpinatwhichyoucan
measureorgenerateananalogordigitalsignal.Asinglephysicalchannelcanincludemorethanoneterminal,asinthecaseofadifferentialanaloginputchanneloradigitalportofeightlines.Thenameusedforacounterphysicalchannelisanexceptionbecausethatphysicalchannelnameisnotthenameoftheterminalwherethecountermeasuresorgeneratesthedigitalsignal.
2. Virtual—acollectionofpropertysettingsthatcanincludeaname,aphysicalchannel,inputterminalconnections,thetypeofmeasurementorgeneration,andscalinginformation.YoucandefineNI-DAQmxvirtualchannelsoutsideatask(global)orinsideatask(local).ConfiguringvirtualchannelsisoptionalinTraditionalNI-DAQ(Legacy)andearlierversions,butisintegraltoeverymeasurementyoutakeinNI-DAQmx.InTraditionalNI-DAQ(Legacy),youconfigurevirtualchannelsinMAX.InNI-DAQmx,youcanconfigurevirtualchannelseitherinMAXorinaprogram,andyoucanconfigurechannelsaspartofataskorseparately.
3. Switch—aswitchchannelrepresentsanyconnectionpointonaswitch.Itmaybemadeupofoneormoresignalwires(commonlyone,two,orfour),dependingontheswitchtopology.Avirtualchannelcannotbecreatedwithaswitchchannel.SwitchchannelsmaybeusedonlyintheNI-DAQmxSwitchfunctionsandVIs.
clock Aperiodicdigitalsignal.CMRR Common-moderejectionratio—ameasureoftheability
ofaninstrumenttorejectinterferencefromacommon-modesignal,usuallyexpressedindecibels(dB).
codewidth ThesmallestdetectablechangeinaninputvoltageofaDAQdevice.
cold-junctioncompensation
Amethodofcompensatingforinaccuraciesinthermocouplecircuits.
CompactDAQ AnarchitectureorchassisforCSeriesdevices.configurationtree
ReferstotheleftwindowinMAX,whichcontainsitemssuchasDataNeighborhoodandDevicesandInterfaces.
counter/timer Acircuitthatcountsdigitaledges.Countersandtimersusuallyhavefrom16bitsto48bits(sometimesmore)countingcapability.Thetotalnumberofcountspossibleequals2N,whereNisthenumberofbitsinthecounter.Whentheedgescountedareproducedbyaclock,elapsedtimecanbecomputedfromthenumberofedgescountediftheclockfrequencyisknown.
convertclock TheclockonamultiplexeddevicethatdirectlycausesADCconversions.
customscale AmethodofinstructingNI-DAQmxtoapplyadditionalscalingtoyourdata.RefertotheCreateScalefunction/VIinyourreferencehelp.
DDAC Digital-to-analogconverter—anelectronicdevice,oftenan
integratedcircuit,thatconvertsadigitalvalueintoacorrespondinganalogvoltageorcurrent.
DAQ Refertodataacquisition.DAQAssistant
Agraphicalinterfaceforconfiguringmeasurementtasks,virtualchannels,andscales.
DAQdevice Adevicethatacquiresorgeneratesdataandcancontainmultiplechannelsandconversiondevices.DAQdevicesincludeplug-indevices,PCMCIAcards,andDAQPaddevices,whichconnecttoacomputerUSBor1394(FireWire)port.SCXImodulesareconsideredDAQdevices.
data Samples.dataacquisition(DAQ)
1. Acquiringandmeasuringanalogordigitalelectricalsignalsfromsensors,transducers,andtestprobesorfixtures.
2. Generatinganalogordigitalelectricalsignals.
dB Decibel—theunitforexpressingalogarithmicmeasureoftheratiooftwosignallevels:dB=20log10V1/V2,forsignalsinvolts.
DC directcurrentdelayfromsample
Theamountoftimetowaitafterreceivingasampleclockedgebeforebeginningtheacquisitionofasample.
delayfromstart
TheamountoftimetowaitafterreceivingaStartTriggerbeforebeginningtheoperation.
determinism Characteristicofasystemthatdescribeshowconsistentlyitcanrespondtoexternaleventsorperformoperationswithinagiventimelimit.
device 1. Aninstrumentorcontrolleryoucanaccessasasingleentitythatcontrolsormonitorsreal-worldI/O
points.Adeviceoftenisconnectedtoahostcomputerthroughsometypeofcommunicationnetwork.
2. SeealsoDAQdeviceandmeasurementdevice.
digital ATTLsignal.Refertoedge.DIO digitalinput/outputDMA directmemoryaccess—Amethodoftransferringdata
betweenabufferandadevicethatisusedmostoftenforhigh-speedoperations.
driver Softwareuniquetothedeviceortypeofdevice,andincludesthesetofcommandsthedeviceaccepts.
drop-downlistbox
Agraphicalboxwithadownarrowbuttonthatletsyouselectvaluesoroptionsfromalist.Toselectavalueoroptionintheselectionbox,clickthedownarrowforacompletelistofvaluesoroptions,thenuseyourarrowkeysormousetoselectavalueoroptionfromthelist.
DSUB D-subminiatureconnectorDUT deviceundertest—adeviceusedfortestingpurposes.
EESeries Astandardarchitectureforinstrumentation-class,
multichanneldataacquisitiondevices.edge AdigitaledgeisasinglerisingorfallingTTLtransition.An
analogedgeisdefinedbytheslope,level,andhysteresissettings.
event Adigitalsignalproducedfromadeviceorcircuit.Foranadvanceddiscussionofevents,refertoEvents.
excitation Supplyingavoltageorcurrentsourcetoenergizeasensororcircuit.
Ffalltime Thetimeforasignaltotransitionfrom90%to10%ofthe
maximumsignalamplitude.filtering Atypeofsignalconditioningthatyoucanusetoremove
unwantedfrequencycomponentsfromthesignalyouaremeasuring.
FIFO AtypeofmemorythatimplementsaFirstInFirstOutstrategyinwhichsamplesareremovedintheordertheywerewritten.FIFOsaretypicallyusedasintermediatebuffersbetweenanADCorDACandthememorybuffer.
floatingsignalsources
Signalsourceswithvoltagesignalsthatarenotconnectedtoanabsolutereferenceorsystemground.
Ggain Thefactorbywhichasignalisamplified,oftenexpressedin
decibels(dB).Gainasafunctionoffrequencyiscommonlyreferredtoasthemagnitudeofthefrequencyresponsefunction.
groundedsignalsources
Signalsourceswithvoltagesignalsthatarereferencedtoasystemground,suchastheearthorabuildingground.Groundedsignalsourcesarealsocalledreferencedsignalsources.
Hhardware Thephysicalcomponentsofacomputersystem,suchasthe
circuitboards,plug-inboards,chassis,enclosures,peripherals,andcables.
hardwaretiming
Ameansofcontrollingsignalgeneration.Adigitalsignal,suchasaclockonaDAQdevice,controlstherateofgeneration.
hardwaretriggering
Aformoftriggeringinwhichthesourceofthetriggerisananalogordigitalsignal.RefertoSoftwareTrigger.
hex Hexadecimal—abase-16numberingsystem.hysteresis Awindowaroundatriggerlevelthatisoftenusedtoreduce
falsetriggeringduetonoiseorjitterinthesignal.Hz Hertz—cyclespersecondofaperiodicsignal.
IIEEEP1451
FamilyofIEEEstandardsdefiningavarietyofsmarttransducerinterfaces.AllofthestandardswithinthisfamilysupporttheconceptofaTEDSthatprovidesself-identificationandplugandplayoperationtotransducers.
IEEEP1451.4
AnIEEEstandardthatdefinestheconceptofplugandplaysensorswithanalogsignals.ThisisaccomplishedwiththeadditionofaTEDSinmemory,typicallyanEEPROM,embeddedwithinthesensorandcommunicatedthroughasimple,low-costserialconnection.
instrumentdriver
Refertodriver.
internalchannel
AphysicalchannelnotaccessiblefromanI/Oconnector.Internalchannelsareoftenusedforcalibrationandareintendedforadvancedapplications.
interrupt Amethodwherebyadevicenotifiesthecomputerofsomeconditiononthedevicethatrequiresthecomputer'sattention.Whenthisconditionisarequestfordataoranotificationofavailabledata,interruptsareusedasadatatransfermechanism.
interruptlevel
Therelativepriorityatwhichadevicecaninterrupt.
I/O Input/Output—thetransferofdatato/fromacomputersysteminvolvingcommunicationschannels,operatorinterfacedevices,and/ordataacquisitionandcontrolinterfaces.
IRQ InterruptReQuest.ISA IndustryStandardArchitecture—Alsoreferstoacommon
PCexpansionbus.isolation Atypeofsignalconditioninginwhichyouisolatethe
transducersignalsfromthecomputer.Isolationmakessurethemeasurementsfromthemeasurementdevicearenotaffectedbydifferencesingroundpotentials.
Jjitter Theamountoftimethattheloopcycletimevariesfromthedesired
time.
LLED light-emittingdiode—asemiconductorlightsource.line Anindividualsignalinadigitalport.Thedifference
betweenabitandalineisthatthebitreferstotheactualdatatransferred,andthelinereferstothehardwarethebitistransferredon.However,thetermslineandbitarefairlyinterchangeable.Forexample,an8-bitportisthesameasaportwitheightlines.
lineardisplacement
Movementinonedirectionalongasingleaxis.
lineardisplacementsensor
Adevicethatmeasureslineardisplacement.
linearization Atypeofsignalconditioninginwhichsoftwarelinearizesthevoltagelevelsfromtransducers,sothevoltagescanbescaledtomeasurephysicalphenomena.
LSB leastsignificantbit—oftenusedtorefertothesmallestvoltagechangedetectablebyanA/DconverterorthesmallestvoltagechangethatcanbegeneratedbyaD/Aconverter.
LVDT Linear-voltagedifferentialtransformer—Asensorusedtomeasurelineardisplacement.AnLVDTconsistsofapassivetransformwithoneprimaryandtwosecondarywindings.TheprimarywindingisexcitedbyanaudiofrequencyrangeACvoltage,whoseimbalancebetweenthesecondarywindings,isproportionaltothedisplacement.Thesecondarywindingsareidentical,butarenormallyconnectedwithoppositepolarity,sothetransduceratrestingpositionwillhavezerooutputvoltage.
MMSeries Astandardarchitectureforinstrumentation-class,
multichanneldataacquisitiondevices.MAX Measurement&AutomationExplorer—Acentralized
configurationenvironmentthatallowsyoutoconfigureallofyourNationalInstrumentsdevices.
measurementdevice
DAQdevicessuchastheMSeriesmultifunctionI/O(MIO)devices,SCXIsignalconditioningmodules,andswitchmodules.
memorybuffer
Refertobuffer.
memorymapping
Atechniqueforreadingandwritingtoadevicedirectlyfromyourprogram,whichavoidstheoverheadofdelegatingthereadsandwritestokernel-levelsoftware.Delegationtothekernelissafer,butslower.Memorymappingislesssafebecauseanentire4KBpageofmemorymustbeexposedtoyourprogramforthistowork,butitisfaster.
microphone Atransducerthatconvertsacousticalwavesintoelectricalsignals.
MIO multifunctionI/O—Designatesacategoryofdataacquisitiondevicesthathavemultipleanaloginputchannels,digitalI/Ochannels,timing,andoptionally,analogoutputchannels.AnMIOproductcanbeconsideredaminiaturemixedsignaltester,duetoitsbroadrangeofsignaltypesandflexibility.ItisalsoknownasmultifunctionDAQ.AnESeriesdeviceisanexampleofanMIOdevice.
module Aboardassemblyanditsassociatedmechanicalparts,frontpanel,optionalshields,andsoon.Amodulecontainseverythingrequiredtooccupyoneormoreslotsinamainframe.SCXIandPXIdevicesaremodules.
multiplexed AnSCXIoperatingmodeinwhichanaloginputchannels
mode aremultiplexedintoonemoduleoutputsothatthecabledDAQdevicehasaccesstothemultiplexedoutputaswellastheoutputsonallothermultiplexedmodulesinthechassisthroughtheSCXIbus.Alsocalledserialmode.
multiplexer Aswitchingdevicewithmultipleterminalsthatsequentiallyconnectseachofitsterminalstoasingleterminal,typicallyathighspeeds.Oftenusedtomeasureseveralsignalswithasingleanaloginputchannel.
multithreading Runningtasksofanapplicationforashortamountoftimetogivetheimpressionofmultipletasksrunningsimultaneously.
NNI-DAQ DriversoftwareincludedwithallNImeasurementdevices.
NI-DAQisanextensivelibraryofVIsandfunctionsyoucancallfromanapplicationdevelopmentenvironment(ADE),suchasLabVIEW,toprogramallthefeaturesofanNImeasurementdevice,suchasconfiguring,acquiringandgeneratingdatafrom,andsendingdatatothedevice.
NI-DAQ7.x IncludestwoNI-DAQdrivers—NI-DAQmxandTraditionalNI-DAQ(Legacy)—eachwithitsownAPI,hardwareconfiguration,andsoftwareconfiguration.
NI-DAQmx ThelatestNI-DAQdriverwithnewVIs,functions,anddevelopmenttoolsforcontrollingmeasurementdevices.TheadvantagesofNI-DAQmxoverearlierversionsofNI-DAQincludetheDAQAssistantforconfiguringchannelsandmeasurementtasksforyourdeviceforuseinLabVIEW,LabWindows/CVI,andMeasurementStudio;increasedperformancesuchasfastersingle-pointanalogI/O;andasimplerAPIforcreatingDAQapplicationsusingfewerfunctionsandVIsthanearlierversionsofNI-DAQ.
NI-DAQmxSimulatedDevice
AreplicaofadevicecreatedusingtheNI-DAQmxSimulatedDeviceoptionintheCreateNewmenuofMAXforthepurposeofoperatingafunctionorprogramwithouthardware.AnNI-DAQmxsimulateddevicebehavessimilarlytoaphysicaldevice.Itsdriverisloaded,andprogramsusingitarefullyverified.
nonlinearity Ameasureinpercentageoffull-scalerange(FSR)oftheworst-casedeviationfromtheidealtransferfunction—astraightline.
ThisspecificationisincludedonlyforDAQproducts,suchassignalconditioningproducts,thatdonothaveanADC.BecauseaproductwiththisspecificationcanalsobeusedwithaDAQproductwithanADC,thisnonlinearityspecificationmustbeaddedtotherelativeaccuracy
specificationoftheDAQproductwiththeADC.
NRSE Nonreferencedsingle-endedmode—allmeasurementsaremadewithrespecttoacommon(NRSE)measurementsystemreference,butthevoltageatthisreferencecanvarywithrespecttothemeasurementsystemground.
Oonboard Providedbythedataacquisitiondevice.onboardchannels
Channelsprovidedbytheplug-indataacquisitiondevice.
onboardclock
Thedefaultsourceforaparticularclock.Usually,thedevicehasdedicatedacircuitforproducingthissignalanditsonlypurposeistoactasthesourceforacertainclock.
onboardmemory
Memoryprovidedbyadevicefortemporarystorageofinputoroutputdata.Typically,onboardmemoryisaFIFO,whichisdistinctfromcomputermemory.
operatingsystem
Base-levelsoftwarethatcontrolsacomputer,runsprograms,interactswithusers,andcommunicateswithinstalledhardwareorperipheraldevices.AlsoreferredtoasOS.
Pparallelmode
AtypeofSCXIoperatingmodeinwhichthemodulesendseachofitsinputchannelsdirectlytoaseparateanaloginputchannelofthedeviceconnectedtothemodule.
patternI/O patterninputandoutput—adigitalI/Ooperationonwhichaclocksignalinitiatesadigitaltransfer.Becausetheclocksignalisaconstantfrequency,youcangenerateandreceivepatternsataconstantrate.
PCI peripheralcomponentinterconnect—ahigh-performanceexpansionbusarchitectureoriginallydevelopedbyInteltoreplaceISAandEISA.PCIhasachievedwidespreadacceptanceasastandardforPCsandworkstations,anditoffersatheoreticalmaximumtransferrateof132Mbytes/s.
PCMCIA Anexpansionbusarchitecturethathasfoundwidespreadacceptanceasadefactostandardinnotebook-sizecomputers.PCMCIAoriginatedasaspecificationforadd-onmemorycardswrittenbythePersonalComputerMemoryCardInternationalAssociation.
PFI programmablefunctioninterface—generalpurposeinputterminals,fixedpurposeoutputterminals.ThenameofthefixedoutputsignalisoftenplacedontheI/Oconnectornexttotheterminalasahint.
physicalchannel
Refertochannel.
PID proportionalintegralderivative—Combinationofproportional,integral,andderivativecontrolactions.Referstoacontrolmethodinwhichthecontrolleroutputisproportionaltotheerror,itstimehistory,andtherateatwhichitischanging.Theerroristhedifferencebetweentheobservedanddesiredvaluesofavariablethatisundercontrolaction.
pin Refertoterminal.
Poisson'sRatio
Thenegativeratioofthestraininthetransversedirection(perpendiculartotheforce)tothestrainintheaxialdirection(paralleltotheforce).
port Acollectionofdigitallines.Usuallythelinesaregroupedintoeithera8-bitor32-bitport.MostESeriesdeviceshaveone8-bitport.
portwidth Thenumberoflinesinaport.Forexample,mostESeriesdeviceshaveoneportwitheightlines;therefore,theportwidthiseight.
positionsensor
Refertolineardisplacementsensor.
posttriggersamples
IfthereisnoReferenceTrigger,posttriggersamplesarethedataacquiredafterthetaskisstarted.IfthereisaReferenceTrigger,thisisthedataacquiredaftertheReferenceTrigger.
plugandplaydevices
DevicesthatdonotrequireDIPswitchesorjumperstoconfigureresourcesonthedevices.Alsocalledswitchlessdevices.
plugandplaysensors
AtransducerwithanassociatedTEDS—includesbothVirtualTEDSandsmartTEDSsensors.
pretriggersamples
DataacquiredbeforetheoccurrenceoftheReferenceTrigger.
pretriggering Thetechniqueusedonameasurementdevicetokeepacircularbufferfilledwithsamples,sothatwhentheReferenceTriggerconditionsaremet,thebufferincludessamplesleadinguptothetriggerconditionaswellassamplesacquiredimmediatelyafterthetrigger.
programmedI/O
Adatatransfermechanisminwhichabufferisnotusedandinstead,thecomputerreadsandwritesdirectlytothedevice.
propagationdelay
Theamountoftimerequiredforasignaltopassthroughacircuit.
pulsed Aformofcountersignalgenerationbywhichapulseis
output generatedwhenacounterreachesacertainvalue.PWM pulse-widthmodulationPXI PCIeXtensionsforInstrumentation—arugged,open
systemformodularinstrumentationbasedonCompactPCI,withspecialmechanical,electrical,andsoftwarefeatures.ThePXIstandardwasoriginallydevelopedbyNationalInstrumentsin1997andisnowmanagedbythePXISystemsAlliance.
PXItriggerbus
ThetimingbusthatconnectsPXIDAQdevicesdirectly,bymeansofconnectorsbuiltintothebackplaneofthePXIchassis,forprecisesynchronizationoffunctions.ThisbusisfunctionallyequivalenttotheRTSIbusforPCIDAQdevices.
Rrange Theminimumandmaximumanalogsignallevelsthatthe
ADCcandigitize.raw Datathathasnotbeenchangedinanyway.Forinput,data
isreturnedexactlyasreceivedfromthedevice.Foroutput,dataiswrittenasistothedevice.Refertounscaledandscaled.
realtime Apropertyofaneventorsysteminwhichsamplesareprocessedastheyareacquiredinsteadofbeingaccumulatedandprocessedatalatertime.
referencedsignalsource
Signalsourceswithvoltagesignalsthatarereferencedtoasystemground,suchastheearthorabuildingground.Alsocalledgroundedsignalsources.
resolution Thesmallestamountofinputsignalchangethatadeviceorsensorcandetect.Thetermdiscriminationisalsousedforresolution.
risetime Thetimeforasignaltotransitionfrom10%to90%ofthemaximumsignalamplitude.
route Aconnectionbetweenapairofterminals.Anytimethesourceordestinationterminalofasignalisspecified,arouteiscreated.
RSE Referencedsingle-endedmode—allmeasurementsaremadewithrespecttoacommonreferencemeasurementsystemoraground.Alsocalledagroundedmeasurementsystem.
RTD Resistancetemperaturedetector—ametallicprobethatmeasurestemperaturebasedonitscoefficientofresistivity.
RTSIbus Real-timesystemintegrationbus—theNItimingbusthatconnectsDAQdevicesdirectly,bymeansofconnectorsontopofthedevices,forprecisesynchronizationoffunctions.ThisbusisfunctionallyequivalenttothePXITriggerbusforPXIDAQdevices.
RVDT rotaryvariabledifferentialtransformer—asensorwhoseoutputsignalrepresentstherotationoftheshaft.
Ss secondsS samples.Refertosample.S/s samplespersecond—usedtoexpresstherateatwhicha
measurementdevicesamplesananalogsignal.sample Asinglemeasurementfromasinglechannelor,foroutput,
asinglegenerationtoasinglechannel.sampleclock
Theclockthatinitiatesanacquisitionofonesamplefromeachchannelinthescanlist.Forexample,witheachsampleclockpulse,MSeriesdevicesacquireasampleoneachanaloginputchannelinataskbymultiplexingeachchannelthroughasingleADC.Onsimultaneoussamplingdevices,thesampleclockinitiatesthesimultaneousacquisitionofonesamplefromeachchannelinthetaskthroughadedicated,per-channelADC.Nomultiplexing(andthereforenoconvertclock)isnecessaryforSSeriesdevices.
sampleclockrate
Refertosamplerate.
samplerate Thenumberofsamplesperchannelpersecond.Forexample,asamplerateof10S/smeanssamplingeachchannel10timespersecond.
scale Datathathasbeenmathematicallytransformedintoengineeringunits.Othermanipulationsalsocanbedonesuchasreorderingtomatchthechannelorder.
scanning Methodofsequentiallyconnectingchannels.SCC Signalconditioningcomponent—lowchannelcountanalog
ordigitalI/OmodulesforconditioningDAQsystems.SCXI SignalConditioningeXtensionsforInstrumentation—the
NIproductlineforconditioninglow-levelsignalswithinanexternalchassisnearsensorssothatonlyhigh-levelsignalsaresenttomeasurementdevicesinthenoisyPC
environment.SCXIisanopenstandardavailableforallvendors.
sensor Adevicethatrespondstoaphysicalstimulus(heat,light,sound,pressure,motion,flow,andsoon)andproducesacorrespondingelectricalsignal.
signal Ameansofconveyinginformation.Ananalogwaveform,aclock,andasingledigital(TTL)edgeareallexamplesofsignals.
signalconditioning
Themanipulationofsignalstopreparethemfordigitizing.
smartTEDSsensor
Atransducerwithabuilt-inself-identificationEEPROMthatprovidestheTEDS.
softwaretiming
Ameansofcontrollingsignalgeneration.Thesoftware,suchasNI-DAQmx,andtheoperatingsystemcontroltherateofgeneration.
softwaretrigger
AVIorfunctionthat,whenitexecutes,triggersanactionsuchasstartinganacquisition.
sourceimpedance
Aparameterofsignalsourcesthatreflectscurrent-drivingabilityofvoltagesources(lowerisbetter)andthevoltage-drivingabilityofcurrentsources(higherisbetter).
staticAO Analogoutputoperationsthatusesoftwaretiming.staticdigitalI/O
Software-timeddigitalI/Ooperationsthatdonotinvolvetheuseofcontrolsignalsindatatransfers.Alsoknownassoftware-timedI/OorunstrobedI/O.
strain Theamountofdeformationofabodyduetoanappliedforce.
strobedI/O Anyoperationinwhicheverydatatransferistimedbyhardwaresignals.Inthecaseofsampleclocktiming,thishardwaresignalisaclockedge.InthecaseofhandshakingI/O,hardwaresignalsinvolvetwoorthreehandshakinglines.
STC systemtimingcontrollersynchronous 1. Hardware—asignalthatoccursorisacteduponin
synchronywithanothersignal,suchasareferenceclock.
2. Software—aVIorfunctionthatbeginsanoperationandreturnsonlywhentheoperationiscomplete.
Ttask InNI-DAQmx,acollectionofoneormorechannels,
timing,andtriggeringandotherpropertiesthatapplytothetaskitself.Conceptually,ataskrepresentsameasurementorgenerationyouwanttoperform.
taskbuffer Refertobuffer.TCR temperaturecoefficientofresistance—theaverage
resistancechangeperonedegreeattemperaturesbetween0°Cand100°C.
TEDS transducerelectronicdatasheet—standardizeddatastructure,definedbyIEEE1451.4,fordescribingsensors,typicallystoredinnonvolatilememorywithinasensor.Themanufacturerofthesensorstores,intothismemory,initialinformationsuchasmanufacturername,sensortype,modelnumber,serialnumber,andcalibrationdata.TheTEDSdatastructurealsoincludesspaceforcustominformationsuchaschannelID,location,position,direction,tagnumber,etc.Alternatively,theTEDSdatamaybestoredinafileordatabaserecordasaVirtualTEDS.ForinformationonIEEE1451.4-compliantTEDSsensors,refertowww.ni.com/pnp.
TEDSClassISensor
AsmartTEDSsensorwithaconstant-currentpoweredtransducerwithatwo-wireinterface,suchasanaccelerometer.ClassItransducersalsoincludediodesoranalogswitcheswithwhichthemultiplexingoftheanalogsignalwiththedigitalTEDSinformationonthesinglepairofwiresispossible.Thedigitalportionofthemixed-modeinterface(Class1orClass2)isbasedonthe1-WireprotocolfromMaxim/DallasSemiconductor.
TEDSClassIISensor
AsmartTEDSsensorwithseparatewiresfortheanaloganddigitalportionsoftheTEDSmixed-modeinterface.Theanaloginput/outputofthetransducerisleftunmodified,andthedigitalTEDScircuitisaddedinparallel,suchasthermocouples,RTDs,andbridge-based
sensors.Thedigitalportionofthemixed-modeinterface(Class1orClass2)isbasedonthe1-WireprotocolfromMaxim/DallasSemiconductor.
terminal AnamedlocationonaDAQdevicewhereasignaliseithergenerated(outputorproduced)oracquired(inputorconsumed).
terminalcount
Whencountingup,anNbitcounterreachesitsterminalcountat2N-1.AnNbitcountercountingdownreachesitsterminalcountat0.
thermistor Asemiconductorsensorthatproducesarepeatablechangeinelectricalresistanceasafunctionoftemperature.Mostthermistorshaveanegativetemperaturecoefficient.
thermocouple Atemperaturesensorcreatedbyjoiningtwodissimilarmetals.Thejunctionproducesasmallvoltageasafunctionofthetemperature.
threshold Thevoltagelevelasignalmustreachforatriggertooccur.
tick Adigitaledgeofaclock.timebase Aclockthatisdivideddowntoproduceanotherclockora
clockprovidedtoacounterformeasuringelapsedtime.TraditionalNI-DAQ(Legacy)
AnupgradeoftheearlierversionofNI-DAQ.TraditionalNI-DAQ(Legacy)hasthesameVIsandfunctionsandworksthesamewayasNI-DAQ6.9.x,exceptyoucanusebothTraditionalNI-DAQ(Legacy)andNI-DAQmxonthesamecomputer,andsomehardwareisnolongersupported.
transducer Refertosensor.transducerexcitation
Atypeofsignalconditioningthatusesexternalvoltagesandcurrentstoexcitethecircuitryofasignalconditioningsystemintomeasuringphysicalphenomena.
trigger Anysignalthatcausesadevicetoperformanaction,suchasstartinganacquisition.
TTL Transistor-transistorlogic—asignalhavingtwodiscretelevels,ahighandalowlevel.
Uunipolar Asignalrangethatisalwayspositive(forexample,0to+10
V).unscaled Samplesintheintegerformthatthehardwareproducesor
requires.Althoughnomathematicaltransformationsareappliedtounscaleddata,othermanipulationsmaybedonesuchasreorderingtomatchthechannelorder.
unstrobedI/O
RefertostaticdigitalI/O.
USBDAQ
AUSB-basedfamilyofdevicesusedforanaloginput,analogoutput,digitalinput/output,andcounter/timerapplications.SomeexampledevicesincludetheNIUSB-9201,NIUSB-9211,NIUSB-9215,NIUSB-9221,NIUSB-9233,andNIUSB-9237devices.ThesedevicesarealsoreferredtoasUSBDAQwithIntegratedSignalConditioning.
VV voltsVI Refertovirtualinstrument.virtualchannel
Refertochannel.
virtualinstrument
AprograminLabVIEWthatmodelstheappearanceandfunctionofaphysicalinstrument.
VISA VirtualInstrumentationSoftwareArchitecture.
Wwaveformdatatype
ALabVIEWdatatypethatbundlestiminginformationalongwiththedata.
WDT Refertowaveformdatatype.
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