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WhenALT/CHOPswitchisreleased(ALTMODE),theinputsignalsappliedrespectivelytoCHlandCH2appearsonthe
screenalternativelyateachsweep.Thissettingisusedwhenthesweeptimeisshortin2-channelobservation.
WhenALT/CHOPswitchisengaged(CHOPMODE),theinputsignalsappliedtoCH1andCH2areswitchedatabout250KHz
Wheninthedualchanneloperation(DUALorADDmode),theCHlorCH2signalmustbeselectedforthetriggeringsource
signalbymeansoftheSOURCEswitch.IfbothCHlandCH2signalsareinasynchronizedrelationship,bothwaveformscanbe
displayedstationary;ifnot,onlythesignalselectedbytheSOURCEswitchcanbestationary.IftheTRIG.ALTpushswitchis
engaged,bothwaveformscanbedisplayedstationary.
AnalgebraicsumoftheCH1andCH2signalscanbedisplayedonthescreenbysettingtheVERTMODEswitchtotheADD
State.ThedisplayedsignalisthedifferencebetweenCHlandCH2signalsiftheCh2INVpushswitchisengaged.
Foraccurateadditionorsubtraction,itisaprerequisitethatthesensitivitiesofthetwochannelsareadjustedaccuratelyatthe
samevaluebymeansoftheVARIABLEknobs.VerticalpositioningcanbemadewiththePOSITIONknobofeitherchannel.
Inviewofthelinearityoftheverticalamplifiers,itismostadvantagetosetbothknobsintheirmid-positions.
Propertriggeringisessentialforefficientoperationofanoscilloscope.Theusermustbethoroughlyfamiliarwiththe
triggeringfunctionsandprocedures.
(1)FunctionsofMODEswitch:
AUTO:WhentheAUTOswitchisengaged,automaticsweepoperationisselected.inautomaticsweepoperation,thesweep
generatorfreerunstogenerateasweepwithoutatriggersignal.However,itautomaticallyswitchestotriggeredsweep
operationifanacceptabletriggersourcesignalispresent.TheAUTOpositionishandywhenfirstsettingupthescopeto
observeawaveform;Itprovidessweepforwaveformobservationuntilothercontrolscanproper1yset.Oncethecontrols
areset,operationisoftenswitchbacktotheNORMtriggeringmode,sinceitismoresensitive.Automaticsweepmustbe
usedforDCmeasurementsansignalsofsuchlowamplitudethattheywillnottriggerthesweep.
independentandatthesametimeappearonthescreen.Thissettingisusedwhenthesweeptimeislongin2-channelobservation
4.5ADDOperation
4.6Triggering
17
NORM:TheNORMswitchprovidesnormalredsweepoperationThesweepremainsatrestuntiltheselectedtrigger
sourcesignalcrossesthethresholdlevelsetbytheTRIGLEVELcontrol.Thetriggercausesonesweeptobegenerated.
afterwhichsweepagainremainsatrestuntiltriggered.IntheNORMposition,therewillbenotraceunless
anadequatetriggersignalispresent-IntheALTmodeofdualtraceoperationwithNORMsweepselected,therewill
betraceunlessbothchannel1and2signalsareadequatefortriggering.
TV-V:SettingtheMODEswitchtotheTV-Vpositionpermitsselectionofverticalsyncpulsesforsweeptriggeringwhen
viewingcompositevideowaveforms.Verticalsyncpulsesareselectedastriggertopermitviewingofverticalfields
andframesofvideo.Asweeptimeof2ms/DIVisappropriateforviewingfieldsofvideoand5ms/DIVforcomplete
frames(twointerlacedfields)ofvideo.
TVH:SettingtheMODEswitchtotheTV-Hpositionpermitsselectionofhorizontalsyncpulsesforsweeptriggeringwhen
viewingcompositevideowaveforms.Horizontalsyncpulsesareselectedastriggertopermitviewingofhorizontal
fieldsofvideoAsweeptimeofabout10us/DIVisappropriatefordisplayinglinesofvideo.TheSWPVARcontrol
canbesettodisplaytheexactnumberofwaveformsdesired.
isoscilloscopesynchronizeswithonly()polarity,thatis,thesyncpulsesarenegativeandthevideoispositiveas
showninFigure4
(2)FunctionsofSOURCEswitch:
Thedisplayedsignalitselforatriggersignalwhichhasatime
relationshipwiththedisplayedsignalisrequiredtobeappliedtothe
triggercircuittodisplayastationarysignalontheCRTscreen.
TheSOURCEswitchisusedforselectingsuchatriggeringsource
CHl/CH2:Theinternaltriggermethodwhichisusedmostcommonly.Thesignalappliedtotheverticalinputterminal
isbranchedofffromthepreamplifierandisfedtothetriggercircuitthroughtheVERTMODEswitch.Sincethe
triggeringsignalisthemeasuredsignalitself,astablewavefromcanbereadilydisplayedontheCRTscreen.When
intheDUALorADDoperation,thesignalselectedbytheSOURCEswitchisusedasthetriggeringsourcesigna1.
trigge.
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.
Th-
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Figure4-5
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