Line:TheACpowerlinefrequencysignalisusedasthetriggeringsignal.Thismethodiseffectivewhenthemeasured
signalhasarelationshipwiththeAClinefrequency,especiallyformeasurementsoflowlevelACnoiseofaudio
equipment,thyristorcircuits,etc.
EXT:Thesweepistriggeredwithanexternalsignalappliedtotheexternaltriggerinputterminal.Anexternalsignal
whichhasaperiodicrelationshipwithrespecttothemeasuredsignalisused.Sincethemeasuredsignalisnotused
asthetriggeringsignal,thewaveformscanbedisplayedmoreindependentthanthemeasuredsignal.
(3)FunctionsofTRIGLEVELcontrolandSLOPEswitch:
Asweeptriggerisdevelopedwhenthetriggersourcesignalcrossesapresetthresholdlevel.RotationoftheTRIGLEVEL
controlvariesthethresholdlevel.Inthe"+"direction,thetriggeringthresholdshiftstoamorepositivevalue,andinthe"-"
direction,thetriggeringthresholdshiftstoamorenegativevalue.Whenthecontroliscentered,thethresholdlevelissetat
theapproximateaverageofthesignalusedasthetriggeringsource.
TheTRIGLEVELcontroladjuststhestartofthesweeptoalmostanydesiredpointonawaveform.Onsinewavesignals,
thephaseatwhichsweepbeginsisvariable.NotethatiftheTRIGLEVELcontrolisrotatedtowarditsextreme+or-setting,
nosweepwillbedevelopedinheNORMtriggermodebecausetriggeringthresholdexceedsthepeakamplitudeofthe
syncsignal.
Slope
"-"Range
Figure4--6
Level
+
-
Slope
"+"Range
19
WhentheTRIGSLOPEswitchissettothe(+)position(up),
thesweepisdevelopedfromthetriggersourcewaveformasit
crossesthethresholdlevelinapositive-goingdirection.When
theTRIGSLOPEcontrolissettothe(-)position(down),asweep
triggerisdevelopedformthetriggersourcewaveformasit
crossesthethresholdlevelinanegative-goingdirection.This
switchselectstheslope(polarity)triggeringsignalasshownin
Figure4-6
(4)FunctionofTRIGALTswitch:
TheTRIGALTswitchisusedtoselectalternatetriggeringandalternatedisplaywhentheDUAL-traceVERTMODEis
selected(theswitchhasoneffectintheCH1,CH2,orADDmodes).Inthealternatetriggeringmode(whendual-traceoperation
isselected),thetriggersourcealternatesbetweenchannellandchannel2witheachsweep.Thisisconvenientforchecking
amplitudes,waveshape,orwaveformperiodmeasurements,andevenpermitssimultaneousobservationoftwowaveformswhich
arenot-relatedinfrequencyorperiod.However,thissettingisnotsuitableforphaseortimingcomparisonmeasurements.For
suchmeasurements,bothtracesmustbetriggeredbythesamesyncsignal.
WhentheCHOPandtheTRIGALTswitchesarebothengagedduringdual-traceoperation,synchronizationofthedisplayisnot
possiblebecausethechoppingsignalbecomesthetrigger.UsetheALTmodebyitself,orselectCH1orCH2astriggersource.
SettheTIMEDIVcontroltodisplaythedesirednumberofcyclesofewaveform.Iftherearetoomanycyclesdisplayedfor
goodresolution,switchtoafastersweepspeedIfonlyalineisdisplayed,tryaslowersweepspeed.Whenthesweepspeedis
fasterthanthewaveformbeingobserved,onlypartofitwillbedisplayed,whichmayappearasastraightlineforasquarewave
orpulsewaveform.
Whenacertainpartofthedisplayedwaveformisneededtobeexpandedtimewise,afaster
sweepspeedmaybeused.However,iftherequiredportionisapartfromthestartingpoint
ofthesweep,therequiredportionmayrunofftheCRTscreen.Insuchacase,push
thex1MAGbutton.Whenthishasbeendone,thedisplayedwaveformwillbe
expanded10timestotherightandletwiththecenterofscreenasthecenterof
xpansion.Thesweeptimeduringthemagnificationoperationisasfollows:
(ValueindicatedbyTIME/DIVswitch)x1/10
Thus,theunmagnifiedmaximumsweepspeed(luebeincreased
withthemagnificationasfollows: luSec/DIVx1/10=100nSec/DIV
4.7TIME/DlVcontrol
4.8SweepMagnification
/th
.
in
0f
e
Sc/DIV)can
10xmagnification
Anypartcanbecoveredby
meansofPOSITIONcontrol
Figure4-7
20