lecroy 11_LTXXX-OM-E_Ch7 电路图.pdf

《lecroy 11_LTXXX-OM-E_Ch7 电路图.pdf》由会员分享，可在线阅读，更多相关《lecroy 11_LTXXX-OM-E_Ch7 电路图.pdf（11页珍藏版）》请在收音机爱好者资料库上搜索。

1、LTXXX-OM-E Rev BISSUED: January200275 P P A AR RT T T T WWOO L L OO OO K KI I N N G G DD E E E E P PE E R R Part Twoof the manualcovers the Waverunnerfeatures youlluse formore advanced waveform operations: RIS and sequence sampling, SMART Trigger, Advanced waveformprocessing. It alsolooks deeperinto

2、operations alreadycovered inPart One. Use Part Twoas anadvanced guide and a reference forunderstanding important functions of your digitaloscilloscope. RadioFans.CN 收音机爱 好者资料库 76ISSUED: January2002LTXXX-OM-E Rev B CH A P T E RSE V E N:A QuestionofTimebase InPart One you sawhowtoadjust andset uptimeb

3、ase. Next, take a closerlookat the Waverunnertimebase sampling modes. Inthis chapter, see how Tochoose a sampling mode Touse single-shot orRIS modes Touse sequence mode Tosample externally RadioFans.CN 收音机爱 好者资料库 LTXXX-OM-E Rev BISSUED: January200277 CH A P T E RSE V E NA QuestionofTimebase ChooseaS

4、amplingMode Dependingonyour timebase, youcanchooseanyof threesamplingmodes: single-shot, RIS (Random InterleavedSampling), or roll mode. Inaddition, ontimebases suitedto single-shot androll, theacquisition memorycanbesubdividedintouser-definedsegments togivesequencemode. SINGLE-SHOT WAVERUNNERS BASI

5、C CAPTURE TECHNIQUE A single-shot acquisitionis aseries of digitizedvoltagevalues sampledon theinput signal at auniform rate. It is alsoaseries of measureddatavalues associatedwithasingletrigger event. Theacquisitionis typically stoppedadefinednumber of samples after this event occurs: anumber deter

6、minedbytheselectedtrigger delayandmeasuredbythetimebase. Thewaveforms horizontal position andwaveform displayingeneral is determinedusingthetrigger event as thedefinition of timezero. Youcanchooseeither apre- or post-trigger delay. Pre-trigger delayis thetimefrom theleft-handedgeof the Waverunner gr

7、idforwardtothetrigger event, whilepost-trigger delayis thetimeback totheevent. Youcan samplethewaveform inarangestartingwell beforethetrigger event uptothemoment theevent occurs. This is 100% pre-trigger, andit allows youtoseethewaveform leadingupto thepoint at whichthetrigger conditionwas met andth

8、etrigger occurred. (Waverunner offers uptoonemillionpoints of pre-trigger information.)Post-trigger delay, ontheother hand, allows youtosamplethewaveform startingat the equivalent of 10 000 divisions after theevent occurred. BecauseeachWaverunner input channel has adedicatedADC (Analog-to-Digital Co

9、nverter), thevoltageon eachis sampledandmeasuredat thesameinstant. This allows veryreliabletimemeasurements betweenthe channels. Onfast timebasesettings, themaximum single-shot samplingrateis used. But for slower timebases, the samplingrateis decreasedandthenumber of datasamples maintained. Therelat

10、ionshipbetweenWaverunner samplerate, memoryandtimecanbesimplydefinedas: Memory RateSample 1 timeCapture=, and DivisionTime 10 timeCapture =. RadioFans.CN 收音机爱 好者资料库 PA R TTW O:L O O K I N GD E E P E R 78ISSUED: January2002LTXXX-OM-E Rev B RIS FOR HIGHER SAMPLE RATES RIS (RandomInterleavedSampling)is

11、 anacquisitiontechniquethat allows effectivesamplingrates higher than themaximumsingle-shot samplingrate. It is usedonrepetitivewaveforms withastabletrigger. Themaximum effectiveWaverunner samplingrateof 25 GS/s can beachievedwithRIS bymaking50 single-shot acquisitions at 500 MS/s or 200 MS/s, depen

12、dingonmodel. Thebins thus acquiredarepositionedapproximately40 ps apart. Theprocess of acquiringthesebins andsatisfyingthetimeconstraint is arandomone. Therelativetime betweenADC samplinginstants andtheevent trigger provides thenecessaryvariation, measuredbythe timebaseto5 ps resolution. It takes Wa

13、verunner 30 trigger events tocompletea1 GS/s RIS acquisition, and230 events for a25 GS/s acquisition. But sometimes thescopeneeds manymorethanthis. It theninterleaves thesesegments (Fig. 1)to provideawaveformcoveringatimeinterval that is amultipleof themaximumsingle-shot samplingrate. However, there

14、al-timeinterval over which Waverunner collects thewaveformdatais muchlonger, and depends onthetrigger rateandtheamount of interleavingrequired. Theoscilloscopeis capableof acquiring approximately40 000 RIS segments per second. Segment 1 Segment 3 Segment 2 Finalcapture Figure 1. Buildup of an RIS wa

15、veform. ROLL DISPLAY IN REAL-TIME Waverunner roll modedisplays inreal timeincomingpoints insingle-shot acquisitions that haveasufficiently lowdatarate. At timebasesettings of0.5 s/div theoscilloscoperolls theincomingdatacontinuouslyacross thescreenuntil atrigger event is detectedandtheacquisitionis

16、complete. Evenwhenreal-timedisplayis not possible, thedatawill continueto beacquired. This works inthesamewayas astrip-chart recorder: thelatest datais usedtoupdatethetracedisplay. Waveformmathandparameter calculations areperformedonthe completedwaveforms, after thereal-timedisplayhas stopped. CH A

17、P T E RSE V E N:A QuestionofTimebase LTXXX-OM-E Rev BISSUED: January200279 SEQUENCE WORKING WITH SEGMENTS Insequencemode, thecompletewaveformconsists of anumber of fixed-sizesegments (Fig. 2)acquiredin single-shot mode(seeWaverunner specifications for thelimits). Youselect thenumber of segments to b

18、e captured, andcanthenselect eachsegment, individually, anduseit for processingwithMathandMeasuretools. Sequenceoffers anumber of uniquecapabilities. Withit, youcanlimit deadtimebetweentrigger events for consecutivesegments. Waverunner cancaptureinfinedetail complicatedsequences of events over large

19、time intervals, whileignoringtheuninterestingperiods betweentheevents. Youcanalsomaketimemeasurements betweenevents onselectedsegments usingthefull precisionof theacquisitiontimebase. Trigger timestamps of 1 ns resolutionaregivenfor eachof thesegments intheText & Times Status menu. Eachindividual se

20、gment can bezoomedor usedas input tomathfunctions. Waverunner uses thesequencetimebasesettingtodeterminethecapturedurationof eachsegment: 10 xtime/div. Theoscilloscopeuses this setting with thedesirednumber of segments, maximumsegment lengthandtotal availablememory todeterminetheactual number of sam

21、ples or segments, andtimeor points. However, thedisplayof thecompletewaveformwithall its segments maynot entirelyfill thescreen. Sequencemodecanalsobeusedinremoteoperationtotakefull advantageof Waverunners highdatatransfer capability(seeChapter 12, “Use Waverunner with PC,” andtheRemote Control Manu

22、al). Segment 1 Segment 2 Segment 2 TriggerTriggerTrigger Figure 2. How Waverunner captures segments. See page 83 for how to obtain a sequence status summary. PA R TTW O:L O O K I N GD E E P E R 80ISSUED: January2002LTXXX-OM-E Rev B PAIRING CHANNELS (LT364SERIES ONLY) A pair of channelscanbecombinedo

23、nchannel2or 3,withchannels1and4disabledoravailableonlyfor triggering. Onthesepairedchannelsthemaximumsamplingrateisdoubledandtherecordlengthisincreasedbytwotimes. Channelsarecombinedtoincreasesamplerateormemorysizeorbothinordertocaptureandviewasignalinallits detail.Whencombined,thechannels(liketheEX

24、T BNC input)thatarenotinvolvedinthecombinationremain availablefortriggering,eventhoughtheyarenotdisplayed.Itispreferabletoselect“Automatic” tocombinechannels andhavetheremainingacquisitionchannelsavailablefortriggering.Thechannelsavailablefortriggeringonlywouldbe indicatedby “trigonly” intheAcquisit

25、ionSummaryField. Refer tothe“AcquisitionModes” tablein AppendixA for maximumsamplerates. Combining of Channels CH A P T E RSE V E N:A QuestionofTimebase LTXXX-OM-E Rev BISSUED: January200281 UseaSampling Mode SET UP FOR SINGLE-SHOT OR RIS 1.Press TIMEBASE SETUP andaccess theTIMEBASE SETUP menus. 2.U

26、sethesemenus toset uptheWaverunner timebasefor Single-Shot or RIS. ToselectSingle-Shotfor displayof datacollectedduringsuccessive single-shot acquisitions fromtheinput channels, orRISfor ahigher samplingratewitharepetitiveinput signal andstabletrigger. Toselect fromaninternal or external clocksource

27、. Seepage83 for external clock. ToswitchSequencemodeOnorOff. Usetheknobto choosethenumber of segments. Seenext page. Toselect themaximumnumber of samples to be acquired, usingthemenuknob. PA R TTW O:L O O K I N GD E E P E R 82ISSUED: January2002LTXXX-OM-E Rev B SET UP FOR SEQUENCE CAPTURE 3.Activate

28、sequencemodeusingtheSequencemenuandthenusethese menus todo sequencesampling. T TI IP P: : Press SCOPE STATUS and select “Text and Times” toobtaina status report ona trace ormemorys sequence segment range. ToselectSingle-Shotfor sequencesampling. ToselectInternalorexternalECL,OV,TTLclockmodes.Select

29、internalunlessusinganexternalclocksignal(seenext page). Youcanselect atime-out for sequencemodeusingtheUTILITIES, SpecialModes,andTimebaseTrigger menu. ToturnSequenceOnorOff. Toselect withtheknobthemaximumrecordlength, in samples, for eachsequencesegment. N NO OT TE E: : Insequence mode: Press the S

30、INGLE buttonand Waverunnerwillfillthe chosennumberof segments and thenstopcapturing. But if there are not enoughtriggerevents tofillthe segments, Waverunnerwillnot stopcapturing untilyou press STOP. If you press NORMAL the segments will be filled and the data processed and displayed. Then, if more t

31、riggerevents occur, Waverunnerwill restart capturing fromthe first segment. Whenyou press AUTO, capturing willalsobe restarted fromthe first segment, if the time betweentwoconsecutive triggers exceeds a selected time-out. However, avoid anyunnecessarybuttonpushing and knob turning inSequence mode. C

32、H A P T E RSE V E N:A QuestionofTimebase LTXXX-OM-E Rev BISSUED: January200283 OBTAIN A SEQUENCE STATUS SUMMARY Displayasummaryof thestatus of your sequenceacquisition. 4.Press SCOPE STATUS toshowtheSTATUS menus. 5.Press thebuttontoselectText & Times. T TI IP P: : Press PRINT SCREEN todocument yours

33、tatus summaryand make a hard copy. Printing (and storage) operations willinclude undisplayed text. Press the SCOPE STA TUS button for a full status summary of your sequence acquisition. U se the Select segment menu and its button and knob to scroll down the segment list. PA R TTW O:L O O K I N GD E

34、E P E R 84ISSUED: January2002LTXXX-OM-E Rev B OR SAMPLE EXTERNALLY Useanexternal clockat afixedfrequency(seeAppendix)tocontrol and synchronizethesamplingwithanexternal signal sourceconnectedtothe Waverunner rear EXT signal input. This menuis inactivewhen theexternal sampleclockis beingused. Single-S

35、hotis selectedbydefault. Tospecifytheeffectivethresholdfor samplingtheEXT input: 1.3 V withECL, 0.0 V with0V, or +1.5 V withTTLselected. ToturnSequenceOnorOff. Usetheknobtoset the number of segments. Toselect withtheknobthemaximumrecordlength, in samples, for eachsegment. N NO OT TE E: : Externalclo

36、ckmodes are available onlyif the EXT triggerisNOTthe triggersource. Trigger time stamps and the AUTO sequence time-out feature are unavailable whenyou use anexternal clocksignal. And inter-segment dead time isNOTguaranteed. Externalclocktime/divis expressed insamples perdivision, as is the triggerde

37、lay, whichcanbe adjusted normally. Noattempt is made tomeasure the time difference betweenthe triggerand the externalclock, sosuccessiveacquisitions of the same signalcanappeartojitteronthe screen. Waverunnerrequires a numberof pulses torecognize the externalclocksignal. It stops capturing onlywhenthe triggerconditions have beensatisfied and the appropriate numberof data points have beenaccumulated. Anyadjustment tothe TIME/DIV knob automaticallyreturns the scope tonormal(internal) clockoperation. CH A P T E RSE V E N:A QuestionofTimebase LTXXX-OM-E Rev BISSUED: January200285 BLANK PAGE