lecroy 06_LTXXX-OM-E_Ch2 电路图.pdf

28ISSUED: January2002LTXXX-OM-E Rev B CH A P T E RTW O:SimplyTrigger Inthis chapter, see how Tocontroltriggers Toset upanEdge trigger Tore-armtriggering Todetermine level, coupling and slope Touse Windowtrigger Toobtaina summaryof yourtriggerand systemstatus RadioFans.CN 收音机爱 好者资料库 LTXXX-OM-E Rev BISSUED: January200229 CH A P T E RTW OSimplyTrigger EdgeTriggeronSimpleSignals Waverunner uses manywaveform capturetechniques that trigger onfeatures andconditions, whichyoudefine. Thesetriggers fall intotwomajor categories: Edge activatedbybasic waveform features or conditions suchas apositiveor negativeslope, and holdoff SMART Trigger sophisticatedtriggers that enableyoutousebasic andcomplexconditions for triggering. SeeChapter 8, “Trigger Smart.” UsetheEdgetrigger typefor simplesignals, andtheSMART Trigger typefor signals withrarer features such as glitches. CONTROL TRIGGERING Horizontal: Turn DELAY toadjust thetriggers horizontal position. Youcanadjust thetriggers positionfrom 0% to100% pre-trigger, from left toright onthegrid. DELAY can alsobeusedfor settingthepost-trigger, intimeunits, upto10 000 divisions, inincrements of 0.1 division. Thetrigger locationis shown bythearrowat thegridbottom, as shown hereat near right. Post-trigger delayis labeledinthetrigger delayfield, wherethe arrowbecomes horizontal, as shown hereat far right. Vertical: Turn TRIGGER LEVEL toadjust thetriggers vertical threshold. Turnthis knobtoadjust thelevel of thetrigger sourceor thehighlightedtrace. Level defines thesourcevoltage at whichthetrigger will generateanevent achangeintheinput signal that satisfies thetrigger conditions. Arrows on bothsides of thegridshowthethresholdposition. But thesearrows areonly visibleif thetrigger sourceis displayedandthesourcesignal DC coupled. RadioFans.CN 收音机爱 好者资料库 PA R TON E:G E T T I N GS T A R T E D 30ISSUED: January2002LTXXX-OM-E Rev B SET UP AN EDGE TRIGGER 1.Press TRIGGER SETUP toaccess thesemenus: Usethem to select thetrigger source, thesources coupling, theslope positive or negative andtheamount of trigger holdoff bytimeor events. 1.Select “Edge” or “SMART”: “Edge” is selectedbydefault. T TI IP P: : Once set, triggerleveland coupling pass unchanged from triggertype totriggertype foreachtriggersource. 2.Select thetrigger source. This couldbeasignal onachannel, the linevoltagethat powers theWaverunner, or theEXT BNC connector. 3.Select thecouplingfor thetrigger source. 4.Placethetrigger point onthepositiveor negativeslopeof the selectedsource, or choosetodefineawindow . When Windowis selectedfrom theabovemenu, a menuappears herethat allows youtodefinethe windows size. Seepage33. Toholdoff from triggeringfor adefinedtime, or number of events, after aparticular trigger event. Use this buttontoselect Time or Events, andtheknobto set thevalue. Offdeactivates theholdoff. SeeChapter 8, “Trigger Smart.” 5.Turn DELAY toadjust thetriggers horizontal position, andtheamount of pre-trigger, as desired. 6.Turn TRIGGER LEVEL toadjust thetrigger voltagelevel. RadioFans.CN 收音机爱 好者资料库 CH A P T E RTW O:SimplyTrigger LTXXX-OM-E Rev BISSUED: January200231 TODE T E RMIN ETRIGGE RLE VE L, COUPL IN G AN DSL OPE Leveldefines the source voltage at which the trigger circuit will generate an event: a change in the input signal that satisfies the trigger conditions. The selected trigger level is associated with the chosen trigger source. Trigger level is specified in volts and normally remains unchanged when you change the vertical gain or offset. The amplitude and range of the trigger level are limited as follows: 5 screen divisions with a channel as the trigger source 0.5 V with E XT as the trigger source 5 V with E XT/ 10 as the trigger source N one with L IN E as the trigger source (zero crossing is used). Couplingrefers to the type of signal coupling at the input of the trigger circuit. A s with the trigger level, you can select the coupling independently for each source. Change the trigger source and you can change the coupling. You can choose from these coupling types: DC: A ll the signals frequency components are coupled to the trigger circuit for high frequency bursts or where the use of A C coupling would shift the effective trigger level. A C: The signal is capacitively coupled, DC levels are rejected and frequencies below 50 Hz attenuated. L F RE J: The signal is coupled through a capacitive high-pass filter network, DC is rejected and signal frequencies below 50 kHz are attenuated. For stable triggering on medium to high frequency signals. HF RE J: Signals are DC coupled to the trigger circuit, and a low-pass filter network attenuates frequencies above 50 kHz; used for triggering on low frequencies. HF: Use only when needed for triggering on high-frequency repetitive signals. HF is automatically overridden and set to A C when incompatible with trigger characteristics such as those of SMA RT Trigger. Slopedetermines the direction of the trigger voltage transition used for generating a particular trigger event. You can choose a positive or negative slope. L ike coupling, the selected slope is associated with the chosen trigger source. Triggerlevel Positive Slope Trigger Figure 1. E dge trigger works on the selected edge at the chosen level. The slope positive here is highlighted on the trigger icon. PA R TON E:G E T T I N GS T A R T E D 32ISSUED: January2002LTXXX-OM-E Rev B TORE-ARM ATRIGGE R Three trigger re-arming modes A U TO, N ORMA L , and SIN GL E are available for all types of triggers. In addition, STOP cancels the capture in all three modes. Press AUTO to activate AU TO mode: the trace will automatically be displayed if no trigger occurs soon after. But if a signal does occur, Waverunner behaves as if in N ORMA L mode. Press NORMAL to enter N ORMA L mode and continuously update the display while there is a valid trigger. If there is no valid trigger, the last signal is retained and the warning “SL OW TRIGGE R” is displayed in the trigger status field. Press SINGLE to enter SIN GL E mode: the Waverunner will wait for a single trigger to occur, then display the signal and stop capturing. If no trigger occurs, you can press this button again to manually trigger the scope. Press STOP to halt the capture made in AU TO, N ORMA L or SIN GL E re-arming modes. Press STOP to prevent capture of a new signal, or while a single-shot capture is under way to keep the last captured signal. TORE COGN IZETRIGGE RICON S Trigger icons allow immediate on-screen recognition of the current trigger conditions. There is an icon for each trigger. The more heavily marked transitions on the icon indicate the slope on which the trigger will be generated. The icons are annotated with information on the trigger settings. This icon, for example, represents an E dge trigger set up to trigger on the positive slope, at a level of 0.008 V , with a holdoff time of 50 ns. CH A P T E RTW O:SimplyTrigger LTXXX-OM-E Rev BISSUED: January200233 USE WINDOW TRIGGER Definearegionwhoseboundaries extendaboveandbelowtheselectedtrigger level. A trigger event will occur whenthesignal leaves this windowregionineither directionandpasses intotheupper or lower region(Fig. 2). Thenext trigger will occur whenthesignal againpasses intothewindowregion. 1.Select. 2.Thenusetodefinethesizeof thewindowregion. A bar at theleft-handsideof thegridwill visuallyindicatethewindows height. WINDOWREGION TriggerLevel Triggers Time Lower Region Upper Region Figure 2. Window Trigger: triggers when the signal leaves the window region. The arrows indicate where triggers occur when the signal leaves the window region. PA R TON E:G E T T I N GS T A R T E D 34ISSUED: January2002LTXXX-OM-E Rev B TRIGGER SOURCE The trigger source may be one of the following: The acquisition channel signal (CH 1, CH 2, CH 3 or CH 4) conditioned for the overall voltage gain, coupling, andbandwidth. The line voltage that powers the oscilloscope (LINE). This can be used to provide a stable display of signals synchronous withthepower line. Couplingandlevel arenot relevant for this selection. Thesignal applied to theEXT BNC connector (EXT). This can be used to trigger the oscilloscope within arangeof0.5 V on EXT and5 V withEXT/10 as thetrigger source. Level Level defines thesourcevoltageat whichthetrigger circuit will generateanevent (achangeintheinput signal that satisfies thetrigger conditions). Theselectedtrigger level is associatedwiththechosentrigger source. Note that thetrigger level is specifiedinvolts andnormallyremains unchangedwhenthevertical gainor offset is modified. TheAmplitudeandRangeof thetrigger level arelimitedas follows: 5 screendivisions withachannel as thetrigger source 5 V withEXT/10 nonewithLINE as thetrigger source(zerocrossingis used) Note:Note:Note:Note: Once specified, TriggerLeveland Coupling are the only parameters that pass unchanged fromtriggermode totriggermode foreachtriggersource. CH A P T E RTW O:SimplyTrigger LTXXX-OM-E Rev BISSUED: January200235 OBTAIN A TRIGGER STATUS SUMMARY Displayasummaryof thestatus of your trigger, as well as timebase, vertical sensitivity, probeattenuation, and offset andcouplingfor eachchannel. 1.Press SCOPE STATUS toshowtheSTATUS menus. 2.Press thebuttontoselect Acquisition. T TI IP P: : Press PRINT SCREEN todocument yourstatus summaryand make a hard copy. Press PANELS whenyou have a setting you want to reuse (see the next chapterformore onthis). Press the SCOPE STA TUS button for access to full-screen summaries of your Waverunners system status and other functional status. See Chapter8, “TriggerSmart,” formore about Edge triggerand allabout the SMART Triggertypes.