lecroy 08_LTXXX-OM-E_Ch4 电路图.pdf

44ISSUED: January2002LTXXX-OM-E Rev B CH A P T E RFO U R:ChooseaMeasureTool Inthis chapter, see how Tocontroltime cursors Tocontrolamplitude cursors Touse cursors instandard display Toselect a standard parameter RadioFans.CN 收音机爱 好者资料库 LTXXX-OM-E Rev BISSUED: January200245 CH A P T E RFO U RChooseaMeasureTool MeasurewithCursors Cursors areimportant tools that aidyouinmeasuringsignal values. Cursors aremarkers lines, cross-hairs, or arrows that youcanmovearoundthegridor thewaveform itself. Usecursors tomakefast, accurate measurements andtoeliminateguesswork. Therearetwobasic types: Time (Frequency)cursors aremarkers that youmovehorizontallyalongthewaveform. Placethem at a desiredlocationalongthetimeaxis toreadthesignals amplitudeat theselectedtime. Amplitude (Voltage)cursors arelines that youmoveverticallyonthegridtomeasuretheamplitudeof a signal. CONTROL THE TIME CURSORS 1.Press DISPLAY andmakesurethat Standard is selectedinthetopmenu. 2.Press MEASURE TOOLS todisplaytheMEASURE menus. T TI IP P: : Press SINGLE as a smoothwaytostopyour Waverunnerscope and allowmeasurement of the displayed waveform. 3.Press thebuttontoselect 4.Press thebuttontoselect 5.Press thebuttontoselect 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 46ISSUED: January2002LTXXX-OM-E Rev B 6.TurntheknobfortomovetheAbsoluteTimecursor. Watchthiscross-hair marker moveupanddownalongyour displayedwaveform.Asit moves,thecursorstimevalue inrelationtothetrigger point isshownbeneaththegrid,anditsvoltagevalueinthetracelabel. 7.Press thebuttontoselectT TI IP P: :Select“Diff measured times are relative to the trigger point. InRelativemode, you control a pair of amplitude or time cursors, and get readings on the difference between the two in amplitude, or time and amplitude. WH E N INPE RSIST E N CEMODE In persistence mode, amplitude cursors are the same as in Standard display, while time cursors are vertical bars running down the screen and moving across it. T TI IP P: : Toset time-cursoramplitude units involts ordecibels. Press UTILITIES toaccess and select SpecialModes. Then select the Cursors Measure menu toaccess and use the Read time cursoramplitudes inmenu toselect the desired unit. PA R TON E:G E T T I N GS T A R T E D 50ISSUED: January2002LTXXX-OM-E Rev B MeasureAutomaticallywithParameters Parameters aremeasurement tools that determineawiderangeof signal properties. Usethem to automatically calculatetimeandvoltagevalues. Thereareparameter modes for theamplitudeandtimedomains, custom parameter groups, andparameters for pass andfail testing. Youcanmakecommonmeasurements on one signal ineither thestandardvoltage(amplitude)or standardtimemodes. Onmorethan onesignal, select parameters from aCustom categoryandusethem todetermineuptofivequantities at once. Pass andfail parameters canbecustomized, too. Youcanaccumulateanddisplaystatistics oneachparameters sweeps, average, lowest, highest andstandarddeviation. SeeChapter 11, “Parameter Analysis,” for howto customizeparameters, andfor adescriptionof each. A special display is automatically used with parameters, whose data are listed beneath the grid (see next page for display setup). Shown here: a Full-Screen, Quad-grid parameter display. Top of facing page: the Standard, Single-grid, parameter display. CH A P T E RFO U R:ChooseaMeasureTool LTXXX-OM-E Rev BISSUED: January200251 CHOOSE A STANDARD PARAMETER 1.Press MEASURE TOOLS todisplaytheMEASURE menus. 2.Press thebuttontoselect Standard Voltage will beselectedbydefault inthemodemenu, shown below , andalist of fiveparameters will appear beneaththegrid. This list will changewhenStandard Time is selected. 3.Usethesemenus toset upfor parameters. Toenableparameters,cursorsor neither.WhileParametersisselected, statisticsaccumulation(seebelow)goeson,evenif not shown. Toselect themode. Standard Voltage measures for asinglesignal: peak- to-peak(theamplitudebetweenthemaximum andminimum sample values), meanof all samplevalues, standarddeviation, root meansquare of all samplevalues, andsignal amplitude. Standard Time measures for asinglesignal: period, widthat 50% of amplitude, risetimeat 1090% of amplitude, fall timeat 9010% of amplitude, andthedelayfrom thefirst trigger to thefirst 50% amplitudepoint. SeeChapter 11 for “Custom,” “Pass,” and“Fail.” Toautomaticallycalculatethedisplayedparameters average, lowest, highest andstandarddeviation, andnumber of sweeps used. Toselect thetraceonwhichtheparameters aretobemeasured. This menuindicates thosetraces displayed. Toset thestartingpoint in screendivisions for parameter measurements, usingtheknob. TurnTrackOn, usingthe button. Control of thestartingandendpoints is linkedand theycanbemovedtogether usingtheknob. Toset theendpoint inscreendivisions for parameter measurements, usingtheknob. Alsoindicates thetotal number of datapoints usedfor themeasurements. PA R TON E:G E T T I N GS T A R T E D 52ISSUED: January2002LTXXX-OM-E Rev B 4.Press DISPLAY toset upthedisplay to select parameter gridstyles, for example usingDISPLAY SETUP. Seetheprecedingchapter. TURN OFF CURSORS AND PARAMETERS 1.Press MEASURE TOOLS toreturntotheMEASURE menus. 2.Press thebuttontoselect T TI IP P: : Toclearparameter“statistics” press: CLEAR SWEEPS CH A P T E RFO U R:ChooseaMeasureTool LTXXX-OM-E Rev BISSUED: January200253 TORE COGN IZEPARAME T E RSYMBOL S The algorithms that allow Waverunner to determine pulse-waveform parameters detect the particular situations where the mathematical formulas can be applied. Sometimes you should interpret the results with caution. In these cases the scope alerts you by displaying a symbol under the grid between the name of the parameter and its value. These symbols act as information or warnings: The parameter has been determined for several periods (up to 100), and the average of those values has been taken. The parameter has been determined over an integral number of periods. The parameter has been calculated on a histogram. Insufficient data to determine the parameter. A mplitude histogram is flat within statistical fluctuations; minimum and maximum are used to assign top and base. Only an upper limit could be estimated (the actual value of the parameter may be smaller than the displayed value). The signal is partially in overflow. The signal is partially in underflow. The signal is partially in overflow and in underflow.