Lesson-13-The-Oscilloscope

1Lesson13TheOscilloscopeOneofmostimportantelectronictestandmeasuringinstrumentsistheoscilloscope.Itiswidelyuseddesignwork,trouble-shootingandsignalmonitoring,manufacturingandproduction-linetesting,andmanyotherapplicationswheretheobservationofanelectricalwaveformisdesired.1Oscilloscopesrangefromthebasic,orgeneral-purposetypes,tothespecial-purposetypes.2Thegeneralpurposeoscilloscopeissuitableforanyoftheusualapplicationsinservicingcommunications,scientific,orindustrialworkwherethefrequencyofthesignaltobeobserveddoesnotgreatlyexceed500kHz.3Fig.13-1isasimpleblockdiagramthatshowshowananalogoscilloscopedisplayameasuredsignal.Whenyouconnectanoscilloscopeprobetoacircuit,thevoltagesignaltravelsthroughtheprobetotheverticalsystemoftheoscilloscope.Thesignaltravelsdirectlytotheverticaldeflectionplatesofthecathoderaytube(CRT).Voltageappliedtothesedeflectionplatescausesaglowingdottomove(anelectronbeamhittingphosphorinsidetheCRTcreatestheglowingdot).Apositivevoltagecausesthedottomoveupwhileanegativevoltagecausesthedottomovedown.Dependingonhowyousettheverticalscale(volts/divcontrol),anattenuatorreducesthesignalvoltageoranamplifierincreasesthesignalvoltage.2Thesignalalsotravelstothetriggersystemtostartortriggera“horizontalsweep”.Horizontalsweepisatermreferringtotheactionofthehorizontalsystemcausingtheglowingdottomoveacrossthescreen.4Triggeringthehoriontalsystemcausesthehorizontaltimebasetomovetheglowingdotacrossthescreenfromlefttorightwithinaspecifictimeinterval.Thetriggerisnecessarytostabilizearepeatingsignal,resultinginaclearpictureasshowninFig.13-2(b).5Inconclusion,touseananalogoscilloscope,youneedtoadjustthreebasicsettingstoaccommodateanincomingsignal:Theattenuationoramplificationofthesignal.Usethevolts/divcontroltoadjusttheamplitudeofthesignalbeforeitisappliedtotheverticaldeflectionplates.Thetimebase.Usethesec/divcontroltosettheamountoftimeperdivisionrepresentedhorizontallyacrossthescreen.Thetriggeringoftheoscilloscope.Usethetriggerleveltostabilizearepeatingsignal.Also,adjustingthefocusandintensitycontrolsenablesyoutocreateasharp,visibledisplay.Fig.13-3isdiagramofoscilloscope’spanel.NewWordsoscilloscope[ɔˈsiləskəup]示波器trouble[ˈtrʌbl]-shoot[ʃu:t]故障探测3monitor[ˈmɔnitə]监视,监听production[prəˈdʌkʃən]-line流水线,生产线general[ˈdʒenərəl]-purpose[ˈpə:pəs]通用的special[ˈspeʃəl]-purpose专用的probe[prəub]探针,调查attenuator[əˈtenjueitə]衰减器glowing[ˈɡləuiŋ]发光的phosphor[ˈfɔsfə]荧光粉trigger[ˈtriɡə]触发器accommodate[əˈkɔmədeit]容纳incoming[ˈinˌkʌmiŋ]接踵而来的cathode[ˈkæθəud]ray[rei]tube[tju:b]阴极射线管vertical[ˈvə:tikəl]system垂直系统verticaldeflection[diˈflekʃən]plates[pleit]垂直偏转板verticalsweep[swi:p]垂直扫描horizontal[ˌhɔriˈzɔntəl]system水平系统horizontalsweep水平扫描ramp[ræmp]timebase[beis]signal[ˈsiɡnəl]锯齿波时基信号