示波器的使用及声速的测量.ppt

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1、示波器的使用ApplicationofOscilloscopeTheLabcenterofphysicsBasicstructure返回oscilloscopetubeCircuitelectrongunelectronbeamLeveldeflectorverticaldeflectorFluorescentscreendisplayprincipleofOscilloscopesinusoidalwavesawtoothwaveEvenrotationofthedrum–evenmotionoftheelectronbea

2、malongthex-direction.Motionofthepeniny-direction–deviationofthebeaminy-directionproportionaltothemeasuredvoltage.Aquestion:Theelectronbeammovingalongx-directionreachestheendofthescreenatsomepointandhastojumpbackandstartwritingagainfromthebeginningofthescreen.Howcom

3、ethatyounormallyonlyseeonecurveonthescreenatanytime?Bytheway,howfastdoesthebeamgofromlefttoright?Theansweristriggering.Afterdrawingonecurve(sinusoidal,triangular,square…)onthescreentheelectronbeamreturnsbacktoitsstartingpoint,butitdoesnotstartdrawinganothercurve,b

4、eforethevoltagereachessomepresetvalue–triggerlevel.triggerlevelLissajousFigures李萨如图线与频率比HorizontalintersectionVerticalintersectionFunctiongenerator空气中声速的测量MeasurementofSoundVelocityinAirTheLab'centerofphysicsIntroductionAcousticsmaybedefinedasthegeneration,transmiss

5、ion,andreceptionofenergyintheformofvibrationalwavesinthematter.Astheatomsormoleculesofafluidorsolidaredisplacedfromtheirnormalconfiguration,aninternalelasticrestoringforcearises.Examplesincludingthetensile(张力)forceproducedwhenaspringisstretched.Itisthiselasticrestor

6、ingforce,coupledwithinertia(惰性)ofthesystem,thatenablesmattertoparticipate(参与)inoscillatoryvibrationsandtherebygenerateandtransmitacousticwaves.Themostfamiliaracousticphenomenonisthatassociatedwithofsound.Fortheaverageyoungperson,avibrationaldisturbanceisinterpreteda

7、ssoundifitsfrequencyliesintherangeofabout20to20000Hz.Howeverinabroadersenseacousticalsoincludestheultrasonicfrequenciesabove20000Hzandtheinfrasonicfrequenciesbelow20Hz.Themeasurementofspeedofsoundisofinterestingforunderstandingthemainpropertyofsound.Onecaneasilyobta

8、inthevelocityofsoundthroughthefollowingexpression:Purpose学会用不同的方法测定空气中的声速。掌握数字式函数发生器、示波器的使用方法。学会用逐差法处理测量结果，并对结果的不确定度进行分析。Experimentalmetho