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1、Chapter8ProcessAutomaticControlSystem過程自動控制系統(tǒng)8.1IllustrativeSystem圖解系統(tǒng)CommunicationSystem通信系統(tǒng)AMbroadcastsystem調(diào)幅廣播系統(tǒng)audio音頻的,聲頻的microphone擴音器,麥克風(fēng)transmitter發(fā)送器receiver接收器antenna天線processor處理器transmittingsystem發(fā)送系統(tǒng)receivingsystem接收系統(tǒng)AmplitudeModulation調(diào)幅amplitude振幅modulation調(diào)制radiofrequency無線
2、電頻率射頻lowerfrequency低頻audiblefrequency可聽頻率radiofrequencycurrent射頻電流electromagneticwave電磁波radiate輻射filter過濾，濾波measurementsystem測量系統(tǒng)thermometer溫度計linearizer線性化電路register寄存器icebath冰浴器proportional成比例的，比例的correction修正，校正error誤差displayregister顯示寄存器reproduction再現(xiàn)modify修改，改變bimetallicstrip雙金屬條，,雙金屬片b
3、end彎曲mechanism機構(gòu)，機械裝置dial刻度盤mechanicalswitch機械開關(guān)radiator散熱器ACommunicationSystemThefirstsystemweshallillustrateisthecommunicationssystem.Theinputcanbespeech,music,ordatathatisproducedatonelocationandtransmittedefficientlyoverlongdistances,permittingfaithfulrecoveryoftheoriginalinput.Theexampl
4、echosen,thefamiliarAMbroadcastsystemisshownschematicallyinFigure8.1。ThelettersAMstandforAmplitudeModulation.Theymeanthattheamplitudeormagnitudeofaradiofrequency(RF)signaliscausedtovaryaccordingtothemagnitudeofalower-frequencysignal(audio,correspondingtoaudiblefrequencies).Thefunctionoftransm
5、itterinanAMbroadcastsystemistoaccepttheinputsignalfromaninputdevice(microphone),usethissignaltocontroltheamplitudeofaradiofrequencysignal(eachbroadcaststationisassigneditsownradiofrequency),anddrivetheoutputdevice(theantenna)witharadiofrequencycurrenttoproduceelectromagneticwavesradiatingint
6、ospace.Thereceivingsystemconsistsofaninputdevice(theantenna),aprocessor(thereceiver),andanoutputdevice(theloudspeaker).Thefunctionsofthereceiveraretoamplifyorincreasethestrengthoftherelativelyweaksignalobtainedfromtheantenna,tofilterorselectthedesiredradiofrequencysignalfromthesignalsofallot
7、herbroadcaststations,torecovertheaudiosignalfromtheamplitudevariationsoftheradiofrequencysignal,andtodrivealoudspeakerwiththisaudiosignal.AMeasurementsystemAsecondsystemisameasurementsystem.Thepurposeofthissystemistoacquireinformationfromsuitabletr
