Process Automatic Control System

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1、Chapter8ProcessAutomaticControlSystem过程自动控制系统8.1IllustrativeSystem图解系统CommunicationSystem通信系统AMbroadcastsystem调幅广播系统audio音频的,声频的microphone扩音器,麦克风transmitter发送器receiver接收器antenna天线processor处理器transmittingsystem发送系统receivingsystem接收系统AmplitudeModulation调幅amplitude振幅modulation调制radiofrequency无线

2、电频率射频lowerfrequency低频audiblefrequency可听频率radiofrequencycurrent射频电流electromagneticwave电磁波radiate辐射filter过滤，滤波measurementsystem测量系统thermometer温度计linearizer线性化电路register寄存器icebath冰浴器proportional成比例的，比例的correction修正，校正error误差displayregister显示寄存器reproduction再现modify修改，改变bimetallicstrip双金属条，,双金属片b

3、end弯曲mechanism机构，机械装置dial刻度盘mechanicalswitch机械开关radiator散热器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