《電氣信息類專業(yè)英語》課件第5章

Part5ProcessControl5.1IntroductionstoProcessControl5.2SensorandItsCharacteristics 5.3StandardThermocouplesTypes5.4PIDControllers5.5IntelligentControl

5.1.1語言現(xiàn)象——面試(personalinterview)

去外企應聘工作或申請出國留學簽證，都需要用英語面試。那么面試英語時自我介紹該怎樣講呢?在與西方人交談時，應注意哪些問題呢？

盡管一般在簡歷中對自己的教育背景作了介紹，但在面試時，面試官還有可能就此方面提問，還是應該事先做點準備。5.1IntroductionstoProcessControl

1．面試時常問的問題

當問及教育背景時，應注意簡明扼要，實話實說。如：

I：Whatisyourmajor？

A：MymajorisBusinessAdministration.Iamespeciallyinterestedin“Marketing”。

這樣回答不僅回答了問題，還順帶一句介紹了自己較為感興趣的方面，簡明扼要。再如：

I：Whichuniversityareyouattending？

A：IamattendingxxxUniversity.

I：Haveyoureceivedanydegrees？

A：Yes.First,IreceivedmyBachelordegreeinEnglishLiterature,andthenanMBAdegree.

I：Whatcoursedidyoulikebest？

A：ProjectManagement.IwasveryinterestedinthiscoursewhenIwasastudent.AndIthinkit’sveryusefulformypresentwork.

I：Doyoufeelthatyouhavereceivedagoodgeneraltraining？

A：Yes,IhavestudiedinanEnglishtrainingprogramandacomputertrainingprogramsinceIgraduatedfromuniversity.IamcurrentlystudyingFinanceatatrainingschool.當問及工作經(jīng)驗時，應注意顯露實力，避免炫耀。如：

I：Haveyoueverbeenemployed？Yourresumesaysyouhavehadone-yearexperienceworkinginaforeignrepresentativeofficeinShanghai,mayIaskwhyyouleft？

A：Iworkedinaforeignofficeforoneyear.However,Ilefttheretwoyearsagobecausetheworktheygavemewasratherdull.Ifoundanotherjobthatismoreinteresting.

I：Haveyoudoneanyworkinthisfield？Whathaveyoulearnedfromthejobsyouhavehad？

A：Ihavelearnedalotaboutbusiness,andknowsomebasicofficeskills.Inaddition,Ilearnedatmypreviousjobshowtocooperatewithmycolleagues.

I：What’syoumajorweakpoint？

A：Ihaven’tbeeninvolvedininternationalbusiness,soIdon’thaveanyexperience,butIhavestudiedthiscourseintheInternationalBusinessTrainingCenterofthexxxCompany.

I：Doesyourpresentemployerknowyouarelookingforanotherjob？

A：No,Ihaven’tdiscussedmycareerplanswithmypresentemployer,butIamsurehewillunderstand.當問及性格愛好時，應注意表現(xiàn)積極、合作的一面。如：

I：Whatkindofpersonalitydoyouthinkyouhave？

A：Ialwaysapproachthingsveryenthusiastically.WhenIbeginsomething,Idon’tliketoleaveithalfdone.Ican’tconcentrateonsomethingnewuntilthefirstthingisfinished.

I：Whatisthemostimportantthingforyoutobehappy？

A：Differentpeoplehavedifferentideas.Ithinkthemostimportantthingformeishavingagoodrelationshipwithmyfamilymembersandmyfriends.Myfamilyhasalwaysbeenverycloseknit,andmyfriendsandIspendalotoftimetogether.WithoutthatIwouldbemuchlesshappythanIam.

I：Whatmakesyouangry？

A：Dishonesty.It’sunacceptable.

I：Whatareyourpersonalweaknesses？

A：I’mafraidI’mapoortalker.I’mnotcomfortabletalkingwiththepeoplewhomIhavejustmetforthefirsttime.Thatisnotverygoodforbusiness,soIhavebeenstudyingpublicspeaking.

I：Areyoumoreofaleaderorafollower？

A：Idon’ttrytoleadpeople.I’drathercooperatewitheverybody,andgetthejobdonebyworkingtogether.

當問及工作要求時，應表示出我能勝任。如：

I：DoyouthinkyoucanmakeyourselfeasilyunderstoodinEnglish？

A：Yes,inmostcircumstances.

I：Areyouavailablefortravel？

A：Yes,Iliketraveling.Iamyoung,andunmarried.It’snoproblemformetotravelfrequently.

I：Howaboutovertimework？

A：Overtimeworkisverycommonincompanies.Icanworkovertimeifit’snecessary,butIdon’tthinkwewillworkovertimeeveryday.

I：Doyoulikeregularwork？

A：No,Idon’tlikeregularwork.Iaminterestedindifferentprojectswithnewopportunitiesandnewchallenge,butIcandoregularworkifthecompanyneedsmetodoso.

I：Whatsalarydoyouexpect?

A：Shallwediscussmyresponsibilitieswithyourcompanyfirst？Ithinksalaryiscloselyrelatedtotheresponsibilitiesofthejob.

I：Doyouworkwellunderpressure?

A：Workingunderpressureisexcitingandchallenging.Idon’tmindworkingunderpressure.Iworkwellunderthesecircumstances.Peoplecan,Ican.

I：Doyouhaveanyparticularconditionsthatyouwouldlikethecompanytotakeintoconsideration？

A：No,nothinginparticular.

I：Howsooncanyoubeginworkingforus？

A：Ineedabouttwotothreeweeksfornecessaryformalities.Iwillquitthentransfertoyourcompany.

當面試結(jié)束時，應禮貌道別。如：

I：Anyquestions？

A：WhenwillIknowyourdecision？

I：Wewillnotifyyouofourdecisionbymail,isthisconvenientforyou？

I：Ofcourse,thankyouforyourinterestinourcompany.

A：Thankyou,Mr.Smith.Goodbye.(Thankyouforyourtime.)

I：Youwillbehearingfromusverysoon.Pleasesendthenextapplicationonyourwayout.

A：OK.Thankyouverymuch.

此外，面試官還可能問及你的家庭情況，如家人對你的影響等，也應事先有所準備。

2．面試英語自我介紹的常用基本句子

Inoticedthatyouadvertisedajobinthismorning’spaper.

我看到你們在今早的報紙上刊登的招聘廣告。

I’mcomingforyouradvertisementfor…我是來應聘你們廣告上的……職位的。

Ihaveappliedforthepositionof…我申請了貴公司的……職位。

Doyouhaveanyjobforapart-timer?你們需要兼職嗎?

I’dliketoknowifyouneedanyfull-timesecretary.我想知道你們是否需要全職秘書?

I’mlookingforajob.Arethereanyvacancies?我在找工作，請問你們有空缺嗎?

3．面試英語自我介紹的常用句型

IgottheBachelor’sDegreeinElectricalEngineeringandtookacourseintyping.

我獲得了電氣工程工學學士學位，還學過打字。

Ihaven’tdoneanythinglikethatbefore.我以前沒有做過這種工作。

IthinkI’mquitefitforassistant’sjob.我覺得我很適合做助理的工作。

Iusedtoworkasasale’smanager.我以前做銷售經(jīng)理。

I’mquitefamiliarwithediting.我做過很多編輯工作。

Iwantajobwithavacationeveryyear.我想找個每年都能度假的工作。

Iwasthinkingofajobinaschool.我打算到學校找份工作。

Iworkedintheaccountingsectionofamanufacturerofelectricalproducts.

我曾在電子產(chǎn)品制造商的會計組工作。

Iloveplayingtennis.我喜歡打網(wǎng)球。5.1.2SpecifiedEnglishWords

thelike同樣的東西，同類的事情

inletn.插入物；入口，進口

outletn.出口，排放孔；電源插座；銷路；發(fā)泄的方法；批發(fā)商店

ensuevi.跟著發(fā)生，接著發(fā)生；繼起vt.追求

deviationn.偏差；背離；誤差

thermocouplen.熱電偶

thermistorn.熱敏電阻；電熱調(diào)節(jié)器

throttlen.節(jié)流閥；風門vt.使……窒息；使……節(jié)流vi.節(jié)流，減速；窒息

tremendousadj.極大的，巨大的；驚人的

manipulatedvariable操縱量；被控變量

setpoint設定值；調(diào)整點；凝結(jié)點

foulingn.污染；污垢v.弄臟；犯規(guī)(foul的ing形式)

batchprocess間歇過程，斷續(xù)過程，分批過程

psigabbr.poundspersquareinch,gauge磅/平方英寸(表壓)

modelingn.建模，造型；立體感adj.制造模型的5.1.3Text

IntroductionstoProcessControl

Automaticprocesscontrolisconcernedwithmaintainingprocessvariables,temperatures,pressures,flows,compositions,andthelikeatsomedesiredoperationvalue.Processesaredynamicinnature.Changesarealwaysoccurring,andifactionsarenottaken,theimportantprocessvariables-thoserelatedtosafety,productquality,andproductionrates-willnotachievedesignconditions.

Athermostatisasimpleexampleforaclosedcontrolloop.Itconstantlymeasuresthecurrenttemperatureandcontrolstheheater’svalvesettingtoincreaseordecreasetheroomtemperatureaccordingtotheuser-definedsetting.Asimplemethodswitchestheheatereithercompletelyon,orcompletelyoff,andanovershootandundershootofthecontrolledtemperaturemustbeexpected.Amoreexpensivemethodvariestheamountofheatprovidedbytheheaterdependingonthedifferencebetweentherequiredtemperature(the“setpoint”)andtheactualtemperature.Thisminimizesover/undershoot.

Inordertofixideas,letusconsideraheatexchangerinwhichaprocessstreamisheatedbycondensingsteam.TheprocessissketchedinFig.5.1.Fig.5.1Heatexchanger

Thepurposeofthisunitistoheattheprocessfluidfromsomeinlettemperature,Ti(t),uptoacertaindesiredoutlettemperature,T(t).Asmentioned,theheatingmediumiscondensingsteam.

Theenergygainedbytheprocessfluidisequaltotheheatreleasedbythesteam,providedtherearenoheatlossestosurroundings,thatis,theheatexchangerandpipingarewellinsulated.

Inthisprocesstherearemanyvariablesthatcanchange,causingtheoutlettemperaturetodeviatefromitsdesiredvalue.Ifthishappens,someactionsmustbetakentocorrectforthisdeviation.Thatis,theobjectiveistocontroltheoutletprocesstemperaturetomaintainitsdesiredvalue.

OnewaytoaccomplishthisobjectiveisbyfirstmeasuringthetemperatureT(t),thencomparingittoitsdesiredvalue,and,basedonthiscomparison,decidingwhattodotocorrectforanydeviation.Theflowofsteamcanbeusedtocorrectforthedeviation.Thisis,ifthetemperatureisaboveitsdesiredvalue,thenthesteamvalvecanbethrottledbacktocutthesteamflow(energy)totheheatexchanger.Ifthetemperatureisbelowitsdesiredvalue,thesteamvalvecouldbeopenedsomemoretoincreasethesteamflow(energy)totheexchanger.Allofthesecanbedonemanuallybytheoperator,andsincetheprocedureisfairlystraightforward,itshouldpresentnoproblem.However,sinceinmostprocessplantstherearehundredsofvariablesthatmustbemaintainedatsomedesiredvalue,thiscorrectionprocedurewouldrequireatremendousnumberofoperators.Consequently,wewouldliketoaccomplishthiscontrolautomatically.Thatis,wewanttohaveinstrumentsthatcontrolthevariableswithoutrequiringinterventionfromtheoperator.Thisiswhatwemeanbyautomaticprocesscontrol.

Toaccomplishthisobjectiveacontrolsystemmustbedesignedandimplemented.ApossiblecontrolsystemanditsbasiccomponentsareshowninFig.5.2.Thefirstthingtodoistomeasuretheoutlettemperatureoftheprocessstream.Asensor(thermocouple,thermistors,etc)doesthis.Thissensor,alsooftencalledtheprimaryelement,isconnectedphysicallytoatransmitter,alsocalledthesecondaryelement,whichtakestheoutputfromthesensorandconvertsittoasignalstrongenoughtobetransmittedtoacontroller.Thecontroller,alsocalledthe“brain”ofthecontrolsystem,thenreceivesthesignal,whichisrelatedtothetemperature,andcomparesitwithdesiredvalue.Dependingonthiscomparison,thecontrollerdecideswhattodotomaintainthetemperatureatitsdesiredvalue.Basedonthisdecision,thecontrollerthensendsanothersignaltofinalcontrolelement,oftenacontrolvalvebutnotalways,whichinturnmanipulatesthesteamflow.

Fig.5.2Heatexchangercontrolloop

Ineverycontrolsystem,thethreebasicoperationsmustbepresentperformed.TheyareMeasurement(M),Decision(D)andAction(A).Thedecision-makingoperationinsomesystemisrathersimple,whileinothersitismorecomplex.Theengineerdesigningacontrolsystemmustbesurethattheactiontakenaffectsthevariabletobecontrolled,thatis,thattheactiontakenaffectsthemeasuredvalue.Otherwise,thesystemisnotcontrollingandwillprobablydomoreharmthangood.

Tobesuccessfulinpracticeofautomaticprocesscontrol,theengineermustfirstunderstandtheprinciplesofprocessengineering.Forthestudyofprocessautomaticcontrolitisalsoimportanttounderstandhowprocessesbehavedynamically.Consequently,itisnecessarytodevelopthesetofequationsthatdescribedifferentprocesses.Thisiscalledmodeling.Todothis,theknowledgeofthebasicprinciplesmentionedinthepreviousparagraphandofmathematicsthroughdifferentialisneeded.InprocesscontroltheLaplacetransformsareusedheavily.Thisgreatlysimplifiesthesolutionofdifferentialequationsandthedynamicanalysisofprocessesandtheircontrolsystems.

Anotherimportant“tool”forthestudyandpracticeofprocesscontroliscomputersimulation.Manyoftheequationsdevelopedtodescribeprocessarenonlinearinnatureand,consequently,themostexactwaytosolvethemisbynumericalmethods;thismeanscomputersolution.Thecomputersolutionofprocessmodelsiscalledsimulation.

Notes

1．Theenergygainedbytheprocessfluidisequaltotheheatreleasedbythesteam,providedtherearenoheatlossestosurroundings,thatis,theheatexchangerandpipingarewellinsulated.

只要周圍沒有熱損耗，即熱交換器和管道是絕熱的，過程流體獲得的熱量就等于蒸汽釋放的熱量。

2．Inthisprocesstherearemanyvariablesthatcanchange,causingtheoutlettemperaturetodeviatefromitsdesiredvalue.

在這個過程中很多變量會發(fā)生變化，繼而導致出口溫度偏離期望值?

3．Thatis,wewanttohaveinstrumentsthatcontrolthevariableswithoutrequiringinterventionfromtheoperator.

就是說，我們想利用設備來控制變量，而無需操作人員介入?5.1.4ReadingMaterials

TypesofControlSystems

Processcontrolisextensivelyusedinindustryandenablesmassproductionofcontinuousprocessessuchasoilrefining,papermanufacturing,chemicals,powerplantsandmanyotherindustries.Processcontrolenablesautomation,withwhichasmallstaffofoperatingpersonnelcanoperateacomplexprocessfromacentralcontrolroom.

Itisnecessarytodefinesometermsusedinthefieldofautomaticprocesscontrol.Thefirsttermiscontrolledvariable.Thisisthevariablethatmustbemaintainedorcontrolledatsomedesiredvalue.Intheprecedingexample,theprocessoutlettemperature,T(t),isthecontrolledvariable.Thesecondtermissetpoint,thedesiredvalueofcontrolledvariable.Themanipulatedvariableisthevariableusedtomaintainthecontrolledvariableatitssetpoint.Intheexample,theflowofsteamisthemanipulatedvariable.Finally,anyvariablethatcancausethecontrolledvariabletodeviateawayfromsetpointisdefinedasadisturbanceorupset.Inmostprocessthereareanumberofdifferentdisturbances.Asanexample,intheheatexchangershowninFig.5.1,possibledisturbancesareinletprocesstemperatureTi(t),theprocessflowq(t),thequalityoftheenergyofthesteam,ambientconditions,processfluidcomposition,fouling,andsoon.Whatisimportanthereistounderstandthatintheprocessindustries,mostoftenitisbecauseofthisdisturbancethatautomaticprocesscontrolisneeded.Iftherewerenodisturbances,design-operatingconditionswouldprevailandtherewouldbenonecessityofcontinuously“policing”theprocess.

Acommonlyusedcontroldevicecalledaprogrammablelogiccontroller,oraPLC,isusedtoreadasetofdigitalandanaloginputs,applyasetoflogicstatements,andgenerateasetofanaloganddigitaloutputs.Usingtheexampleinthepreviousparagraph,theroomtemperaturewouldbeaninputtothePLC.Thelogicalstatementswouldcomparethesetpointtotheinputtemperatureanddeterminewhethermoreorlessheatingwasnecessarytokeepthetemperatureconstant.APLCoutputwouldtheneitheropenorclosethehotwatervalve,anincrementalamount,dependingonwhethermoreorlesshotwaterwasneeded.LargermorecomplexsystemscanbecontrolledbyaDistributedControlSystem(DCS)orSupervisoryControlandDataAcquisition(SCADA)System.

Inpractice,processcontrolsystemscanbecharacterizedasoneormoreofthefollowingforms:

Discrete.

Foundinmanymanufacturing,motionandpackagingapplications.Roboticassembly,suchasthatfoundinautomotiveproduction,canbecharacterizedasdiscreteprocesscontrol.Mostdiscretemanufacturinginvolvestheproductionofdiscretepiecesofproduct,suchasmetalstamping.

Batch.Someapplicationsrequirethatspecificquantitiesofrawmaterialsbecombinedinspecificwaysforparticulardurationstoproduceanintermediateorendresult.Oneexampleistheproductionofadhesivesandglues,whichnormallyrequiresthemixingofrawmaterialsinaheatedvesselforaperiodoftimetoformaquantityofendproduct.Otherimportantexamplesaretheproductionoffood,beveragesandmedicine.Batchprocessesaregenerallyusedtoproducearelativelylowtointermediatequantityofproductperyear(afewpoundstomillionsofpounds).

Continuous.Often,aphysicalsystemisrepresentedthroughvariablesthataresmoothanduninterruptedintime.Thecontrolofthewatertemperatureinaheatingjacket,forexample,isanexampleofcontinuousprocesscontrol.Someimportantcontinuousprocessesaretheproductionoffuels,chemicalsandplastics.Continuousprocessesinmanufacturingareusedtoproduceverylargequantitiesofproductperyear(millionstobillionsofpounds).

Applicationshavingelementsofdiscrete,batchandcontinuousprocesscontrolareoftencalledhybridapplications.5.1.5Homework

1．Pleasesumupthemainpointsofthetextinseveralsentences.

2．TranslatethefollowingsentencesintoChinese.

(1)ThiskindofnonlinearPIDcontrollerholdsaflexiblegain-schedulebyselectingitsparameterssimply.

(2)AsabasicpartofaVirtualManufacturingPlatform,manufacturingsystemmodelingiscriticaltothesuccessofprocesscontrolinamultirobotvirtualmanufacturingenvironment.

(3)Aprocesscontrolalertoccurswhenasuccessionofdatapointsshowsatypicalpatternthatwaspossiblycausedbychangestothelaboratoryormanufacturingprocess.

(4)Thatis,wewanttohaveinstrumentsthatcontrolthevariableswithoutrequiringinterventionfromtheoperator.

(5)Theexperimentresultdemonstratesitsperformanceandcontroleffectivenesscanmeettherequirementofpracticalprocesscontrol.

5.2.1語言現(xiàn)象——科技文獻檢索

文獻是在存儲、檢索、利用或傳遞記錄信息的過程中，可作為一個單元處理的，在載體內(nèi)、載體上或依附載體而存儲有信息或數(shù)據(jù)的載體。文獻具有知識、載體、記錄方式三要素。文獻本身固有的性質(zhì)分別是知識性、客觀物質(zhì)性、人工記錄性和動態(tài)發(fā)展性。5.2SensorandItsCharacteristics隨著科學技術的迅速發(fā)展，科技文獻，尤其是尖端科學文獻增加速度更快，且倍增周期逐年縮短?？萍嘉墨I種類繁多，有學術論文、科技報告、學位論文和科技會議文獻等原始文獻，也有在此基礎上經(jīng)整理、加工、壓縮、提煉后編制成的各種檢索工具，如書目、題錄、索引、文摘、百科全書、手冊、年鑒和名錄等。進行科學研究、撰寫學位和學術論文、進行畢業(yè)設計、從事產(chǎn)品的開發(fā)和進行發(fā)明創(chuàng)造等工作，都要檢索相關的文獻。因此，文獻檢索是科技人員必備的基本技能，是科學研究的先期工作，是知識更新的手段，也是能力培養(yǎng)的重要途徑。

1．文獻的形式

各類專業(yè)文獻種類繁多，形態(tài)各異。從形式/載體上分為以下幾種：

紙質(zhì)型(Printedform)。也叫印刷型，是以紙張為存儲介質(zhì)，以手寫、印刷為記錄手段而存在的一種傳統(tǒng)的文獻形式。

縮微型(Microform)?？s微型以感光材料為存儲介質(zhì)，以縮微照相為記錄手段而存在的一種文獻形式。

聲像/視聽型(Audio-Visualform)。聲像/視聽型又稱為視聽資料或直感資料，以磁性材料和光學材料為存儲介質(zhì)。機讀/電子型(MachineReadableform)。機讀/電子型全稱為計算機可讀型文獻，以磁性材料(磁帶、磁盤或光盤等)為存儲介質(zhì)。

2．文獻的級別

專業(yè)文獻從級別上可分為下面幾種：

一次文獻/信息(primaryLiterature/info)，即原始文獻，如期刊文獻(Journalliterature)、科技報告(Sci-Techreport)、學術會議論文集(Proceedings)、專利(Patentspecification)、論文(Paper)、學位論文(Thesis)等。

二次文獻/信息(secondaryliterature/info)，即檢索工具，如條目(entryreferencecitationrecord)、文摘(Abstract)、索引(Index)、目錄(Catalog)、題錄(Bibliography)等。

三次文獻(Tertiaryliterature/info)，如詞典或百科全書等參考書(Referencebook)，屬于參考性文獻。

3．文獻的類型與識別

文獻的類型有很多，一般分為以下幾類：

科技圖書(Sci-Techbook)，主要包括專著(Monograph)、文選(Anthology)、教材(Textbook)和參考書(Referencebook)等；科技期刊(Sci-TechJournal)，主要包括雜志(magazine)、不定期的連續(xù)出版物(serial)和期刊(periodical)等；科技報告(Sci-TechReport)；專利文獻(PatentDocument)，主要包括專利說明書(Patentspecification)和專利公告(bulletin)等；會議文獻(Conferencepaper)；學位論文(Dissertation,Thesis)；其他標準文獻、產(chǎn)品資料、技術檔案、政府出版物等。

4．文獻/信息檢索(Literature/

InformationRetrieval/

Access)

文獻檢索的手段分為手檢(書本型工具/期刊)和機檢(數(shù)據(jù)庫系統(tǒng))。其中手檢是對相關的印刷型資源進行檢索，包括各種檢索工具和專業(yè)期刊。計算機檢索包括光盤數(shù)據(jù)庫檢索、網(wǎng)絡數(shù)據(jù)庫檢索(比較流行的檢索方式)和互聯(lián)網(wǎng)信息檢索(使用搜索引擎進行互聯(lián)網(wǎng)信息檢索)。目前常用的中文網(wǎng)絡數(shù)據(jù)庫有CNKI系列數(shù)據(jù)庫(，包括中國期刊全文數(shù)據(jù)庫、中國優(yōu)秀博碩論文數(shù)據(jù)庫和中國專利數(shù)據(jù)庫)、超星數(shù)字圖書館()、萬方數(shù)據(jù)庫(/qikan)和維普數(shù)據(jù)庫()等。

英文數(shù)據(jù)庫有CSA數(shù)據(jù)庫、SpringerLINK全文電子期刊、EBSCO數(shù)據(jù)庫、OCLC數(shù)據(jù)庫、IEL數(shù)據(jù)庫、《不列顛百科全書》網(wǎng)絡版和WorldSciNet電子期刊等。

互聯(lián)網(wǎng)信息檢索是指借助于搜索引擎進行互聯(lián)網(wǎng)信息檢索，常用的WWW搜索引擎主要有：

/

除了常規(guī)的WWW搜索引擎外，還可以使用FTP搜索引擎，其功能是搜集匿名FTP服務器提供的目錄列表以及向用戶提供文件信息的查詢服務。由于FTP搜索引擎專門針對各種文件，因而相對WWW搜索引擎，尋找軟件、圖像、電影和音樂等文件時，使用FTP搜索引擎更加便捷。常用的FTP搜索引擎主要有：

北大天網(wǎng)FTP：

清華大學：/，/北京大學：，/，/

中國科學技術大學：/

浙江大學：/

北京郵電大學：/，/

華中理工大學：/

上海交通大學：/，/哈爾濱工業(yè)大學：/

西安交通大學：/，/，/

香港中文大學：ftp://ftp.cuhk.hk/，.hk/，.hk/

5．檢索點/途徑(AccessPoint)

檢索點是檢索系統(tǒng)預先設置的用戶可用于檢索的途徑。

分類(Classified)：按文獻所屬的學科類別來檢索文獻。在檢索文獻之前應根據(jù)課題的主要內(nèi)容以及數(shù)據(jù)庫所采用的分類表，確定分類號。

主題(Subject)：從文獻的主題概念出發(fā)，通過主題詞或關鍵詞檢索文獻。

題名(Title)：根據(jù)文獻題名來檢索文獻。文獻題名主要指書名、刊名、篇名等。題名允許中、英文混合或者是題名的一部分。著者(Author)：通過著者[個人著者、團體著者(CorporateAuthor/Authors’Affiliation)]的名稱來檢索文獻。

號碼檢索：通過號碼(Code/Coden)如ISBN(InternationalStandardBookNumber)號、ISSN號、專利號、標準號、報告號等來檢索文獻。5.2.2SpecifiedEnglishWords

sensorn.傳感器

mercury-in-glassthermometer玻璃水銀溫度計；水銀溫度計；汞柱玻璃溫度計

calibratevt.測定……的口徑，標定，校準……的刻度(或分度)，定……的刻度

straingauge應變儀；變形測量器；應變儀；變形測量器

foilvt.挫??；阻止，擋開；襯托；貼箔于n.箔，金屬薄片；葉形片；襯托，烘托

etchvt.蝕刻；鮮明地描述；銘記vi.蝕刻n.刻蝕；腐蝕劑

serpentineadj.陰險的；蜿蜒的；彎彎曲曲的vt.使迂回曲折地行進n.蛇紋石

resinn.樹脂；松香vt.涂樹脂；用樹脂處理

modestadj.謙虛的，謙遜的，純潔的，不太多的，不過分的，適度的，適中的

responsivityn.響應率；反應性

piezoresistiveadj.壓電電阻的；壓電電阻效應的

microscopicadj.用顯微鏡可見的；微觀的

MEMSabbr.微電子機械系統(tǒng)(Micro-electromechanicalSystems)

fullscalerange量程

degradationn.降格，降級；退化；墮落

hysteresisn.磁滯(現(xiàn)象)

aliasingn.別名使用；混淆現(xiàn)象

calibrationn.標定，校正，調(diào)節(jié),口徑測定，刻度，分等級5.2.3Text

SensorandItsCharacteristics

Thisisanintroductiontosomeofthephysicalprinciplesthatunderliesensorsininstrumentsystems.Itisnotintendedtobedefinitive,orverydetailed,buttogivethereaderanideaofwhatisreadilyachievablewiththevarioussystems.

Asensor(alsocalleddetectors)isadevicethatmeasuresameasurableattributeandconvertsitintoasignalwhichcanbereadbyanobserverorbyaninstrument.Forexample,amercury-in-glassthermometerconvertsthemeasuredtemperatureintoexpansionandcontractionofaliquidwhichcanbereadonacalibratedglasstube.Athermocoupleconvertstemperaturetoanoutputvoltagewhichcanbereadbyavoltmeter.Foraccuracy,mostsensorsarecalibratedagainstknownstandards.

Atconstanttemperature,theresistanceRofametalorsemiconductorelementofareaA,lengthl,resistivity

,is

R＝l

/A(5-2-1)

andwhentheelementisstrainedthischangesbyanamount

so

Atypicalstraingaugeconsistsofametalfoil,photo-etchedtoformaserpentinepattern,andmountedonaresinbackingfilm.Thisisthenattachedtothestructuretobemonitoredwithadhesive.Metalsensor-elementsaredominatedbythegeometrictermsintheaboveequationandthereforetheyarerelativelytemperatureindependentandhaveamodestgaugefactor(i.e.responsivity)ofabout2.Semiconductorelementscanexploitalargepiezoresistiveeffectyieldinggaugefactorsof150.However,thisisattheexpenseoftemperaturestabilityandsomesortofcompensationschemeisusuallyrequiredinpractice.

Straingaugesarewidelyusedinmanyapplications;theyaresmall,cheap,sensitiveandreliable,andmanyvariables(e.g.pressure)canbeusedtocausestrain.

Asensor’ssensitivityindicateshowmuchthesensor’soutputchangeswhenthemeasuredquantitychanges.Forinstance,ifthemercuryinathermometermoves1

cmwhenthetemperaturechangesby1℃,thesensitivityis1

cm/℃(itisbasicallytheslopeDy/Dxassumingalinearcharacteristic).Sensorsthatmeasureverysmallchangesmusthaveveryhighsensitivities.Sensorsalsohaveanimpactonwhattheymeasure;forinstance,aroomtemperaturethermometerinsertedintoahotcupofliquidcoolstheliquidwhiletheliquidheatsthethermometer.Sensorsneedtobedesignedtohaveasmalleffectonwhatismeasured;makingthesensorsmalleroftenimprovesthisandmayintroduceotheradvantages.

TechnologicalprogressallowsmoreandmoresensorstobemanufacturedonamicroscopicscaleasmicrosensorsusingMEMStechnology.Inmostcases,amicrosensorreachesasignificantlyhigherspeedandsensitivitycomparedwithmacroscopicapproaches.

Agoodsensorissensitivetothemeasuredpropertyonly,isinsensitivetoanyotherpropertylikelytobeencounteredinitsapplication,anddoesnotinfluencethemeasuredproperty.

Idealsensorsaredesignedtobelinearorlineartosomesimplemathematicalfunctionofthemeasurement,typicallylogarithmic.Theoutputsignalofsuchasensorislinearlyproportionaltothevalueorsimplefunctionofthemeasuredproperty.Thesensitivityisthendefinedastheratiobetweenoutputsignalandmeasuredproperty.Forexample,ifasensormeasurestemperatureandhasavoltageoutput,thesensitivityisaconstantwiththeunit[V/K];thissensorislinearbecausetheratioisconstantatallpointsofmeasurement.

Ifthesensorisnotideal,severaltypesofdeviationscanbeobserved:

Thesensitivitymayinpracticedifferfromthevaluespecified.Thisiscalledasensitivityerror,butthesensorisstilllinear.

Sincetherangeoftheoutputsignalisalwayslimited,theoutputsignalwilleventuallyreachaminimumormaximumwhenthemeasuredpropertyexceedsthelimits.Thefullscalerangedefinesthemaximumandminimumvaluesofthemeasuredproperty.

Iftheoutputsignalisnotzerowhenthemeasuredpropertyiszero,thesensorhasanoffsetorbias.Thisisdefinedastheoutputofthesensoratzeroinput.

Ifthesensitivityisnotconstantovertherangeofthesensor,thisiscallednonlinearity.Usuallythisisdefinedbytheamounttheoutputdifferencefromidealbehavioroverthefullrangeofthesensor,oftennotedasapercentageofthefullrange.

Ifthedeviationiscausedbyarapidchangeofthemeasuredpropertyovertime,thereisadynamicerror.Often,thisbehaviorisdescribedwithabodeplotshowingsensitivityerrorandphaseshiftasfunctionofthefrequencyofaperiodicinputsignal.

Iftheoutputsignalslowlychangesindependentofthemeasuredproperty,thisisdefinedasdrift.Longtermdriftusuallyindicatesaslowdegradationofsensorpropertiesoveralongperiodoftime.

Noiseisarandomdeviationofthesignalthatvariesintime.

Hysteresisisanerrorcausedbywhenthemeasuredpropertyreversesdirection,butthereissomefinitelagintimeforthesensortorespond,creatingadifferentoffseterrorinonedirectionthanintheother.

Ifthesensorhasadigitaloutput,theoutputisessentiallyanapproximationofthemeasuredproperty.Theapproximationerrorisalsocalleddigitizationerror.

Ifthesignalismonitoreddigitally,limitationofthesamplingfrequencyalsocancauseadynamicer