傳感器外文翻譯

1、 BasicknowledgeoftransducersAtransducerisadevicewhichconvertsthequantitybeingmeasuredintoanoptical,mechanical,or-morecommonly-electricalsignal.Theenergy-conversionprocessthattakesplaceisreferredtoastransduction.Transducersareclassifiedaccordingtothetransductionprincipleinvolvedandtheformofthemeasure

2、d.Thusaresistancetransducerformeasuringdisplacementisclassifiedasaresistancedisplacementtransducer.Otherclassificationexamplesarepressurebellows,forcediaphragm,pressureflapper-nozzle,andsoon.1、TransducerElementsAlthoughthereareexception,mosttransducersconsistofasensingelementandaconversionorcontrole

3、lement.Forexample,diaphragms,bellows,straintubesandrings,bourdontubes,andcantileversaresensingelementswhichrespondtochangesinpressureorforceandconvertthesephysicalquantitiesintoadisplacement.Thisdisplacementmaythenbeusedtochangeanelectricalparametersuchasvoltage,resistance,capacitance,orinductance.S

4、uchcombinationofmechanicalandelectricalelementsformelectromechanicaltransducingdevicesortransducers.Similarcombinationcanbemadeforotherenergyinputsuchasthermal.Photo,magneticandchemical,givingthermoelectric,photoelectric,electromaanetic,andelectrochemicaltransducersrespectively.2、TransducerSensitivi

5、tyTherelationshipbetweenthemeasuredandthetransduceroutputsignalisusuallyobtainedbycalibrationtestsandisreferredtoasthetransducersensitivityK1=output-signalincrement/measuredincrement.Inpractice,thetransducersensitivityisusuallyknown,and,bymeasuringtheoutputsignal,theinputquantityisdeterminedfrominpu

6、t=output-signalincrement/K1.3、CharacteristicsofanIdealTransducerThehightransducershouldexhibitthefollowingcharacteristicshighfidelity-thetransduceroutputwaveformshapebeafaithfulreproductionofthemeasured;thereshouldbeminimumdistortion.Thereshouldbeminimuminterferencewiththequantitybeingmeasured;thepr

7、esenceofthetransducershouldnotalterthemeasuredinanyway.Size.Thetransducermustbecapableofbeingplacedexactlywhereitisneeded.Thereshouldbealinearrelationshipbetweenthemeasuredandthetransducersignal.Thetransducershouldhaveminimumsensitivitytoexternaleffects,pressuretransducers,forexample,areoftensubject

8、edtoexternaleffectssuchvibrationandtemperature.Thenaturalfrequencyofthetransducershouldbewellseparatedfromthefrequencyandharmonicsofthemeasurand.4、ElectricalTransducersElectricaltransducersexhibitmanyoftheidealcharacteristics.Inadditiontheyofferhighsensitivityaswellaspromotingthepossibleofremoteindi

9、cationormesdurement.Electricaltransducerscanbedividedintotwodistinctgroups:variable-control-parametertypes,whichinclude:resistancecapacitanceinductancemutual-inductancetypesThesetransducersallrelyonexternalexcitationvoltagefortheiroperation.self-generatingtypes,whichincludeelectromagneticthermoelect

10、ricphotoemissivepiezo-electrictypesTheseallthemselvesproduceanoutputvoltageinresponsetothemeasurandinputandtheireffectsarereversible.Forexample,apiezo-electrictransducernormallyproducesanoutputvoltageinresponsetothedeformationofacrystallinematerial;however,ifanalternatingvoltageisappliedacrossthemat

11、erial,thetransducerexhibitsthereversibleeffectbydeformingorvibratingatthefrequencyofthealternatingvoltage.5、ResistanceTransducersResistancetransducersmaybedividedintotwogroups,asfollows:Thosewhichexperiencealargeresistancechange,measuredbyusingpotential-dividermethods.Potentiometersareinthisgroup.Th

12、osewhichexperienceasmallresistancechange,measuredbybridge-circuitmethods.Examplesofthisgroupincludestraingaugesandresistancethermometers.PotentiometersAlinearwire-woundpotentiometerconsistsofanumberofturnsresistancewirewoundaroundanon-conductingformer,togetherwithawipingcontactwhichtravelsoverthebar

13、wires.Theconstructionprinciplesareshowninfigurewhichindicatethatthewiperdisplacementcanberotary,translational,oracombinationofbothtogiveahelical-typemotion.Theexcitationvoltagemaybeeithera.c.ord.c.andtheoutputvoltageisproportionaltotheinputmotion,providedthemeasuringdevicehasaresistancewhichismuchgr

14、eaterthanthepotentiometerresistance.Suchpotentiometerssufferfromthelinkedproblemofresolutionandelectricalnoise.Resolutionisdefinedasthesmallestdetectablechangeininputandisdependentonthecross-sectionalareaofthewindingsandtheareaoftheslidingcontact.Theoutputvoltageisthusaserialsofstepsasthecontactmove

15、sfromonewiretonext.Electricalnoisemaybegeneratedbyvariationincontactresistance,bymechanicalwearduetocontactfriction,andbycontactvibrationtransmittedfromthesensingelement.Inaddition,themotionbeingmeasuredmayexperiencesignificantmechanicalloadingbytheinertiaandfrictionofthemovingpartsofthepotentiomete

16、r.Thewearonthecontactingsurfacelimitsthelifeofapotentiometertoafinitenumberoffullstrokesorrotationsusuallyreferredtointhemanufacturesspecificationasthenumberofcyclesoflifeexpectancy,atypicalvaluebeing20*1000000cycles.TheoutputvoltageV0oftheunloadpotentiometercircuitisdeterminedasfollows.Letresistanc

17、eR1=xi/xt*Rtwherexi=inputdisplacement,xt=maximumpossibledisplacement,Rttotalresistanceofthepotentiometer.ThenoutputvoltageV0=V*R1/(R1+(Rt-R1)=V*R1/Rt=V*xi/xt*Rt/Rt=V*xi/xt.Thisshowsthatthereisastraight-linerelationshipbetweenoutputvoltageandinputdisplacementfortheunloadedpotentiometer.Itwouldseentha

18、thighsensitivitycouldbeachievedsimplybyincreasingtheexcitationvoltageV.however,themaximumvalueofVisdeterminedbythemaximumpowerdissipationPofthefinewiresofthepotentiometerwindingandisgivenbyV=(PRt)1/2.ResistanceStrainGaugesResistancestraingaugesaretransducerswhichexhibitachangeinelectricalresistancei

19、nresponsetomechanicalstrain.Theymaybeofthebondedorunbondedvariety.bondedstraingaugesUsinganadhesive,thesegaugesarebonded,orcemented,directlyontothesurfaceofthebodyorstructurewhichisbeingexamined.Examplesofbondedgaugesarefinewiregaugescementedtopaperbackingphoto-etchedgridsofconductingfoilonanepoxy-r

20、esinbackingasinglesemiconductorfilamentmountedonanepoxy-resinbackingwithcopperornickelleads.Resistancegaugescanbemadeupassingleelementstomeasuringstraininonedirectiononly,oracombinationofelementssuchasrosetteswillpermitsimultaneousmeasurementsinmorethanonedirection.unbondedstraingaugesAtypicalunbond

21、ed-strain-gaugearrangementshowsfineresistancewiresstretchedaroundsupportsinsuchawaythatthedeflectionofthecantileverspringsystemchangesthetensioninthewiresandthusalterstheresistanceofwire.Suchanarrangementmaybefoundincommerciallyavailableforce,load,orpressuretransducers.ResistanceTemperatureTransduce

22、rsThematerialsforthesecanbedividedintotwomaingroups:a)metalssuchasplatinum,copper,tungsten,andnickelwhichexhibitandincreaseinresistanceasthetemperaturerises;theyhaveapositivetemperaturecoefficientofresistance.b)semiconductors,suchasthermistorswhichuseoxidesofmanganese,cobalt,chromium,ornickel.Thesee

23、xhibitlargenon-linearresistancechangeswithtemperaturevariationandnormallyhaveanegativetemperaturecoefficientofresistance.a)metalresistancetemperaturetransducersThesedepend,formanypracticalpurposeandwithinanarrowtemperaturerange,upontherelationshipRl=R0*l+a*(bl-b2)whereacoefficientofresistanceinC-l,a

24、ndROresistanceinohmsatthereferencetemperatureb0=0CatthereferencetemperaturerangeC.Theinternationalpracticaltemperaturescaleisbasedontheplatinumresistancethermometer,whichcoversthetemperaturerange-259.35Cto63O.5C.b)thermistorresistancetemperaturetransducersThermistorsaretemperature-sensitiveresistors

25、whichexhibitlargenon-linerresistancechangeswithtemperaturevariation.Ingeneral,theyhaveanegativetemperaturecoefficient.Forsmalltemperatureincrementsthevariationinresistanceisreasonablylinear;but,iflargetemperaturechangesareexperienced,speciallinearizingtechniquesareusedinthemeasuringcircuitstoproduce

26、alinearrelationshipofresistanceagainsttemperature.Thermistorsarenormallymadeintheformofsemiconductordiscsenclosedinglassvitreousenamel.Sincetheycanbemadeassmallaslmm,quiterapidresponsetimesarepossible.PhotoconductiveCellsThephotoconductivecell,usesalight-sensitivesemiconductormaterial.Theresistanceb

27、etweenthemetalelectrodesdecreaseastheintensityofthelightstrikingthesemiconductorincreases.Commonsemiconductormaterialsusedforphoto-conductivecellsarecadmiumsulphide,leadsulphide,andcopper-dopedgermanium.Theusefulrangeoffrequenciesisdeterminedbymaterialused.Cadmiumsulphideismainlysuitableforvisibleli

28、ght,whereasleadsulphidehasitspeakresponseintheinfra-redregionandis,therefore,mostsuitableforflame-failuredetectionandtemperaturemeasurement.PhotoemissiveCellsWhenlightstrikesthecathodeofthephotoemissivecellaregivensufficientenergytoarrivethecathode.Thepositiveanodeattractstheseelectrons,producingacu

29、rrentwhichflowsthroughresistorRandresultinginanoutputvoltageV.PhotoelectricallygeneratedvoltageV=Ip.RlWhereIp=photoelectriccurrent(A),andphotoelectriccurrentIp=Kt.BWhereKt=sensitivity(A/im),andB=illuminationinput(lumen)Althoughtheoutputvoltagedoesgiveagoodindicationofthemagnitudeofillumination,thece

30、llsaremoreoftenusedforcountingorcontrolpurpose,wherethelightstrikingthecathodecanbeinterrupted.6、CapacitiveTransducersThecapacitancecanthusmadetovarybychangingeithertherelativepermittivity,theeffectivearea,orthedistanceseparatingtheplates.Thecharacteristiccurvesindicatethatvariationsofareaandrelativ

31、epermittivitygivealinearrelationshiponlyoverasmallrangeofspacings.Thusthesensitivityishighforsmallvaluesofd.Unlikethepotentionmeter,thevariable-distancecapacitivetransducerhasaninfiniteresolutionmakingitmostsuitableformeasuringsmallincrementsofdisplacementorquantitieswhichmaybechangedtoproduceadispl

32、acement.7、InductiveTransducersTheinductancecanthusbemadetovarybychangingthereluctanceoftheinductivecircuit.Measuringtechniquesusedwithcapacitiveandinductivetransducers:a)A.C.excitedbridgesusingdifferentialcapacitorsinductors.b)A.C.potentiometercircuitsfordynamicmeasurements.D.C.circuitstogiveavoltag

33、eproportionaltovelocityforacapacitor.Frequency-modulationmethods,wherethechangeofCorLvariesthefrequencyofanoscillationcircuit.Importantfeaturesofcapacitiveandinductivetransducersareasfollows:resolutioninfiniteaccuracy+-0.1%offullscaleisquoteddisplacementranges25*10-6mto10-3mrisetimelessthan50uspossi

34、bleTypicalmeasurandsaredisplacement,pressure,vibration,sound,andliquidlevel.8、LinearVariable-differentialTtransformer9、Piezo-electricTransducers10、ElectromagneticTransducers11、ThermoelectricTransducers12、PhotoelectricCells13、MechanicalTransducersandSensingElements 傳感器的基礎(chǔ)知識(shí)傳感器是一種把被測(cè)量轉(zhuǎn)換為光的、機(jī)械的或者更平常的電信

35、號(hào)的裝置。能量轉(zhuǎn)換的過程稱之為換能。按照轉(zhuǎn)換原理和測(cè)量形式對(duì)傳感器進(jìn)行分類。用來測(cè)量位移的電阻式傳感器被歸為電阻式位移傳感器。分類如壓力波紋管、壓力膜和壓力閥等。1、傳感器元件除特例外，大多數(shù)的傳感器都由敏感元件、轉(zhuǎn)換元件或控制元件組成。如振動(dòng)膜、波紋管、應(yīng)力管和應(yīng)力環(huán)、低音管和懸臂都是敏感元件，它們對(duì)壓力和力作出響應(yīng)把物理量轉(zhuǎn)變成位移。然后位移可以改變電參數(shù)，如電壓、電阻、電容或者感應(yīng)系數(shù)。機(jī)械式和電子式元件合并形成機(jī)電式傳感設(shè)備或傳感器。這樣的組合可用來輸入能量信號(hào)。熱的，光的，磁的和化學(xué)的相互結(jié)合產(chǎn)生的熱電式、光電式、電磁式和電化學(xué)式傳感器。2、傳感器靈敏度通過校正測(cè)量系統(tǒng)獲得的被測(cè)物理

36、量和傳感器輸出信號(hào)的關(guān)系叫做傳感器靈敏度K1,也就是K1=輸出信號(hào)增量/測(cè)量增量。實(shí)際中，傳感器的靈敏度是已知的，并且通過測(cè)量輸出信號(hào)，輸入量由下式?jīng)Q定，輸入量=輸出信號(hào)增量/K1。3、理想傳感器的特性高保真性：傳感器輸出波形應(yīng)該真實(shí)可靠地再現(xiàn)被測(cè)量，并且失真很小?？蓽y(cè)量最小的干擾，任何時(shí)候傳感器的出現(xiàn)不能改變被測(cè)量。尺寸：傳感器必須能正確地放在所需的地方。被測(cè)量和傳感器信號(hào)之間應(yīng)該有一個(gè)線性關(guān)系。傳感器對(duì)外部影響的靈敏度應(yīng)該小，例如壓力傳感器經(jīng)常受到外部振動(dòng)和溫度的響。傳感器的固有頻率應(yīng)該避開被測(cè)量的頻率和諧波。4、電傳感器電傳感器具有許多理想特性。它們不僅實(shí)現(xiàn)遠(yuǎn)程測(cè)量和顯示，還能提供高靈敏

37、度。電傳感器可分為兩大類。a)變參數(shù)型，包括：電阻式；電容式；iii自感應(yīng)式；互感應(yīng)式；這些傳感器的工作依靠外部電壓。b)自激型，包括：電磁式；熱電式；光柵式；壓電式。這些傳感器根據(jù)測(cè)量輸入值產(chǎn)生輸出電壓，而且這一過程是可逆的。比如，在一般情況下，壓電式傳感器可根據(jù)晶體材料的變形產(chǎn)生一個(gè)輸出電壓；但是，如果在材料上施加一個(gè)可變電壓，傳感器可以通過變形或與變電壓同頻率的振動(dòng)來體現(xiàn)可逆效應(yīng)。5、電阻式傳感器電阻式傳感器可以分為兩大類：那些表現(xiàn)為大電阻變化的物理量可通過分壓方式進(jìn)行測(cè)量，電位器就屬于此類。那些表現(xiàn)為小電阻變化的物理量可通過橋電路方式進(jìn)行測(cè)量，這一類包括應(yīng)變儀和電阻溫度計(jì)。電位器繞線式

38、電位器由許多繞在非導(dǎo)體骨架的電阻絲以及滑行在線圈上的觸頭組成。結(jié)構(gòu)原理如圖，觸頭能夠轉(zhuǎn)動(dòng)、直線式運(yùn)動(dòng)或者兩運(yùn)動(dòng)合成的螺旋式運(yùn)動(dòng)。如果測(cè)量設(shè)備的電阻比電位器的電阻大，那么電壓既可以是交流也可以是直流，且輸出電壓與輸入運(yùn)動(dòng)成正比。這樣的電位器存在著分辨率和電子噪聲的問題。分辨率是指傳感器能檢測(cè)到的最小的輸入增量，分辨率大小取決于線圈與滑動(dòng)觸頭圍成的面積。因此，輸出電壓為觸頭從一端移到另一端時(shí)一系列階躍。電子噪聲可以通過接觸電阻的振動(dòng)、觸頭摩擦形成的機(jī)械磨損以及從敏感元件傳出的觸頭振動(dòng)產(chǎn)生。另外，測(cè)得的運(yùn)動(dòng)量可以通過慣性和電位器中移動(dòng)元件的摩擦獲得較大的機(jī)械載荷。觸頭表面的磨損將電位器的壽命限制為多少轉(zhuǎn)。通常指的是生產(chǎn)商在說明書中提及的“壽命轉(zhuǎn)數(shù)”，一個(gè)典型值為20*1000000轉(zhuǎn)?？蛰d電位器電路的輸出電壓V0由下式?jīng)Q定：設(shè)電阻R1=xi/xt*Rt,其中xi為輸入位移，xt為最大可能位移，Rt為電位器的電阻。那么輸入電壓V0=V*R1/(R1+(Rt-R1)=V*R1/Rt=V*xi/xt*Rt/Rt=V*xi/xt上式表明，對(duì)于空載電位器輸出電壓和輸入位移呈直線關(guān)系。通過提高激勵(lì)電壓V可以獲得高的靈敏度。但是，V的最大值由電位器線圈金屬絲的功率損耗P決定，即V=(PRt)l/2。電阻應(yīng)變儀電阻應(yīng)變儀是由機(jī)械應(yīng)變產(chǎn)生電阻變化的傳感