傳感器專業(yè)名詞英文解釋教學(xué)教材

精品文檔精品文檔精品文檔精品文檔BrieflydefinethefollowingtermsTransducerAtransducerisadevicethatconvertsasignalfromonephysicalformtoacorrespondingsignalhavingadifferentphysicalform.SensorAsensorconvertsaphysicalsignalintoanelectricalsignal(i.e.,amicrophone).ActuatorAnactuatorisadevicethatconvertselectricalenergyintophysicalenergy(i.e.,aloudspeaker).LinearityThelinearitydescribestheclosenessbetweenthecalibrationcurveandaspecifiedstraightline.SensitivityThesensitivityisdefinedintermsoftherelationshipbetweeninputphysicalsignalandoutputelectricalsignal.Itisgenerallytheratiobetweenasmallchangeinelectricalsignaltoasmallchangeinphysicalsignal.Thesensitivityistheslopeofthecalibrationcurve.HysteresisThehysteresisreferstothediffereneebetweentwooutputvaluesthatcorrespondtothesameinput,dependingonthedirection(increasingordecreasing)ofsuccessiveinputvalues.Thatis,similarlytothemagnetizationinferromagneticmaterials,itcanhappenthattheoutputcorrespondingtoagiveninputdependsonwhetherthepreviousinputwashigherorlowerthanthepresentone.Somesensorsdonotreturntothesameoutputvaluewhentheinputstimulusiscycledupordown.Thewidthoftheexpectederrorintermsofthemeasuredquantityisdefinedasthehysteresis.RepeatabilityTherepeatabilityistheclosenessofagreementbetweensuccessiveresultsobtainedwiththesamemethodunderthesameconditionsandinashorttimeinterval.命=(2~3)冬loo%Yfs^-samplestandarddeviationStrain(mechanical)Fractionalchangeinlength △L/L.GagefactorThegagefactorisdefinedasthefractionalchangeinresistaneedividedbythestrain.PiezoresistiveeffectThechangeinresistivityasaresultofamechanicalstressiscalledthepiezoresistiveeffect.directpiezoelectriceffect.thephenomenonofgenerationofavoltageundermechanicalstressisreferredtoasthepiezoelectriceffect.conversepiezoelectriceffect.Themechanicalstrainproducedinthecrystalunderelectricstressiscalledtheconversepiezoelectriceffect.NumericalApertureThe"acceptaneecone"defineshowmuchlightwillbeacceptedintothefiberandultimatelyhowmuchremainsinthefiber,andisreferredtoasthenumericalaperture.ExtrinsicsensorTheopticalfiberplaysnopartinachievingthemodulatingbutsimplyactsasatransmissionmedium;theseareextrinsicsensors.Intrinsicsensors(fiberopticsensor)Theopticalfiberplaysamajorroleinmodulatingtheenergyfromthesource;thesearereferredtoasintrinsicsensors.HumidityaquantityrepresentingtheamountofwatervaporintheatmosphereoragasAbsolutehumidityAbsolutehumidityisthemassofwatervaporperunitvolumeofair.RelativehumidityTheratiooftheactualvapordensitytothetheoreticalmaximum(saturation)vapordensityatthesametemperature,expressedasapercentage.Therelativehumidityistheratiooftheactualvaporpressuretothesaturationvaporpressureatgiventemperature.佃)PeltiereffectWhentwodissimilarmetalsareconnectedtogether,asmallvoltagecalledathermojunctionvoltageisgeneratedatthejunction.ThisiscalledthePeltiereffect.LawofHomogeneousConductorsForagivenpairofhomogeneousconductorsformingaclosedloop,theSeebeckemfdependsonlyonthetemperaturesofthejunctions,andnotonthetemperaturedistributionalongthelengthoftheconductors.LawofintermediatemetalsAthird(intermediate)metalwirecanbeinsertedinserieswithoneofthewireswithoutchangingthevoltagereading(providedthatthetwonewjunctionsareatthesametemperature).Ifthereisathirdmetalintroducedintothethermocouplecircuit,itwillnotadverselyeffectthereading,ifandonlyifthetwojunctionsofthethirdmetalareatthesametemperatures.Bernoulli'stheoremBernoullidquationstatesthatenergyisapproximatelyconservedacrossaconstrictioninapipe.Bernoulli'sequatioP/(p?g)+?v2/g+y=constant(p=density;g=accelerationofgravity;v=fluidvelocity;y=elevation)DescribethefollowingdevicesandhowtheyworkStraingageThestraingaugeusuallyconsistsofwire,baking,thinpaper,andleadwelded.Thewireisarrangedintheformofagridinordertoobtainhigherresistances.ParallelplateCapacitiveSensorTheparallelplateCapacitiveSensorisafunctionofthedistaneed(cm)betweentheTOC\o"1-5"\h\zelectrodesofastructure,thesurfaceareaA(cm2)oftheelectrodes,andthepermittivity ￡(8.8510F/mforair)ofthedielectricbetweentheelectrodes;therefore:C_A_ ；°A"T_ dDifferentialCapacitiveSensorAdifferentialcapacitorconsistsoftwovariablecapacitorssoarrangedthattheyundergothesamechange,butinoppositedirections.Theamplifiercircuit,dependingonitsconfiguration,cangenerateavoltageproportionaltoC1-C2orC1/C2or(C1-C2)/(C1+C2).VariableReluctanceSensorsAtypicalsingle-coilvariable-reluctancedisplacementsensorisillustratedintheFigurebelow.Thesensorconsistsofthreeelements:aferromagneticcore,avariableairgap,andaferromagneticplate.Basedonchangeinthereluctanceofamagneticfluxpath.Self-inductanceLofthecoilis:,W2L=RmReluctancecanbegivenas: Rm=Variable-ReluctanceTachogeneratorsItconsistsofaferromagnetic,toothedwheelattachedtoarotatingshaft,acoilandamagnet.Thewheelrotatesincloseproximitytothepolepiece,thuscausingthefluxlinkedbythecoiltochange.Thesensorsoutputdependsonthespeedoftherotationofthewheelandthenumberofteeth.LVDTAnLVDTconsistsofthreecoils,aformandacore.Thecoilsarewoundonahollowform.Theprimaryisexcitedbysomeacsource.Fluxformedbytheprimaryislinkedtothetwosecondarycoils,inducinganacvoltageineachcoil.Acoreisinsidetheformer.Itcanslidefreelythroughthecenteroftheform.Inmanyapplications,thetwosecondarycoilsareconnectedinseriesopposition.Thenthetwovoltageswillsubtract;thatis,thedifferentialvoltageisformed.Whenthecoreiscentrallylocated,thenetvoltageiszero.Whenthecoreismovedtooneside,thenetvoltagewillincrease.CompressionModePiezoelectricAccelerometersUprightcompressiondesignssandwichthepiezoelectriccrystalbetweenaseismicmassandrigidmountingbase.Apre-loadstudorscrewsecuresthesensingelementtothemountingbase.Whenthesensorisaccelerated,theseismicmassincreasesordecreasestheamountofcompressionforceactinguponthecrystal,andaproportionalelectricaloutputresults.ShearmodeaccelerometerShearmodeaccelerometerdesignsbond,or “sandwichen$ngtlrmaterialbetweenacenterpostandseismicmass.Acompressionringorstudappliesapreloadforcerequiredtocreatearigidlinearstructure.Underacceleration,themasscausesashearstresstobeappliedtothesensingmaterial.Thisstressresultsinaproportionalelectricaloutputbythepiezoelectricmaterial.Theyrepresentthetraditionalorhistoricalaccelerometerdesign.PsychrometerApsychrometercontainstwoidenticalthermometersOnesensor,thedrybulb,measurestheambienttemperature.Theothersensor,thewetbulb,isinawettedcondition.Inoperation,waterevaporationcoolsthewettedthermometer,resultinginameasurablediffereneebetweenitandtheambient,ordrybulbmeasurement.Whenthewetbulbreachesitsmaximumtemperaturedepression,thehumidityisdeterminedbycomparingthewetbulb/drybulbtemperaturesonapsychrometricchartDunmoresensorTheDunmoresensorusesadilutelithiumchloridesolutioninapolyvinylacetatebinderonaninsulatingsubstrate.Theresistaneeofthesensor,measuredbetweenabifilargrid,isafunctionofther.h.ofthesurroundingair.MOSCapacitorCCDsaretypicallyfabricatedonap-typesubstrate.Inordertoimplementthe“buried”channelathtyperegionisformedonitssurface.Ainsulator,intheformofasilicondioxidelayerisgrownontopofthen-region.Thecapacitorisfinishedoffbyplacingoneormoreelectrodes,alsocalledgates,ontopoftheinsulatingsilicondioxide.Fullframetransfer(FFT)ItconsistsofaparallelCCDshiftregister,aserialCCDshiftregisterandasignalsensingoutputamplifierTheimagepixelareverticallytransferredintoahorizontalserialregister,andthechargesarehorizontallyshiftedout.Interlinetransfer(ILT)Thereadoutregionsareinterspacedbetweentheimagingregions,andareshieldedfromthelight.Attheendoftheintegrationperiod,thechargesaretransferredhorizontallytotheverticalreadoutregistersinparallel,andthenreadoutline-by-lineinamannersimilartoFFT.ILTdoesavoidsmearbutwiththecostofthesensitiveimagingareas.Frametransfer(FT)Thearrayisgroupedintotwosections:theimagesectionandthestoragesection.Thesetwosectionsareidentical,exceptthatthestoragesectionisshieldedfromthelight.Duringthereadout,chargesaretransferedline-by-lineintothestoragesectionbyapplyingthesameclockingtobothsections.Attheendoftheintegrationperiod,chargesinthestoragesectionaretransferredline-by-lineamannersimilartoFFT.proximitysensorsProximitysensorsdetectobjectsthatarenearbutwithouttouchingthem.Thesesensorsareusedfornear-fieldroboticoperations.Time-of-flightsensorsTime-of-flightsensorsestimatetherangebymeasuringthetimeelapsedbetweenthetransmissionandreturnofapulseTriangulationsensorsTriangulationsensorsmeasurerangebydetectingagivenpointontheobjectsurfacefromtwodifferentpointsofviewataknowndistaneefromeachother.Knowingthisdistaneeandthetwoviewanglesfromtherespectivepointstotheaimedsurfacepoint,asimplegeometricaloperationyieldstherange.ThermalInfraredDetectorsThermalinfrareddetectorsconvertincomingradiationintoheat,raisingthetemperatureofthethermaldetector.Photon-typedetectorsPhoton-typedetectorsreacttothephotonsemittedbytheobject.Theinfraredradiationcauseschangesintheelectricalpropertiesofphoton-typedetectors.Therearetwomaintypesofphotoninfrareddetectors.OneiscalledPhotoconductivedetector,whichexhibitincreasedconductivitywithreceivedradiation.AnotherisnamedasPhotovoltaicdetector,thisdeviceconvertsreceivedradiationintoelectriccurrent.shocktubeConstructionofashocktubeisquitesimple:itconsistsofalongtube,closedatbothends,separatedintotwochambersbyadiaphragm,asshownintheFig.below.Apressuredifferentialisbuiltupacrossthediaphragm,andthediaphragmisburst,eitherdirectlybythepressuredifferentialorinitiatedbymeansofanexternallycontrolledprobe.Rupturingofthediaphragmcausesashockwave.Theshocktubeprovidesthenearestthingtoatransientpressure “standard.ThermocoupleAthermocoupleconsistsoftwoelectricalconductorsmadeofdifferentmetalsthatarejoinedatoneend.Noteparticularlythattwojunctionsarealwaysrequired.Ingeneral,onesensethedesiredorunknowntemperature;thisoneweshallcallthehotormeasuringjunction.Thesecondwillusuallybemaintainedataknownfixedtemperature;thisoneweshallrefertoasthecoldorrefereneejunction.Whenthetwojunctionsareatdifferenttemperatures,avoltageisdevelopedacrossthejunction.BimetallicstripthermometerTwodissimilarmetalsarebondedtogetherintowhatiscalledabimetallicstrip.Sineetwometalshavedifferentcoefficientofthermalexpansion,onemetalwillexpandsmorethandoesanothermetalastemperatureincreases,causingthebimetallicstriptocurlupwardsassketched.RTDAresistaneetemperaturedetectorisbasicallyeitheralong,smalldiametermetalwirewoundinacoiloranetchedgridonasubstrate,muchlikeastraingage.Theresistaneeof

anRTDincreaseswithincreasingtemperature.Three-wireBridgeAclevercircuitdesignedtoeliminatetheleadwireresistaneeerroriscalledathree-wireRTDbridgecircuit,assketchedtotheright.3-WirebridgeIfwiresAandBareperfectlymatchedinlength(wiresAandBhavethesamelength,andthusthesameresistanee,),theirimpedanceeffectswillcancelbecauseeachisinanoppositelegofthebridge.Thethirdwire,C,actsasasenseleadandcarriesnocurrent.ThermistorAthermistorissimilartoanRTD,butasemiconductormaterialisusedinsteadofametal.Achangeintemperaturecausestheelectricalresistanceofthesemiconductormaterialtochange.Positivetemperaturecoefficient(PTC)andandnegativetemperaturecoefficient(NTC)unitsareavailable.Seismic(Absolute)AcelerationPickupsItconsistisofamass,aspring,andadamperarrangement,asshownintheFigurebelow.Figy(t)=theabsolutedisplacementofthemassMx(t)=theabsolutedisplacementofthebasez二y(t)-x(t)z—therelativemotionbetweenthemassandthebasem—massc—dampingconstantk—springconstantSeismic(Absolute)DisplacementPickupsTherelativedisplacementz(theoutputofthesensor)isproportionaltotheapplieddisplacement.Alowvalueofwnisneeded(wnshouldbemuchlessthanthelowestvibrationfrequencyforaccuratedisplacementmeasurement.)SeismicAccelerometer

Therelativedisplacementz(theoutputofthesensor)isproportionaltotheappliedacceleration.ahighwnisneededtomeasureaccuratelyhigh-frequency.Increasingwnwillincreasetherangeoffrequencyforwhichtheamplitude-ratiocurveisrelativelyflat;27)SeismicVelocityPickup(movingcoiltype)Onetypeofvelocitytransducerisbasedonalineargenerator.Whenacoilcutsthemagneticfieldlinesaroundamagnet,avoltageisinducedinthecoil,andthisvoltageisdependentonthespeedofthecoilrela