脈沖調制紅外光源（反射型）電壓5.7V,電流80-90mA，波長2-16um,運行溫度-20度到80度，壽命大于40000小時，可用于各種氣體檢測FeaturesThermalblackbodysourceBroadbandIRemissionElectronicallypulsed,nomovingpartsFastheatingandcoolingratesWidemodulationfrequencybandLowpowerconsumptionLongtermstabilityCompactpackagingTO39,3pinsApplicationsInfraredspectroscopyNondispersiveinfrareddetectionPhotacousticgasdetection ProductSummary principleofoperationTheEMIRS200isaversatilethermalinfraredlightemitter.Theemissioncanbedirectlymodulatedbyvaryingtheelectricalinputsignal.Thisdeviceisbestsuitedtoreplaceexisting,mechanicallychoppedlampsolutions,thuseliminatingmovingparts.ConventionallampswithTungstenfilamentsworkundervacuumandarethereforeencapsulatedinglass.Thisprotectionisnolongertransparentforwavelengthsexceeding5 mandlimitstheirapplicationrange.TheEMIRS200exhibitsabroadbandIRemissionfromNIRto20 m.TheEMIRS200isbasedonasiliconchipusingadvancedmicrostructurefabricationtechnologies.Itconsistsofathinfilmresistorsupportedonathermallyandelectricallyinsulatingmembrane.TheheatingreliesontheJouleeffectinthemicrofilament.Thelowthermalmassofthesupportingmembranestructurepermitstoheatandcoolthemicrofilamentwithveryshorttimeconstantsof11msand17msrespectively.Thisallowsafastdirectmodulationoftheemittedinfraredlight.AuniquepatentedtechnologyallowsmanufacturingofhighlyreliablemodulatedIRsourceswithtrueblackbodycharacteristicsandveryhighemissivity.Emissivityhigherthan0.9isachievedforwavelengthsupto15 m. Thesourcecanbee.g.drivenwithasquarewaveinconstantvoltageorinconstantcurrentmode.Thetimeevolutionofthevariousparametersduringasquarewavemodulationwithconstantvoltageisdepictedinfigure3.Duetothelowerresistanceatthebeginningoftheheatingcycle,thecurrentandtheinputpowerexhibitanovershoot.Thereforetheconstantvoltagemodesupportsslightlyfasterheatingratescomparedtotheconstantcurrentmode.ThefrequencyresponseofthetotalIRemissioninfigure4hasbeenmeasuredwithadrivingsquarewavevoltageofconstantamplitude.ThemodulationdepthisMicrosystemsdefinedastheamplitudeofthesinecomponentatthefundamentalfrequencyofthedrivingsquarewave.Amodulationdepthof50%isachievedat24Hz.Themodulationdepthcanbefurtherenhancedsignificantlyinaconstanttemperaturemode,i.e.thedrivevoltageisincreasedforhigherfrequenciestomaintainthesamepeaktemperatureattheendoftheheatingcycle.Thismodeworksbestforasymmetricdutycycleswithshorterheatingperiods. OperatingconditionsThesourcecanbeoperatedincontinuous(cw)orinpulsedmode.Itsfastheatingandcoolingtimeconstantsof11msand17msrespectivelymakeitidealfordetectionschemesthatrelyonamodulatedlightsource,suchasphotoacousticdetectionandphasesensitivetechniquesforthesuppressionofDCcomponentsandthereductionof1/fnoise.TheheatingelementexhibitsahighTCRvalue.Thismeansthatacurrentflowingthroughtheresistorinducesaself-heatingoftheelementandthereforeanincreaseintheresistorvalue.Thedatainfigure2.showthetypicalriseinresistancewithincreasingelectricalpower. LifetimeLifetimetestsarepermanentlyongoing.Theseareperformedforsquaremodulationwith30Hzfrequencyand50:50dutycycleatelectricalpowerlevelsof350mW,400mWand450mW.Overthemeasured40 000h,nodegradationhasbeenobserved.Themeasuredintensityvariationwaswithintheaccuracyoftheopticaldetector( 5%).Thesourceshavebeenoperatedatambientatmosphere,whichindicatesthatahermeticsealingoftheTOpackageisnotrequired.Theuseofthesourceatmaximumratingsmayresultinashorterlifethanoperationatlowertemperatures. TheEMIRS200exhibitstrueblack-bodycharacteristics.Theemissionspectrainfigure5havebeenmeasuredwithaFouriertransformIRspectrometerfordifferentelectricalpowerlevels.ThemeasuredcurveshavebeenfittedwithaPlanckdistributionfunction.Thespectrashowexcellentagreementwiththetheoreticalblackbodyemission.Theextractedsourcetemperaturevariesfrom350 Cto550 C,thepeakwavelengthsaresituatedatabout3.5 mto4.5 m.TheEMIRS200exhibitstrueblack-bodycharacteristics.Theemissionspectrainfigure5havebeenmeasuredwithaFouriertransformIRspectrometerfordifferentelectricalpowerlevels.ThemeasuredcurveshavebeenfittedwithaPlanckdistributionfunction.Thespectrashowexcellentagreementwiththetheoreticalblackbodyemission.Theextractedsourcetemperaturevariesfrom350 Cto550 C,thepeakwavelengthsaresituatedatabout3.5 mto4.5 m.