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piD-TECH®eVxeVxUserManualIntroductionThisManualistohelpfamiliarizepiD-TECH®eVxuserswiththephotoionizationsensor,includingprincipleofoperation,technicalcharacteristics,aswellassomePIDspecificapplicationfeatures.TheManualwillinstructusershowtoeasilyincorporateBaseline’ssensorintotheirproducts.Green0to10,000ppm043-310Purple0to2000ppm043-311Red0to200ppm043-312Yellow0to20ppm043-313Blue0to2ppm043-314piD-TECH®eVxUserManualRev1.02of28Section1:PrinciplesofOperation.................................................................................3 Section2:DesignOverview..........................................................................................5 Section3:Specifications................................................................................................6 3.1Performance.........................................................................................................6 Section4:ApplicationNotes.........................................................................................7 4.1PoweringUptheSensorafterStorage.................................................................7 4.2SignalRange........................................................................................................7 4.3MinimumDetectableQuantity............................................................................8 4.4Linearity...............................................................................................................9 4.5MoistureEffects.................................................................................................10 4.6Calibration..........................................................................................................11 4.7SpanDrift...........................................................................................................11 4.8SensorLifeSpan................................................................................................11 4.9BalanceGasEffects...........................................................................................12 4.10TemperatureEffect..........................................................................................12 4.11ResponseFactors.............................................................................................13 4.12ResponseTime(T90/T10)...............................................................................13 4.13ElectricalCharacteristics.................................................................................14 4.14SensorMaintenance.........................................................................................14 Section5:IntrinsicSafety............................................................................................15 5.1piD-TECH®SafetyCertifications......................................................................15 5.2SpecialConditionsforSafeUse........................................................................15 AppendixI:IonizationPotentials.................................................................................16 AppendixII:ResponseFactors.....................................................................................21 AppendixIII:ServiceableItemsandInstructions........................................................23piD-TECH®eVxUserManualRev1.03of28Section1:PrinciplesofOperationThePhotoionizationDetector(PID)isoneofthemostwidelyusedgasdetectiontechniques.PID’sarecommonlyappliedinportableinstrumentsfordetectionofawidevarietyoforganiccompoundsandsomeinorganicgasesinambientair.AtypicalPIDblockdiagramisshownbelow.Moleculesofinterest(1)arebeingexposedtohigh-energyVacuumUltraViolet(VUV)radiation(2),generatedbythegasdischargelamp(3).Asaresult,somepercentageofthesemoleculesisbeingionized,i.e.convertedintopositivelychargedionsandnegativelychargedelectronsaccordingtothefollowingequation:M+photon--M++e-Tobeionized,themoleculeMshouldhaveitsIonizationPotential(IP)smallerthantheenergyofUVlampphotons(E).Asarule,thebiggerthedifferenceisbetweenEanIP,thelargerthedetector’sresponse.BothEandIPareusuallymeasuredinelectron-volts(eV).FortheIonizationPotentialsofvariouschemicals,refertoAppendixI.PIDlampsaretypicallyavailablewithnominalphotonenergiesbetween8.3and11.7eV.ThepiD-TECH®plusisequippedwitha10.6eVlamp.A10.0eVlampisalsoavailable.Thepairofelectrodes(4,5)islocatedintheionizationvolumenearthelampwindow.Thepolarizingelectrode(4)isconnectedtotheHighVoltageDCsource(7),thesignalelectrode(5)isattachedtotheamplifier(6)input.Theelectricfield,createdbythesetwoelectrodes,forcesbothelectronsandionstodrifttowardstheirrespectiveelectrode,creatingasmallcurrent.Thiscurrentisamplifiedbytheamplifierchipandtheoutputanalogsignalisrecordedand/ordisplayedindigitaloranalogformat.Theoutputsignalisproportionaltotheconcentrationofionizablemoleculesindetector’schamberandthusservesasameasureofconcentration.Majoraircomponents(N2,O2,andCO2)haveionizationpotentialsgreaterthantheUVlampandthereforearenotdetected.Forthisreason,PIDisveryusefulfordetecti