WPCC  ?3\@OwmEyP˱vs7DlXѝy6Z9ǖǺ \Kv~Yw= :ދ$3} :uj(:~!8όm 3~@~+3u p./ʍz?BÚbd wׅCQ,xJu;R["9+B<23f|x˳c20dLCp뷁L2 eWp[=) jmcbeѣe=R$d 5`Fpb͚6ѽQrNҨ8t+d;RTWɃ=Zmj7R}8fz|!.\ϓz*Jz %)wvŘ[od_jR}fbЕ*sѣIb]kWeƟJr HAU: %RUHX 0O?E  0On 04 B UH . UH w 4/ <6X9`("Courier 10cpiX<09Z 0Courier (W1) Regular  '   X)XXXX? ' xdE!?     EMCGD024  < EMCGUIDELINEDOCUMENT   L   PAGE  1    ? ' xdE!? ('2$  T!     )   X)XXXX? ' xdE!?  Preparedby DanBivins ,EMC     D     EMCGD024   EMC,OAQPS,EPA  <      D     August24,1993  ? ' xdEr!?('2$  T!   #|x <6X9`("Courier 10cpiXx6X@;X@( T$   d  )   X)XXXX? ' xdE!?  Preparedby DanBivins ,EMB     D     EMTICGD024   TechnicalSupportDivision,OAQPS,EPA D     August24,1993  ? ' xdEr!?<09Z 0Courier (W1) Regular  '   X)XXXX? ' xdE!?     EMTICGD024  < EMTICGUIDELINEDOCUMENT   L   PAGE  1    ? ' xdE!? <09Z 0Courier (W1) Regular{$  T!   X)XXX,X   ? ' $xdE$!?  @..EMISSIONMEASUREMENTTECHNICALINFORMATIONCENTER@JJ"GUIDELINEDOCUMENT? ' $xdE$!?    TEMPERATUREMEASUREMENTSANDCALIBRATIONOFTYPEKTHERMOCOUPLESINHIGHTEMPERATURESTACKS  INTRODUCTION  6    AcommontypeofthermocouplematerialistheKtype.TherearesomelimitationsfortheapplicationofanythermocoupletypebutthediscussionherewillbelimitedtotheapplicationoftheKtype.Themanufacturer'sspecificationsareastartingpointforassuranceofaccuracyfortemperaturemeasurementwiththethermocouple.Themanufacturerusuallyspecifiestheaccuracy,andtemperaturerangeforthegiveapplication. DISCUSSION    Oncethethermocouplehasbeenplacedinastack(withtheassumptionthatitisplacedinaprotectivesheathandlooselyinsulatedforprotectionfromtheharshstackgases)themanufacturer'scalibrationdatahasbeenaltered.Manufacturer'sspecificationsarefromdataobtainedunderideallaboratoryconditions.ItwouldbeimpracticaltoremovethethermocouplefromthestackroutinelytocalibrateitagainstareferencethermocoupleinthelaboratoryforQApurposesbecauseoftheobviousenvironmentaldifferences.Oneimportantdifferenceisthetemperatureprofileofthethermocoupleinthestackthaninthelab.Onepossiblealternativewayofcalibratingthethermocouplewouldbetocompareresultsofareferencethermometerorothertemperaturemeasurementdeviceplacedinthestacknearthethermocouple.AnotheralternativewouldbetoslideeitheranRorStypethermocouplethathavebeencalibratedinathermologylabintotheprotectivesheath,alongsidetheoneinquestion,formakingreferencecomparisonsforaccuracy.DriftunderidealconditionsforatypicaltypeKthermocoupleisaround.25to.5percentforevery1000operatinghours.Therefore,toensurethattheusualmanufacturers"outofthebox"initialaccuracy(0.75percent)plusabout1.25percentdrift(TotalCD=2.0percent)isnotexceeded,thethermocouplecalibrationshouldbeverifiedevery3monthsorreplaced.TypeKthermocouples,evenwithlargewiregaugesizes,willeventuallyfailifsubjectedtosustainedtemperaturesabove2000degreesFahrenheit.Evenshortexcursionswillshortentheusefullifeofthethermocouple.Othertypesofthermocouplesshouldbeconsideredforsustainedtemperaturesabove2000degreesFahrenheit.TheNationalInstituteofStandardsandTechnology(NIST)wasthereferenceforthisinformationandtheexpertcontactatNISTisMr.GeorgeBurns,ElectricalEngineerfortheThermocoupleGroup.Hisnumberis(301)9754817. .*4 X  X)XXX)