Platinum Resistance Thermometer Calibrations

1 Page 1 NBSMeasurementServices: ResearchInformationCenter ilSallonaiBureauofStandards Gaithersburg,Maryland20899 JAN 61988 PlatinumResistance ThermometerCalibrations THERMODYNAMICTEMPERATURE FundamentalL»w»definingThermodynamicT... Open at page → 2 Page 2 CenterforBasicStandards TheCenterforBasicStandardsdevelopsandmaintainstinescientificcompetencesandlaboratoryfacilitiesnec- essarytopreserveandcontinuetorefinethebasephysicalquantitiesuponwhichtheNation'smeasurement syste... Open at page → 3 Page 3 NBSMEASUREMENTSERVICES: PlatinumResistanceThermometerCalibrations B.W.Mangum TemperatureandPressureDivision CenterforBasicStandards NationalMeasurementLaboratory NationalBureauofStandards Gaithersburg,MD20899 U.S.DEPARTM... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:87-619875 NationalBureauofStandardsSpecialPublication250-22 Natl.Bur.Stand.(U.S.),Spec.Publ.250-22,364pages(Oct.1987) CODEN:XNBSAV Certaincommercialequipment,instruments,ormaterialsarei... Open at page → 5 Page 5 PREFACE Calibrations andrelatedmeasurement services oftheNationalBureauof Standardsprovidethemeansformakersandusersofmeasuringtoolstoachieve levels ofmeasurement accuracy thatarenecessary toattain quality, productivity a... Open at page → 6 Page 6 theCenterforBasicStandards. Itdescribescalibration technology and procedures utilized inconnectionwithNBSServiceIdentification Numbers from33010Cto33120MlistedintheNBSCalibration ServicesUsersGuide 1986-88/Revised (pages... Open at page → 7 Page 7 TABLEOFCONTENTS I. INTRODUCTION 1 II. DESCRIPTIONOFSERVICES 2 II.1. TypesofThermometersCalibrated 2 11.2. TemperatureRangesofCalibrations andTabulation ofServices 2 11.3. MeasurementAssurancePrograms 2 11.4. Uncertaintyo... Open at page → 8 Page 8 111.2. PrimaryStandards(SPRTs)DesignsandConstruction. . 40 III.2.a.Long-stemPRTs ^3 III.2.b.Capsule-type PRTs 43 111.3. IndustrialPRT(IPRT)Designs 44 IV. DESCRIPTION OFCALIBRATIONSYSTEM 82 IV.1. Fixed-PointCells 82 IV.1.... Open at page → 9 Page 9 V.2.C. Thetriplepointofwater 195 V.2.d.Normalboilingpointofoxygen 199 V.3. ComparisonCalibrationofPRTsBelow90K 200 Self-HeatingEffects 203 V.5. Dataanalysis 206 V.6. CalibrationReport 21 4 VI. UNCERTAINTIES OFCALIBRATION... Open at page → 10 Page 10 VIII. FUTUREPLANS 334 VIII.1.AutomateCalibrationofLong-stemSPRTs 334 VIII.2.AutomateCalibration ofCapsule-typeSPRTs 334 VIII.3.InstallCheckTemperatureFixedPoint 334 VIII.4.PreparationofBack-upTinandZincFixed-point Cells... Open at page → 11 Page 11 PLATINUMRESISTANCETHERMOMETERCALIBRATIONS I. INTRODUCTION TheNationalBureauofStandards (NBS)employstheInternational PracticalTemperatureScaleof1968,AmendedEditionof1975 [IPTS-68 (75)] ^ 2 andthe1976Provisional 0.5Kto30KT... Open at page → 12 Page 12 II.DESCRIPTION OFSERVICES 11.1.TypesofThermometersCalibrated NBSprovidescalibrationservicesforstandardplatinumresistance thermometers (SPRTs)from13.8IKto903-89K.Bothlong-stem-typeand capsule-typeSPRTsarecalibrated,provid... Open at page → 13 Page 13 necessary,suggestions forimprovements inmeasurement ordocumentation are made. Inthepast,measurements atmostofthelaboratories agreedwiththose oftheNBStowithin±5mK.InthehigherlevelofuncertaintyMAP,NBS conductsanassessment... Open at page → 14 Page 14 point,±0.11mKatthetinpoint,and±0.05mKattheoxygenpoint. To thesevaluesatthetinandzincpoints,onemustaddtheuncertainties resultingfromthesystematicerrorscausedbysampleimpurities. Thetinand zincfreezing-point cellsusedincali... Open at page → 15 Page 15 II.6.GuideforObtainingCalibrationofSPRTsattheNBS. Thefollowingguidesareintendedforusersandthoseimmediately connectedwiththeapplication ofSPRTswhoareinterested inobtaining calibrationservicesattheNBSorforthosewhoareplanni... Open at page → 16 Page 16 insuranceinstructions arefurnished,returnshipmentwillbemadeby commoncarriercollectanduninsured. TheriskoflossordamageinhandlingortestingofanyitembyNBS isassumedbythecustomer,exceptwhenitisdetermined bytheNBSthat suchloss... Open at page → 17 Page 17 46cm(18"). Themaximumoveralllengthofglass-sheathed SPRTsshallbe 1meter. ThemaximumoveralllengthofSPRTsthathavesheathsofthinmetal islimitedbytheheighttotheceilingoftheNBScalibrationlaboratory; SPRTsupto4meterscanbeaccommo... Open at page → 18 Page 18 II.6.C.2. Capsule-typeSPRTs Thecapsule-typeSPRTsarenotgenerallycalibratedabovethetin-point temperature attheNBS.Becauseoftheuncertainelectricalinsulation characteristics betweentheleadsatthezincpoint,anycalibrationperfor... Open at page → 19 Page 19 II.6.0.^. Non-standard platinumresistancethermometers Averyspecialconfiguration ofplatinumresistancethermometermaybe desiredforcertainapplications. Forthecalibrationofsuchthermometers, theusermaycontacttheNBSconcerningth... Open at page → 20 Page 20 usershallassumethereponsibllity ofinstructinghisshippingdepartment concerningpackagingandthedesiredcarrierforshippinghisSPRT. II.7.NBSContacts Directinquiries totheattentionof:WilliamBigge,Temperatureand PressureDivision... Open at page → 21 Page 21 TableII.1 . TabulationofServices 33020C 3301OC LongStemPRT LongStemPRT -50°Cto500°Cor630°C 183°Cto500°Cor63O°C 33030c Calorimetric-type PRT -50°Cto150°C 330^100 Capsule-type PRT 13Kto600K 33050c Capsule-type PRT(includin... Open at page → 22 Page 22 TableII.2.Estimatedstandarddeviations(S.D.)(la)ofvaluesofW(and theirequivalents intemperature, t)ofsomeplatinumresistance thermometers atthetemperaturefixedpoints. W(Zn) W(Sn) W(0 ) SPRT S.D.ofW S.D.oft S.D.ofW S.D.oft S... Open at page → 24 Page 24 FigureII.1.Theerroratvarioustemperatures propagatedfromerrorsmadein thecalibration ofaplatinumresistancethermometer. Thecurvesshow theerror[i.e.,departurefromtheIPTS-68(75)] invaluesof temperatures causedbyaunitpositive(... Open at page → 25 Page 25 ERRORINDEGREESPERDEGREEERRORINCALIBRATION OJ ro — o — ui 4i» OJ ro 15 Open at page → 26 Page 26 III.DESIGNPHILOSOPHYANDTHEORY III.1. Specifications ofSPRTs III.1.a.Limitsofa TheIPTS-68(75)'' isbasedontheassignedvaluesofthetemperatures of anumberofreproducibleequilibriumstates(definingfixedpoints)andon standardinstr... Open at page → 27 Page 27 Ill.l.b. Supplementary InformationonSPRTs Theapparatus,methodsandproceduresdescribed inthissection representgoodpracticeatthepresenttime. AnSPRTshouldbesodesignedandconstructed thatthefour-terminal resistanceelementisasf... Open at page → 28 Page 28 alsoasaresultofrapidcoolingwhenathermometer istransferredrapidly fromanenvironmentabove500°Ctoroomtemperature. Thislatterincreasein resistance isduetoquenched-in, non-equilibrium concentrations ofvacancy defectsandisreta... Open at page → 29 Page 29 thermometers shouldnotexceed4x10 R(0°C )(equivalent toabout 1mK), -7 andfortheverybestthermometers.willnotexceed 5x10 R(0°C)overa reasonableperiodofusewhenthesearehandledwithextremecare. For SPRTsusedonlyattemperatures o... Open at page → 30 Page 30 ''• AW^(T^g) =bj^(T^g-273-15K)+e^(T^g-273.15 K)^(T^g-373.15K) (III.4) wheretheconstantsaredeterminedfromthemeasureddeviations atthe condensation pointofoxygen(orthetriplepointofargon,seeNoted,Table Ill.l)andtheboilingpoi... Open at page → 31 Page 31 III.I.e.1.2.Therangefrom0°C(273-15K)to630.74°C(903.89K) From0°Cto630.74°Cthetemperaturet^gisdefinedby ^68 =^'^ [^^)(^^ _l)oc (III.8) wheret'isdefinedbytheequation f.l[W(f *6(yjl^Kyj^ -1) (III.9a) WithW(t')=R(t')/R(0°C).T... Open at page → 32 Page 32 wasformulatedsuchthatitsfirstandsecondderivativeswouldhavethesame valuesat0°Casthoseobtainedfrom t=f+0.045(|^)(|^ -l]°C (III.8) and t'=-[W(t')-1] +6[^][^ -l) (III.9a) a s s withthermometerconstants and a=3.9259668 x10 ^... Open at page → 33 Page 33 dt dt dt and dAW(t) — = +^e^t(t-75). (III.U) At0°C,differentiation ofthereferencefunction(Eq.(III.10))yields rdWMt) ^ _ 3.28 _J_ I ^- 20 " (III.15) j=0 ^ 1 20 (where = y-^g Ija^)andEq.(III.U)yields dAW.(t) (-^t )^ = (111... Open at page → 34 Page 34 =a-a*. (III.20) WhenEq.(III.17)and(III.20)arecombined, (^)=i -a*. (III.21) ' OB\ Thederivativeoftheformulationbetween0°Cand630.74°Cisobtained bydifferentiating Eq.(III.8)andtheequation W(t' )= 1+At'+Bt'^ (III.22) Therere... Open at page → 35 Page 35 Bysubtracting Eq.(III.27)fromEq.(III.21), thedifference inthe derivatives at0°Cofthetwoformulations becomes rdW(t) ^ rdW(t) i .fMill "I . * A .^^^ ^"dt-^Qg - ^~5t-^Q^ =^"^0 = ^ - -0799955 • ^^^^-28) Fromtherelations and... Open at page → 36 Page 36 ^dwai> ^ 0.000^5(a* -a)-100(B* -B) ^ dt ^0 0.99955 Uii.i^; TheavaluesofSPRTscalibrated atNBSinthepastrangebetween 3.925X10 ^ °C ^andabout3-927x10 ^°C~^andtheBvaluesbetween -5.872 Xlo''''°C~^and-5.877 xlo"'''°C~^;botha*an... Open at page → 37 Page 37 ThevariationamongSPRTsisyetanothersourceofuncertainty; i.e., eventhoughthemeasurements withSPRTsaremadeatthesametemperature (hotness),theydonotyieldexactlythesamevaluesoftemperature. Some 11-17 dataexist, buttherearenosy... Open at page → 38 Page 38 employing asinglethermometer overanintervalofafewdaysinanattemptto determinetheerrorattributable tovariations inthetemperatures ofthe fixedpointcells,itincludesboththevariations inthetemperature (6t^)of manyfreezesindiff... Open at page → 39 Page 39 6t-(§-)6W. 1 (III.38) wasevaluatedasafunctionofthetemperature. Whenthecalibrationerrorat aparticularfixedpointwasconsidered, thecalibrationmeasurements atthe otherfixedpointsweretakentobecorrect. Thefollowingcaseshavebee... Open at page → 40 Page 40 Inthediscussion, thevariationsinthemeasurements atthefixedpointswill bedescribed intermsoftheresistanceratio,W(t^)=R(t^)/R(0°C),the ratioofobservedresistance atthefixed-pointtemperature t^tothatat 0°C. Thevariations inW(... Open at page → 41 Page 41 where A=a(1+6/100°C) (III.29) and =-10^a6°C ^ (III.30) Theconstants oftheIPTS-68(75) Eqs.(III.9a)and(III.9b)are determinedbymeasurements oftheSPRTresistance atthetriplepointof water,thesteampointorthetinpoint,andthezincp... Open at page → 42 Page 42 |L.= T+0^}^[-^^,3_ +2+a)t'^+2(sz+sa+za)f - sza] sza ' = 1 (111.^6) Equation(III.46)willbeemployedtoconvert 9t'/3(joto3t/3(jo. FromEq.(III.41 ), ^ 0)^ =At^+Bt^^ (III.47) and 0)=At'+Bt'^, (III.48) z z z wheret^isthedefined... Open at page → 43 Page 43 t^t'-tt'^ [(a)^t^- 0)t^)+2(0)t„ - aa^t)t'] zz, TzzT zTTz do) + dt'=0 (III.52) t„t(t -t„) t„t(t -t„)TzzT TzzT Aftertransferring, Eq.(III.52)becomes 3t' ^^'^^" ^'^ ^= ^ ^ . (III.53) 3co„ oo„t(2t'-t ) - 0)t^(2t' -t„) i iz z... Open at page → 44 Page 44 Althoughbothequations (III.56)and(III.57)canbeconvertedtotermsoft byemployingtherelationgivenbyEq.(III.8),theequationsgivenare simplierandmorepracticaltouse.Aftercalculatingdt/dw^or9t/3a3^att', thent'canbeconvertedtotacc... Open at page → 45 Page 45 and FigureII. 1showstheerrorthattheexperimenterwouldencounterforerrors of6a)an( s (hotness) . of6a)and6ajcorresponding toaunitpositiveerroroftemperature S 2 2.90.188K(-182.962°C)to273-15K(0°C) From-182.962°Cto0°C,thetemp... Open at page → 46 Page 46 Theexperimenter mustdeterminehisobservational error6W(t). Thedeviation AW^(t)isrepresented (inthistemperaturerangeandat100°C)bythe function AW^(t)=bj^t+e^t^(t-100°C), (III.67) andtheconstants ofthedeviationequationaredet... Open at page → 47 Page 47 AWq=Wq-W*(deviation attheoxygenNBP) (III.72) AW =W-W*(deviationatthesteampoint). (III.73) 3 3 S Whenthedeviations attheoxygenNBPandthesteampointareappliedto Eq.(III.67),thereresults ^^0=^^0 " ^^O^S (III.74) AWg=b^tg+ ^n^... Open at page → 48 Page 48 For8AW(t)/3AWg, tt^(t--100) -t-t^(t-100) ^f^=-V (III.80) ."^^"^s ttht^ -100) -t^t^(t -100) s00 0ss andwhen =100°Cissubstitutedwhereversimplification canbemade, :iAur^^ t[t^(t--100)-t^(t-100)] 9AWlt)= 0_0 (j^^^Q^) ^^^s tt... Open at page → 49 Page 49 2 2 -a ' [tVTF-¥y -*«1 '3 ^ [y^t-V) -B'] tf. (111.85, TzzT TzzT Equation(III.85)isthensubstituted forAWinEqs.(III.76)and(III.77). TheEq.(III.78)forthedifferential coefficient ofaAW(t)/3AWQ remains unchanged. Becausethetr... Open at page → 50 Page 50 whichsimplifies to 3AW t(t -t ) s s z s , , - i I Z T 9AW 3 For -r ,Eq.(III.85)becomes z s ^ T_s ^ 1^ 3oo t„t (t -t„) t„t(t -t„) ' ^111. zTzz TTzz T whichsimplifies to 3AW t(t -t„ s s s T (III.92) 3oj t(t -t^) • z z z T... Open at page → 51 Page 51 ice-pointresistance ofabout25.5^anditsresistoriswoundfromabout 61cmof0.075mmdiameterwire. Thewireisobtained"harddrawn",asitis somewhateasiertohandleinthiscondition, butitisannealedafterthe resistorisformed. Althoughwires... Open at page → 52 Page 52 thatareusedtosupporttheinsulationduringmachining. A"carbidetipped" toolshouldbeusedforthecuttingprocess. Unfortunately, attemptsto removethemetalchemicallyfromthemicaresultincontaminating themica. Syntheticsapphire,howev... Open at page → 53 Page 53 thermometer. Golddoesnotseemtocontaminate theplatinumandiseasily worked. Measurement oftheresistor.maybefacilitated ifthefourleadsare madeofthesamematerialwiththefourleadshavingthesamelengthsand diameterssothattheleadsha... Open at page → 54 Page 54 thermometer aredifferent,however. FigureIII.4showstwodesignsofthe capsule-typePRT. III.3.IndustrialPRT(IPRT)Designs Therearemanydifferentdesignsfortheindustrialplatinumresistance thermometer (IPRT). ThedesignforagivenIPR... Open at page → 55 Page 55 TableIII.1. DefiningfixedpointsoftheIPTS-68(75)' Equilibriumstate Assignedvalueof International Practical Temperature Equilibriumbetweenthesolid,liquidandvaporphases ofequilibriumhydrogen(triplepointofequilibrium hydroge... Open at page → 56 Page 56 TableIII.2.Coefficients a.ofthereferencefunctionfor J Platinumresistancethermometers fortherangefrom13.81K to273.15K j a. J j a . J 0 38.59276 10 239.50285 1 43.4i|8 37 1 1 524.64944 2 39.10887 12 -319.799 81 3 38.69352... Open at page → 57 Page 57 TableIII.3.ValuesofW^^„roC^ra) ,accordingtothedatagiven LLl-DODO inTableIII.2,atthefixed-pointtemperatures. Fixedpoint T^q(K) tgQ(°C) W^^^.^g e-H^triple 13.81 -259.34 0.00141208 e-H^17.042K 17.042 -256.108 0.00253445 e-H... Open at page → 58 Page 58 TableIII.4.ValuesofW valuesofT^„. CCT-( (T^g)accordingtoEquation(III.3;atinteeral 68 CCT-DO 68 68 CCT-68 58 68 W ( T CCT-68 68 13 0.00123063 56 0.09842337 99 0.28197988 ^^ 0.00145974 57 0.10240777 100 0.28630204 15 0.001... Open at page → 59 Page 59 TableIII.4.(Continued) ValuesofW (T ) CCT-68^68^ 8 accordingtoEquation (Ill.3)atintegralvaluesof * 6 68 CCT-68 d8 60 ^nrT(^Q ^ Q LLiDODO ' ^68"^*"cCT-68^68 142 0.4651 1858 186 0.64763808 230 0.82682529 143 0.46931385 187... Open at page → 60 Page 60 FigureIII.l. Syntheticsapphireformforthermometer. Syntheticsapphire disksareemployedtokeeptheplatinumwiresseparatedina"bird-cage" typeSPRT. Acentrallylocated,heaviergageplatinumwiremaintainsthe spacingsbetweenthedisks. 5... Open at page → 62 Page 62 FigureIII.2.Construction ofthecoilsofsomethermometers. (a)Coiledfilamentonmicacross. (b)Singlelayerfilamentonmicacross. (c)Coiledfilamentontwistedglassribbon. (d)CoiledfilamentinglassU-tube. (e)Singlelayerfilamentaroundt... Open at page → 63 Page 63 53 Open at page → 64 Page 64 TWOTWIN-BORE SILICATUBES 54 Open at page → 65 Page 65 PLATINUMWIRE STEATITERING PLATINUMWIRE CEMENT TWIN-BORESILICATUBE PLATINUMWIRE PLATINUMSHEATH STEATITE RING CEMENT (e) COIL LENGTH 55 Open at page → 66 Page 66 FigureIII.3-"Head"ofSPRT. Theupperheadisthatofalong-stem thermometer. Theinternalleadsarebroughtoutthroughhermeticseals andareconnectedtoexternalcopperleadsattheleft. Thetwobottom PRTsareofthecapsuletype. 56 Open at page → 67 Page 67 57 Open at page → 68 Page 68 FigureIII.4."Heads"ofthreeSPRTs. Inthecenterofthefigureisa capsule-type SPRTwithleadsbroughtoutthroughglassseals. The capsulebodyisplatinum. Thebottomcapsule-type SPRTshowsthe thermometerleadsbroughtoutthroughindividualm... Open at page → 70 Page 70 FigureIII.5.Construction ofthecoilsofsomethermometers. Filament threadedthroughfour-holeceramictubes(CourtesyoftheRosemount EngineeringCompany.) 60 Open at page → 71 Page 71 61 Open at page → 72 Page 72 FigureIII.6.Construction ofthecoilsofsomethermometers. Coiled filamentonhelicallygrovedceramic. (CourtesyoftheMincoProducts, Inc.) 62 Open at page → 73 Page 73 63 Open at page → 74 Page 74 FigureIII.7a.ExampleofanIPRT. RosemountModel132MC. (Courtesyof RosemountEngineering Co.,Inc.) 64 Open at page → 75 Page 75 MODEL132IVIC PLATINUMRESISTANCE TEMPERATURESENSOR PRODUCTDATASHEET2266 Hightemperaturecapability Strainfreeelement* Hermeticallysealed iI m4 GeneralDescription TheModel132MC isaplatinum resistance temperaturesensordesign... Open at page → 76 Page 76 FigureIII.7b.Dimensional drawingofIPRTofFig.III.7a.(Courtesyof RosemountEngineeringCo.,Inc.) 66 Open at page → 77 Page 77 DimensionalDrawing 0.250"DIA. •X"±0.05" 0.50"(MAX.) SENSITIVELENGTH(REF. 7/16-20UNJF -3ATHREAD(REF.) PERMS33656 -4 0.062"DIA.(2PLACES) IDENTIFICATIONDATA RECEPTACLE,10SHELL,6PIN PERMIL--C-83723/llA o o o o o o A B c D E... Open at page → 78 Page 78 FigureIII.8.Exampleofh igh-stabi1ityIPRT. RosemountModel162N. (CourtesyofRosemountEngineering Co.,Inc.) 68 Open at page → 79 Page 79 PERFORMANCE SPECIFICATIONS TEMPERATURERANGE -200°Cto400°C. RESISTANCE-TEMPERATURE RELATIONSHIP TheModel162N iscalibrated usingthesame equationsusedtodefinetheInternational Practical TemperatureScaleof1968.Thenominalresis... Open at page → 80 Page 80 FigureIII.9.ExampleofsurfacesensortypeIPRT. RosemountModel118ME. (CourtesyofRosemountEngineeringCo.,Inc.) 70 Open at page → 81 Page 81 PRODUCTDATASHEET2101 MIODEL118ME PLATINUMRESISTANCE Generalpurposesurfacesensor Ruggedconstruction,smallsize Strain-freeelement 1.SCOPE TheModel118MEsurfacetemperaturesen- sorisdesignedtooperateintherange-200°C to+200°C.... Open at page → 82 Page 82 FigureIII.10a.Exampleofhigh-stability, limitedrangeIPRT. Rosemount Model171. (CourtesyofRosemountEngineeringCo.,Inc.) 72 Open at page → 83 Page 83 PRODUCTDATASHEET2023 MODEL171SERIES PRESSUREINSENSITIVE TEMPERATURESENSORS Designedforprecisionoceantemperaturemeasurement Pressureinsensitiveto3000psia Timeconstantof310/WSat3fpsdroprate GENERAL Model171SeriesPlatinumRe... Open at page → 84 Page 84 FigureIII.10b.Dataanddimensional drawingsofRosemountModel171IPRT showninFig.III.10a.(CourtesyofRosemountEngineeringCo.,Inc.) 74 Open at page → 85 Page 85 6.Pressure.Thissensorshallwithstandapressure of10,000psi,usingwaterasthepressurizingmedium, (Forreference:theerrorshallbelessthan0.01°Cat 3000psia.) 7.Repeatability.Thesensorshallwithstand 10 shocksbetween-2°Cand+35°Cwit... Open at page → 86 Page 86 Figure 111.11. Modelofhigh-stability, limitedrangeIPRT. RosemountModel 171CG/EG. (CourtesyofRosemountEngineering Co.,Inc.) 76 Open at page → 87 Page 87 PRODUCTDATASHEET2009 MODEL171CG/EG FASTRESPONSE OCEANOGRAPHIC TEMPERATURESENSORS Designedforprecisionoceantemperaturemeasurement Pressureinsensitivedownto20,000feet Superioranti-foulingoption Timeconstantof60MSata3fpsdro... Open at page → 88 Page 88 FigureIII.12a.ExampleofminiatureIPRT. RosemountModel146MB.(Courtesy ofRosemountEngineeringCo.,Inc.) 78 Open at page → 89 Page 89 PRODUCTDATASHEET2156 MODEL146IVIB PLATINUMRESISTANCE TEMPERATURESENSOR Fluidorsurfacemeasurements Miniaturesize(0.30"length) Highreliability GENERALDESCRIPTION TheModel146MBSurfaceSensorisdesignedto operatefrom-260°Cto+1... Open at page → 90 Page 90 FigureIII.12b.Specifications forIPRTofFig.III.12a.RosemountModel 146MB.(CourtesyofRosemountEngineeringCo.,Inc.) 80 Open at page → 91 Page 91 DIMENSIONALDRAWING MODEL146MB 0.3" (MAX.) -0.062"DIA.(MAX.) METALLIC OXIDE // II I I I I I I I I I.J n 1 1 1 1 1 1 1 1 .JUU SCHEMATIC DIAGRAM 0.075"DIA.(MAX.) LEADS, 28GA.COPPER, TEFLON*INSULATED RESISTANCE-TEMPERATURE R... Open at page → 92 Page 92 IV.DESCRIPTION OFCALIBRATIONSYSTEM ThecalibrationofanSPRTontheIPTS-68(75) involvesthemeasurement of theresistancewhenthethermometer isateachofthetemperatures ofthe prescribeddefiningfixedpoints. Thissectiondealswiththeeq... Open at page → 93 Page 93 realizedinasealedglasscell(FigureIV.2)containing ice,water,andwater vapor. Whenthecellisinuse,itmaybeplacedinanordinarycrushed-ice- waterbath.FigureIV.2showsthecellandoneoftheice-bathsystemsused atNBS. Forpreparationofth... Open at page → 94 Page 94 raisedhighenoughtoseethemantleduringthefreezingprocess,the magnification ofthecylinderofwaterwillgivetheimpressionthatthecell isorisabouttobefrozensolidwithicealthoughthecoatingoficeonthe wellmaystillbeaslittleas 1or2mmt... Open at page → 95 Page 95 about0.2mK/(mA) .Thebushingreducesthisheatingbyafactoroffiveor moredependinguponitsfitwiththewellandtheSPRT. Toeliminatethe 19 ambientroomradiation (fromceilinglightsinparticular), aheavyblack feltcloth(A)coversthetopoft... Open at page → 96 Page 96 (combinedasasinglecomponentintheillustration) areexpectedtoforma solidsolutionwiththemajorcomponent. (Mostbinarymetalsystemsonwhich dataexistdonotformacontinuousseriesofsolidsolutions;variousdegrees ofimmiscibilityareusu... Open at page → 97 Page 97 soluteconcentration inthesolid(S)tothatintheliquid(L)iscalledthe solutedistributioncoefficient (k)and,asgiveninFiguresIV.3andIV.4,is lessthanunityforsolutesthatdepressthefreezingpointandisgreater thanunityforsolutesthate... Open at page → 98 Page 98 relativesolutecomposition ofthefreezinginterfaceresultingfromthis expressionforvariousvaluesofk.FigureIV.5comparesthecurvefor k=0.4,replottedonalinearscale,withthecurvethatwouldbeobtained foracorresponding equilibriumfre... Open at page → 99 Page 99 k< 1becomesrelativelyconcentrated intheliquidintheregionofthe interface. Whentherecoveryfromthesupercool isnominallycomplete,the highconcentration ofimpurities intheliquidattheinterfacewillbe reducedbydiffusionandthetemp... Open at page → 100 Page 100 Therefore,knowledgeofthepressurewithin ± 1torrisadequatefor determining thetemperatureofatin-pointcell. Thetinsampleforthefreezing-point cellmustbeofhighpurity (nominally >99 .9995^pure)andthefreezingapparatusmustbedesig... Open at page → 101 Page 101 afewdegreesbelowthetinfreezingpoint. After 1hourhaselapsed,the inductionheaterpowerisincreasedsothatthetinsamplewillmeltandflow intotnecruciblewithinabout15minutes. Next,thesampleisallowedto cooltoaboutroomtemperature, t... Open at page → 102 Page 102 temperature, afterafewseconds,willsuddenlydecreaseveryrapidly,perhaps asmuchas20or25°C.Assoonasitstemperaturestopsdecreasing, thecell isimmediatelyloweredintothefurnaceagain;subsequently, thecell temperature willincrease... Open at page → 103 Page 103 Inthereductionofthecalibrationdata,thetemperature atthepointof immersionoftheSPRTinthetin-pointcellisemployed. Thevalueof temperatureassignedinthetextoftheIPTS-68(75) isadjustedforthe departurefromtheequilibriumcondition... Open at page → 104 Page 104 sampleisallowedtocoolandtheassemblyofthezinc-pointcelliscarried outinthesamemannerasthatusedforthetinsample. Torealizethefreezingpointofzincwithanuncertainty ofabout ±0.002"C,thefurnaceusedtoprovidetheheatneednotbeveryco... Open at page → 105 Page 105 Caremustbeexercised toavoidmeltingaholeintheinnerfreezeor looseningthemantleonthewellsuchthatitslidestothebottomofthe crucible. Toensurethatnomeltingandnoexcessivefreezingoccurs,the thermometer ispreheatedtoatemperatures... Open at page → 106 Page 106 heliumenhancesthethermalcontactbetweenthewallsofthewellsandthe thermometers andpreventscondensiblegasesfromenteringthewells. The copperblock(P)andshields (FandL)aremaintainedundervacuum. Theyare initiallycooledbyadmittin... Open at page → 107 Page 107 byFiberfraxpaperandsurrounded byanichromewireheater(mainheater,0) whichextendsthefulllengthofthethreeblocks. Theheaterwirefits closelywithineachofthetwoholesof51cmlengthsoftwo-holeovalalumina tubing. Thesealuminatubingsa... Open at page → 108 Page 108 ends,andtoreduceundesirable heatconvectioncurrents. Thecentering leavesasmallannularairspacebetweenthetubeandthealuminainsulators ofthemainheaterintheregionofthecenterblock;thethermalcontactof theendblockswiththesurround... Open at page → 109 Page 109 closetolerancesneededforgoodthermalcontact,thezinc-pointcellsarenot permittedtocooltoroomtemperature inthefurnace. Otherwise, the borosilicate glasstubewouldbecrushedduetothedifferential contraction betweenthealuminumtop... Open at page → 110 Page 110 Thecontrolofeachfurnacewasmadeveryflexibleinthatseveral combinations ofmanualandautomaticcontrolsmaybeselectedforoperating thefurnace,includingtheprovisionforindependently settingthetemperature offsetbetweenthecenterandt... Open at page → 111 Page 111 groupofcapsule-type SPRTsmantainsthe"nationalscale"(NBS-55). TheNBS versionofIPTS-68(75) [NBS-IPTS-68 (75)]isachievedbymakingreferenceto theNBS-55scaleandutilizingthepublisheddifferencesbetweentheNBS-55 scaleandtheIPTS-6... Open at page → 112 Page 112 thetopofthecryostatandthenjointoheaviercopperleads. Theexternal copperleadsarethermallyinsulatedtominimizeboththetemperaturechange oftheleadsandanypossiblegradientchangebetweenleads. Theresistance ofthecoppersectionsofth... Open at page → 113 Page 113 resistorasthereferenceresistor; and,(3)aCromemcomicro-computer which controlsoperationoftheautomaticbridge. IV.4.a.Directcurrentcomparatorresistancebridge GENERALDESCRIPTION (FromtheGuidelineInstrumentsDirectCurrentCompa... Open at page → 114 Page 114 Specifications Range ; Stability: Diallinearity: DialResolution; Accuracy : 0.01ohmto10megohms: 0.01ohmto10kilohmsasafourterminalmeasurement 1kilohmto10megohmsasatwoterminalmeasurement ±0.2ppmoffullscale ±0.02ppmoffullsc... Open at page → 115 Page 115 RecorderOutput 0-10voltsat 1mAmaximum. Dimensions : 20"widex15"highxI9V2"deep(51x38x50cm) Weight : 95lbs.(43kg) LinePower: 115volts,60Hzor230volts,50Hz,100wattsmaximum Fuse: 2Ampere,locatedbelowlineplugonrearofcabinet. R... Open at page → 116 Page 116 areequalandoppositethereiszeroresultant dofluxinthecore.This balanceconditioncanbedetectedbymodulationofthecorepermeabilityusing theprinciple ofthesecondharmonicmodulator[FigureIV.25(b)] The amplitudeofthedoublefrequency... Open at page → 117 Page 117 drops. Theratioofresistorscannowbeobtainedfromtheratioofcurrents ifasuitabledeviceisavailableformeasurement ofthecurrentratio. The DirectCurrentComparator issuchadevice. BasicOperation Thetworesistorstobecomparedaresuppl... Open at page → 118 Page 118 and s Thissimplebridgewouldhavethedisadvantage ofrequiringsimultaneous manualbalancesforbothvoltageandampere-turns .Insuchanarrangement highlystablecurrentsupplieswouldbeessential. Inapracticalformofthe bridge(FigureIV.2... Open at page → 119 Page 119 IntheDirectCurrentComparatorBridge,differentcurrentsflowinthe tworesistors toproducethesamevoltageacrosseach: s and (IV.9) Thegreatestpowerisnowdissipatedinthesmallestresistance. TheModel9975ResistanceBridgeisa10:1ratiob... Open at page → 120 Page 120 Automaticbalanceofthenetampere-turnsisachieved bymeansofan open-loopcontrol,whichgivescoarsebalance. Theopen-loopcontrolis provided byanampere-turntrackingsignalgenerator,whoseoutputis proportional totheampere-turns onth... Open at page → 121 Page 121 -9 10 V "~8 Voltagenoiselimit=—— =10 or0.01ppm 10 X10 b)CurrentNoise Currentnoiselimitstheresolution at0.3mioroampere-turns .Itis expressedinproportional partsofampere-turnsinthecomparator: _r r V .n-.^0.3X10AT Currentno... Open at page → 122 Page 122 resolutionof 1microhm,andanaccuracylimitedbytheresolution ortoone 7 partin10 .Thespeedofthemeasurement isdependentuponmanyfactors,but generallyrangesbetween 6secondsatthehighestcurrentand30secondsat thelowest. BasicBridg... Open at page → 123 Page 123 revisedmicroprocessor programisavailablethatwhensubstituted forthe standardprogramwillreturnanextradigitonthe488bus.Someother programchangeshavealsobeenmadetobothversionsoftheprogram. Finally, thebasicbridgehasbeenprovid... Open at page → 124 Page 124 compensated byoccasionallymeasuring astandardresistorwiththebridgeand workingwithresistanceratios. Oneofthemultiplexer portsisnormally reservedforthispurposeforalloftheautomaticbridges. . ' 'it IV.4.c.Precisionresistors... Open at page → 125 Page 125 J E- O a a: DO o COce E- O J Id a o Q <to Qcr:CO 2M2 •a:o,a: HS3 CO<f- o oo. o --^ Dd o ^ E-" CO COME M •>-' CO Dd DC Q CO> a: cdE •a; ^ Q E- CO:s CO :ss CO^ oooooooooooooooo Q DC < Q 2 < E- CO Cd CCCO Cd2 a,(X CM(\JOO O... Open at page → 126 Page 126 FigureIV.1.Holderforcapsule-typeplatinumresistancethermometers. Calibrationmeasurements areperformedintheholderatthetriplepoint ofwater,thetinpoint,andthenormalboilingpointofoxygen. , ^ A.Elastomertubingtoheliumgassource... Open at page → 127 Page 127 117 Open at page → 128 Page 128 FigureIV.2.Watertriple-point cellinanicebath. A.Heavyblackfeltshieldagainstambientradiation. B.Polyethylene tubeforguidingtheSPRTintothethermometerwell. C.WaterVapor. -D.Borosilicate glasscell. E.Waterfromicebath. F.Ther... Open at page → 129 Page 129 119 Open at page → 130 Page 130 FigureIV.3.Binaryphasediagramofasystemthatiscompletelymisciblein bothsolidandliquidphases. Thesolidusandliquiduscurvesrepresent composition, respectively, ofthesolidandliquidphasesthatcan coexistinequilibrium. Theleftsid... Open at page → 131 Page 131 TEMPERATURE D 121 Open at page → 132 Page 132 gureIV.4.Enlargement ofabinaryphasediagramintheregionofhigh purityofeachcomponent. Thesolutedistributioncoefficient kistaken tobeconstant. Figure(a)represents aphasediagramwhenk< 1and figure(b)whenk>1.Theheavylinesonthel... Open at page → 133 Page 133 123 Open at page → 134 Page 134 FigureIV.5.Comparisonofcomputedfreezingcurvesforequilibriumandserai- equilibriumfreezingprocessesofacompletelymiscible(insolidand liquidphases)binarysystemwithconstantsolutedistribution coefficient (k=0.4).Thesolidlinere... Open at page → 135 Page 135 RELATIVEDEPRESSIONOFFREEZINGPOINT I I I I I (Jl 4^ OJ ro —o o > OJ o . O Ncn m 00 CD O I CD COmo moo ^c:^ 2m cz<o m rn mN mmo m O d CD (Z Tl m M m o cz < m "Tl o II o • 4^ T / / / V 1 r 125 Open at page → 136 Page 136 FigureIV.6.Comparisonofrelativesoluteconcentrations ofthesolidphase atthefreezinginterfaceduringequilibriumandsemi-equilibrium freezingprocessesofacompletelymiscible(insolidandliquid)binary systemwithconstantsolutedistri... Open at page → 137 Page 137 RELATIVESOLUTECONCENTRATION INSOLID,S/L, 127 Open at page → 138 Page 138 FigureIV.7.Dependence ofsoluteconcentration uponthefreezingrate. (a)Theconcentration ofsoluteintheregionnearthefreezing interfaceduringanequilibriumfreezewiththesolid-liquid interfaceadvancingatanegligiblerate. Therearen... Open at page → 139 Page 139 129 Open at page → 140 Page 140 FigureIV.8.Metalfreezing-point cell. A.Platinumresistancethermometer. B.Toheliumgassupplyandpressuregauge. C.Thermometerstemsealwithsiliconerubber. D.Siliconerubbercap. E.Insulation,washedFiberfrax. F.Thermometerguidetub... Open at page → 141 Page 141 131 Open at page → 142 Page 142 FigureIV.9.Arrangementforfillingthefreezing-point cellwithmetal samplebyinductionheating. A.Borosilicate glassenvelope. B.Metalsample. C.Graphitesampleholderandfunnel. D.Graphitecrucible. E.Inductionheatercoils. F."0"rin... Open at page → 143 Page 143 133 Open at page → 144 Page 144 gureIV.10.Apparatusandmethodforinstallinggraphitethermometerwell andlidinthegraphitecruciblecontainingthemoltenmetalfreezing- pointsample. A.Stainlesssteelpusherrod. B.Gassealwithsiliconerubber. Permitslinearmotionofthep... Open at page → 145 Page 145 135 Open at page → 146 Page 146 gureIV.11. Afreezingcurveoftinobtainedusinganacbridgewiththe headoftheSPRTadaptedforcoaxialconnectors. Thefurnacewas controlledtobe0.9Kbelowthetinfreezing-point temperature. The massoftinsamplewas1300g. 136 Open at page → 147 Page 147 THERMOMETERRESISTANCE,ohms Io«j If::*cnCD^ooCO czs '—ro c_>j Ic* i-NO _p:i cr> cjo<^ -P^ cr>oo cz5 rN:> -P^ THERMOMETERRESISTANCE,48.230xx,ohms 137 Open at page → 148 Page 148 FigureIV.12.Consecutivemeasurements oftheresistanceofanSPRTinthe sametinfreeze. Anacbridgewasemployedinthemeasurements. Followingeachequilibriumresistanceobservation, theSPRTwas completelywithdrawnfromthetin-pointcell,pr... Open at page → 149 Page 149 139 Open at page → 150 Page 150 FigureIV.13.Immersioncharacteristics ofanSPRTinatin-pointcell.The datashowthattheindications oftheSPRTareverynearlythesame betweenabout8or 10cmabovethebottomandthebottomofthe thermometerwell. 140 Open at page → 151 Page 151 OBSERVEDRELATIVETEMPERATURE,mK p p O o 3 141 Open at page → 152 Page 152 gureIV.14.Comparisonoftinfreezing-point temperatures (determinedfrom plateaux)forcellswithvariousresistanceratiosR(0°C)/R(4.2K).The prefixes 5and6indicatesamplesnominally99.999percentpure(LotNo. 6637)andsamplesnominally9... Open at page → 153 Page 153 [V) O m CO C/) > CJl o m o o o o o X^ - cn o I o cn I Oo '(J) I o cn O 4^ ATmK I I oo "1 r o o o o o— H +0-H I 1o X0 czs CO COm m:a3 3> c-> m CO CD CO 1 era m ID mlW I gl^ 1 g2hK) 1 H 1 F?H— O 143 Open at page → 154 Page 154 FigureIV.15. Afreezingcurveofzincobtainedusinganacbridge. Thehead oftheSPRThadbeenadaptedforcoaxialconnectors. Thefurnacewas controlledat0.9Kbelowthezincpoint. Themassofzincsamplewas 1280g.TwocoldSPRTswereinsertedinthece... Open at page → 155 Page 155 THERMOMETER RESISTANCE ,ohms Q_ t>JOJ ——————r\Dror\3r\:roror)rNjr>j -[^cno^-vjoO(^0~r)C>J^cncr)-sioD THERMOMETER RESISTANCE ,65.56xx.ohms 145 Open at page → 156 Page 156 gureIV.16.Consecutivemeasurements oftheresistanceofanSPRTinthe samezincfreeze. Anacbridgewasemployedinthemeasurements. Followingeachequilibriumresistanceobservation, theSPRTwas completelywithdrawnfromthezinc-pointcell,ex... Open at page → 157 Page 157 RESISTANCE 147 Open at page → 158 Page 158 FigureIV.17.Immersioncharacteristics ofanSPRTinazinc-pointcell. The datashowthattheindications oftheSPRTareverynearlythesame I betweenabout8or10cmabovethebottomandatthebottomofthe thermometerwell. 148 Open at page → 159 Page 159 OBSERVEDRELATIVETEMPERATURE,mK P P o OJ ro — o 149 Open at page → 160 Page 160 FigureIV.18.Cryostatforcomparisoncalibration ofthermometers with referencestandardsattheoxygennormalboilingpoint. A.Thermometerwell;eightwellsarelocatedaroundthecopperblock. TheSPRTsaresealedatthetopwithmoldedsiliconerub... Open at page → 161 Page 161 151 Open at page → 162 Page 162 FigureIV.19.Schematicoffurnacebodyandcore. A.Stainlesssteeltube,11.^cmo.d.x0.76mmwall. B.Stainlesssteeltubes(6);3-20mmo.d.x0.013mmwall. C.Insulation,Fiberfraxmats. D.Stainlesssteeltube. E.Insulation,Fiberfraxmatsandmicas... Open at page → 163 Page 163 153 Open at page → 164 Page 164 FigureIV.20.Verticaltemperatureprofileoftin-pointfurnaceat235°C. Theverticaldistancesarerelativetothetopofthetopcoreblock;the thermometerresistances arerelativetothatobservedat25.4cmfromthe topofthetopcoreblock(closetoth... Open at page → 165 Page 165 TIN-POINTFURNACE TESTTEMPERATURE :235°C cmm 0 20 o 24 Q_ o 28 32 36 40- 44- 48 52 10 12 _14 16 20 O CD LlJ o Qrr m ^ us o [- h- o CD 1 o m O X ox OXD OD OD REFERENCE TEMPERATURE' CD Mo Mo 0.1°C TEMPERATURECONTROLSETTINGS... Open at page → 166 Page 166 FigureIV.21.Cryostatfortheintercomparison ofcapsule-type SPRTs. A.GuidefordirectingtransfertubeintoliquidheliumDewar. B.Metalbellowstopermitdifferentialexpansionbetweenthecentral tubeandthesupportingthermometerblockwell.... Open at page → 167 Page 167 157 Open at page → 168 Page 168 FigureIV.22.Thermometercomparisonblock. A.Stainlesssteeltubetosupportthermometercomparisonblock. B.Manganinleadsforthermometers andcopperleadsforblockheater. C.Platinumleadsofresistancethermometer. D.Stainlesssteelwellfo... Open at page → 169 Page 169 159 Open at page → 170 Page 170 FigureIV.23.Schematicofwiringcapsule-type platinumresistance thermometers inthecoppercomparisonblockofthecryostatfor calibration. Toavoidexcessiveheatingofthecopperblock,thebridge connections tothethermometers, wiredinse... Open at page → 171 Page 171 161 Open at page → 172 Page 172 FigureIV.24.Thermaltie-downs. A.Centralsupporttube(stainlesssteel)forthermometerblock. B.Roundedcorner,tangenttothebottomofthegroovesforwires. C.Roundbottomgroovesincylinder"D"withwirescementedinplace. D.Coppercylinderso... Open at page → 173 Page 173 163 Open at page → 174 Page 174 FigureIV.25(a). CurrentComparator 164 Open at page → 175 Page 175 165 Open at page → 176 Page 176 FigureIV.25(b) .WindingsonCores 166 Open at page → 177 Page 177 167 Open at page → 178 Page 178 FigureIV.26(a). KelvinBridge 168 Open at page → 180 Page 180 FigureIV.26(b).ConjugateKelvinBridge 170 Open at page → 182 Page 182 FigureIV.27.D.C.ComparatorBridgeBasicOperation 172 Open at page → 183 Page 183 173 Open at page → 184 Page 184 FigureIV.28.D.C.ComparatorBridgewithAutomaticAmpere-TurnBalance 174 Open at page → 185 Page 185 175 Open at page → 186 Page 186 FigureIV.29. Methodsofcomparisonofresistors. 176 Open at page → 188 Page 188 FigureIV.30. Model9975BlockDiagram; <10kJ^Mode. 178 Open at page → 189 Page 189 TRACKING (7) CONTROL II2I602 18VOLT (8j POWERSUPPLY 1122202 SQUARE WAVE OSCILLATOR AMP TURN (\ ) BALANCE\>-~y/ FLUX(7) DETECTOR^ AMPLIFIER II2I502 SLAVE(i) CURRENT^ SUPPLY II2I703 MASTER® CURRENT SUPPLY II22I02 NANOVOLT... Open at page → 190 Page 190 FigureIV.31. Model9975BlockDiagram; >10kfiMode. I i 180 Open at page → 191 Page 191 TURN BALANCE 18VOLTW POWERSUPPLY 1122202 TRACKING CONTROL II2I602 SLAVE® CURRENT SUPPLY II2I703 SQUARE WAVE OSCILLATOR FLUX (J) DETECTOR AMPLIFIER II2I502 ULUJ MASTER® CURRENT SUPPLY II22I02 MASTER (ij) CURRENT PROGRAMME... Open at page → 192 Page 192 FigureIV.32.Model9975SimplifiedSchematic: <10kQMode 182 Open at page → 193 Page 193 AT.TRACKINGSIGNALGENERATOR SQUARE WAVE OSCILLATOR MODEL9975 SIMPLIFIEDSCHEMATIC <IOKMODE 183 Open at page → 194 Page 194 ureIV.33.Simplifiedcircuitfortheautomaticresistancethermometer bridge. N.through are240-turnwindings, R.through are \ D lb nominallyequalstandardresistors,andR^istheresistancethermometer beingmeasured. 18A Open at page → 195 Page 195 STAGE I (INSIDE) R R R R M5> GENERATOR N N N STAGE5 (OUTSIDE) Nx N <z> DETECTOR 185 Open at page → 196 Page 196 FigureIV.34.Activeshieldarrangementforthetransformerfifthstage. 186 Open at page → 197 Page 197 187 Open at page → 198 Page 198 V.OPERATIONALPROCEDURES WhenanSPRTisreceivedforcalibration, atestfolderispreparedfor itanda3~digitcodeassignedtothatthermometer. Atagcontainingthat 3-digitcodeisphysicallyattachedtotheSPRT. Thecodenumbers,running from000... Open at page → 199 Page 199 whatcorresponds toabout0.75mKduringthecourseofcalibration, the completecalibrationprocess,includingtheinitialannealingat^50°C,is repeated. Insomethermometer designs, thechangesintheR(TPW)readings havebeenfoundtobeontheav... Open at page → 200 Page 200 tothatat4K)ofspecimenstakenfromzincbarsfromwhichtheSRM7^0zinc sampleswerepreparedrangedfrom33,000to38,000,indicatingthatthezinc sampleshaveveryhighpurity. Thezincsampleswerepreparedfromastartingmaterialthatwasselected fr... Open at page → 201 Page 201 V.2.a.3. Preparationofzinc-pointfreeze Liquidzincisfoundtosupercoolonly0.02°Cto0.06°C.Ontheday priortothezinc-pointcalibrationofthePRTs,thefurnacecontrolissetat atemperature about5°Cabovethezincpointandthezincsampleismel... Open at page → 202 Page 202 differfromthefirstreadingbymorethan0.5mK :ifthedifference is larger,measurements onsomeofthetestPRTsthatwerecalibratedlastare repeatedusinganotherzincfreeze. ThetestPRTsonwhichthemeasurements aretoberepeatedaredecidedont... Open at page → 203 Page 203 barsabout5cmacrosstheflatsideandabout60cmlong. Eachofthetin samples (1300geach)werereceivedfromtheNBS-OSRMintheformoftwohalf cylinders(eachabout10cmlong)sealedinapolyethylene bag. Thesamples hadbeencutfromthebarswithacar... Open at page → 204 Page 204 monitoring PRTisusedwiththetin-pointcellfromthatusedwiththezinc- pointcell,sothatanypossibleeffectonthePRTwhenusedatanotherfixed pointisavoided. Aswiththezinc-pointcell,themonitoringPRTusedwith thetin-pointcellservesalso... Open at page → 205 Page 205 Becauseoftheeffectofthehydrostaticheadofliquidtin,the temperaturewherethemidpoint ofthePRTsensorislocatedduring measurements inthetin-pointcellisslightlyhigherthantheequilibrium freezingtemperature oftinat 1atmospherepre... Open at page → 206 Page 206 hydrostaticheadofwaterthatcorresponds toapressureslightlyhigherthan thevaporpressureofwater. Hence,ifthebubblecontainsonlywatervapor, itshouldcollapsewhentheTPWcellisinthebottomendupposition.) TopreparetheTPWcellforuse,t... Open at page → 207 Page 207 withthethermometerwellandtheoutercellwall,subsequentfreezingofthe waterbelowthislayercandevelopenoughpressuretopossiblyrupturethe 33 glasscell. Therefore,wheneveralayeroficeisabouttobridge(orhas bridged)betweenthethermom... Open at page → 208 Page 208 DuringstorageoftheTPWcellinanicebath,thefrozenmantleofice growsslowlyandirregularlyuntilitcontactsandattachesitselftothe outerwallsofthecell. Thecellisoccasionallyremovedfromtheicebath andtheexcessicemeltedbywarmingwitho... Open at page → 209 Page 209 thermometer currentisoncontinuously foratleast5minutesforthe thermometer tocometothermalequilibrium. V.2.d. Normalboilingpointofoxygen Thecalibration ofPRTsatthenormalboilingpointofoxygen (-182.962 °C,oxygenpoint)isreali... Open at page → 210 Page 210 thetemperatures ofthecopperblockandthetwoshieldsarenearlythesame, theinnershieldisallowedto"float"withoutelectricpowerinput. The outershieldiscontrolledrelativetothetemperature ofthecopperblockby meansofdifferential ther... Open at page → 211 Page 211 simultaneously bymeasurements madewithtwoGuildlinebridgesorone Guildlinebridgeandanautomaticacbridge. Thecryostat(Fig.IV.21)wasdesignedsuchthatthecentralcorecould remainstationarywhenthecryostatassemblyisloweredtoexposet... Open at page → 212 Page 212 The0-ringsealJbetweenthecryostatandtheinnerheliumDewarisclosed. Fortheinitialcooldown,liquidnitrogenisintroducedthroughAintothe innerDewaranditsvaporpressureisreducedtoabout1/3atmosphere by pumpingthroughL.Forheatexchang... Open at page → 213 Page 213 driftwilldecreasetolessthan10pifi/minin 1minute;at90K,however,more than30minutesarerequiredbeforethistemperaturedriftratecanbe reached. Measurements areconsideredunsatisfactory ifthethermometerdrift ismorethan5yt^/minute... Open at page → 214 Page 214 surroundings anduponthethermalresistances betweenthem. Insome situations, 5minutesorlongermayberequiredtoreachthesteadystate condition. ThemagnitudeoftheselfheatingdependsupontheJouleheating andupontherateofheattransferf... Open at page → 215 Page 215 accuracy,valuesof shouldbeused. (ThePRTalsomusthavebeen calibratedfor"zero-current" measurements.) ThetotalselfheatingofaPRTisdescribedalsointermsofthechange intheobservedresistancecausedbyachangeintheJouleheatingorthe c... Open at page → 216 Page 216 adjustedfortheexternalselfheatingofthePRT. Incalibrations atthe otherfixedpoints(tin,zinc,andoxygen),theobservedresistances ofthe PRTatacontinuouscurrentof 1mAarealsocorrelatedwiththetemperature oftheoutersurfaceofthePRT... Open at page → 217 Page 217 theIPTS-68(75)specifications.) Below0°C,theWversusTrelationofthe PRTisgivenby W(T)=W*(T)+AW^(T) (V.il) whereW*(T)isthereferencefunctiondefinedby T . r InW*(T)+3.28i-^„ ... ^, T= A a. L T-^o J K (V.5) j=0 J ^-^^ andAW^(T)... Open at page → 218 Page 218 Bydefinition tandTarerelatedbyt=T-273.15K.Equation(V.8)is equivalentto t' = [W(t')-l]+6 [ t' (V.9) a 100°C 100°C where a=A+B(100°C) (V.10) and 6 = -8(100°C)^ (V.1 1 ) A+8(100°C) Above0°C,theconstantsAand8ofEq.(V.8)areobt... Open at page → 219 Page 219 wherea* (=3.9259668 x10 °C )istheathatcorresponds tothe IPTS-68(75)referencefunction.FromEq.(V.4) AW^(tQ) =WCt^) -W^Ct^). (V.15) where WCt^)=R(tQ)/R(0°C)q (V.16) TablesofW(T)arecalculated atintegralvaluesoftfrom-I83°Cto0... Open at page → 220 Page 220 R(TPW)readingwouldbeexpectedtobesmallerthantheR(TPW) reading becauseoftheextrastrainresistancethatwasintroducedbythebumpingof theSPRTbutlaterpartiallyremovedbyannealingatthezincpoint. Onthe otherhand,iftheSPRTwerebumpedi... Open at page → 221 Page 221 calibrated attheNBSinthepast,isemployedintheconversion. The uncertainty intheadjustments ofthevaluefromR(TPW)toR(0°C)inthis _Q mannerislessthan±1x10 R(0°C)forPRTsthatmeettheIPTS-68(75) specification thatW(100°C)benotless... Open at page → 222 Page 222 where ^qq'p_58 ^"^68^ resistanceratiogivenbythereferencefunction 20 InW (T )+3.28 . J=0 Thecoefficients a.ofthisreferencefunctionaregiveninTableIII.2.The J deviationsAW.(T,o)atthetemperatures ofthedefiningfixedpointsare... Open at page → 223 Page 223 368 2 +CT 368 (V.25) wheretheconstantsaredetermined bythemeasureddeviations atthetriple pointandthecondensation pointofoxygen(orthetriplepointofargon)and bythefirstderivativeofthedeviationfunctionatthecondensation pointo... Open at page → 224 Page 224 calibratedareIndicative ofthequalityofreproduction oftheNBS-IPTS- 68(75)bythePRT.Systematicdifferenceswouldindicatethattheequations beinguseddonotadequatelytransfertheNBSIPTS-68(75) tothePRTbeing calibrated . V.6.Calibra... Open at page → 226 Page 226 FigureV.I.Platinumresistancethermometers at33cmimmersioninanice bath.Temperatureprofilefromthemidpointofthethermometer coilout totheicebathwith 1mAcurrent. A. Platinumcoilsofcoiledfilamentthermometer; onlycoilsofone side... Open at page → 227 Page 227 217 Open at page → 228 Page 228 gureV.2.Platinumresistancethermometers at33cmimmersioninawater triple-point cell.Temperatureprofilefromthemidpointofthe thermometer coilouttotheice-waterinterfacewith 1raAcurrent. A. Platinumcoilsofcoiledfilamentthermome... Open at page → 229 Page 229 219 Open at page → 230 Page 230 VI.UNCERTAINTIES OFCALIBRATION Inacalibrationlaboratory, itisextremelyimportantthatthe laboratory's ownmeasurement errorsbesosmallthattheresultsoftheusers ofthecalibratedinstruments willnotbeaffectedbythoseerrors. This m... Open at page → 231 Page 231 thatemployNBScalibratedSPRTstostandardizetheirfreezing-point cellsof tinandzincbeforecalibratingtestSPRTs,thereferenceSPRTscanserveas theircheckSPRTs.) Withtheoxygen-point calibrationapparatus, asecond referencestandardS... Open at page → 232 Page 232 well,reachesthezinc-pointtemperature atacoolingrateof0.1°Cto0.2°C perminute. Thezincsupercoolsbelowthezincpointby0.02°Cto0.06°C (asmeasuredbytheSPRT)beforetherecalescenceoccurs. Thesubsequentrise towardtheplateautemperat... Open at page → 233 Page 233 meltingpoint,thevalueofdt/dpis+5.7xio °C/torror+2.7^ xlo °C/cm columnofliquidzinc. Theimmersioncharacteristics ofanSPRTweretestedinoneofthezinc- pointcellsthathasbeendescribedhere. Theobservedresistances areshown inFig.I... Open at page → 234 Page 234 measurements wereononlyonethermometer E;otherSPRTsmayshowbetteror worsereproducibility.) FigureVI.3showsmoreclearlyhowtheobservations obtainedwith thermometer Echangedwitheachcalibration. ThesymbolsA,,and are associatedw... Open at page → 235 Page 235 untilthemeltingiscompleted,andthenrisesagain. Thereisnoreasonto raisethetemperatureofthetinmorethanafewtenthsofadegreeabovethe meltingpoint. Inafurnacewithlargetemperaturegradients,precautions shouldbetakentomakecertaint... Open at page → 236 Page 236 inboththefirstandlastmeasurements inaseriesofSPRTcalibrations. Thosemeasurementsmustagreetowithin0.5mKorthetestthermometers are calibratedagainusinganewfreeze. AtNBSasingleSPRTissetasideand usedonlyforthispurposeofexperi... Open at page → 237 Page 237 "Test"SPRTEwasrepeatedlycalibratedinsevensuccessivebatchesof calibrations, asstatedpreviously, andthismeantsevenmeasurements atthe tinpoint. Theresultsofthosecalibrations areshowninFigs.VI.2,VI. 3 andVI.4andinTableVI.1.... Open at page → 238 Page 238 ±0.44mK,assumingthatR(Sn)andR(Zn),respectively, havebeendetermined withouterror. Vl.l.d. Randomuncertainties attheoxygennormalboilingpoint Theoxygennormalboilingpointcalibration isrealizedattheNBSby referencetotheNBS-55s... Open at page → 239 Page 239 of3ppmintheR(TPW)readingscorrespondscloselyto0.8mK:suchalarge increaseintheR(TPW)readingsaftermeasurements atthetinpointhasseldom beenobserved. Itseemsthatthelengthoftime(approximately 30minutes, includingthetimeinthepre... Open at page → 240 Page 240 thehydrostaticheadinthecellmaybeobscuredbythevariationsinthe totalselfheatingbecauseofvariations inthethermalcontactofthePRTin thecellwhentheverticallocationofthePRTisadjusted. Hence,totest fortheeffectofthehydrostatiche... Open at page → 241 Page 241 T/K-T /K=-120,887.78M/T^j. + 1213-53295/T,„ - 4.3159552 (VI.1) +6.4J40756M7 X10 68 -3.56638846 x10^T^ 68 whichisvalidintherange273Kto730K. Thedifferencesfoundandtheestimatedmeasurementuncertainties atthe threedefiningfix... Open at page → 242 Page 242 inobtainingtheNBS-IPTS-68 (tabular)scale,thedeviationplotexhibitssome "noise ." TherelationbetweentheNBS-IPTS-68andtheIPTS-68(75)canbeassessed frommeasurements, e.g.,atthefixedpoints,employingthermometers thathave beenca... Open at page → 243 Page 243 +09 calibrations attheoxygenpointofabout _ 2 9 '^^* regionfrom 13-81Kto90.188K,theuncertaintyresultingfromsystematicerrorsrelative totheNBS-IPTS-68 (75)wirescaleisestimatedtobe$±0.5mKoverthe entirerange. VI.3.Propagation... Open at page → 244 Page 244 ±2mKbetween54Kand90K,and±5mKbetween90Kand273K.Itshouldbe pointedoutthat,inadditiontounaccountedforvariations intheplatinum wire,aspreadinthetemperaturevaluesmayarisealsofromincomplete definitions ofthematerialsthatdefine... Open at page → 245 Page 245 wheret.isthetemperatureattributed tothecalibrationfixedpointandW 1 1 isthevalueoftheresistanceratio,R(t.)/R(0°C),attributed tothat temperature. Theanalysismaybesimpliedbyconvertinganyerrorinthe valueoftemperatureattribut... Open at page → 246 Page 246 where A=a(1+6/100) (VI.6) and B=-10^a6 (VI.7) Also,fromEqs.(VI.6)and(VI.7) and a=(A+100B) (VI.8) 4 6=-10B/(A+100B). (VI.9) Fromthedefinitionofa,itfollowsthat a=[W(100°C)-1]/100°C (VI.10) AtT=273.15K(ort=0°C)thereferencef... Open at page → 247 Page 247 Substractlng Eq.(VI.12)fromEq.(VI.11)andsubstituting in AW^(t)=b^t+e^t(t-100) (VI.13) at100°C,thereresults b,,=a-a* (VI.U) WhenEq.(VI.13)issolvedfore,,att =(AW^(tQ) -b^tQ)/t^(tQ -100). (VI.15) Thus,bothcoefficients b^^an... Open at page → 248 Page 248 {d[AW^(t)]/dt}Q =-[2.64659gb^ +0.0199308gAW^ ( )]. (VI.18) Again,sinceAW^Ct^)rangesfromabout-2.0x10 to+1x10 ,the contribution ofb^tothederivative attheoxygenpointcanbecomparableto thatofthemeasuredvalueofAW^Ct^). (Theval... Open at page → 249 Page 249 thatwerereceivedduring2-1/2yearsshowstheaveragetobecloserto -7-2 -10-2 -5.8768 X10 °C andtherangetobeabout 4x10 °C ). Asurveyof28 capsule-type PRTsshowsthatthederivatives attheNBPofoxygenofthe deviationfunctionscouldbe3x... Open at page → 250 Page 250 a= ^, +BdOO-f) (VI.26) WhenEq.(VI.26)isdifferentiated withrespecttoW, da=dW/t' , (VI.27) ifanassumedaverage Bisused. Bysubstituting Eq.(VI.5)forAinEq. (VI.23),theeffectofachangeintemperatureonWisobtainedas ,^ .dW= [ ^" ^... Open at page → 251 Page 251 andfrom W(T)=W*(T) +AW.(T) (VI.32) 6W*(T) =-6AW.(T) . (VI.33) 1 (Theeffectofanerrorofresistanceratiomeasurement6W(T)bytheuserof thePRTisnotconsidered inthisdiscussion; thaterrorcanbebestestimated bytheuserandcombinedwith... Open at page → 252 Page 252 andissmallerbetweenabout30Kand87Kfortheleastsquarestreatmentof thedatathanforthefixed-pointtreatmentbutatothertemperatures the effectislargerfortheleast-squares method. Sincetheleast-squares method involvestheminimizatio... Open at page → 253 Page 253 upwardanddownwardandcausesrelativelylargerdeviations atthelower temperatures thandoesthefixed-point treatment. However,theoverall averagedeviationissmallerfortheleast-squares method. Theleast-squares treatment oferrorsof... Open at page → 254 Page 254 possibleerrorsofmeasurements atthetinpointortheuseofanaverageB, isconsideredunlikely. Althoughthereissomeexperimental scatterinthedata,particularly belowabout20K,definitesystematicdifferencesareshownbytheresultsof thefix... Open at page → 255 Page 255 whentheleast-squares treatment ofthedataisemployed. Intheleast- squarestreatment ofthedata,anyerrorintheregion13Kto90Kis distributedbothupwardanddownwardintemperature. Sincetheleast-squares treatmentminimizes thedeviatio... Open at page → 256 Page 256 determinehowwellcalibrations areretainedastheSPRTsaresubjectedto conditionsofuse. Forconvenienceofcomparisonofsuccessivecalibrations attheNBSand, atthesametime,toshowthedegreetowhichtheSPRTscanretaintheir calibrations, t... Open at page → 257 Page 257 andthoseofW(Zn)areabouttwicethoseobservedwiththecheckSPRTs,the calibrations oftheSPRTshavebeenretainedclosetothelimitofcalibration measurements attheNBS. TheuserofanSPRTthatwascalibrated attheNBS canlookuponFiguresVI.25,... Open at page → 258 Page 258 calibration isretained. (TheSPRTshavebeenshippedandreceivedfroma numberoflaboratories, somelocatedacrossthecontinent.) Theresultsshow alsothatSPRTscanbeemployedreliablyinprecisetemperaturemeasurements. WhentheseSPRTswere... Open at page → 259 Page 259 manycalibrationpointsthatcanbeanalyzedbyaleast-squares methodsothat thecontributionfromanerrorinanyoneobservationwouldbenegligible. Accidentalagreementoftwouser-laboratory calibrations canresultif thesameerrorismadeinbot... Open at page → 260 Page 260 thelaboratory isstandard,and(4)whethertheresistanceunitiscloseto ournationalunitofresistance. Whencalibration iscompleted, theSPRTsare returnedtotheNBSforrecalibration andshipmenttothenextparticipating laboratory. TheSPR... Open at page → 261 Page 261 TableVI.1.Estimatedstandarddeviations (S.D.)(lo)ofvaluesofW(and theirequivalents intemperature, t)ofsomeplatinumresistance thermometers atthetemperaturefixedpoints. SPRT W(Zn) W(Sn) WCO^) S.D.ofW S.D.oft S.D.ofW S.D.oft... Open at page → 262 Page 262 TableVI.2.Differencesbetweenthermodynamic temperatureandT--0. DO Uncertainty t(°C) T/K-T^g/K^g Random Systematic (99?confidencelimits) 100 231.9681 419.58 -0.0252 -0.0439 -0.0658 ±0.001 8 ±0.0022 ±0.0028 ±0.00054 ±0.001... Open at page → 264 Page 264 FigureVI.1.ValuesofWforcheckSPRT200fromobservations ofthe resistances atthezincfreezingpointandattheTPW.Thesequenceof zinc-pointobservations isrepresented bythesymbolsintheorder0,A, andO. 254 Open at page → 265 Page 265 RESISTANCERATIO,R(Zn/R(0°C) > 3D m CO CO —i 3> Z n 3D O o > I— CD 3D > CD > Oi CO o CJl CT3 CO tn CJl cn cn a> oo tn CD o cn o> 00 cn cn cn T o> I o t> > o t> > CD o o o CO .>o d> >o >o o > o >o o> o oc> o> ooei to o> CS... Open at page → 266 Page 266 FigureVI.2.ValuesofWofSPRTs(relativetothefirstcalibration) obtainedattheNationalBureauofStandardsfromaseriesof calibrations attheTPWandatthezinc,tin,andoxygenpoints. V 'Thermometers A,B,C,andDwereemployedintheMeasurement... Open at page → 267 Page 267 RESISTANCERATIODIFFERENCE,RATIOUNITS(10 o o o >oOn OO< > 3> — t —00 00o Xo oscO< XBtOO 333-<<: ?«:;^^ J> o m CO z o ZD o X© COO<3 —o > ^o 3D I> O Z 00 Z3 CO X T Om— -J> CO s m "CO ^m X o • ^COOOa CO ::J QCOrvi00 j-^zz -o... Open at page → 268 Page 268 FigureVI.3.Observedvaluesofresistances attheTPW(convertedtoR(0'C)) andatthezinc,tin,andoxygenpointsandthevaluesofWcalculated fromtheobservations forthermometer Ecalibratedsuccessively in batches74Dto74J.Thesequenceofobse... Open at page → 269 Page 269 >CO 1—J> c00 -D — t o INU ISI 3-n 00 3D m CO > Z o m —t o X INI => m 3D S o CO 3 m 3 — 1 m 3D > CD O 3D ATI INI 3 oX z CO 3 00 > — 1 o O INI 3 CO 3 o bCD r-> C00 R(0,).6.2227 R(Sn),48.3400 R(Zn).65.6064 R(0°C),25.5390 I... Open at page → 270 Page 270 FigureVI.4.Deviations,relativetothefirstcalibration, ofvaluesofW(t) (intermsofcorresponding valuesoftemperature) ofsucceeding calibrations ofthermometer E. 260 Open at page → 271 Page 271 261 Open at page → 272 Page 272 FigureVI.5.ValuesofWforcheckSPRT199fromobservations ofthe resistance atthetinfreezingpointandattheTPW.Thesequenceof tin-pointobservations isrepresented bythesymbolsintheorder0,A, and. 262 Open at page → 273 Page 273 RESISTANCERATIO,R(Sn)/R(0°C) oo CD CD CO CO a> C3 CO CO ro Ni tn 33 m (/» 00 — t > > 3D CD > 1 1 1 1 1 I 1 > 1O 1 1 1 1_ O D> — O> — c_ > O o "T^ *^ - t — —— O — to^ o> — CD > o O > o O m o> >o - -n > o cr>— >o in--*—> «... Open at page → 274 Page 274 FigureVI.6.Deviations (intermsofthecorresponding valuesoftemperature) fromtheaveragevalueofR(0°C)foreachPRT,calculatedfromthe observedvaluesofR(TPW)forPRTscalibratedbetweenJune1972andJuly 1973. 264 Open at page → 275 Page 275 0.5 0.5 0.5 1 1 1 1 1 1 b 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 I I o — o o o O a OO o — o o A°<^ ^ 8 o 0 A ° s o A o a o —o_ g o 0 ° ° A „ * o o— o o — o— « ff>—A Ck— o o o o ^o _ A — A A 0 n A A oA AA A ° o A o o... Open at page → 276 Page 276 FigureVI.7.Deviations (intermsofthecorresponding valuesoftemperature) fromtheaveragevalueofR(0°C)foreachPRT,calculatedfromthe observedvaluesofR(TPW)forPRTscalibratedbetweenAugust1973and July1974. : 266 Open at page → 277 Page 277 DEVIATIONSFROMTHEMEAN.mK T~r~ Oa I oo o CJ1cn I I I I > t> Co >o a > >o o > o> > o| CO CO oe> >o > o o> o o- a oOa O aO aO o o O o ><> ocj ao> o I K> O ocoO J_JL_L_ r~r-i— I I I a>|>n -O > >a -O > o l> a> o t> n > >o >O... Open at page → 278 Page 278 FigureVI.8.ObservedvaluesofresistanceforcheckSPRT250attheoxygen pointandattheTPW[convertedtoR(0°C)]andvaluesofWcalculated fromtheobservations. 268 Open at page → 279 Page 279 RESISTANCERATIO,R(0,)/R(0°C) RESISTANCE,R(0°C)Ohms 3D S O f— CD 3D O "I I I I I I I Ir 1—I I I I I h+ -+ -4- -+ -M- -+ -+ I ILJL_L 1= "1— r- I 1 IT— r o+ o+ o+ o 3D o o+ —30 3o JL o I I I I I I I I IL I I 1 I oo zX m-< O... Open at page → 280 Page 280 FigureVI.9.DeviationofInternational PracticalTemperaturesfrom thermodynamic temperatures intherangefrom275Kto730K.The estimateduncertainties atthedefiningfixedpointspublishedinthe originaltextoftheIPTS-68areshownbytheerr... Open at page → 281 Page 281 05 CO 271 Open at page → 282 Page 282 gureVI.10.ComparisonoftheNBS-IPTS-58 (tabular)temperaturescalewith theNBS-IPTS-68temperaturescale. NBS-IPTS-68 (tabular) isatabular scalebasedoncombiningtheNBS-1955scaleandthepublisheddifferences betweentheNBS-1955scalea... Open at page → 283 Page 283 t[nBS-IPTS-68(TABULAR)]-T[nBS-IPTS- 68] ,mK 1 o - o o XI c m cn O 00 O o Z2 ODOD CO t/) T)Tl COCO CD00 > CD CI r- > XI o o o I I I I o o o o o o o o o > o OD CO O o > CO o -uo CDDO 00 C/5 > d CO I V>CD X 00 273 Open at page → 284 Page 284 FigureVI.11. Errorsatvarioustemperaturespropagatedfromerrorsmade calibrationofaPRTwhentheAlfreezingpointisincluded. The designations arethesameasinFig.II.1. 274 Open at page → 285 Page 285 ERRORINDEGREESPERDEGREEERRORINCALIBRATION o o 275 Open at page → 286 Page 286 FigureVI.12.Effectoferrorsintherealizationofthefixedpointsabove 0°Conthecalibrationofaplatinumresistancethermometer inthe region13Kto90K.Theerrorsintroducedinthecalibrationwhenthe least-squares treatment isemployedarecom... Open at page → 287 Page 287 ERRORINKELVINSPERKERRORINCALIBRATION I o I I I I I I I I o 11 r m OJO C 33 cn 00 OJ O 33 3) O 33 > o 00 o m > CO H CO O c > m I O m > H (/) O c > ^'^ ^ 33 33 O 33 11TT o > CD > OJ OJ OJ() pJOJ X m o -Q o CO X m o O m 33... Open at page → 288 Page 288 FigureVI.13.Effectofthreetimesmoredataintheregion 13Kto20Kand theeffectofthreetimesmoredataintheregion5^Kto90Konthe resultsofleastsquarestreatmentofthecalibrationdatawithanerror equivalent tounitpositivetemperature atthe... Open at page → 289 Page 289 279 Open at page → 290 Page 290 FigureVI.1^.Effectofanerrorintherealizationofafixedpointonthe calibration ofaplatinumresistancethermometer intheregion 13Kto 90K.Thefigureshowstheresultingerrorwiththeleast-squares treatmentandtheresultingerrorwiththefix... Open at page → 291 Page 291 281 Open at page → 292 Page 292 gureVI.15.Effectofanerrorintherealizationofafixedpointonthe calibration ofaplatinumresistancethermometer intheregion 13Kto 90K.Thefigureshowstheresultingerrorwiththeleast-squares treatmentandtheresultingerrorwiththefixed... Open at page → 293 Page 293 283 Open at page → 294 Page 294 gureVI.16.Effectofanerrorinthecalibrationdataattemperatures midwaybetweenthefixedpointsonthecalibrationofaplatinum resistancethermometer intheregion13Kto90K.Thefigureshowsthe resultingerrorwiththeleast-squares treatmento... Open at page → 295 Page 295 285 Open at page → 296 Page 296 gureVI.17.Measureddeviations ofthevaluesoftemperatures, givenbythe IPTS-68formulationsobtainedforeachthermometer bytheleast-squares treatmentofthecalibrationdata,fromthoseoftheNBS-IPTS-68scaleat temperatures ofintercompa... Open at page → 297 Page 297 m m > — I c 33 CD OO DEVIATIONS ,mK O Bo CO > >^ o> O X>®O C30C Dt> «o > o o o o o 00 o o O>x€lO t>o OJOJOJTJ (NOno— 3) OJ 'Xi-b-H OJC>JW"0 OJw<>' £>WN)H 287 Open at page → 298 Page 298 FigureVI.18.Measureddeviations ofthevaluesoftemperatures, givenbythe IPTS-68formulationsobtainedforeachthermometer bytheleast-squares treatmentofthecalibrationdata,fromthoseoftheNBS-IPTS-68scaleat temperatures ofintercor... Open at page → 299 Page 299 DEVIATIONS,mK o o>®><S oscBJ> <>si>K) 9 [>onx<ji >o OJOiOJu -t^-Ci-Ci :d "i^oj —H <9O X WWOJ1) OicnuiX ji1>J—H 289 Open at page → 300 Page 300 gureVI.19.Measureddeviationsofthevaluesoftemperatures, givenbythe IPTS-68formulationsobtainedforeachthermometer bytheleast-squares treatmentofthecalibrationdata,fromthoseoftheNBS-IPTS-68scaleat temperatures ofintercompar... Open at page → 301 Page 301 DEVIATIONS,mK r\5 o >o C>DOX xO o o > >XO t>OCX [>9 K3K X>O OJOJOJW"D .->J <J1CDX x»roojH o o 05 O to o OIB x:>o Xmo 291 Open at page → 302 Page 302 FigureVI.20.Measureddeviations ofthevaluesoftemperatures, givenbythe IPTS-68formulationsobtainedforeachthermometer bytheleast-squares treatmentofthecalibrationdata,fromthoseoftheNBS-IPTS-68scaleat temperatures ofintercom... Open at page → 303 Page 303 DEVIATIONS,mK OCQDt>O O <S>COCl> DQSiX O 0 0C-x>O (jjoj <->JojOJ "D toID^p 9^zo c>jro'-bL>jro— t 293 Open at page → 304 Page 304 FigureVI.21 .Measureddeviations ofthevaluesoftemperatures, givenbythe IPTS-68formulationsobtainedforeachthermometer bytheleast-squares treatmentofthecalibration data,fromthoseoftheNBS-IPTS-68scaleat temperatures ofinterc... Open at page → 305 Page 305 I IN3 DEVIATIONS,mK o <Mno 66 t?6 9 cm )0 96^^c^D at) ^^>q]o<;> 06^ Q o oo>6 4^ 4:. ;^^T) —rPO13 OJKj— 'ojH 9 i^>6 ^4i^ ^-TJ w rv)roro— jiwK)— '-tiH [Oxc!^ D69> cm 295 Open at page → 306 Page 306 FigureVI.22.Measureddeviations ofthevaluesoftemperatures, givenbythe IPTS-68formulationsobtainedforeachthermometer bythefixed-point treatmentofthecalibrationdata,fromthoseoftheNBS-IPTS-68scaleat temperatures ofintercompa... Open at page → 307 Page 307 DEVIATIONS,mK I I I ITT et>o aB> Ex Ir I I I I I ODEx>O ©-• <X ©o o>o wOJ OlUl :d w^OJ H l>®X OJOJOJ-D H I I I I I I I &»©0 X >o 5>O®Xd> I I I I I I I CSX »<O<^ o> O XO ®[36> <J>^o o<2> a OJOJ (jj(jj OJrv) k) tc.OJ X>> O... Open at page → 308 Page 308 FigureVI.23.Measureddeviationsofthevaluesoftemperatures, givenbythe IPTS-68formulationsobtainedforeachthermometer bythefixed-point treatmentofthecalibrationdata,fromthoseoftheNBS-IPTS-68scaleat temperatures ofintercompar... Open at page → 309 Page 309 DEVIATIONS ,mK I I I I I I I I I X e» <3>DS I I I I I I I—TT o> <3> Ox X a (3»» (SB O X>O ^^-t>T) .——-3 ^OJro 1 <S>B>© CD O 4i^-C. (>o[NJrof\i 04K)— o 1 I I I ++ + »©o I I I I 1 I 1r >OD X3 O 18)><tO X> t>JWWOJ"O <J303po... Open at page → 310 Page 310 FigureVI.24.ValuesofWofSPRTs(relativetothefirstcalibrationofthe series)obtainedattheNationalBureauofStandardsfromaseriesof calibrations attheTPWandatthezinc,tin,andoxygenpoints. Thermometers A,B,C,andDwereemployedinaMeas... Open at page → 311 Page 311 RESISTANCERATIODIFFERENCE,RATIOUNITS(10" ) I o CD o o 1 I \ \ \ r >oOn oO< > ISI -o — t — (/» 3D m CO — t J> z o !- X© o J» CIo CD ' 3D J> O Z OO 31CO X Xo cEaC>< 333 -<<: > m 00 »a< «ota CO S m <D O • 3D ^ COo oj 4*. -*... Open at page → 312 Page 312 FigureVI.25.Deviations,relativetothefirstcalibrationoftheseries, valuesofW(t)(interrasofcorresponding valuesoftemperature) of succeedingcalibrations ofthermometer A. 302 Open at page → 313 Page 313 303 Open at page → 314 Page 314 FigureVI.26.Deviations,relativetothefirstcalibrationoftheseries, valuesofW(t)(intermsofcorresponding valuesoftemperature) of succeedingcalibrations ofthermometer B. 304 Open at page → 315 Page 315 305 Open at page → 316 Page 316 FigureVI.27.Deviations,relativetothefirstcalibrationoftheseries,of valuesofW(t)(intermsofcorresponding valuesoftemperature) of succeedingcalibrations ofthermometer C. 306 Open at page → 317 Page 317 307 Open at page → 318 Page 318 FigureVI.28.Deviations,relativetothefirstcalibrationoftheseries,of valuesofW(t)(intermsofcorresponding valuesoftemperature) of succeedingcalibrations ofthermometer D. 308 Open at page → 319 Page 319 309 Open at page → 320 Page 320 FigureVI.29.Standarddeviations ofcalibrations ofvariouslaboratories comparedtotheNationalBureauofStandards'calibrationofthreeSPRTs ' nearthefixedpoints. 310 Open at page → 321 Page 321 lA o STANDARDDEVIATIONSFROMNBSCALIBRATION,±mK CD tn— » CJI CJl CD CD CD CD CD oo CO > I — 00 DO > DO > DO m CO o CO I 00 1 1 1 1 1 1II < (g) r 1 1 11! 11! > oo 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 CO "O DO —1 1 s > >« oO... Open at page → 322 Page 322 VII.INTERNALQUALITYCONTROLS Inordertomaintainproperqualitycontrolofthecalibrationprocess and,consequently, ofthecalibrations themselves,certaincheckstandardsare maintained fortestingthevarioustemperaturefixedpointsandals... Open at page → 323 Page 323 preparationandmanipulation thatarefollowedforinitiating thefreezeby withdrawing thecellfromthefurnacewell. Fortheoxygen-point comparisoncalibration, asecondreferencestandard SPRTisusedasthecheckSPRTtomonitortheconsistenc... Open at page → 324 Page 324 calibrationbatch74Cto74J(approximately one-halfyear),W(Zn)wasfoundto befairlyconstantanditsrangecorresponds toaboutO.'^mK.Thestandard deviationofthevaluesofW(Zn)wascomputedafterdividingthedatainto threeintervals:72Gto72K... Open at page → 325 Page 325 stability.) Fromcalibrationbatch72Kto74J,mostoftheobservedvaluesof W(Sn)arewithin±0.3mK.ThenoticeablechangeintheW(Sn)readingafter calibrationbatch72KsuggeststhatthecheckSPRTwas"bumped"slightly. (Therewasarelativelylargei... Open at page → 326 Page 326 firststandardineverygroupoftestthermometers calibrated. Comparisons aremadeattemperatures nearthefixedpointsandoccasionally atother temperatures. FigureVII.6showsthedifferencesbetweenthecomputedvalues oftemperature ofthe... Open at page → 328 Page 328 gureVII.1.ObservedvaluesofresistanceforcheckSPRT200atthezinc freezingpointandattheTPW(convertedtoR(0°C)). Thesequenceof zinc-pointobservations isrepresented bythesymbolsintheorder0,A ,andO;theR(0°C)valuesarerepresented b... Open at page → 329 Page 329 RESISTANCE, R(Zn)Ohms 03 at CO — t > z o Z CO 3D J>O 1 1 1 —o> 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 I I 1 ' ' 1 1 o> + _ >o+ t> + o CI>+o £X5+ <X>+ ISO+ 3D * rsi —. =j ZINC POINT CHECK PRT 200 > -h-... Open at page → 330 Page 330 FigureVII.2.ValuesofWforcheckSPRT200fromobservations ofthe resistances atthezincfreezingpointandattheTPW.Thesequenceof zinc-pointobservations isrepresented bythesymbolsintheorder0,A, a,andO. 320 Open at page → 331 Page 331 RESISTANCERATIO,R(Zn/R(0°C) IS3 CJ1 a> CO cn CD NJ cn OJ CD cn cn cn 1 r cn CD oo tn CD o o t> ' o t> > o cn a> 00 cn cn cn > o o CD oOca cca? >o ct> oo oo o o Oo oo o oo oO oO [S3 OO oO o OO OO oo oo o O C-5 -a 33 O o o... Open at page → 332 Page 332 FigureVII.3.ObservedvaluesofresistanceforcheckSPRT199atthetin freezingpointandattheTPW(convertedtoR(0°C)). Thesequenceof tin-pointobservations isrepresented bythesymbolsintheorder0,A, and;theR(0°C)valuesarerepresented by... Open at page → 333 Page 333 RESISTANCE. R(Sn)Ohms 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 • 1 + >d ' 1 I - - - » + «> - c- 3 =. -\-> o g^ - -j- > o :2o - o>f ^ ' CO - — CD >o-|- - O > o-f- - a +o - m... Open at page → 334 Page 334 gureMIl.U. ValuesofWforcheckSPRT199fromobservations ofthe resistance atthetinfreezingpointandattheTPW.Thesequenceof tin-pointobservations isrepresented bythesymbolsintheorder0,A, ando. 324 Open at page → 335 Page 335 RESISTANCERATIO.R(Sn)/R(0°C) CO CO ro CD oo CO r-o <y> i-o C3 00 ro CA —I 3> Z O CD 30 3> CD _ 1 1 1 1 1 I 1 > 'o 1 1 1 i o> ot> > o - o*> 1 — O 1-> o> CO > o _ n > o o m o> > o -n > o >o > - c_ >o > o -> o - Z o 3 o> o>... Open at page → 336 Page 336 ureVII.5.ObservedvaluesofresistanceforcheckSPRT250attheoxygen pointandattheTPW(convertedtoR(0°C)),andvaluesofWcalculated fromtheobservations. Theoxygen-pointobservations arerepresentedby thesymbolOandtheR(0°C)valuesarere... Open at page → 337 Page 337 RESISTANCERATIO,R(0,)/R(0°C) RESISTANCE.RICC)Ohms CO —I > I — CO o 00 1 1 1 1 1 1 1 1 1 1 ' 1 1 1 1 1 1 1 1 1 1 1 1 1-|o 1 1 1 1 1 1 1 1 1 1. _.o <_ o 0 CJ T 1 1 OXYGEN 1 CHECK PI o s- - _ o o 4- - - o 1 -1- - n:- %^o+ -... Open at page → 338 Page 338 FigureVII.6.Measureddeviations ofthevaluesoftemperatureofthesecond referencestandardplatinumresistancethermometerfromthoseofthe firstreferencestandard. 328 Open at page → 339 Page 339 DEVIATIONS ,mK p Id p CD I I p o O o o 9 1^9 6 6 Oo <^9 X <^ c5>6po ODCS ^O 9 tf9- no Ok 9P> 9 ti^5 99 c?93, OJWWOJC>JOJ CTiCJ1^OJro— X >O6 W l)—o ID00 33 329 Open at page → 340 Page 340 gureVII.7.PlotofBversusAforSPRTscalibratedattheNBSoverthe periodfrom1968until1984.SeeFigureVII.8. 330 Open at page → 341 Page 341 10^XB+580 O) X 00 CjO 00 CD 00 cn 4^ CD C/1 CD Ul cn CD CD L-T. 00 CD Ul CD • . •• t* • • • 4 •»^ 331 Open at page → 342 Page 342 FigureVII.8.Plotof6versusaforSPRTscalibratedattheNBSoverthe periodfrom1968until1984.Thevaluesplottedhereareforthesame SPRTsasthoseofFigureVII.7. 332 Open at page → 343 Page 343 de1ta (JD CD cn CD CD CO 4:^ CD CD cn cn C7^ CD CD Ul CD •• • ••• LP. 333 Open at page → 344 Page 344 VIII.FUTUREPLANS Wearecurrentlyautomating,modernizing, andimprovingthePlatinum ResistanceThermometerCalibrationLaboratory. Whenimplemented,thisshould resultingreaterefficiencyofoperationandinimprovement ofservice. Also,t... Open at page → 345 Page 345 Consequently, anapparatusforrealizingthisfixedpointwillbeprepared,as willtheappropriatecryostat foritsuse. Atthepresenttime,theoxygen pointismaintainedonlyonawirescaleatNBS. VIII.6.PrepareforRevisionofIPTS Arevisionofthe... Open at page → 346 Page 346 IX.REFERENCES [I] TheInternational PracticalTemperatureScaleof1968,AmendedEdition of1975",Metrologia J_2, 7-17(1976). [2] "The1976Provisional 0.5Kto30KTemperatureScale",Metrologia j_5, 65-68(1979). [3] R.E.Bedford,M.Duri... Open at page → 347 Page 347 [12] H.J,HogeandF.G.Brickwedde ,"Intercomparison ofPlatinumResistance ThermometersBetween-190°Cand °C" ,J.Res.Nat,Bur.Stand.28, 217-240(February19^2)RP1i^54. [13] M.R.M.Moussa, H.VanDijk,M.Durieux,"ComparisonofPlatinum R... Open at page → 348 Page 348 [25] R.D.Cutkosky,"AutomaticResistanceThermometerBridgesforNewand SpecialApplications", Temperature, ItsMeasurement andControlin ScienceandIndustry ,Vol.5(AmericanInstituteofPhysics,NewYork, 1982) pp.711-713. [26]TheInte... Open at page → 349 Page 349 [35] OfthefiveTPWcellswheretheinnerandtheouterwaterwere intentionally mixedbyalternatelyinvertinganduprightingthecells, thetemperatures thatwereobservedforfourofthecellswere essentiallythesameasthosebeforemixing. Forthef... Open at page → 350 Page 350 [45] L.A.GuildnerandR.E.Edsinger,"DeviationofInternational Practical TemperaturesfromThermodynamicTemperatures intheTemperatureRange from273-16Kto730K",J.Res.Nat.Bur.Stand.80A,703(1976). [46] E.H.McLaren,"Intercomparison... Open at page → 351 Page 351 X. BIBLIOGRAPHY Arelevantbibliography inadditiontotheReferences isgivenbelow. X.I.NBSPublications G.T.Furukawa, W.G.Saba,D,M.Sweger ,andH,H.Plumb,"Normal BoilingPointandTriplePointTemperatures ofNeon",Metrologia 6, 35-37... Open at page → 352 Page 352 G.T.Furukawa,W.R.Bigge,J.L.Riddle,andM.L.Reilly,"The FreezingPointofAluminumasaTemperatureStandard",Temperature Measurement 1975 ,389-397,editedbyB.F.BillingandT.J.Quinn,Inst. Phys .Conf.Ser .No.26(TheInstituteofPhysics,... Open at page → 353 Page 353 G.T.Furukawa,"Reproducibility ofthetriplepointofargoninsealed transportable cells",Temperature, ItsMeasurement andControlinScience andIndustry .Vol.5(AmericanInstituteofPhysics,NewYork,1982) pp.239-2M8. GeorgeT.Furukawaa... Open at page → 354 Page 354 XI.APPENDIX XI.1.TypicalCalibrationReport Open at page → 355 Page 355 U.S.DEPARTMENTOFCOMMERCE NATIONALBUREAUOFSTANDARDS NATIONALMEASUREMENTLABORATORY GAITHERSBURG, MP20899 REPORTOFCALIBRATION PLATINUMRESISTANCETHERMOMETER SERIALNO.1990421 SUBMITTEDBY PLATINUMRESISTANCE THERMOMETRYLABORATO... Open at page → 356 Page 356 -2- Temperatures between0"^Cand630.7/,'^ConthenewInternational lYacticrjlTemperature Scaleof1968(IPTS-6S)aredefinedbythe indications (resistancevalues)ofstandardplatinumresistance thermometers andthefollowingexpressions:... Open at page → 357 Page 357 -3 - CAUTION: ThevaluesofA,B,andbonthenew1968scaleare distinctlydifferent frointhecorresponding valuesontheold19/.8 or1927scale. Thevaluesofaand arealsodifferentbuton]y triviallyso. Temperatures below0°Conthenew1968scale... Open at page → 358 Page 358 successivevaluesinthesecondcolumn. Thesereciprocalfirstdifferences areincludedtofacilitateinterpolation. Theerrorintroduced byusing linearinterpolationwillbelessthan0.0001°C. Therangeofthistabledoesnotimplythatthisthermo... Open at page → 359 Page 359 -5 - 349 Open at page → 360 Page 360 6 Footnotetotheerrorpropagationcurvesonpage5. Thecurvesshowtheerror atvarious temperatures thatwouldbe propagated byerrors made inthecalibration ofastandard platinum resistancethermometer. Eachcurveshowstheerror(i.e.,dep... Open at page → 361 Page 361 IF'7S--6STABLEFOR|-<ESIS'[ANi:;E TFIEl'MOliF I'F'R {-^->0/]--->\ TEMF',, F^ESISTANCI-:;; INVERSE TEMP, RF,:;. J,o 1Alv|i...E INVERSE t::if:g„c: rat:[ci ij ;i:i--- 1-- „ miEgi: F'at'to rirf , 150 ,3F:'".^l 1J 149 0 -148 '... Open at page → 362 Page 362 TA1-;l.J-::FGF^RESISTANCETHERMUMi: jER 1 EMF' „ RESISIANCE INVERSE TEMP, RESISTANCE INVERS EGi„C RAT1 0 D[l-'E„ DEG,C RATIO DIFE, 100 ~"•' C' / „594647 „5''b/' . r,607023 242 „10 242,,21 242-3 1 50 .799C)70 -• - lC:'- ,'... Open at page → 363 Page 363 IF-'TS-68TABLEFORRESISTANCETHERMOMFTER1990421 TEMP. RESIS-TANr:£ INVERS DEG„C RATIO 0 :i:I"-F. 0 1»uuuuuu 250„75 1 1.0039S7 2!50 „3:3 2 1 ,.007972 250.91 3 1„011957 250„93 1.015940 251„06' 5 1=019922 251 „14 6 1u023902 2... Open at page → 364 Page 364 IF'T368TA!;;;i...Eforresis"rANC:ETHE1441METER19904:;:'l •e::mf'' , F%ESIS1ANC:E INVERSE TEMP. RESISTANCE INVERS^ lEGnC RATIO DIEF„ FjFlG ,. 1." RATIO DIF'E. 100 150 1„584553 10 1 1„;396549 1!5 1 1„'5383<:S1 O^'o" 102 1.4... Open at page → 365 Page 365 IF'TS' "ABLEFORRESISTANCErHERMuMETER 1990421 T'EMP . DEG„ I '. 200 20 1 202 20-3 204 205 206 207 20!:::; 210 211 212 21 ; 21- ! 21 ::i 21<S 217 2IS 219 220 231 240 241 242 24S 249 v!~;o RESISTANC:!;;: RATIO 1„773491 1„77... Open at page → 366 Page 366 1:F-'TS6STABL.E F-CiRRESlS"rANCE fhlERMOME TEMF'' DEG„ i ;•;(')() li )'7 :!09 10 :i, :i. :;].2 1;3 !1^'i- 11& -'(.) ".'"'I 324 30 31 •-1--i ..;> .,"1 ..J 340 341 342 344 345 347 349 :-!50 RESISrANC:E: RAT10 2,142641 2„14... Open at page → 367 Page 367 j:fTS63TAEI,FFORRESIS"rANC;l:v (MCiME'lER1.990^21. TEMP „ DEG-C '100 401 1-02 403 404 405 406 ^107 40S: ^!-09 i). 10 ^1- :l. :! 412 413 4iA 4- 1 S 43.6 41 7 -t-1e 4- 1 9 42(:) 421 422 423 424 425 427 42S 429 430 431 432... Open at page → 368 Page 368 F^ESIS' EEOF^;f:esisi"aN!: INVEF^SE THERMOMETER 1.990421 •EMR. RESISTANi::E i:i\Pv'FF>SE EG.C RAT1 0 DIFE„ ITEG„C RAno ITI !•F. 500 2r84-602 '4 „ 1 5 550 3„014456 299„44 50 1 2=849401 294 „25 551 3„017794 502 2„852793 29... Open at page → 369 Page 369 IF'TSASTABLEFORRESISTANCE TI-tERMOMETER 1990A7!.i T'EMF' . RESISTANCE INVE:F';Si PA I"Tfl ij .1. (F i< &00 .-, ].79S90 304„9 60 1 305„1 0 60'2 136444 :30^;:. „ "'"' 603 1S9719 305 ,. 60A- 192y93 305.44 605 196266 305„ 60... Open at page → 370 Page 370 NBS-n4A(REV.2.60) U.S.DEPT.OFCOMM. BIBLIOGRAPHICDATA SHEET(Seeinstructions) 1.PUBLICATIONOR REPORTNO. NBS/SP-250/22 2.PerformingOrgan.ReportN043.PublicationDate October1987 4.TITLEANDSUBTITLE NBSMeasurementServices : Pla... Open at page → 371 Page 371 PUBLICATIONS INTHESP250SERIESFROMTHECENTERFORRADIATIONRESEARCH NBSMeasurement Services: SpectralRadianceCalibrations J.H.Walker,R.O.Saunders, andA,T.Hattenburg NBSMeasurement Services: FarUltravioletDetectorStandards L.R... Open at page → 372 Page 372 U.S.DepartmentofCommerce NationalBureauofStandards Gaithersburg,MD20899 OfficialBusiness PenaltyforPrivateUse$300 Open at page →