Standard Cell Calibrations

1 Page 1 U.S.DepartmentofCommerce NationalBureauofStandards Open at page → 2 Page 2 CenterforBasicStandards TheCenterforBasicStandardsdevelopsandmaintainsthescientificcompetencesandlaboratoryfacilitiesnec- essarytopreserveandcontinuetorefinethebasephysicalquantitiesuponwhichtheNation'smeasurement system... Open at page → 3 Page 3 NBSMEASUREMENTSERVICES: STANDARDCELLCALIBRATIONS BruceF.Field CenterforBasicStandards NationalMeasurementLaboratory NationalBureauofStandards Gaithersburg,MD20899 U.S.DEPARTMENTOFCOMMERCE,ClarenceJ.Brown,ActingSecretary... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:87-619872 NationalBureauofStandardsSpecialPublication250-24 Natl.Bur.Stand.(U.S.),Spec.Publ.250-24,52pages(Oct.1987) CODEN:XNBSAV Certaincommercialequipment,instruments,ormaterialsareid... Open at page → 5 Page 5 PREFACE CalibrationsandrelatedmeasurementservicesoftheNationalBureauof Standardsprovidethemeansformakersandusersofmeasuringtoolstoachieve levelsofmeasurementaccuracythatarenecessarytoattainquality, productivityandcompeti... Open at page → 6 Page 6 CalibrationServicesUsersGuide. Inquiriesconcerningthecontentsofthese documentsmaybedirectedtotheauthorortooneofthetechnicalcontact personsidentifiedintheUsersGuide(SP-250) . Suggestionsforimprovingtheeffectiveness anduse... Open at page → 7 Page 7 TableofContents page ListofFigures vii ListofTables viii Abstract 1 1.Introduction 1 2. DescriptionofService 2 RegularCalibration 2 VoltTransferProgram 4 3. CalibrationApparatusandMeasurementApproach 4 VoltageDifferenceM... Open at page → 8 Page 8 TableofContents(cont) page 6.QualityControlProcedures 26 MeasurementSystemVerification 26 MeasurementAssuranceforClientStandards 31 7.Bibliography 31 Appendices A RedundantMeasurementDesigns 35 B RegularCalibrationTestRe... Open at page → 9 Page 9 ListofFigtires Figure page 1.Simplifiedmeasuring circuit 5 2.Twomeasurementconfigurations toeliminatepositional errors(P) 6 3.Blockdiagramofthetwomeasurementsystemsusedfor comparisonofpairsofstandardcells 7 4. Simplified... Open at page → 10 Page 10 ListofTables page TableI. UncertaintiesintheAssignmentoftheMeanemfs ofthePrimaryReferenceGroups 14 TableII. UncertaintiesintheAssignmentoftheMeanemf oftheWorkingGroup 19 TableIII.UncertaintiesintheAssignmentoftheMeanemf... Open at page → 11 Page 11 NBSMEASUREMENTSERVICES:STANDARDCELLCALIBRATIONS BruceF.Field Abstract -ThisdocumentdescribestheproceduresusedatNBStocahbrate standardcellsintermsoftheU.S.LegalVolt.Thetwocalibrationservicesthat areofferedbytheElectricity... Open at page → 12 Page 12 uncertainty isincludedfortransportation effects,longtermdriftsoftheemfsof thecells,ormeasurementerrorsintheclient'slaboratory. VoltTransferProgram TheVoltTransferProgram(VTP)isameasurement assuranceprogram designedtodete... Open at page → 13 Page 13 shouldalsobetransportedbymessenger,andwiththeenclosureactivated orunderpowerifpossible. 3)Saturatedstandard cellsoftheshippabletypehousedinportable thermoregulated enclosuresshouldbepackedcarefullyandshippedunder powerif... Open at page → 14 Page 14 VoltTransferProgram TheVoltTransferProgramexperimentconsistsoffourphases. 1)PreliminaryLaboratoryStudy .DuringthisphaseNBSpersonnelwill discusswithclientlaboratorypersonnelvariousaspectsoftheexperiment, suggestexperiment... Open at page → 15 Page 15 Measuring Instrument + - + + Fig.1.Simplifiedmeasuringcircuit. Twocellsareconnectedinseriesopposition(oneunknown,onereference)and thesmallvoltagedifferenceisreadusingadigitalvoltmeter(DVM).Inanideal situationthedifferenc... Open at page → 16 Page 16 Takingthedifferencebetweenthetwoexpressionsgives E -E=2,{Ei -E2) , thusyieldinganestimateofE^ -E2freeofP.Thepairofmeasurementsaresaid tobe"left-right"balanced.Thatis,ifthereisapositionaleffectitisbalancedout ofthefinalre... Open at page → 17 Page 17 MeasurementApparatus TwovoltagemeasuringsystemsarecurrentlyinuseatNBSforcell comparisons. Exceptfortheswitchingsystems,theyareidentical.Onesystem (SystemVTP)isusedforcomparisonofNBSprimarystandardswithNBS workingstandard... Open at page → 18 Page 18 andtopermitaccesstothedatafromothermachinesevenwhilemeasurements arebeingmade.Asummaryofthebasicstatistics isprintedaftereach measurement set. Thedigitalvoltmetersusedtomakethedifferencemeasurements are6-1/2digit high-re... Open at page → 19 Page 19 seriesoppositiontotheDVMin"normal"or"reversed"polarity.Thematrix crossbarswitchesareactuatedbymomentarilyenergizingtheswitchsolenoids, andthenpermanentmagnetswithintheswitcheslatchthecontactscloseduntil asecondreleasesol... Open at page → 20 Page 20 monitoringthetemperatureusingthesedevices.Thetemperature scale embodiedinthetemperature deviceistakenascorrect,primarilybecause accurateknowledgeofthetemperature isunnecessary. Cellemfsarecorrected onlyforsmallchangesint... Open at page → 21 Page 21 Whentwoweaklycoupledsuperconductors areirradiatedwithmicrowave energy,theassembly(aJosephsonjunction)canbeusedtoproduceprecise voltagesdescribedbythefollowingequation: E=nf/(2e/h) wherenisanintegerandfisthefrequencyofthe... Open at page → 22 Page 22 ThedifferencebetweenthearrayandZenerreference isthenmeasuredby averagingseveralreadings(Ej)ofthedigitalvoltmeter. Low-thermal-emf reversingswitchAisreversedandseveralmorereadings(E2)aretakento eliminateoffsetsinthedigita... Open at page → 23 Page 23 StandardCellComparisons Twostandardcellgroups(consistingof10cellstotalandconsideredtobethe NBSprimarygroups)arecalibratedintermsof2e/hatweeklyintervals.The calibrations consistofmaking cellcomparisonmeasurements (using r... Open at page → 24 Page 24 TABLE I UNCERTAINTIESINTHEASSIGNMENTOFTHEMEANEMFS OFTHEPRIMARYGROUPS Sourceofuncertainty 1std.dev.estimate (ppm) Microwavefrequency 0.005 AssignmentofZenerreferencegroupusingArray 0.007 RandomuncertaintyofcomparisonofZen... Open at page → 25 Page 25 singlecell-Zenercomparison. Becauseoftheredundantmeasurements ofthe measurementdesign,theuncertaintyofthedifferenceofthemeanoftheZener referencegrouptothemeanoftheprimarygroupis0.012p.V.Two measurementdesignsaremadeforPr... Open at page → 26 Page 26 laboratorystaffareusedtodeterminethemodels.Figure6showsthetypical behaviorofthemeanemfofsixcellsinPrimaryGroupAplottedagainsttime. ThelineplottedinFig.6istheleast-squares fittedlinetothedata;theresidual standarddeviation... Open at page → 27 Page 27 potentiometersandcomparedtounsaturatedstandardcells.Theseunsaturated cellswerecompared totheprimarycellsusingamanualpotentiometer. Becauseofthedifficultyofthesemeasurements theyweremadeonlymonthly andtheyaredescribedinde... Open at page → 28 Page 28 Thisprocedure ismodifiedasnecessarywhencellsshowerraticbehavioror temperature-regulated enclosures fail.Atpresenttheprimarycellsconsistof twogroups,indifferentthermoregulated enclosures,thatareindependently comparedtoeac... Open at page → 29 Page 29 TABLE II UNCERTAINTIESINTHEASSIGNMENTOFTHE MEANEMFOFTHEWORKINGGROUP Sourceofuncertainty 1std.dev.estimate (ppm) Assignmentofprimarygroup(fromTableI) 0.023 Day-to-dayfluctuationofprimarygroups 0.028 DVMscaleerror 0.005 Ra... Open at page → 30 Page 30 thermalemfsintheseswitchesthatdonotcanceloncellreversalhavebeen measuredtobe0.015|iV(0.015ppm). TheRSStotaluncertaintyinassigningavaluetothemeanemfofeither workinggroupisestimatedtobe0.040ppm. RegularCalibration Calibrat... Open at page → 31 Page 31 TABLE III UNCERTAINTIESINTHEASSIGNMENTOFTHE MEANEMFOFACLIENTCELL Sourceofuncertainty 1std.dev.estimate (ppm) Uncertaintyofassignmenttoworkinggroup 0.040 Changeinworkinggroupduringtheday 0.040 DVMscaleerror 0.010 Randomun... Open at page → 32 Page 32 included. Enclosuresmonitoredbymercury-in-glass thermometers are assignedanuncertaintyequivalenttohalfthesmallestgraduationmarkedon thethermometer,approximately 0.5ppmforaresolutionof0.01°C.Forcells calibratedinNBSoilbat... Open at page → 33 Page 33 MeasurementoftheTransportStandardatNBS Thetransportstandardconsistsofacommercialthermoregulated enclosure usuallycontaining4saturatedshippablestandard cells,operatingatan internaltemperatureof30°Cor32°C.Thetemperature is... Open at page → 34 Page 34 toseeiftheyarestatisticallyincontrolwithrespecttotheexpectedvalues determinedfrommeasurements atNBSandotherlaboratories. UponitsreturntoNBS,thestandardisagaincomparedtoWorkingGroupAas beforeand,whenthestandardhasstabiliz... Open at page → 35 Page 35 Althoughthedifferenceintheunitsasdeterminedfromeachofthefourcellsin thetransportstandardshouldagree,onoccasionsomecellsshowabnormal behavior,usuallyexcessive drift,orexcessivelylongrecoveryfromphysical shockorelectricald... Open at page → 36 Page 36 temperature.Thethermistorbridgedoesnotproperlyreflectthechangeofthe temperatureofthecellinthiscase,probablyduetoatemperature sensitive componentofthebridgecircuitrythatisatroomtemperature.Anuncertainty estimateof0.05ppmi... Open at page → 37 Page 37 998.300 998.200- > 998.000 998.100- . E LU 997.900 997.800 12/25/85 2/25/86 4/25/86 6/25/86 8/25/86 10/25/86 Fig.10.DailyDVMreadingsofthe1000|iVZenersource. Beforeeachdailysetofcellcomparisonsthemeasurementsystemreadsthe... Open at page → 38 Page 38 circumstances. Thestandarddeviationisafunctionoftheindividualcellgroup beingmeasured,andcontrollimitsfornewlyarrivedclientcellgroupsarenot wellknown.Eachday,apooledstandarddeviationfromallthemeasurement designsthatareinc... Open at page → 39 Page 39 offsetvoltageareprintedforeachcellgroupmeasured.Thechangeingroup temperaturecorrectionandmeanemfarecalculatedbysubtractingthevalues obtainedforthepreviousday'sreadingsfromthecurrentday'sreadings. Ifany ofthevaluesexceedp... Open at page → 40 Page 40 workinggroupsbasedonfourormoremonthsofdata.Eachdaythevaluesof theworkinggroupsarecalculatedbasedonthedailyintercomparisons ofthe primarygroupsagainsttheworkinggroupsandthepredictedvaluesofthe primarygroups.Themeasurement... Open at page → 41 Page 41 October1,1986,themeanclosureerrorwas-0.0009|iVwithastandarddeviation ofthemeanof0.0017|iV. MeasurementAssuranceforClientStandards StandardsshippedtoNBSintemperatureregulatedenclosuresunderpowerare handcarriedfromtheBuild... Open at page → 42 Page 42 8. Eicke,W.G.,"MakingprecisionvoltagemeasurementonZenerdiodes," IEEETrans.,PaperCP63-416(1963). 9. Natrella,M.G.,Experimental Statistics,NBSHandbook91,pp.18-1,18-4 (1963). 10.Dunfee,B.L.,"Methodforcalibratingastandardvol... Open at page → 43 Page 43 23.Finnegan,T.F.,Denenstein, A.,andLangenberg, D.N.,"acJosephson EffectDeterminationofe/h:AStandardofElectrochemical PotentialBased onMacroscopicQuantumPhaseCoherenceinSuperconductors," Phys. Rev.B,Vol.4,No.5,pp.1487-152... Open at page → 44 Page 44 36.Koep,K.J.,"Theuseofasolidstatedcvoltagetransportstandardto transferthedcvoltinaregionalstandardcellMAPprogram,"Proc.1984 Meas.Sci.Conf.,pp.142-146(1984). 37.Murray,W,andDencher, P.,"High-accuracy voltagetransferusinga... Open at page → 45 Page 45 AppendixA -RedundantMeasurementDesigns Redundantmeasurementdesignsareusedforallstandardcellcomparisonsas theyareefficientinprovidingthemaximumamountofinformationper measurementandprovideinformationaboutpossiblesystematic... Open at page → 46 Page 46 4x6Design -24observations Dservd.i'ion nigni <^Dservd.tionijeix nigni nuniDer ceil ceil nuniDer ceil ceil 1 ivi VI AJ. io Yf^ AO rift 9 rvl A-O 1A YQAO q A.O iO Y1 A_L rv'* A Y9 ID YRAD rvo c o 17 Yd.A^ rvo D xvZ Y^^AD 1... Open at page → 47 Page 47 U.S.DepartmentofCommerce NATIONALBUREAUOFSTANDARDS NationalMeasurementLaboratory Gaithersburg,MD20899 REPORTOFCALIBRATION DCVoltageStandard DescriptionofStandard: StandardCellEnclosure ModelXXXXXXXXXXXXXXXXX Containing4S... Open at page → 48 Page 48 StandardCellEnclosure ModelXXXXXXXXXXXXXXXXX Page2 Theseuncertaintyfigurescontainnoallowancefortheeffectsoftransportationuponthisstandard. Theminimumuncertaintyduetosucheffectsunderverycarefullycontrolledtransportconditi... Open at page → 49 Page 49 U.S.DepartmentofCommerce NATIONALBUREAUOFSTANDARDS NationalMeasurementLaboratory Gaithersburg,MD20899 REPORTOFCALIBRATION DCVoltageStandard DescriptionofStandard: UnsaturatedStandardCell ModelNo.XXXXXXXXXXXX SerialNo.XXX... Open at page → 50 Page 50 U.S.DepartmentofCommerce NATIONALBUREAU OFSTANDARDS NationalMeasurementLaboratory Gaithersburg, MD20899 REPORT OFTEST Determination ofV'p5qq- V]<\-qs Laboratory: (LAB) xxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxx xx... Open at page → 51 Page 51 Page2 Thisuncertainty, thedifferencecitedabove,andtheresults ofanyadjustmentsmadetothevaluesofthereferencecells whosenumbersaregivenabovearevalidonlyunderconditions approximating thoseunderwhichthisexperimentwasperformed... Open at page → 52 Page 52 AppendixD-SOFTWARE Allsoftwareforcontrollingthemeasurementsystems,reducingthecelldata, andproducingtestreports,waswrittenin-housespecificallyfortheintended application.Atpresentthesoftwareisintransition;aminicomputerused... Open at page → 53 Page 53 Thisprogramcanalsobeusedtoviewormodifyanyofthedatafilescontaining celldifferenceobservationsorcellemfs. Thefollowingprogramsoperateontheoldminicomputerandareintheprocess ofbeingconvertedtorunonthenewminicomputer. VFORMAT... Open at page → 54 Page 54 NBS-114A(REV.2-8C) U.S.DEPT.OFCOMM. BIBLIOGRAPHICDATA SHEET(Seeinstructions) 1.PUBLICATIONOR REPORTNO. NBS/SP-250/24 2.PerformingOrgan.ReportNo, 3.PublicationDate October1987 4.TITLEANDSUBTITLE NBSMeasurement Services: S... Open at page → 55 Page 55 PUBLICATIONS INTHESP250SERIESFROMTHECENTERFORRADIATIONRESEARCH SP250-1 NBSMeasurement Services: SP250-12 SpectralRadianceCalibrations J.H.Walker,R.D.Saunders, andA.T.Hattenburg NBSMeasurement Services: SP250-13 FarUltrav... Open at page → 56 Page 56 U.S.DepartmentofCommerce NationalBureauofStandards Gaithersburg,MD20899 OfficialBusiness PenaltytorPrivateUse$300 Open at page →