AC DC Difference Calibrations

1 Page 1 NISTMeasurementServices: NEWNISTPUBLICATION June12,198? AC-DCDifferenceCalibrations U.S.DepartmentofCommerce NationalInstituteofStandardsandTechnology Open at page → 2 Page 2 CenterforBasicStandards TheCenterforBasicStandardsdevelopsandmaintainsthescientificcompetenciesandlaboratoryfacilitiesnec- essarytopreserveandcontinuetorefinethebasephysicalquantitiesuponwhichtheNation'smeasurement syste... Open at page → 3 Page 3 NISTMEASUREMENTSERVICES: AC-DCDifferenceCalibrations J.R.Kinard,J.R.Hastings,T.E.Lipe,andC.B.Childers CenterforBasicStandards NationalMeasurementLaboratory NationalInstituteofStandardsandTechnology Gaithersburg,MD20899 M... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:89-600736 NationalInstituteofStandardsandTechnologySpecialPublication250-27 Natl.Inst.Stand.Technol.Spec.Publ.250-27,308pages(May1989) CODEN:NSPUE2 Certaincommercialequipment,instrument... Open at page → 5 Page 5 PREFACE Calibrations andrelatedmeasurement servicesoftheNationalInstitute of StandardsandTechnologyprovidethemeansformakersandusersofmeasuring toolstoachievelevelsofmeasurementaccuracythatarenecessarytoattain quality,pro... Open at page → 6 Page 6 Thepresentpublication, SP250-27,NISTMeasurementServices: AC-DC DifferenceCalibrations, byJosephR.Kinard,JohnR.Hastings,ThomasE. Lipe ,andCliftonB.Childers, isoneofapproximately 20documentsinthenew seriespublishedorinprep... Open at page → 7 Page 7 INTRODUCTION Theprimarypurposeofthispublication istocollectandsununarize the specializedinformationneededtooperatetheac-dcdifferencelaboratoryand calibrationserviceatNIST(Gaithersburg) .Thisdocumentshouldbeusedin conjunc... Open at page → 8 Page 8 Sections14,15,and16areinstructions foroperatingthecomparatorsystems. TheywerepreparedforusebytheNISTstaffandhavenotbeenreviewedas thoroughly astheprecedingsections. Nevertheless, theycanbehelpfulto non-NISTreadersinteres... Open at page → 9 Page 9 AnnotatedTableofContents "AC-DCDifference Calibrations atNBS , "byJ.R. Kinard,inProc .Meas .Sci.Conf . .Irvine,CA,Jan. 1986,pp.3-8.AnoverviewoftheNBScalibration service for thermal converters, including descriptions ofth... Open at page → 10 Page 10 page (7) "Theoretical Analysis of the AC/DC Transfer 130 Difference of the NPL Multijunction Thermal ConverterOvertheFrequencyRangeDCto100kHz," byF.J.Wilkins,IEEETrans.Instrum.Meas . .IM-21, pp.334-340, Nov.1972. Provide... Open at page → 11 Page 11 page (13) "ADual-Channel Automated Comparator forAC-DC 186 DifferenceMeasurements," byE.S.WilliamsandJ. R.Kinard,IEEETrans.Instrum.Meas . .IM-34,pp. 290-294,June1985. Describes theNBSautomated comparator systems used for... Open at page → 12 Page 12 page (18) "ReportofCalibration." Asamplereport. 294 NOTE: Section(4)initsoriginalformincludedreprintsofthree paperstomakeiteasytorefertothem. Sincethesepapersare alsoincludedinthepresentcompilation assections (6) ,(8) ,a... Open at page → 13 Page 13 TopicalIndex Topic Sections Specifications fortheService 1,18 Anoverviewofthecalibrationservice,includingthefrequency dependenceoftheuppervoltageandcurrentlimitsandtheuncertainties of thecalibrations, isgivenin(1).Sectio... Open at page → 14 Page 14 GlossaryofCommonAC-DCAcronyms AC: alternatingcurrent AV: alternatingvoltage DC: directcurrent DV: directvoltage TE: thermoelement TC: thermalconverter TCC: thermalcurrentconverter TVC: thermalvoltageconverter SJTE: singl... Open at page → 15 Page 15 Section 1 AC-DCDIFFERENCECALIBRATIONSATNBS* JosephR.Kinard ElectricityDivision NationalBureauofStandards ABSTRACT TheNBS(Gaithersburg) calibration serviceforthermalvoltageandcurrent convertersreliesonagroupofprimarymulti... Open at page → 16 Page 16 MULTIJUNCTIONTHERMALCONVERTERS Overthepastseveral years aseries ofcomparisons hasledtothe establishment ofagroupofeightMJTC'sastheNBSprimarystandardsforac- dcdifference [a]-[c]. Theseconvertersareconstructedwithbifilarhe... Open at page → 17 Page 17 Theextensionofthefrequencyrangeabove100kHzwasachievedbytheuseof converters (NBSC-set)madewithcylindrical, deposited-carbon resistors mountedcoaxiallyinmetalcylinderswith5mAor10mAUHFtypeTE's[g] . Twotechniques wereusedtoe... Open at page → 18 Page 18 CALIBRATIONMETHODSANDUNCERTAINTIES Thecalibration ofcustomer'sTVC'sandTCC'sisperformedbycomparingthe testunittoNBSstandardswhoseac-dcdifferenceshavebeencharacterized as describedabove. Inthecaseofvoltage, thetestandstand... Open at page → 19 Page 19 REFERENCES [a]Hermach, F.L.andFlach, D.R. ,"AnInvestigation ofMultifunction ThermalConverters," IEEETrans.Instrum.Meas . .Vol.IM-25,Dec.1976, pp.524-528. [b]Hermach, F.L. ,"AnInvestigation oftheUncertainties oftheNBSTher... Open at page → 20 Page 20 TABLEI. AC-DCDIFFERENCECALIBRATIONSERVICE Frequency : 2-5 rlZ 5-20 Hz 20-20k Hz 20-50 KnZ 50-100 0. KnZ 1-0.5 C.5-1 nnZ VoltageLimits(V) 50 100 1000* 1000 1000* 100 100 CurrentLimits(A) 0.05 0.05 16 UNCERTAINTY(partsperm... Open at page → 21 Page 21 225 200 175^1 CL ^150 ^125 c -100 - rd : QJ , 50 - C 25r 0 IHz + + + + + + + + + + + + + + + + + + + + J—I I I 1 1III I I III IIII I I I IIIIII I I I 1 1 1III + + + + I L-t I I + I I I I IIII! I I I I IIIll 10Hz 100Hz Ik... Open at page → 22 Page 22 10Hz 100Hz IkHz 10kHz Frequency 100kHz IMHz Figure3.Uncertainties -forCoaxial ThermalVoltageConverters 5 V£100V Specia1Tes t £ Q. a c fd 225 200 + + + + + 175 + + + + + 150 + + + + + 125 + + + + + 100 + + +— 1 — 75 + + +... Open at page → 23 Page 23 225 200 >— ^ E CL 150 125 c -100 +> j_ u50 c 75 25 - 0 IHz I I I + + + + + + + + + + + + + + + + + + + H + I -H + I I I I I I I1 1 I I I I I I I1 1 I I I I I I I1 1 I I I I I I Ill 100kHz10Hz 100Hz IkHz 10kHz Frequency F... Open at page → 24 Page 24 IEEETRANSACTIONSONINSTRUMENTATION ANDMEASUREMENT, VOL.IM-25,NO.4,DECEMBER1976 489 Section2 AC-DCComparators forAudio-Frequency Currentand VoltageMeasurements ofHighAccuracy FRANCIS L.HERMACH,FELLOW,IEEE Abstract—Thispape... Open at page → 25 Page 25 490 IEEETRANSACTIONSONINSTKUMENTAriONANDMKASUHEMKNT.DECKMBKR1976 commonerrorofmeasuringavoltageorcurrentofun- knownwaveformwithanaverage-orpeak-responding instrumentscaledintermsofthermsvalueofasinewave canbecomeveryseri... Open at page → 26 Page 26 HERMACH:AC-DCCOMPARATORSOFHIGHACCURACY 491 . y . Fig.1.Simultaneousac-dccomparator. currentconverters(TCC's),withrangesupto20Aor more. Transformerscanalsobeusedtoprovidevoltageranges. OnlytheheateroftheTCneedstobeswitche... Open at page → 27 Page 27 492 IEEETRANSACTIONS (JNINSTRUMENTATION ANDMEASIIHEMRNT, IJKCEMBKR 1976 r Fig.2.Sequentialac-dctransfer. Fig..3.BasicTCfeedbackcircuit. needed,particularly inthetestofanotherinstrument whichmustitselfbegrounded. Atypical... Open at page → 28 Page 28 HERMACH:AC-DCCOMPARATORSOFHIGHACCURACY reactancesofthecoils.Therangecanbemuchgreaterfor anelectrostaticinstrument,butthetorque/weight ratio islowatmoderatevoltages,andsurfacefilmscancause ac-dcdifferencesthataredifficult... Open at page → 29 Page 29 494 IEEETRANSACTIONSONINSTRUMENTATION ANOMEASUREMENT,DECEMBER 1976 developments.Alistofreferencespublishedbetween1945 and1975onhighaccuracyaudio-frequencyac-dccurrent andvoltagecomparators isavailableonrequestfromthe Ele... Open at page → 30 Page 30 Section3 AC-DCTransferInstruments forCurrentand VoltageMeasurements* FRANCISL.HERMACHf Introduction THE basicelectricalunitsaremaintainedbygroups ofstandardcellsandresistors.Withthesestand- ardsandadcpotentiometer, measu... Open at page → 31 Page 31 236 IRETRANSACTIONSONINSTRUMENTATION December Udf Im=BiP. J 0T ThusifUandBeachhavethesamevahieondirectas onalternatingcurrent,theinstrumenthasthesame response, df. Theinstantaneoustorqueoftheusualtwo-element electrostati... Open at page → 32 Page 32 1958 Hermach:AC-DCTransferInstruments forCurrentandVoltageMeasurements 237 mostnationalstandardizing laboratories. Ingeneral, therearethreeratherdistinctstepsinacompletede- termination.Theseare:1)choiceoftwodififerenttyp... Open at page → 33 Page 33 238 IRETRANSACTIONSONINSTRUMENTATION December ducesothererrorsaswell,sothattheelectrodynamic ac-dctransferinstrumentsdesignedandconstructedat theU.S.NationalBureauofStandards^^andtheNa- tionalPhysicalLaboratory ofSouthAf... Open at page → 34 Page 34 1938 Hermach:AC-DCTransferInstruments forCurrentandVoltageMeasurements 239 instrumentshavingnoble-metal conductors). Special transformersandresistorshavebeenconstructedand testedtopermitthemeasurement ofcurrentandof volt... Open at page → 35 Page 35 240 IRETRANSACTIONSONINSTRUMENTATION December required,makingpossibleaconvenientportableacces- sorytoadcpotentiometer, which,inarecentlyim- provedmodel(seeFig.2)providesrangesof7.5mato 20amperesand0.5to600voltswithanaccu... Open at page → 36 Page 36 Section4 NBSIR84-2903 ANINVESTIGATIONOFTHE UNCERTAINTIESOFTHENBSTHERMAL VOLTAGEANDCURRENTCONVERTERS F.L.Hermach U.S.DEPARTMENTOFCOMMERCE NationalBureauofStandards CenterforBasicStandards ElectricityDivision Gaithersburg,... Open at page → 37 Page 37 TABLEOFCONTENTS Page Summary 1 I. INTRODUCTION 3 A.ScopeofContractandReports 3 B.PresentNBSStandards 3 C.RangesandUncertainties ofCalibrations 4 II. SYNOPSISOFTHEAC-DCSTUDY 5 III. MJTC'sANDCOMPARATOR 7 A.Comparator 7 B.C... Open at page → 38 Page 38 TableofContents(Continued) Page XVI. ACKNOWLEDGEMENTS 40 REFERENCES 41 TABLES: 1 ComparisonofFourMJTC's 43 2 DifferencesBetween1981&1976EvaluationsofMJTC's.... 44 3 ResultsofComparisons ofFXandFYwithMJTC's 45 4 Resultsof... Open at page → 39 Page 39 TableofContents(Continued) FIGURES: Page 1 RoadMap 67 2 ComparisonsofMJTC's 68 3 50mAto5mAComparisons 69 M 50mAto1AComparisons 70 5 Comparatorwithn-Compensation 71 6 DiagramofEMFComparator 72 APPENDICES: 1 n-Corapensatio... Open at page → 40 Page 40 ANINVESTIGATIONOFTHEUNCERTAINTIESOFTHE NBSTHERMALVOLTAGEANDCURRENTCONVERTERS SUMMARY Thisinvestigationrequiredacompleteredetermination oftheac-dc differencesoftheNBSac-dctransferstandards,from20Hzto100kHz. It involvedthe... Open at page → 41 Page 41 8. Combiningtheseestimatesandrandomerrorsinalogicalwayto arriveatestimatesoftheuncertainties ofeachofthemanyreferenceand workingstandards(followingBIPMCommitteeguidelines), 9. Carryingoutanumberoflargelymathematical stud... Open at page → 42 Page 42 I.INTRODUCTION A. ScopeofContractandReports Inbrief,thisinvestigation, performedundercontractwithNBS, requiredatheoreticalandexperimentalanalysisoftheuncertainties in maintainingandusingtheNBSac-dctransferstandardsforcur... Open at page → 43 Page 43 twoselectedTE*swereusedwithspecialseriesresistorsasthermalvoltage convertersupto500Vto10ppm.Anemfcomparatorwasdevelopedtocompare theac-dcdifferencesofpairsofconvertersto±2ppm. Fifteencomparisonsofadjacentorsimilarrangesa... Open at page → 44 Page 44 Frequency 2-5 Hz 5-20 Hz 20-20k Hz 20-50 kHz 50-100 0.1-0.5 kHz MHz 0.5-1 MHz Voltagelimits(V) 50 100 1000^ 1000 600 100 100 Currentlimits(A) 0,05 0.05 202 15 - Uncertainty(percent) 3 MultirangeTVCs 0.02 0.01 0.005 0.007... Open at page → 45 Page 45 ThesameemfcomparatorandthesameornewtypesofTE'scouldhave beenusedforthebaseandforthesecomparisons, asbefore. However, Itwas verydesirabletouse,Instead,agroupofthenewermultlJunctionthermal converters(MJTC's)andanewcomparat... Open at page → 46 Page 46 AblockdiagramofthesemajorstepsintheevaluationoftheNBSac-dc referenceandworkingstandardsisshovminfigure 1 . Analysesandtestswerealsomadeoftheimportantproblemofaccurately deducingthed'softhemanyrangesofthe and TVCsetswhent... Open at page → 47 Page 47 (2)WhenthetwoTE'3haveequaln's,(n-lAE/EAI,whereIIsthe heatercurrentandEtheoutputemf),thesteady-statebalanceisIndependent ofsmallchangesintheacanddcsupplies,greatlyreducingtheuncertainty Inthemeasurementandtheneedtokeepthe... Open at page → 48 Page 48 thatItwassignificant, electromagnetic interference (EMI)canbe particularlytroublesomeatTVfrequencies,whereleadsarenearaquarter wavelengthandsopickupelectromagnetic energyefficiently. AsimpledirecttestwasdevisedtoseeifEMI... Open at page → 49 Page 49 current,I^.Fromthis »l^il+d),sothatanunknownaccurrentcanbe measureddirectly, Ifdisknown,byobservingtheemfwithI^^appliedand measuringthetwopolaritiesofdccurrentwhichgivethesameemf.Thesame formulasapplyforTVC's,withVreplac... Open at page → 50 Page 50 standards,becausesourcesofsystematicerroraremorelikelytobe discovered insuchcomparisonsthanbysimplyrepeatingmeasurements onone standard,orcomparinglikestandards. Theresultsoftheevaluations(includingrepeattestsondifferent... Open at page → 51 Page 51 ThesameMJTC'swereevaluatedin1976[4]aspartofalargergroup. Table2showsthedifferencesbetweenthepresentassignmentsandthoseof 1976.Theyaregratifyingly small,indicatingthehighstabilityaswellas thelowac-dcdifferences ofthesethe... Open at page → 52 Page 52 Themeasuredd'sweregratlfyingly small.Therewasnoappreciable d fromThomsonandPeltiereffectsintheheatersofanyofthethreeTE's. Thereweresmalllow-frequency errorsat30Hz,andevidenceofimpedance errors(about 1ppmat10kHz)intheTVCr... Open at page → 53 Page 53 primaryset.AllofthemhaveEvanohmheatersandshouldhavelow thermoelectric errors. Theseweredeterminedfromthe1-kHzMJTCtests,and wereindependentoffrequency. Theimportantcriterionisthatthemeasured differencesbetweeneachpairofTE... Open at page → 54 Page 54 results,errorsfromsmalldifferences Inthereactancesoftheresistors couldbelargelyeliminated, andtheTE'scouldbeevaluatedascurrent converters. Theresultsofthesemeasurements areshownintable4.Exceptat 30Hz,therewasnosignifican... Open at page → 55 Page 55 (table3).Thereactanceerrorsshouldbecompletelynegligibleatthis frequency. Toinvestigatethisfurther,F^io-FYwascomparedwithaspecialTVC thatHaddadhadstudiedin1969forhisGWUMaster'sthesisunder CutkoskyCl8].Hehaddeterminedthech... Open at page → 56 Page 56 appendix5Eshowsthatthephaseanglesofthetwopathsmustbeequalto betterthanonemrad.Thisisreadilymeasuredonacommercialimpedance comparator, to100kHz.Whenthephaseanglesarenegligible, thebasic formulaforthismethod,takingintoacco... Open at page → 57 Page 57 closureerrorswereverysmall,requiringadjustmentsofonly0.3ppmor less. ThepooledstandarddeviationSp^oftheaverageoffourdeterminations ofd^-dgwasonly0.28ppm.Thesehighprecisiontestsshowedexcellent performance intheseEvanohm-he... Open at page → 58 Page 58 Forthesemeasurements, Sp^^wasabout1.7ppm,practicallyindependent offrequency. ThisisnotasgoodastheprecisionoftheMJTCcomparator, butislowenoughtomeettheneedsforhigh-current calibrations. The evaluationofFG-1withthe1-ATEagr... Open at page → 59 Page 59 twounusualsourcesoferrorintheac-dccomparisonswerediscovered, castingsomedoubtsontheaccuracyoftheTVCbuild-up. Thefirstofthesewasanunexpectedlylargeerrorcausedbyadooffset voltage,Vqq,intheoutputofthesamedirect-coupled acam... Open at page → 60 Page 60 TheresultsoftheinterrangecomparisonsoftheF-|setareshownin table8,andthevaluesassignedtoeachrange,withdofF^io-FY2from table7asthebasis,areshownintable9.InthecomparisonseachTEis usedattwocurrents,withaseriesresistorofthegi... Open at page → 61 Page 61 and areindicativeoflargePeltiereffectsattheheatertolead-in Junctions. Athigherfrequencies theevenlarger dy^forthe0.6-Vranges(TE's alone)arecausedbyskineffect,whichincreasestheresistanceofthe magneticheaterleads,causingpo... Open at page → 62 Page 62 VIII.UORKINGSTANDARDS A. CurrentStandards Theworkingstandardswhichareusedincalibratingthermalconverters senttoNBSwereevaluatedbydirectcomparison(heatersinseries)withthe corresponding rangesofthereferenceconverters, inthe... Open at page → 63 Page 63 appliedateachstepofthebuild-upcomparisons. ThisIsquitecomplicated unlessthereactancetermsarenegligibleasshowninappendix5Band discussedinthenextsection. Fortunatelythed^variationscausedbyTE'sdecreasewithincreasing range.... Open at page → 64 Page 64 thancertainspecifiedlimitingvalues. AtNBS,d^anddy^canbemeasured bycomparisonwiththereferencestandards,andthephaseanglescanbe determinedcloselyenoughwithacommercialimpedancecomparatorto100kHz. Ifthephaseanglesarenegligibl... Open at page → 65 Page 65 (2)Youdenrecommendsaddingtheestimateoftherandomerrors(suchaa 3Sa)totherssof(1)toobtainthetotaluncertainty. (3)However, itisevidentlydesirabletofollowthemuchmorerecent guidelinesoftheBIPMWorkingGroupontheStatementofUncert... Open at page → 66 Page 66 probabilities willalwaysbelessthanthecorresponding Gaussianoneshavingthesametolerancelimitsandstandard deviation,butusuallybyonlyasmallamount." Thisveryimportantconclusionprovidesasimpleyetgenerallyrealistic methodofcomb... Open at page → 67 Page 67 (9)"Round-Robin" teatsofthreeormoreTE'sorTVC'softhesame range,andothermorecomplexexperimental designs,canalsobeveryvaluable meansofdisclosingsystematicerrors,asiswellknown. (10)Asfigure 1shows,thereareseveralstepsinthede... Open at page → 68 Page 68 ratherflat-toppedconeinaS-dimensional space,withtherangeand frequencyasxandycoordinatesand1/uasthez(vertical)coordinate. The viewsfortheworkingstandardswill,ofcourse,besimilar. XI.RANDOM(STATISTICALLY EVALUATED)ERRORS A.... Open at page → 69 Page 69 arethetruelimitingminimumsofrandomerrorsimposedbythecomparison process. B. OtherConparatora Similartestswerenotmadeforthe1966comparatorandforthe calibrationconsole. Bothhavebeeninuseforlongperiodsoftime. Insteadthepooled... Open at page → 70 Page 70 Theround-robintriadsoffigures3and1,thebuild-upcomparisonsfor theTVC's,andtheccmiparisonsofampere-rangeTE'swithshuntedTE'satlow frequencieswereallexaminedforevidenceofsystematicerrors. D. PooledStandardDeviations Table^^s... Open at page → 71 Page 71 Triadsofcomparisons (roundrobins)areshownInfigures 3and4.In eachofthesetherearetwopathsfromoneTEtoasecond;onedirectandthe otherviathethirdTE.Ifthed2-dipathsdifferbymorethan(2/3)Spg^, thereIsevidenceofsystematicerroratabo... Open at page → 72 Page 72 XIII.COMBINATIONOFUNCERTAINTIES Fromthebasicdimenslonless equationgiveninsectionIII-A ci,p=dg+(N(j-N^)/ngE2^. Heretheexponentofeachvariableis+1or-1 . Fromthetheoryoferrors[16],thepropagation-of-errorformulaforthe fractio... Open at page → 73 Page 73 Extremerigorinmakingthesecalculations didnotseemwarranted, especiallyforthesmallerU's,whichdonoteffecttherssresultsvery much. Inthe tvCbuild-uptheerrorsindeterminingthechangesinthe oftheTE's(FX2andFY2)withcurrentlevelare... Open at page → 74 Page 74 XIV.CONCLUSIONS A. Uncertainties oftheNBSStandards Theoverallresultsofthecalculations oftheuncertainties aregiven intheimportantsummarytable17.Theyapplyatratedcurrentandvoltage, withtheexceptionsshown. Severalconclusions... Open at page → 75 Page 75 randomandsystematiccomponents. However,betterprecisionwouldbethe firststeptoimprovingaccuracies. B. CalibrationUncertainties (1)IfTE'sandTVC'softhesametypeandqualityastheworking standardsarecalibratedwiththecalibrationco... Open at page → 76 Page 76 (5)Acomparisonwasmadeofthed'softheworkingstandardsshownin tables11and13withthevaluespreviouslyassignedfromearliertestsand presentlyusedincalibrationwork.Forthe TVC's,thelargestdifference betweenthed'swas23ppm,onthe600-Vr... Open at page → 77 Page 77 shouldmakeitpossibletocalculatethed^'sfortheotherTVCranges, withoutrecalibrating eachone,whenaTEisreplaced. (M)AC-DCdifferencesaslargeas9ppmhavebeenobservedevenin Evanohm-heater TE*s,soreplacements shouldneverbeusedwitho... Open at page → 78 Page 78 (6)Asexperiencewiththecheckstandardsandthebienniel calibrations oftheworkingstandards isaccumulated, therecommended calibrationperiodsofA-1fortheworkingandreferencestandardsmaysafety berevised. C.OtherRecommendations (1)... Open at page → 79 Page 79 XVI.ACKNOHLEDGEHENTS SincerethanksareexpressedtoJ.R.Hastings, E.S.Williams, C.B.Chllders,andK.B.Krlshnaourthy, whoassistedInthisInvestigation, toN.Belecklforhisencouragement andsupport,toC.Reeveforhishelpful suggestionsa... Open at page → 80 Page 80 REFERENCES 1.ThermalConvertersasAC-DCTransferStandardsforCurrent&Voltage Measurements atAudioFrequencies, F.L.Hermach,Jour.Res.NBS,v.28, no.2,p.121 ,Feb.1952. 2.ThermalConvertersforAudio-Frequency VoltageMeasurements ofH... Open at page → 81 Page 81 9.EvaluationofAC-DCTransferErrorsforThermalConverter-Multiplier Combinations, B.D.Inglls,Metrologla, v.16,p.177,1980. 10.Uncertainties InCalibrations, W.Youden,IRETrans.Instrum. ,v.1-11, p.133.Dec.1962. 11.UncertaintyAss... Open at page → 82 Page 82 Table 1 CoaparlsonsofFourHJTC*s S 30Hz 1kHz 10kHz Date G44 G5C +0.47 +0.15 -0.M4 12/08/81 (B10-41I) (B5-2) -0.10 12/11/81 -0.02 12/11/81 Gr25-1 G5C +0.32 0.00 -0.29 12/11/81 (C10-1) (B5-2) -0.03 12/U/81 Gr25-1 G4l» +0.17... Open at page → 83 Page 83 Table2 DifferencesBetween1981and1976EvaluationsofMJTC*8 **81- ^76(PP") MJTC 044 Gr25-1 G5C G10C NPL14 30Hz +0.2 0.0 +0.3 -0.3 -0.2 1kHz 0.0 0.0 -0.1 0.0 0.0 10kHz +0.1 -0.4 +0.1 0.0 69 Open at page → 84 Page 84 Table3 ResultsofComparisonsofFXandFYwithNJTC*s TE or TVC FX FX Fi5-FX^ Fl5-FX FY FY F^IO-FY F^10-FY I or V 5mA 2.5mA 5V 3V 5mA 3mA 10V 5V 30Hz +0.9 -0.1 +0.8 +0.2 d(ppn) 1kHz -0.3 0.0 -O.M -0.7 +0.2 +0.4 -0.3 +0.1 10kHz... Open at page → 85 Page 85 Table4 ResultsofTVCTestswithTwinResistors <lT-ds(ppm) T S 30Hz 1kHz 20kHz 50kHz FY FX +0.2 +0.2 0.0 -0.2 B5E77 FX +5.0 +2.6 +3.2 +3.7 F5K9 FX -1.6 -1.0 -1.1 -1.2 B5EXG1 FX +2.8 +1.1 +0.9 +1.5 A5EP7 FX -0.1 +0.5 -0.5 -1.3... Open at page → 86 Page 86 Table5 Anpere-RangeCoBparlsons V^s I T S (A) 20Hz 1kHz 20kHz 50kHz W20A#7-1 W10A#0-1 10 ••1 1 17 +10 W10A#0-1 W5A#5-2 5 -5 -2 0 +16 W10A#0-1 W5A#5-1 5 -6 -6 -6 +17 W5A#5-2 W3A#4-1 •fi -1 4 +16 W3A W2A#3-2 2 *3 0 -7 -11 W... Open at page → 87 Page 87 Table6 AC-DCDifferencesof1Ato20ATE*s d(ppin) I TE (A) 20Hz 1kHz 20kHz 50kH W20A#7-1 10 -5 +5 +14 +10 W10A#0-1 5 -6 -6 -3 0 W5A#5-2 3 -] -^ -3 -16 W3A#4-1 2 -2-3 -7 -32 W2A#3-2 1 -5-3 0-21 W1A#7-2 1 -1 -1 +5 -8 W1A#2-2 1... Open at page → 88 Page 88 Table7 ResultsofEvaluationofFX2andFY2 TE I d(ppa) or TVC or V 20Hz 1kH^ 10icHz 20kHz 50kHz100kHz "1 ov +3.9 +2.H +1.3 +1.0 +0.6 +0.3 7 +2.0 +1A +0.6 '+1.6 tl.il 0.0 FY2 5mA +4.7 +3.2 +3.6 +3.5 +3.9 J*J +? ft +?Q 2.5 +2.2... Open at page → 89 Page 89 Table8 ConparlaonaofF^tvc*8 (FXgandFY2TE'a) A-dy-ds(ppn) T S V 20Hz 1kHz 20kHz 50kHz 100kH: F2OO-FX2 F1OO-FY2 100 - -1.1 +0.2 +1.4 +17.8 FIOO-FY2 F5O-FX2 50 - +0.6 -0.8 -2.8 -6.2 F5O-FX2 F3O-FY2 30 - -2.5 -1.6 -2.0 -1.5... Open at page → 90 Page 90 TVC Table9 AC-DCDifferencesof TVC'awithFX2andFY2 d(ppm) V 20Hz 1kHz 20kHz 50kHz 100kHz +27 -6 1 500 +2.5 +1.2 -6.5 -18.6 300 +1.7 +0.4 -7.3 -19.4 300 +3.5 +1.9 -1.8 +15.6 200 +2.7 +1. 1 -2.6 +14.8 200 +2.4 +0.4 -1.7 +6.4... Open at page → 91 Page 91 Table10 CoaparlsonsofWorkingandReferenceStandardTE*3 A(ppm) I Test Standard (mA) 20Hz 1kHz 20kHz 50kHz A3#95 FA 5 +5 +2 +9 +18 G10#57 B10EP2 10 -5 "5 "4 -3 F20#1 W25E1 20 -9 "7 "5 +1 W30#1 W25E1 25 -12 -11 -12 -12 F50#2... Open at page → 92 Page 92 TE Table11 AC-DCDifferencesofWorkingStandardTE*3 AC-DCDifference(ppm) I (mA) 20Hz 1kHz 20kHz 50kHz A5#95 G10#57 F20#1 W30#1 F50#2 BlOO#3 A250#1| W0.5A#0-2 W1A#7-1 W2A#8-3 W3A#9-2 W5A#5-1 W10A#0-3 5 10 20 30 50 ^00 250 (A... Open at page → 93 Page 93 Table12 CoBparisonaofFjtvc*s A-dj-ds(pp«) T e V £UHZ 1Knz £UKnz 7UKnz 1UUKnZ Fyl000-1OE-Fyl «^AAnA Fy600-FY2 600 0 -13 -7 Fy500-10C-Fy1 F7600-F72 500 0 -7 +1 1 FySOO-IOD-Fyl Fy600-Fy2 500 0 0 +35 FySOO-Fyl F7200-F72 200... Open at page → 94 Page 94 Table13 AC-DCDifferencesofFyTVC8 d(pp«) TVC V 20Hz 1kHz 20kHz 50kHz 100kHz Fyl000-10E-Fy1 600 - -2 -15 -2 - FySOO-IOC-Fyl 500 - -2 -9 16 - Fy500-10D-FYl 500 - -2 -2 il0 - Fy600-Fy2 500 -2 -2 +5 +43 F73OO-F7I < 300 -u -2... Open at page → 95 Page 95 Table14 PooledStandardDeviatlona,S pa _Spg(ppaofinputVorI) TypeofTeat Typical (aV)20Hz 1kHz20kHz50kHz100kHzAverage 1.Comparisonof 10-^40 0.11 0.16 MJTC'3 (5)^ (11) Comparisonof ReferenceTE's andF1IOFY2 10 0.20 0.29 Exten... Open at page → 96 Page 96 Table15 EstimatedLimitsofResidualSysteaaticUncertainties (notevaluatedbystatisticalmeans) (Seenotesatendoftable) Limits^±b 1kHz 100kHz ppn SofA ppm %ott A.MJTCComparator &Equipment 1.nVm&averager(2$of - 2 - 2 indication)... Open at page → 97 Page 97 Table15(Continued) Limits,±b,ppa 1kHz 50kHz 100kHz E. 5mAReferenceTE's 1.Residualthermoelectric effects 0.2 0.2 2.Highfrequencyevaluation 0.0 0.5 l>o 0.20 0.54 F.F^10Y2,BaseTVC 1. 1kHzbase 0.2 0.2 2.Highfrequencyextensio... Open at page → 98 Page 98 Table15(Continued) LlMlts,±b,ppa 1kHz 50kHz 100kHz K.ExtensionofVrangefrom200 to1000Vrange(at500V) (3steps) 1.DependenceofdyonV (Avg.for3steps) 2. 3. Dependenceofd^onI TransferFX,FY^toFXg, ^^2 eachstep 0.5 0.2 0.5 0.73 2... Open at page → 99 Page 99 Sections Table15(Continued) NOTES: A,B,&C %ofLerrorsdependonmagnitudeofA- d-j-ds- n-determinedonce,buterroraffectseveryac-dcdetermination. ACeffectsareestimatedresidualsorallowancesforrfi, Inducedvoltages,etc. E-1&F-1 Ma... Open at page → 100 Page 100 Table16 CalculationofUncertainties Se - Spaorb//3, - (ESe^)^''^^ "o -2 SorU(ppn) 1kHz 50kHz 100kHz A.MJTC044 fromtable14-1 Sg-Sp^ 0.16 Sgforcomparator, table15-A Sg-b//3 0.09 SgMJTC's(15-D) Sg-b//3 0.19 0.53 B.Reference... Open at page → 101 Page 101 Table16(Continued) SorU(ppm) 1kHz 50kHz 100kHz E.ReferenceTE's2Ato20A(at10A) (5steps) Spa(14-4C) perstep 1.6 1.7 Sgcomp.(15-B) perstep 0.6 1.3 SgTE»s(15-1) perstep 1.3 2.U After 1stepUq-zSq 4.3 6.4 After5stepsUqj-/sUq 9.... Open at page → 102 Page 102 Table16(Continued) SorU(pp«) 1kHz 50kHz 100kHz H.WorkingTE's5mAto20Arange S (14-6) 2.8 1.7 Sgcomp.(15-C) 0.6 1.2 SpTE»3(15-L) 5mA 2.1 3.1 20A 3.6 5.8 ReferenceTE's(16-B) 5mA 0.4 0.5 (16-E)20A 5j^ 8L2 Uh - 2So 5mA 7.1 7.5... Open at page → 103 Page 103 Table17 SummaryofUncertainties ofNBSAC-DCTransferStandards I.Uncertainties Independent ofMagnitudeofd Uj^ppm Standard 1kHz 50kHz 100kHz MJTC(oneofgroup) 0.53 B Referencebase,5mATE's&10VTVC 0.84 1.0 1.4 C ReferenceTE: 50m... Open at page → 104 Page 104 Table18 CoiparisonofEstimatedCalibrationUncertaintieswith PresentAllowances U(ppn) 1IcHz 5bA 20A 50kHz 5OA 20A WorkingstandardTE's(16-H) Comparison(16-HwithoutSgof ref.stds.) U(rss) Presentallowance 5mA-5A Presentallowan... Open at page → 105 Page 105 Table19 BstlmatedUncertainties forSpeolalTests (CalibrationofaTEorTVCagainstareferencestandard, withMJTCooBparator) U(pp.) 1 1kHz kHz 5mk 50uk 5mk 50bA ReferencestandardTE5-50raA 0.9 1.1 1.0 1.5 Comparison (16B&16Cwithou... Open at page → 106 Page 106 MJTCPrimary Standards 5 -lOVp5 -10mA 20Hz-10kHz frequency extension Special TE's 5mA TEReference Standards 5mA 20Hz-100kHz TEReference Standards 20A 20Hz-50kHz TEWorking Standards 5mA-20A 20Hz-50kHz •buildup' frequency e... Open at page → 107 Page 107 30Hz 1kHz 10kHz Fi9ure2.Comparisons ofhJTC's 93 Open at page → 108 Page 108 50mA 25mA W50E1 W50E2 OF19 Averacre (50mA) -0.7-0.7 -0.1-0.7 0.70.0 -0.7-08 +0 1-0.8 0.80.0 -0.7-06 00-0.5 +0.50.0 +0.7 +0 -1.0-0.1 0.1 0.0 -0.1\ / -0.2 > 0.0\ /+0.1 +0.4 -0.2 +0.1 -0.7\ +0.1 W25E1 W25E2 NPL14 Average s-... Open at page → 109 Page 109 95 Open at page → 110 Page 110 96 Open at page → 111 Page 111 ToDCRev. Comp. Set Read Figure6.DiagramofEMFComparator 97 Open at page → 112 Page 112 APPENDIX 1 n-COMPENSATION andn-MEASUREMENTS A. PrincipleofConpensation ThebasiccircuitoftheMJTCcomparatorwiththen-compensation resistor,R^,includedisshowninfigure5.Eprepresentsanadjustable Lindeckpotentiometer. Attheinit... Open at page → 113 Page 113 B. BaaloTEEquation SinceneitherTEhasaconstantoutputduringacomparisonoftwoTVC's (orTE's)thedevelopmentofthecomparatorequationgiveninappendix 2of C3]isnotdirectlyapplicable. Itwillbeconvenienttouseageneral equationforaTVCw... Open at page → 114 Page 114 But - -niE^gand - " "'^Id' ^^^^ polarityshown,sothat ^a"^d"^2a"^2d"'"^^1a"^1d^"*'^^2a"^2d^~°'^^1a~^1d^ •Combiningtheseequations, andnotingthatq=»n^/n2andraE^-E2»gives,closelyenough, ^-=2-^— i^Te; Sjip-i^ Ifn^>n2,thepoten... Open at page → 115 Page 115 D. PrecautionsInn-Meaaurement Thecharacteristic, n,isconvenientlymeasured,aftertheInitial balanceisobtainedwiththesetkeydown,bychangingtheInputquantity, Q, byabout0.1$,notingthechangeinoutputemfE,thencalculating n=»QAE/E... Open at page → 116 Page 116 E. SquareLawOutputandRMSResponse Itisworthemphasizingthatevenifn*2,sothatE*KI^withKa constant, aTEinherentlyrespondstothetruermscurrent,I.Thiscanbe showneasilyforthesimplestcaseinwhichalloftheheaterisatthesame constantte... Open at page → 117 Page 117 Appendix2 EMI,HarmonicaandDCOffset A. TestforLine-BorneElectromagnetic Interference (EMI) Onlyabout 1 ofheaterpower,overawiderangeoffrequency, can produce0.1$ofratedemfinatypical5-tnATE.ThusTE'saresensitiveto EMI,particu... Open at page → 118 Page 118 InthemoregeneralcaseKissomewhatdependentinE,sothatthe sensitivityofthistestisaffectedslightly. Also,ifbothTE'sinan ac-dccomparisonrespondequallywelltocurrentsatbothfrequencies, there willbenoEMIerror.HowevertheEMItestwil... Open at page → 119 Page 119 Withadcvoltage, v^j,equaltoVappliedandthenreversed,thedc reversaldifference inoutputisAE-2KqV.Thus E=kV^d .8H) where V AE . 03 g-—andu= Notethatthisisproportional tothe1stpowerofu,andthat,forasquare lawTE,gistwicethevalu... Open at page → 120 Page 120 Appendix3 EffectofRelayOff-Time Lettheresponse, E,ofaTEbeapproximated byasimpleexponential withatimeconstant, t^.Thenafterthesteady-stateheatercurrentis turnedoffforatimet^KKt^(theoff-timeoftherelaywhenswitched),we have... Open at page → 121 Page 121 Appendix4 EffectsofBeadHeating A. RelativeEffectivenessofBeadandHeaterPower Widdlshasshown(equation17of[19])thatthemidpointtemperature rise, e„j,oftheheaterofaTEcarryingacurrent,I,takingintoaccount theheatlossthroughthet... Open at page → 122 Page 122 B. AC-DCDifferenceCausedbyBeadHeating OneendoftheheaterofaTVCisgrounded,andthethermocouplecircuit isusuallygroundedalsoforsafetyandtokeepthebeadvoltagelow.Thus halftheheatervoltageisacrossthebead.FromtheformulainsectionV... Open at page → 123 Page 123 C. TwoTE'3inSeries Asimilarbutmoreinvolvedanalysisshowsthatiftwoequal series-connected TE'sareusedinagroundedTVC,theresultantoutputwill alsobeunaffectedbythebeadcurrents. ) 109 Open at page → 124 Page 124 Appendix5 ImpedancesandSubstitutionCorrections IngleshasstudiedthegeneralImpedancerelationships inTV'sandthe effectsofchangingTE's.[9] Howeverthefollowingalternativeapproach, withitsexplicittreatmentofphasedefectangles,w... Open at page → 125 Page 125 Wemayalsowrite Z/R- 1+a+jb and Z./R.- 1+c+1e 33 nn witha,b,candeeachmuchlessthanunityforausefulTVC.Rgand R^i thedcvalues. Then h. 1^a^Jb^p(1^c^Je) . ^g^ R^. 1+ P ' J" wherep-R^/RstS (a+pc)/(l+p)andh-(b+pe)/(1+p).Notethat... Open at page → 126 Page 126 B. SubstitutionCorrections (SeeSectionIX) ConsidertwodifferentTE'softhesamenominal Rj^,eachwithaknownd^ asacurrentconverter,andaknownd^^asavoltageconverter(withno seriesresistor). Thedifference ind^ofaTVCrangewiththesame... Open at page → 127 Page 127 range). ItIsmuchsmallerforhigherranges,evenIfbIslarger(asitmay bebecauseofcapacitivecurrents). AtNBSacommercialimpedancecomparatorhasbeenveryconvenientfor comparingphaseanglestobetterthan 1mradupto100kHz. Itisusedto scre... Open at page → 128 Page 128 Amoreextendedtreatment,includingtheeffectsofphaseangles,leads toaddedtermsin , ande2,similartothosegiveninappendix5B. Theyarenegligible iftheydonotexceedthelimitsgiventhere. D. AC-DCDifferenceofSeriesResistor Foragivenra... Open at page → 129 Page 129 Fromthisandbycontinuing toneglecttermsin andhigher I-21^(1 -8^/8) Theproportionaldifferenceis e- (21^ -I)/I» . Ife»3x1 0~^, 6«0.1x10"^radians. Sincethetwoimpedances, Z,and areinparallel, ThiswillbetrueonlyifZg-Z^/.-0.Thu... Open at page → 130 Page 130 Appendix6 RECOMMENDATION oftheWorkingGroupontheStatementofUncertainties presentedtoComiteInternational desPoidaetMesures Assignmentofexperimentaluncertainties RECOMMENDATION INC-1(1980) 1. Theuncertainty intheresultofame... Open at page → 131 Page 131 variancesandthequantities Ujlikestandarddeviations. Whereappropriate, thecovariancesshouldbetreatedinasimilarway. Thecombineduncertaintyshouldbecharacterized bythenumericalvalue obtainedbyapplyingtheusualmethodforthecomb... Open at page → 132 Page 132 300 Section5 MultijunctionThermalConvertersastheNBS PrimaryAC-DCTransferStandardsforACCurrent andVoltageMeasurements FRANCISL.HERMACH, lifefellow,ieee,JOSEPHR.KINARD,seniormember,ieee, ANDJOHNR.HASTINGS,member,ieee Abstr... Open at page → 133 Page 133 HERMACH eiai:MULTIJUNCTIONTHERMALCONVERTERSASNBSAC-DCTRANSFERSTANDARDS 301 Fig.1.PrecisioncomparatorsystemwithanMJTCandanSJTEcon- nectedasvoltageconverters. ofapairofback-to-backZenerdiodesdirectlyinparallel withtheheate... Open at page → 134 Page 134 302 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT, VOL.IM-36,NO 2,JUNE1987 (a) (b) -0.4^/Rin.9\ -0.8/-0.7 V+0.2y V-0.2/ -0.4 /cio-n -0.05 /B10-44\ +0.6 \-o^ V+0.1 , +0.4 (c) Fig.2.Resultsoftheintercomparisons ofM,ITC"s... Open at page → 135 Page 135 HERMACH eiai.MULTUUNCTIONTHERMALCONVERTERSASNBSACDCTRANSFERSTANDARDS 303 SidA 10mA 25mA 50mA 10kHz 1kHz SJTEs MJTCs Fig.3.Resultsoftheintercomparisons ofMJTCsandSJTE'sascurrent convertersbetween5and50mA.Thenumberstotheri... Open at page → 136 Page 136 304 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT, VOL.lM-36,NO.2,JUNE1987 where istheaverageofthetwopolaritiesofdcvoltage requiredtoproducethesameEMFasV^,and isthe averageofthetwopolaritiesthatproduceanEMF,fj. Thenfro... Open at page → 137 Page 137 HERMACH CIal.:MULTIJUNCTIONTHERMALCONVERTERSASNBSAC-DCTRANSFERSTANDARDS 305 itentersonlyinadifferencetermforthiscomparator, smallerrorsindetermining itarenotsignificantunless5, — 6,islarge. AppendixB EMI,Harmonics,andDCO... Open at page → 138 Page 138 306 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT. VOL.IM-36,NO.2,JUNE1987 References 1 1 ]F.J.Wilkins,"Theoreticalanalysisoftheac/dctransferdifferenceof theNPLmultijunctionthermalconverteroverthefrequencyrangedc to100... Open at page → 139 Page 139 524 Section6 AnInvestigationofMultijunctionThermalConverters FRANCISL.HERMACH,fellow,ieee,andDONALDR.FLACH Abstract—Therelativeac-dedifferencesofagroupofmulti- junctionthermalconverters(MJTC's)havebeendeterminedover thef... Open at page → 140 Page 140 HERMACHANDFLACH:MULTIJUNCTIONTHERMALCONVERTERS 525 0 Fig.1.Comparisoncircuit. 8 PPM 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -0.5 \85rnA ^lOm ClOm/ 82:mA 30 50 100 200300500 1000 FREQUENCY INHz Fig.2.Ac-dodifferencesofTCC's. photoc... Open at page → 141 Page 141 526 IEEETRANSACTIONSONINSTRUMENTATION ANDMEASIIREMKN'i',UECEMHER1976 TABLE I TVCComparisons MJTC MJTC 4- « 1 - -«2(ppm) n V 30Hz 160Hz 1kHz 10kHz B10*2 # B52 9 +04 -0.2 -0.2 -0.4 B10*44 B5*2 9 +06 -0.1 0.0 -0.2 B10*2 810... Open at page → 142 Page 142 HERMACHANDFLACH:MULTIJUNCTIONTHERMALCONVERTERS 527 Fig.4.Reversingbridge. second-order effectonimpedancemagnitude.However thereisapossibilityofdielectriclossintheinsulationat thehigheraudiofrequencies.(Themaximumpower- t... Open at page → 143 Page 143 IEEETRANSACTIONS ON.INSTRUMENTATION ANDMEASUREMENT.DECEMBER1976 Appendix CompensationforChangesinResistance WhenaresistormRisinserieswithMJTCheater, +a),a«1,thecurrent(withnoreactance) is v; ~ (m+l)R{l+a/im+1)) ^ a \ im+... Open at page → 144 Page 144 334 Section 7 TheoreticalAnalysisoftheAC/DCTransfer DifferenceoftheNPLMultijunction ThermalConvertorOvertheFrequency RangeDCto100kHz F.J.WILKINS >4&s/rflcr-Measurements ofthermsvaluesofalternatingcurrentsare frequentlyma... Open at page → 145 Page 145 WILKINS:AC/DCTRANSFERDIFFERENCEOFNPLMULTIJUNCTIONTHERMALCONVERTOR 335 putfromthethermojunctionsthusgivesanaccurateindication ofthemeantemperatureoftheheaterwithrespecttothatof themainstructuralpartoftheconvertor,andbeing... Open at page → 146 Page 146 336 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT,NOVEMBER1972 through (a) Twisted bifilorheater (b) Fig.2.(a)Rectangularelementandconnectingleads,(b)Rectangularelementsmountedinhousing. ^=1 P ^ 2/ i Fig.3.Sectionofhea... Open at page → 147 Page 147 WILKINS:AC/DCTRANSFERDIFFERENCEOFNPLMULTIJUNCTIONTHERMALCONVERTOR 337 =:10"'\which isanextremelysmallvalueanddefinesthe originalclaimofanaccuracyofbetterthan 1in10"^ with greatercertainty.Moreoverthisisanupperlimitasther... Open at page → 148 Page 148 338 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT,NOVEMBER1972 ,I/unitlength i: 1 vyonitlength Heatlinkconnected tooneendofheater Fig.4.Bifilarheatershowingimpedancer i /unitlengthanddistributed admittances^jandjs/unit... Open at page → 149 Page 149 WILKINS:AC/DCTRANSFERDIFFERENCEOFNPLMULTIJUNCTIONTHERMALCONVERTOR 339 TABLE I Heater-Base(PaiaUel) Half-Heater-Half-Heater (ParaUel) Frequency (kHz) C2{P)X 10-'2 tan6 1 (") C3(P)X 10-12 tan62 ^3(P) (") CalculatedAC/DCTra... Open at page → 150 Page 150 340 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT,VOL.IM-21,NO.4,NOVEMBER1972 totheStoutcopperpillaronwhichtheelement ismounted. Theseleadsarecloselytwinnedandshouldnotthereforehave anyextraneousmagneticfieldsurroundin... Open at page → 151 Page 151 Section8 TKermalConverters forAudio-Frequency Voltage Measurements ofHighAccuracy F.L.HERMACH,fellow,ieee,andE.S.WILLIAMS Abstract—Theac-dcdifferencesofareferencegroupofthermo- elementshavebeenevaluatedataudiofrequencies... Open at page → 152 Page 152 HERMACHANDWILLIAMS:THERMALCONVERTERSFORAFVOLTAGEMEASUREMENTS 261 largergroupsonthebasisoflowdcreversaldifferences andhighbeadresistances,andareallmountedinone aluminum enclosure linedwithfoamed plasticfor thermalinsulati... Open at page → 153 Page 153 262 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT DECEMBER Fig.1.Essentialsofthermalvoltageconverters(construction de- tailsnotshown). AThermoelement unit,with5mA100QTE,for0.5V,inbrass cylinder,4cmlongand5.1cmdiameter,... Open at page → 154 Page 154 1966 HERMACHANDWILLIAMS:THERMALCONVERTERSFORAFVOLTAGEMEASUREMENTS 263 deflectionsof arelesscritical iftheTEsarewell matched.) Allofthecomponentsofthecomparatorexceptthe detectorsaremountedinametalboxbehindametal paneltop... Open at page → 155 Page 155 264 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT DECEMBER Fig.4.Intercomparisons ofNBSTEs,andassignedac-dc differencesinppmat2kHz. ferencesfromallknownsources[3]shouldbethesame asat2kHzwithin1ppm.Nomeasuredvaluesatthe... Open at page → 156 Page 156 1966 HERMACHANDWILLIAMS:THERMALCONVERTERSFORAFVOLTAGEMEASUREMENTS 265 throughthe100Vrangesinestablishingthevaluesgiven inTableIIfromthecomparisonsofTableIII. Thecomparisonsat50kHz(whichwerelessprecise) weremadetoverifyth... Open at page → 157 Page 157 266 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT DECEMBER itislessthan0.01°C,andthePeltiererrors,5<pand5p (independent offrequency),arelessthan1ppm.This hasbeenverifiedbycomparisonswithEvanohm-heater TEswhichhadcopper... Open at page → 158 Page 158 1966 HERMACHANDWILLIAMS:THERMALCONVERTERSFORAFVOLTAGEMEASUREMENTS 267 systematicerrors.Thisissomewhatremarkable,since fluctuations inthebestavailablewide-rangeacanddo sourcesgreatlyexceedthis,andmostoftheseTEshave rather... Open at page → 159 Page 159 268 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT plextobeusefulforroutinemeasurements.Theyshow, however,thatifRn<{Ri+R2)/lOO,thesimplifiedequa- tionsalreadyderivedarevalidtoafewpercentofthe computed 61— 52.Theyshowtha... Open at page → 160 Page 160 Section9 JOURNALOFRESEARCHoftheNationalBureauofStandards—C.EngineeringandInstrumentation Vol.75C,Nos.3and4,July-December 1971 ThermalVoltageConvertersandComparatorforVery AccurateACVoltageMeasurements E.S.Williams Instit... Open at page → 161 Page 161 Figure1.Newsetofthermalvoltageconverters. Thesimplesymmetricalgeometryoftheseunits permitsapproximate calculationsoftheirreactances [2].Thecalculationsareinexactbecauseofthenec- essaryassumptionsastoend-effects,andtheyne... Open at page → 162 Page 162 compensation; perfectcompensation ispossibleonly atonefrequency. 3.1000-VTVC Asstatedearlierthecorrectionsforthehighandlow voltagerangesaredetermined relativetothemiddle rangebyintercomparison tests.Itisnecessarythere- f... Open at page → 163 Page 163 Figure3.CrosssectionofhighvoltageTVC. Inpuiendisattheleft.Fixedandadjustableshieldpartsaresupportedbyapolystyreneinsulatorone-halfinch thick. thermoelectric eflfectsintheheaters.Theyalsohave smallreversed-cdifferences (l... Open at page → 164 Page 164 Table5listsintercomparison dataforthesamefre- quenciesforsevenpairingsofthefive1000-VTVCs. Valuesfor600and1000Vdonotdiffersignificantlyand sotheyareallaveragedtogether. Corrections (8)foreachrangeofthenewTVCset arelisted... Open at page → 165 Page 165 acrossalOOO-Odivider,andthiswillaffectthecom- pensationbyabout20percent.Avalueabout10per- centhigherthantheonechosenexperimentallyshould provideasatisfactorycompromiseandreducethe driftbyafactoroffiveormore.Withthecompen... Open at page → 166 Page 166 7.TEComparator Thereareseveralvariationsofbasiccomparator circuitswhichareusedtominimizethedifficulty causedbypowersupplyinstability [1,3].Theyemploy avoltagedividercircuittowhichtwoemfsarecon- nected.Thedivider isadjust... Open at page → 167 Page 167 Figure9.PhotographofTEcomparator. voltageappliedtothegalvanometer circuitischanged bythesameamountandthedeflectionchangeDi isusedineq10and12inappendix2todetermine di.Ameasurement ofEsismadeonlytofindthecor- respondingval... Open at page → 168 Page 168 11.Conclusion TheuseofoneresistorunitfortwoTVCvoltage rangeshasreducedbyabouthalfthetimerequired, overpreviousTVCsets,tomakeacompleteintercom- parisontest.Changesinanymemberofthesetare readilydetectedsincefrequentinterco... Open at page → 169 Page 169 Ifagalvanometer isusedasthedetector,thecurrent through itwithk2closedis,byThevenin'sTheorem, ^96 — mEt—Es Re (6) whereReistheresistanceofthegalvanometer circuit withEtandEs=0.WithEiand heldconstantand pRiinsertedbymeanso... Open at page → 170 Page 170 Section10 ThermalVoltageConvertersforAccurate VoltageMeasurements to30 MegacyclesPerSecond F.L.HERMACH MEMBERAIEE Synopsis: Thermal voltage converters, eachconsistingofaresistorinserieswitha thermoelement inacoaxialline,... Open at page → 171 Page 171 TE Fig.1.Thermalvoltageconverter R=Film-typeresistor1/8in.diameter,2in. long TE=Thermoelement A=Coaxialinputconnector,GR874PB B=Two-pinoutputconnector,ANIOSL Di,Dj=Circularbrassdisks,3/16in.thick, securedtoFwith42-56bras... Open at page → 172 Page 172 •004 •002 00 -0.02 -0.04 -0.06 -OOB -010 -0.12 -014 K-0 038-y^ K=0.03 r i 1 1) 1 K.-O.Z K=0.3 K-0.4 Fig. 4.Com- puted «-c-d-c difference ata function oftlie parametersaand k mittanceofymhosperunitlength.The lineistermina... Open at page → 173 Page 173 ThevaluesofS„forthe1-to20-volt convertershavebeencalculatedbyequa- tion6atafrequencyof40mc,atwhich aandbarestilllessthanunity.The resultsaregiveninthelastcolumnof TableII. When)fe<0.038,distributedcapacitance fromtheresi... Open at page → 174 Page 174 TableIII.ResultsofTestof1-VoltVoltmeter Frequency, AppliedVoltage,* Mc Volts 1 0.997 10 0.998 30 0.998 100 0.999 200 0.982 300 0.945 400 0.883 *Forsamereadingofmillivoltmeter ateachfre- quency sionsasinFig.1butwithacoaxi... Open at page → 175 Page 175 Fig.5.5-voltcon- verterletupfora-c- d-ctestofexperi- mental thermo- couple voltmeter. Lindeck potenti- ometer at right, double-shield con- verterandexperi- mental split-shield element in fore- ground, a-c-d-c switchnotsh... Open at page → 176 Page 176 areinallhigb-frequency apparatus.The useofcoaxialcoonectorscanbemisleading, asanyappreciablelengthof50-ohmcoaxial linewillcauseerrorsduetostandingwaves, unlessthevoltmeterinputimpedance is madeexactlyequaltotheimpedanceo... Open at page → 177 Page 177 Section11 JournalofResearchoftheNationalBureauofStandards Vol.48,No.2,February1952 ResearchPaper2296 ThermalConvertersasAC-DCTransferStandardsfor CurrentandVoltageMeasurementsatAudioFrequencies FrancisL.Hennach Thermalco... Open at page → 178 Page 178 withatestondirectcurrentgivesmoreinformation abouttheperformance ofthetestinstrument. Becausetheac-dcdifferenceofaninstrumentde- pendsupongeometrical factorsthatarerelatively permanent,subsequent testsforcheckingthecon-... Open at page → 179 Page 179 FiniKH]. 7\i/pic(iliheriiialconvciicrs. FlOURE2.MountedthennalcojiverlersandthemodelAand modelBvoltmeterelements. Liketheelcctiodynamic tiansforstandardsusedat lowerfrequencies, theseriesresistor isadjustedin usetogiveth... Open at page → 180 Page 180 meter,whichgenerallysetsthelimitontheaccuracy obtainablewiththisformofpotentiometer. Suchapotentiometerhasbeenincorporated ina panelconstructedfortheaudio-frequency testing. It wasdesignedtohaveadequatestability,freedomf... Open at page → 181 Page 181 shieldsgroundedareusedtominimizeerrorsdueto straycapacitancecurrents.Thealternatingcurrent isadjustedforthedesireddeflectionofthetestinstru- ment,andtheLindeckpotentiometer isadjustedfor an"on-scale"deflectionofthegalvan... Open at page → 182 Page 182 4.Comparison ofactualtransferperformance of thestandardwiththatofsomeotherinstru- ment,preferably ofaC]\iitedifferenttype, whoseperformancehasalsobeenevaluated. Theevaluation oftheseelectrothermic transfer standardswasco... Open at page → 183 Page 183 Theydisclosodsignificantdisagreementsbetweenthe iiinpeic-ninge tlicrmalconvertersandtheelectro- dynamicammeter,Avhichwereconsideredtobedue toalow-frequencyerrorinthe1-and2-ampthermal convertersantlasmallerrorindependento... Open at page → 184 Page 184 responseofthethermalconverteronalternatingand ondirectcurrenttheresponseoftheshuntedmodel Avoltmeterwasgreateronalternatingthanon directcurrent.Theresultsoftestsofthe1-,2-and 5-ampthermalconverters,duplicating thosewith... Open at page → 185 Page 185 niiiipoiiitoftliohealer.* Tliissuppositionwasveri- fiedbyananalysisofthedata,whichshowedthat theditrercnceswerelargerinthosethermalconverters withheatershavinglargerthermoelectric effects. Furtherverificationwassecuredby... Open at page → 186 Page 186 Tlieresultsmaybeconipared witlitheobserved ac-(lcdifferencessbowniintable4.Frominfoiination suppliedbythemantifacturers, the1-,2-,5-,10-,20-, 50-,and200-matbermalconvertershaveheatersof either carbon, nickel-chromium, or... Open at page → 187 Page 187 7'o—tlu';iinl)ici)t toinpcrn tuicindegroos Kelvin q—d/ojl'^andis(approximately) theratio ofthecrestvalueofthecyclic fluctuation oftemperature atthe midpointtotheaverajjjotemperature riseatthemidpoint aj=27r/,where/isthef... Open at page → 188 Page 188 thecurrentatthesliort-circuitcdendwascomputed asapproximately 1/1-^[1-0.0056(aj(7/?n, (5) h where l'=theappliedvoltage /=tliecurrentattheshort-circuitedend /?=theresistanceinthecircuit C=the totalcapacitance toshield oft... Open at page → 189 Page 189 Asuitablelow-rangethermalconvertershouldalso makefeasibleana-cpotentiometerwithaninherent accuracyof0.01percent.Thebasiccircuitfora polarformofsuchapotentiometer (tomeasurethe magnitudebutnotthecomponentsorphaseangleof a... Open at page → 190 Page 190 whereOdeisthequantitymeasuredwiththepotentiometer, 5,istheac-dcdifferenceofthetransferstandard,andQ„r isthea-cvahierequiredfortheobserveddeilcctionofthe testinstrument. Thermol Converter Figure 6.ElementaryformofPolara-c... Open at page → 191 Page 191 oneterminalbyasmallamount andtolowertheotherby aneqiialanionnt. Tliedifferentiaietnialionthenha?!asits boundaryconditions,0=00+ASat2=+/andd~di,-AOat x=—l. Th(!solution is h,,., ,AOs 00=2 (HI) andisthereforeniichanf^ed at... Open at page → 192 Page 192 Theprocedurewillbetoconsiderpandkconstantandto solvefortheperiodicsteady-statetemperature rise,thento approximatepand fcasp= po(1+a9)andk=ko(1+06),toin- troduceradiationloss,andtosolvetheresultingequationby theperturbati... Open at page → 193 Page 193 Foreachfrequencyoftlieharmonicdrivingtermsintlie right-handsideofthisequation,thesolutionoftheequation thatvanishesattheendpointswillbeoftheform(7,cos nw/—C/fcsinnojl,whereUaand f/j,arefunctionsofx.The average value,over... Open at page → 194 Page 194 thesolutionofwhichis Wonow{)utthisvahicofVinthojierttirhinntornicontaiiiiiig X-ineq36,toget an' dx- 2dV Xdx Tlic^olutio^ofthis,withthesameboundary corniilions,is ^ P\ 28J 2HP As\-=jwCi,r(,,wewillneedtorepeatthisj)rocosst... Open at page → 195 Page 195 Section12 ThermalCurrentConvertersforAccurateACCurrent Measurement EARLS.WILLIAMS Abstract—Anew14-rangesetofthermalcurrentconverters consistingofshuntedthermoelements hasbeenconstructed to measureac-dcdifferenceandaccurr... Open at page → 196 Page 196 520 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT,DECEMBER1976 TABLEI ThermalCurrentConverterSet Fourteenrangesarefonnedwithsix shuntsandtwoTVCs(FGandFH) . Current Shunt TVC Range Resistance Current (amperes) (ohms) (m... Open at page → 197 Page 197 WILLIAMS:THERMALCURRENTCONVERTERS 521 aholeinthatpartoftheshuntandtheinsulationtothe otherhalfwhereitissilversoldered. The10-20-Ashuntresistoris5milsthick,10cmwide andabout34cmbetweenpotentialtaps.Afterbeingfolded intobi... Open at page → 198 Page 198 522 IEEETRANSACTIONSONINSTRUMENTATION ANDMEASUREMENT,DECEMBER1976 TABLEII Intercomparisons ofTCC's(ppm) TCC^ TCCj Applied Current Amperes D D FG FH 0.01 Q Q FG30 FH 0.02 +1 +11 FGIOO FH60 0.06 +10 +23 FG300 FH200 0.2 +7... Open at page → 199 Page 199 WILLIAMS:THERMALCURRENTCONVERTERS 523 The20-mArangeandthe1-and10-Arangesarerec- ommendedasminimumreferencepointstobetestedrel- ativetootherstandardsoutsidetheset.Intercomparison determinationswouldbebasedonthe20-mAand1-A... Open at page → 200 Page 200 290 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT,VOL.IM-34,NO.2,JUNE198S Section13 ADual-ChannelAutomatedComparatorforAC-DC DifferenceMeasurements EARLS.WILLIAMSandJOSEPHR.KINARD,seniormember ,ieee Abstract— automated... Open at page → 201 Page 201 WILLIAMSANDKINARD:DUAL-CHANNELAUTOMATEDCONVERTER 291 IEEE 488 IEEE488 DC SOURCE DCDVM ~7K~ AC SOURCE CONTROL FROM IEEE488CH RELAY ACDVM F-REQ. /COUNTER V IEEE488 DUALCHANNELCOMPARATOR 8TD. TVC VOLTAOE NULLING DAC IEEE 48... Open at page → 202 Page 202 292 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT,VOL.IM-34,NO.2,JUNE1985 Fig.2.Automatedac-dcdifferencecalibrationsystem. K3^ Fig.3.Dual-channelac-dcdifferencecomparator. VoltagesarethenappliedtobothTVC'sinthetestsequ... Open at page → 203 Page 203 WILLIAMSANDKINARD:DUAL-CHANNPXAUTOMATEDCONVI'.RTER 293 1008V 100V 18V 18 100 Ik 10k FREQUENCY (Hi) 180k IM Fig.4.Voltageandfrequencylimitsofcalibrationsystem. methodsimilartothatusedbyInghsinasemi-automatic sys- tem[4] .... Open at page → 204 Page 204 294 IEEETRANSACTIONSONINSTRUMENTATIONANDMEASUREMENT,VOL.IM-34,NO.2,JUNE1985 resultstakenovertheoperationalregionrarelydifferbymore than10ppmfromdataobtainedmanually.Thestandarddevia- tionisgenerallylessthan5ppminthemiddl... Open at page → 205 Page 205 Section14 GENERALINSTRUCTIONS FORTHEOPERATIONOFNBSAUTOMATED AC-DCCOMPARATORSYSTEMII ThomasE.Lipe ElectricityDivision NationalBureauofStandards December,1987 191 Open at page → 206 Page 206 INSTRUCTIONS FORTHESETUPANDUSEOF NBSAUTOMATEDAC-DCCOMPARATORSYSTEMII GeneralDescription ThenewNBSautomatedac-dccomparator(System II)was builtin1985-1986toassistintheeverydaycalibration servicesofthegroup. Itisexpectedtha... Open at page → 207 Page 207 Notethattheproductnamesinparenthesesindicate the equipment supportedbythesystemsoftwareasofAugust 27,1987. Futureversionsofthesoftwarewillhavethe capabilitytosupportavarietyofequipment. 3.Although mostoftheequipment inth... Open at page → 208 Page 208 soasnottooverrangeit. iv)MODESELECTAUTO-DC-AC: Thisswitchcontrols the ac-dcrelaysanddetermineswhethertherelaysare undermanualorcomputer control. Inthe'AUTO' position, bothsetsofac-dcrelaysarecontrolled bythedataacquisiti... Open at page → 209 Page 209 overvoltageoccurs,thediodesconduct,blowingoutthe thermal element serving asafuse,andprotectingthe testunitsfrombeingoverranged. Inthecasewherethe calibration voltage islessthantenvolts,aseries voltage-dropping resistorma... Open at page → 210 Page 210 muchmoreefficient methodwhenconfronted withthe outrageously slowaccesstimeoftheModel82901Mdisc driveusedonthe9816computersystem. Note: Thefollowing instructions assumethat the software beingusedisoneither5.25inchor3.5inc... Open at page → 211 Page 211 viii) K9:MENU ->: Gotosetupmenu II. Forthe instrument calibration menulistedabove,pressing theSHIFTkeydownsimultaneously withthedesired function keywillcausethesystemtocalibratean instrument using apreviously defined sta... Open at page → 212 Page 212 disc) ,andthecalibrationmaster fileswillberead fromthesystemvolume. Inthiscase,youwillnotneed tochangefloppydiscs. Attheendofasession,pressingthe'EXIT'key(either setupmenu II,K8)willreturnprocessingtotheBASIC 5.0system.... Open at page → 213 Page 213 INSTRUCTIONSONTHEUSEOFTHESYSTEMSTATUSUTILITY Thesystemstatusutility(SYSTAT)maybecalled from anyofthesupervisoryroutinesintheac-dcsoftware package. SYSTATdisplaysthepresentsystemstatus and allows you tomodifythecharacteri... Open at page → 214 Page 214 iii) K2:MODIFYSERIAL: Allowsyoutochangetheserial interface select code and to modify the transmit/receive speed, iv) K3:WRITETOFILE:WritesoutthenewIEEE-488bus informationtothesystemstatusdatafile. V)K8:SYSTATEXIT:Returns... Open at page → 215 Page 215 INSTRUCTIONSFORUSINGTHEAMPLIFIERGAINCHECKINGUTILITY Introductionandsetup 1.Usinganautomatedac-dccomparatorutilizingamplifiers andanalogintegrators entails knowingtheamplifier gainfactors andthetimeconstants oftheanalog i... Open at page → 216 Page 216 reduced,therawdataandasummaryofthedatawill bedisplayedinturn. 5.Actualchecking oftheamplifier boardbegins by measuringtheoffsetofthefirst-stageamplifierinthe standard channel . This is associated with the first-stage amp... Open at page → 217 Page 217 iii) K8: EXIT: Returnsprocessing to the master calibrationsupervisor. 10.Ifthenewlymeasuredn-testandcalibration constants aretobesaved inadatafile,pressKl: 'SAVE CONSTANTS'. YouwillbeinstructedtoinserttheBinary fileloade... Open at page → 218 Page 218 INSTRUCTIONSFORCREATINGANDMODIFYING STANDARDCALIBRATIONDATAFILES Oneoftheconsiderable advantages of automated calibration systems is theirability toperform calibrationswithinstructionsreadfromadatafileon disc. ForAutomat... Open at page → 219 Page 219 Ifafileistobecreated(KO) ,thesystemwillaskyou toinput afilename (uptoeightcharacters) tobe appendedafterthe"S_",thennotifyyouthatthefile willbecreated,andcreatethefileonthetargetdisc. Thesystemthendisplays thestandard te... Open at page → 220 Page 220 8.After K9: 'ABORTMODE' ispressed to exit the calibration pointdefinitionroutine,theprogramonce againpresentsthecatalogofstandardcalibrationfiles andtheoptionmenu. Theoptionkeysaredescribed below. 9.IfKO:'CREATEFILE'ispr... Open at page → 221 Page 221 14.K2: 'CATALOG' obtains alisting ofall standard calibrationfilesonthedisc,butreturnsprocessingto themastermenu. Toreaccess thefilemodification facility,Kl:'MODIFYFILE'mustbepressedagain. 15.Tomodifyarecord inthefile,pre... Open at page → 222 Page 222 17.Shouldastandardcalibrationfileneedtobedeleted, pressK3:'DELETEFILE'. Theprogramasksforthename ofthecalibrationfiletobedeleted, andpurgesthe filefromthedisc. ASWITHTHERECORDDELETION FACILITY,THEREISNOREDUNDANCY FORTHIS... Open at page → 223 Page 223 INSTRUCTIONS FORCREATINGANDMODIFYING STANDARDCORRECTIONTABLEDATAFILES Anadvantageofthenewautomatedsystemisitsability tostorethecorrectionstothestandardthermalvoltage andcurrentconverters inafiletobereadbythe systemuponbe... Open at page → 224 Page 224 4.ChoosingKO:'CREATEMATRIX'allowsyoutodefine a standardcorrectionfilefromscratch. Afterthekeyis pressed,aheadingispresented,andyouareaskedto enterthenameofthestandardcorrectionfiletobe created. Thisfilenamecanbeuptoeight... Open at page → 225 Page 225 9.Afterthecorrectiontableisfilled,aroutinetocheck theinputdataisrun. Thisbeginswithasetof instructions tofollow forchecking thecorrection information. Pressing CONTINUE afterreading these instructions beginsthe checking... Open at page → 226 Page 226 catalog. Tochoosethedatafileonwhichtooperate, useSHIFT-knobtomovethearrowverticallytothefile tobemodifiedandpressENTER. Ifnoneofthefiles defined onthecurrent targetdiscareofinterest, placethearrowbesidethelastentry inthe... Open at page → 227 Page 227 18.Shouldahardcopyofthecorrectiontableberequired, press K4; 'PRINTMATRIX'. Asusual,theprogramwill displaythecatalog ofalldefined correction data files, andSHIFT-knob isusedtopickthefiletobe printed. Oncethefileisreadinfr... Open at page → 228 Page 228 23.Toupdatethecorrectiontable,thethermalelementmust becheckedbothasavoltageconverterandasacurrent converter. Theprogramwillpromptyoutoenterthenew ac-dcdifferencesasavoltageconverteratthecardinal • frequenciesdefinedinthe... Open at page → 229 Page 229 INSTRUCTIONSFORCALIBRATINGANABBEYTE-20 1.Thissection covers thegeneric instructions for calibrating anAbbeyElectronics ModelTE20thermal transfer standard using "AC_DC_MSTR" . The same calibrationroutine,withsomeminorvari... Open at page → 230 Page 230 appropriatepluginresistorisemployed. Forann-test, theresistor shouldselectthe100voltrange. Make suretheresistorisinthecorrectorientation, usually withtherangemarkingreadingup. 5.Then-testroutinewillload11subroutines from... Open at page → 231 Page 231 iv)Theappliedvoltage,outputEMF,n,andthestandard deviationofthepreviouspointsinthen-test. v)Finally, the fitted characteristic response equation. Whenthevoltageisbroughtuponthedc calibrator, settheoutputswitchonthefrontpa... Open at page → 232 Page 232 12.Ifadatafileforthistestnumberalreadyexists, you mayrunanother n-test, orchoose oneoftheother options. Theseoptionsincludethefollowing: i)KO:N-TEST: Thisoptioninitiates ann-test as describedabove, ii) Kl:AC-DCDIFF. :Ini... Open at page → 233 Page 233 i)K1-K6: CONTINUE WITHMEASUREMENTS: Starts the measurementsequence, ii)K2-K7: STARTSEQUENCE: Ifnoautomatic warmup is desired,thisfunctionsinthesamemannerasK1-K6. If,however,thesystemiscurrentlyinthemidstof anautomatic wa... Open at page → 234 Page 234 menu,continuewiththesequence)aswellassuggestions forremedialactiononyourpart.Asalways, function keyK9:'HARDKILL'willdisconnecttheoutputvoltage fromtheunitsundertest, resetthesupplies, and returnprocessingtotheBallantine1... Open at page → 235 Page 235 i)ThestandardMandNhavenotbeendefinedinadata file. ii)Non-testwasrunonthetestunitandtherefore no testMandNhavebeendefined, iii)Theac-dccorrections forthestandardunithavenot beendefinedinadatafile. iv)Aseriesvoltage-droppi... Open at page → 236 Page 236 INSTRUCTIONSFORCALIBRATINGABALLANTINE1605A 1.Thissection coversthegeneric instructions for calibrating aBallantine 1605Aautomated multirange thermaltransferstandard using"AC_DC_MSTR" . Itis assumed thattheprogramisloaded... Open at page → 237 Page 237 i)KO:STARTINGVOLTS: Theinitialvoltage forthe n-test(defaultis95volts) . ii) Kl:HIGHEST VOLTS: Thefinalvoltage forthe n-test(defaultsto125volts) . iii) K2:VOLTAGESTEP:ThestepbetweenVanddV.This isdefined aseitherapercentag... Open at page → 238 Page 238 8.Asthen-testroutineruns,thevaluesreadfromthe nanovoltmeter aswellasthepresenttestparameters, aredisplayedintheappropriateplacesintherealtime display. Thisfeatureisaniceadvanceovertheolder software, inwhichtestdatatended... Open at page → 239 Page 239 iv) K3: HELP: Invokes theBallantine 1605 help facility. V)K8:EXIT: Exitstheroutine andreturns tothe ac-dcmasterprogramsupervisor, vi) K9:HARDKILL: THISKEYWILLRESETTHEVOLTAGE SUPPLIESANDOPENTHEOUTPUTRELAYTODISCONNECTTHE V... Open at page → 240 Page 240 iv) K5:SYSTEMSTATUS: Displays thepresent system status . V)K9:HARDKILL:ABORTSALLPROCESSING, RESETS THE SUPPLIES, ANDRETURNSPROCESSINGTOTHEBALLANTINE 1605COMMANDOPTIONMENU, vi)K19:SOFTKILL:Stopsprocessing butleavesthe sup... Open at page → 241 Page 241 18.Duringthecalibrationsequence,thedatagathered from thedataacquisition systemandnanovoltmeter willbe displayed inrealtime. Attheconclusion ofeach frequency, the ac-dcdifference results forthat frequencywillbesenttothecu... Open at page → 242 Page 242 properinformation andcontinue themeasurement processnormally. Uponexiting then-testorcalibration routine and returning totheBallantine1605commandoptionmenu, thefunctionkeysdefinedinthismenumaybeusedto restart atestortoex... Open at page → 243 Page 243 INSTRUCTIONSFORCALIBRATINGAFLUKE54OB 1.Thissection coversthegeneric instructions for calibrating aFluke540Bmultirangethermaltransfer standardusing"AC_DC_MSTR" .Itisassumed thatthe program isloadedandinitializedpertheinst... Open at page → 244 Page 244 vii) K6:HEADINGSOFF: Disables headings frombeing printed onthehardcopydevice(defaultisheadings on) . viii) K7: DEGREEOFFIT: Allowsthecharacteristic response equation tobefittedtoanydegree, althoughalinearfitisgenerallygo... Open at page → 245 Page 245 monitorsthestatusbyteofthedcsupplyanditsoutput voltage(viathedcvoltmeter) ,beforeeachreading. If thevoltageexceedsthenominalappliedvoltage, orif thedccalibratorself-destructs, thecomputerwillopen theoutputrelaytodisconne... Open at page → 246 Page 246 pressed, however, processing willbehaltedupon completionofthetestsequence,thesupplies will remain active, theoutput on,andanotheroption menuwillbedisplayed. 13.Thenextlogicalstepistorunanac-dccalibration, and this isinit... Open at page → 247 Page 247 where theDACscanworkwithout beingunder- or overranged. PressCONTINUE,whentheswitchisset, to continueprocessing. 16.Afterprocessingiscontinued,theprogramwillpaint a realtime displaycomposedofthefollowingfivewindows (fromt... Open at page → 248 Page 248 outputrelay,andreturnprocessingtotheFluke 54OB command optionmenu. Ifmanualshutdown hasbeen specified,thefollowingmenuisdisplayed: i)KO: REPEAT VOLTAGE*. This key repeats all frequenciesforthepresentappliedvoltage, ii) K... Open at page → 249 Page 249 INSTRUCTIONSFORCALIBRATINGAGUILDLINE7100A 1.Thissection coversthegeneric instructions for calibrating aGuildline 7100Aautomated multirange thermaltransferstandard using"AC_DC_MSTR" . Itis assumed thattheprogramisloadedan... Open at page → 250 Page 250 about 50kHz.Followtheinstructions inthemanualto setupthehigh-voltageextenderboxifneeded. Nineteensubroutineswillbeloadedfromthesupervisory disc, andseveral variable initializations andfile assignments made. If,intheorigi... Open at page → 251 Page 251 Afterprocessingiscontinued,theprogramwillpaint a realtime displaycomposedofthefollowingfivewindov/s (fromthetop) : i)Thetestnumberandinstrumentidentification, ii)Presenttestdata (theac-dcdifference anddc reversaldata) .... Open at page → 252 Page 252 i)KO: REPEATVOLTAGE: This key repeats all frequenciesforthepresentappliedvoltage, ii) Kl:REPEATFILE:Thiskeywillforcethesystemto repeatthepreviousstandardcalibration file, iii) K2:INSERTNOTE:Usethiskeytoinsertanoteon theh... Open at page → 253 Page 253 INSTRUCTIONSFORCALIBRATINGAHOLTMODEL6A 1.Thissection coversthegeneric instructions for calibrating aHoltModel6Amultirangethermaltransfer standardusing"AC_DC_MSTR" .Itisassumed thatthe program isloadedandinitializedperthe... Open at page → 254 Page 254 thesedefaults. Theoptionsavailableare: i)KO:STARTINGVOLTS: Theinitialvoltage forthe n-test(defaultis120volts) . ii) Kl:HIGHEST VOLTS: Thefinalvoltage forthe n-test(defaultsto150volts) . iii) K2:VOLTAGESTEP:Thestepbetween... Open at page → 255 Page 255 8.Asthen-testroutineruns,thevalues readfromthe nanovoltmeter aswellasthepresenttestparameters, aredisplayedintheappropriateplacesintherealtime display. Thisfeatureisaniceadvanceovertheolder software, inwhichtestdatatende... Open at page → 256 Page 256 iv) K3:HELP: InvokestheHoltModel6Ahelpfacility, v)K8:EXIT:Exitstheroutine andreturns tothe ac-dcmasterprogramsupervisor. vi) K9:HARDKILL:THISKEYWILLRESETTHEVOLTAGE SUPPLIESANDOPENTHEOUTPUTRELAYTODISCONNECTTHE VOLTAGEFROM... Open at page → 257 Page 257 iv) K5:SYSTEMSTATUS: Displays thepresent system status . V)K9:HARDKILL:ABORTSALLPROCESSING, RESETS THE SUPPLIES, ANDRETURNSPROCESSINGTOTHEHOLTMODEL 6ACOMMANDOPTIONMENU, vi)K19:SOFTKILL: Stopsprocessing butleaves the supp... Open at page → 258 Page 258 18.Duringthecalibrationsequence,thedatagathered from thedataacquisition systemandnanovoltmeterwillbe displayed inrealtime. Attheconclusion ofeach frequency, the ac-dcdifference results forthat frequencywillbesenttothecur... Open at page → 259 Page 259 properinformation andcontinue themeasurement processnormally. Uponexiting then-test orcalibration routine and returning totheHoltModel6Acommandoptionmenu,the functionkeysdefined inthismenumaybeusedto restart atestortoexi... Open at page → 260 Page 260 INSTRUCTIONSFORCALIBRATINGAHOLTMODEL11 1.Thissection coversthegeneric instructions for calibrating aHoltmodel 11coaxialthermaltransfer standardusing"AC_DC_MSTR" .Itisassumed thatthe program isloadedandinitializedperthein... Open at page → 261 Page 261 V)K4:EXECUTE: Startsthen-testprocedure, vi) K5: PRINTER OFF: Disables printouts of each individualvoltagestep(defaultisprinteron) . vii) K6:HEADINGSOFF: Disables headings frombeing printed onthehardcopydevice(defaultishe... Open at page → 262 Page 262 toavoid(oratleastlimit)anypossibledamagetothe systemandtestunits. Inthefirstcase,thecomputer monitorsthestatusbyteofthedcsupplyanditsoutput voltage(viathedcvoltmeter) ,beforeeachreading. If thevoltageexceedsthenominalapp... Open at page → 263 Page 263 thesequence, andreturnprocessing totheHolt Model11commandoptionmenu. IftheSHIFTkeyis notpressed,however,processingwillbehaltedupon completionofthetestsequence,thesupplies will remain active, theoutput on,andanotheroption... Open at page → 264 Page 264 detector switch onthefrontpanel. Thisactionwill ensurethattheoutputEMFisdivideddowntoalevel where theDACscanworkwithoutbeingunder- or overranged. PressCONTINUE,whentheswitchisset,to continueprocessing. 16.Afterprocessing... Open at page → 265 Page 265 20.Whentheautomatic calibration test sequence is complete, oriftheautomatic shutdownoptionisin effect,attheendofthefinalfrequencyonthepresent range, thesystemwillresetthesupplies,openthe outputrelay,andreturnprocessingto... Open at page → 266 Page 266 INSTRUCTIONSFORCALIBRATINGANNBSTYPECOAXIALUNIT Thissection coversthegeneric instructions for calibrating an NBStypecoaxial thermal transfer standard (suchasJulieTNB-102s, Hermach-Engelhard coaxial standards, etc.)using"A... Open at page → 267 Page 267 iv) K3:VOLTAGEINC.: Theincrementbetweensuccessive nominallevelsofappliedvoltage(defaultis5V) . V)K4:EXECUTE: Startsthen-testprocedure, vi) K5: PRINTER OFF: Disables printouts of each individualvoltagestep(defaultisprinte... Open at page → 268 Page 268 9.Inthecourseofthen-test,theappliedvoltages are setautomatically, theDACsbalanced, andthedata collectedandreducedwithnooperatorintervention. If aproblemdoesoccur,however,therearetwoprocedures toavoid(oratleastlimit)anypo... Open at page → 269 Page 269 pressed simultaneously withthen-test orac-dc differencekeys(SHIFT-KO orSHIFT-Kl) ,thenthe system will automatically reset thevoltage supplies,opentheoutputrelayuponcompletion of thesequence,andreturnprocessingtotheNBStyp... Open at page → 270 Page 270 15.Inanycase,processingresumeswiththesystemreading theEMFsfromboththetestandstandardchannel. Ifno outputismeasured,thesystempresentsanerrormessage andsuggests corrective action. Youwillthenbe instructedastotheposition in... Open at page → 271 Page 271 continueatthenextvoltagerange,withtheautomatic warmupfacilityineffect. Whentheautomatic calibration test sequence is complete, oriftheautomatic shutdownoptionisin effect,attheendofthefinalfrequencyonthepresent range, the... Open at page → 272 Page 272 optionmenu. Fromthere,pressinganykeywilltakethe actiondescribedbythatkey,andpressing 'EXIT'will exittheprogramandreturnprocessingtotheBASIC5.0 system. 258 Open at page → 273 Page 273 GENERALINSTRUCTIONS FORPREPARINGAC-DCTESTREPORTS GeneralInformation Theac-dctestreport filesare stored in the subdirectory [.REPORTS] oftheac-dcdirectoryonthe VAX.Thereports arecreated andeditedusingEVE (Extensible VAXEd... Open at page → 274 Page 274 screen. Ineithercasethefileisreadytobeedited. 5.TheEVEUsersManualislocatedinroomA-144. Theuse ofEVEisexplained quitewellandthesegeneral instructionswillnotgointoallthegorydetails. A fewpoints,however,areworthmentioning:... Open at page → 275 Page 275 crash,thejournalfilemaynotmakeittothedisc. In thiscase,youwillhavetostartoveratinstruction 4. Togetahardcopyofthereport,typeeither $PRINTfilename.RPT or $LASERfilename.RPT Inthefirstcase,theoutputwillbedirected tothe Hew... Open at page → 276 Page 276 Section15 INSTRUCTIONS FORUSINGTHEMANUALAC-DCDIFFERENCECOMPARATORSYSTEM E.S.WilliamsandC.B.Childers I.General II.PowerSuppliesandControls III.Console IV.TEComparator V.GalvanometerCircuitsandShields VI.AC-DCDifferenceTes... Open at page → 277 Page 277 I.General Thiscomparatorsystemisusedtomakeac-dcdifferencetestsofvoltageand currentconverterspluscertainothertests. Thenominalrangeoftestingis 1to1000Vfrom20Hzto100kHzand5mAto20Afrom20Hzto50kHz; however,withcertainprecaut... Open at page → 278 Page 278 II.PowerSuppliesandControls Thevoltageandcurrentsupplies, amatchingoutputtransformer, andremote controlconnections aremountedinarackwhichstandstotheleftofthe operator . DirectVoltageissuppliedbyaCohudcvoltagecalibrator,M... Open at page → 279 Page 279 Table 1 VoltageMode CurrentMode LoadResistance (Cl) 16V 40V 80V 160V 400V 800V 1600V 20 8 4 2 0.8 0.4 0.2 Short Duringanintercomparison theacanddctestvoltagesareadjustedtoproduce nearlythesameresponse (oroutput)ofthetest... Open at page → 280 Page 280 Figure3.AV-ACControl 0 ^wv'510Q _yNWv"270Q ,—Awv.150Q 200Q 820Q wwif100Q 62Q 36Q 20Q 10Q 1kS2 TenTurns Figure4.Series-Resistance Control 266 Open at page → 281 Page 281 Ill . Console Acpower isconnected tothemonitoring voltmeter andammeter andthe galvanometer lampsasshowninFig. 5. Theac-dcandav-dvtestcircuit diagramsareshowninFigs.6Aand6B. Theinputtoeachcircuitgoesthroughasmallbakelitep... Open at page → 282 Page 282 D.Theac-dc switch hasmake-before-break contacts sothat asthe instruments aredisconnected, andwhiletheyremaindisconnected, the currentsupplyvoltage isappliedatthepointsmarked"D." Ifa different dcsupplyisusedthatrequires a... Open at page → 283 Page 283 Socket Vm Am Galvos.— ^ Galvo. Ampls. i3 I 120/6.3 Power vyulie[ (z) OnOff ± Figure5.ConsolePowerSwitches Am 178Q 900900Q MM 1M 1 AC-DCVm ToDV Supply ^Coil §forJ Fig.6BAVDVCircuits Figure6.AC-DCandAV-DVCircuits 269 Open at page → 284 Page 284 IV.TEComparator Variouscomparatorcircuitscanbeusedtominimizetheeffectofpower-supply instability. Inthiscomparator avoltage-divider circuitisusedtobalance afractionofthelargeroutputEMFagainstthesmallerone. Thebalanceor nu... Open at page → 285 Page 285 Development ofEquations" Theac-dcdifferenceofaTVCisdefinedas 8= (i: whereVaisthea-cvohageandVatheaverageofthe twodirectionsofdc-vohagerequiredtoproducethe sameoutputemf.Inthecircuitoffigure6thea-c andd-cvoltagesareadjust... Open at page → 286 Page 286 Theseequationswerederivedontheassumptionthatonlyonedetectorwouldbe used. Equations (5)and(11)applyifthedetectorisamicrovoltmeter ,and theydifferonlytotheextentthateitherthetestorstandardinstrumentmay havethehigheroutput(... Open at page → 287 Page 287 V.GalvanometerCircuitsandShields Thecomparator C,galvanometeramplifiers A,andsecondarygalvanometers Gare showninFig.7.Theshieldingandshieldgroundsareindashedlines,and switchSiisclosedtoconnectthecomparatorcircuittothesam... Open at page → 288 Page 288 VI.AC-DCDifferenceTests 1.Connectthetestandstandardinstruments tothepowercables,andapplya relativelysmalldcvoltageorcurrent. 2.ConnectthetwooutputEMF'stotheEland Ejjconnectors ontheTE comparator, andbringupthedcinputtoth... Open at page → 289 Page 289 A.Applyacvoltageorcurrent,andadjusttheaccontrolsforanullonthe TGLusingthesetkey. (Thenullpositionmaychange,soitshouldbe checkedbeforemostsettings.) Holdbothkeysdown(thereadkeymaybe locked),andreadtheBGLdeflectionwhilekee... Open at page → 290 Page 290 VII.Grounding Thetestandstandardinstruments aregroundedattheacsource. The switchingcircuithasadirectconnectiontogroundwithnoswitchcontactsin thatline. Ifaswitchwereusedinthegroundline,andifitopenedan instantbeforetheonei... Open at page → 291 Page 291 VIII.CalculationofnE n=M-(E*N) Astraightline(A-B)isdrawnthroughthemost-usedportionofthenvsE plotandextendedtotheinterceptMatE=0. TheslopeNisfoundby readingthedifferencebetweenMandapointontheA-Blineatoneofthe highervalues... Open at page → 292 Page 292 IX.Low-FrequencyTests Ourcalibrationserviceextendsdownto2Hzatlowvoltagesandlowcurrents (notmorethan50Vand50mA) .MostofthestandardTE'shavesignificant ac-dcdifferences atverylowfrequencies. ThemodelC(MHz)TVC'swithUHF therm... Open at page → 293 Page 293 Section16 INSTRUCTIONSFORUSINGTHEMJTCCOMPARISONEQUIPMENT F.L.Hermach -April1981 (revisedNov.1982,July1985,April1986,andNov.1986) I.GENERAL Thisequipment issetupinRoomA144MetrologyBuildingtocomparetheac-dc differences ofm... Open at page → 294 Page 294 Stableacanddcsuppliesarevitaltohighprecision. TheModel303BKintel dcvoltagestandard, RCD-9Optimation oscillator, andPA50TOptimation amplifierarethesameonesusedin1973-1976. Theoutputtransformer inthe PA50Tisusefulonlyto30k... Open at page → 295 Page 295 V.OPERATIONOFTHEEQUIPMENT A.Connections ForTVCcomparisonsconnecttheinputsoftheTVC'sinparallelbymeansofa GR874-Tconnector. Leadimpedances cancauseserious errors athigh frequencies, sothecenteroftheteeisarbitrarilybutreaso... Open at page → 296 Page 296 NextswitchthedividertoRead-1fortwoMJTC's(oranMJTCvsanSJTC)and toRead-2fortwoSJTC's,andswitchthepotentiometer totheTCwiththe highern.Setthefirstdividerdialto0whenintheRead-2position. Turn onthepotentiometer toanappropriat... Open at page → 297 Page 297 F.ACSetting Settheacfrequency, turnontheacswitchontherelaybox,andswitchto AC,withtheRCsettoAC(i.e.,off). Bringuptheacvoltagewhile monitoring thedetector (setkeydown) ,adjustthevoltage tomakeN=0 (midscale) ,andchecktherea... Open at page → 298 Page 298 VI.MAINTENANCEOFTHESETUP A.Inspections 1.Checkthedetectorbatterybeforeeachuse. (The150Bwillnot operateproperlyevenintheacmodeifthebatteryiswaybelowpar.) 2.Checkthevariousconnections, especially thegroundleadtothe conduit... Open at page → 299 Page 299 APPENDIX 1 IndexofChangesintheMJTCSetup 1981 Feb1981 3/11/81 3/25/81 4/3/81 8/24/81 11/6/81 11/30/81 12/11/81 12/14/81 1982 1/19/82 2/12/82 4/19/82 4/22/82 4/26/82 5/5/82 6/7/82 8/27/82 9/30/82 10/7/82 10/8/82 10/25/82 1... Open at page → 300 Page 300 12/9/82 12/10/82 1983 4/18/83 5/18/83 SetupOptimationPA50Tamplifier(modified)andKrohn-HiteMT- 56Rtransformerfortheacsupply. FiTVCconnectors(GeneralRadio874)stabilizedbytinnedcopper wirewedges . Internal 15-/iFseriescapac... Open at page → 301 Page 301 REFERENCES F.L.Hermach,"Aninvestigation oftheuncertainties oftheNBSthermal voltageandcurrentconverters," Nat.Bur.Stand.(US),Rep.NBSIR84- 2903,Apr.1985. F.L.HermachandE.S.Williams,"Thermalconvertersforaudio-frequency volt... Open at page → 302 Page 302 FigureA.DiagramofMJTCSetup K Kintel303Bdcvoltagestandard 0 OptimationRCD-9oscillator A OptimationPA50Tamplifier T Krohn-HiteMT-56Rmatchingtransformer M Weston 1dcmilliammeter S ac-dcrelaybox B thermally-laggedmetaltankfo... Open at page → 303 Page 303 A.Pot'rtoE,(E,is"Test") Rq •Pot'r -vw Eh B.Pot'rto Ef,(Eh is"Test") Read-2 Pot'r Notes: Eh—HigherEiVIF E|—LowerEIVIF SK—SetKey RK—ReadKey D—Divider N—Detector P—Pot'r(200-QOutputRes.isPartofRf) Rq—50-QResistor,inTanl<(to... Open at page → 304 Page 304 Output Rei Re2 DC Line 'b — cr\jo- 30-V DCSupply RelayCoils AC DCRDCAC FigureD.RelayAC-DCTransferSwitch InsideTank Back-to-Back Zener-DlodePair TEHeater asFuse ToTC's FromAC-DCRelayBox FigureE.InputConnections atTank 290 Open at page → 305 Page 305 FORMNBS-M9 (8-B-eo) U.S.DEPARTMENTOFCOMMERCE SAMPLEDATASHEET nationalbureauofstandards TESTNO. DATE - ABCDEFGHIJK a. z V f T p t S K K r ir V rc nu a u a - a °d jj a USCOMM-DC24004-P60 291 Open at page → 306 Page 306 Section17 SCHEDULEFORRECALIBRATIONANDPERIODICCHECKS OFNBSTHERMALCONVERTERS 5-10years Recalibration ofreferencestandards,boththermalvoltageconverters (TVC's)andthermalcurrentconverters(TCC's),includingvoltageand currentbu... Open at page → 307 Page 307 TABLE2.Routinechecksforhigh-frequency thermalvoltage converterstandards.Frequency=1MHz. Voltage Standard Check TVC Standard 0.5V C1P C0.5 1V C1P TDO.D-8-1V 2V C2P TD0.D-8-3V 3V C3P TD0.D-8-3V 5V C6P C5 10V CIO TD0.D-8-10... Open at page → 308 Page 308 Section18 UNITEDSTATESDEPARTMENTOFCOMMERCE NationalBureauofStandards Gaithersburg,MarylandSOBSS REPORTOFCALIBRATION SETOFTHERMALTRANSFERSTANDARDS Manufacturer's Name ModelT,SerialNo.54321 Submittedby Company 'sName City,... Open at page → 309 Page 309 SetofThermalTransferStandards Manufacturer's (brief)NameModelT,SerialNo.54321 SubmittingCompany'sName City,State,ZipCode Itisveryunlikelythatthesevaluesofac-dcdifferenceareinerrorbymore thantheamountslistedinthetablebelo... Open at page → 310 Page 310 NBS-n4A(REV.2.8C) 1PUBLICATIONOR 2.PerformingOrgdn*ReportNo,imPublicdtionDste BIBLIOGRAPHICDATA REPORTNO. SHEET(SeeI'nstruct/ons) NIST/SP-250/27 May1989 4.TITLEANDSUBTITLE NISTMeasurementServices: AC-DCDifferenceCalibrat... Open at page → 311 Page 311 THESP250SERIESONNISTMEASUREMENTSERVICES* SP250-1 SpectralRadianceCalibrations PB87179883 SP250-2 FarUltravioletDetectorStandards PB87227609 SP250-3 RadiometricStandardsintheVacuum Ultraviolet PB87227625 SP250-4 FrickeDos... Open at page → 312 Page 312 U.S.DepartmentofCommerce NationalInstituteofStandardsandTechnology (formerlyNationalBureauofStandards) Gaithersburg,MD20899 OfficialBusiness PenaltyforPrivateUse$300 Open at page →