Multifunction Calibration System

1 Page 1 NAFLINST.OFSTAND&TECHR.I.C. AlllOS3SMmE isurementServices: N!ST REFERENCE PUBLICATIONS; NISTMultifunction CalibrationSystem NIST Special Publication 250^6 NileOldhamandMarkParker U.S.DepartmentofCommerce TechnologyAdmini... Open at page → 2 Page 2 #heNationalInstituteofStandardsandTechnologywasestablished in1988byCongressto"assistindustryin thedevelopmentoftechnology ...neededtoimproveproductquality,tomodernizemanufacturingprocesses,to ensureproductreliability . .... Open at page → 3 Page 3 NISTSpecialPublication250-46 NISTMEASUREMENTSERVICES: NISTMultifunctionCalibrationSystem NileOldhamandMarkParker ElectronicInstrumentationandMetrologyGroup ElectricityDivision ElectronicsandElectricalEngineeringLaborator... Open at page → 4 Page 4 NationalInstituteofStandardsandTechnologySpecialPublication250-46 Natl.Inst.Stand.Technol.Spec.Publ.250-46,28pages(Feb.1998) CODEN:NSPUE2 U.S.GOVERNMENTPRINTINGOFFICE WASHINGTON: 1998 ForsalebytheSuperintendent ofDocumen... Open at page → 5 Page 5 TABLEOFCONTENTS 1.INTRODUCTION 2 2.DESCRIPTIONOFTHEMCS 3 2.1MCSHardware 3 2.2MCSSoftware 4 3.CHARACTERIZINGTHEMCS 6 3.1DCVoltage(DCV) 6 3.2DCCurrent(DCI) 8 3.3DCResistance(DCR) 10 3.4ACVoltage(ACV) 12 3.4.1Voltagesfrom1m... Open at page → 6 Page 6 NISTMULTIFUNCTIONCALIBRATIONSYSTEM NileOldhamandMarkParker ElectronicInstrumentationandMetrologyGroup ElectricityDivision NationalInstituteofStandardsandTechnology Gaithersburg,MD20899 Abstract-TheNISTautomatedMultifunct... Open at page → 7 Page 7 2.DESCRIPTIONOFTHEMCS 2.1MCSHardware' AblockdiagramoftheMCSinstrumentation isshowninFig.1.Thebasicsystemisquitesimple, consistingofacontroller,acharacterizedcalibrator(totestDMMs),andtwocharacterizedDMMs (tocalibratecali... Open at page → 8 Page 8 ThesystemcalibratorandDMMsareperiodicallycharacterizedusingthesupportequipmentand NISTreferencestandardsshowninTable2andinFig.2. Table2 SupportEquipment Function SupportEquipmentandNISTReferenceStandards DCvoltage (DCV)... Open at page → 9 Page 9 10Hz-30IVHZ 0.1Hz-1kHz 10Hz -100kHz 200rTV-1kV 1-200rrV "TT-ERMN. VOLTAGE COMzKlhRS (TVC) MCRO- POTHvmOMETERS (Mp) 1nV-7V acrrALLY SmTl-ES12ED SOURCE (DSS) 2rM-20A THERMflJ. CURRENT OOTA/eTTERS (TCQ CONTRCXIB? AND SOFTWA... Open at page → 10 Page 10 DCR UsedtocalibratetheresistancefunctionoftheMCS caHbratorandDMMs. AC-DCdiff Usedtodeterminetheac-dcdifferenceofthermal voltage/currentconvertersandmicropotentiometers. 4950MTS Softwarethatusesa4950DMMtotestacalibrator,a... Open at page → 11 Page 11 AcontrolchartwithselectedcalibratorcorrectionsisshowninFig.4.Overlongintervals,calibrator correctionstendtodriftlinearlywithtime,soaleast-squares fittothecorrectiontimeseriesis performedandalinearequationisusedtopredictt... Open at page → 12 Page 12 descriptionoftheseuncertaintytypesandmethodsofcombiningthemisgiveninSection5andin reference[6]. TheTypeBstandarduncertaintiesoftheMCScaHbratorforDCVaregiveninTable4.Thesefigures includeuncertaintiesassociatedwiththeDCVsu... Open at page → 13 Page 13 Thedccurrentcorrectionstothecahbrator C^^ci^rerelatedtothecaHbratorsettingSandtheactual calibratoroutputcurrentI^j^^.,by: IcDa=S(l+C,^„). (3) ThesystemDMMsarealsocalibratedatvariouscurrentsbythisprocedure.TheDMMcorrectio... Open at page → 14 Page 14 Table5 MCSTypeBStandardUncertaintiesforDCI CurrentRange CalibratedPoints FullRange 1|a,Ato1mA 20|aA/A+lOnA 40|iA/A+lOnA 1mAto10mA 15|iA/A 30liA/A 10mAto100mA lO^A/A 20liA/A 100mAto1A 20[lA/A 40[lAJA 1Ato10A 25\iA/A 50jiA... Open at page → 15 Page 15 DCRsupportequipmentdescribedintable2)aregiveninTable6. 4T- 3 ? 2- -4-M 1 1 1 1 1 1 1 1 1 1- 1 4 81216202428323640 Time(weeks) ^10ohms(measured) 10ohms(regression) o100k-ohms(measured) -•- 100k-ohms(regression) Fig.6.Cont... Open at page → 16 Page 16 3.4ACVoltage(ACV) Thelow-frequencyACVfunctionoftheMCScalibratorandDMMsisperiodicallycalibratedusing amultirangethermalvoltageconverter(TVC)thathasbeencalibratedagainstasetofNISTreference TVCs,micropotentiometers, andacal... Open at page → 17 Page 17 Thecalibratorcorrectionforeachtestvoltageatfrequency f- isdescribedby: CcAcvi = (V,i -V)/Ku+(e.^-ej/(nej+D.+C.^^y, (7) where V^-= (7^^^ - V_^i)/2{ave.dcvoltage} ^di = (^^di + ^-diM^ {ave.TVCemfwith±DCVapplied} n=theTVCpo... Open at page → 18 Page 18 usedtogenerateuniquecorrections C^^cvhx) forallDMMsofthattype(type-XDMMsforthis example).Thesecorrectionsapplyonlywhenatype-XDMMisconnectedtothecalibratorusingthe sameconnectorsandcablesthatwereusedtoobtainthesetofR^jrea... Open at page → 19 Page 19 TheDMMcorrectionsforeachtestvoltageatfrequency/isdescribedbythefollowingrelationship: Q = (Rr, -RJ/Rr,+(e„,-e,,)/(nej+D,+ (10) whereRj^i^ (Rro-i)+Rn)/^{ave.1-kHzreading} ^Ri ^ (^r(i-i)+ ^ri)/^{^yQ.i^potemfwith1kHzapplied... Open at page → 20 Page 20 TheDMMcorrectionforeachtestvoltageatfrequency/isthengivenby: C,,cvi=(V(l+C,,cvi)-RJ/K. (13) where =theDMMreadingofthetestvoltageat f-. 3.4.4Voltagesfrom1mVto1kVfrom0.01Hzto1kHz Aprogrammable digitallysynthesizedsource(DS... Open at page → 21 Page 21 however,becausethecorrectionsatthesepointsareinterpolatedestimates,theMCSuncertaintiesare somewhatlarger.TheTypeBstandarduncertaintiesoftheMCSACVfunctionaregiveninTable7. 60r 55 ?50 25 20 J 0102030405060708090100 Time(we... Open at page → 22 Page 22 3.5.1Currentsfrom2mAto10Afrom10Hzto100kHz ThereferenceTCCisconnectedtothesystemcahbratorandDMM(bothsettotheACIfunction)as showninFig.10.Thecahbratorisprogrammedforthenominalcurrent/atfrequency//andtheTCC outputemfe„ismea... Open at page → 23 Page 23 TheDMMcorrectionateachfrequency Q^c// isgivenby: dACIi (i(i+c,,„i)-RJ/i- (17) AsthefrequencyincreasesthecahbratorbecomesmoresensitivetotheloadimposedbytheTCCand thetestDMM.Therefore,forthehighestaccuracytestofaparticular... Open at page → 24 Page 24 understood,aleastsquareslinearfittothecorrectiontimeseriesisperformedandalinearequation isusedtopredictthecalibratorcorrectionbetweencalibrations.Thesystemsoftwarealsolinearly interpolatesbetweencalibrationpointstocomput... Open at page → 25 Page 25 Table8 MCSTypeBStandardUncertaintiesforACI CurrentRange CalibratedPoints FullRange 1mAto10A (50+2fmA/A (150+3f)>iA/A Wheref=testfrequencyinkilohertz. 4.CALIBRATIONSANDTESTSUSINGTHEMCS OncethesystemcalibratorandDMMshavebe... Open at page → 26 Page 26 Table10 ConnectionsandconfigurationforaDCIorACIcalibration From To Calibratorcurrentoutputhi DMMcurrentinputhi Calibratorcurrentoutputlo DMMcurrentinputlo Calibratorguardandground Thecalibratorisprogrammed tolocalguard,a... Open at page → 27 Page 27 CertainDMMshavesoftwarecorrectiontablesthatareusedtokeeptheinstrumentwitliinaparticular specification. CorrectiontablesareupdatedbyapplyingareferencesignalfromtheMCScalibrator andtheninitiatingaGPIB"correction"commandtha... Open at page → 28 Page 28 whichchangestheappropriatecorrectionvalueuntiltheDMMdisplaysthepropervaluetowithin aselectabletolerance. 4.3HighAccuracySpecialTestofDMMsandCalibrators ThehighestaccuracytestofaDMMorcalibratorinvolvesdirectcomparisonsaga... Open at page → 29 Page 29 1. Theac-dcdifferenceofthemuhirangeTVC,fZ/y^(see3.4) 2. Thecorrectionofthedcvoltagefunctionofthecahbrator, U^f-.(see3.1). 3. Thestandarddeviationoftheprocessinwhichthecalibratoracvoltageiscomparedtoitsdc voltage, (see3.4... Open at page → 30 Page 30 8.REFERENCES N.M.Oldham,M.E.Parker,A.M.Young,andA.G.Smith,"AHigh-Accuracy10Hz - 1MHzAutomaticACVoltageCalibrationSystem,"IEEETrans.Instrum.Meas.,IM-36, pp.883-887,Dec.1987. N.M.Oldham,"NewLow-VoltageStandardsintheDCto1-M... Open at page → 31 Page 31 THESP250SERIESONNISTMEASUREMENTSERVICES* SP250-1 SpectralRadianceCalibrations PB87179883 SP250-2 FarUltravioletDetectorStandards PB87227609 SP250-3 RadiometricStandards intheVacuum Ultraviolet PB87227625 SP250-4 FrickeDo... Open at page → 32 Page 32 33 5w S3 w o o B-s ^H9 ' (-0rt3I—) -1OP 'ii*' 3-— rti era~—— O O to o 00 I o o 1 I 3 ft n, 00o - 3 n -t n n Open at page →