Unitsystem
Anymeasurementmusthaveaunifiedquantitythatreflectstheunitofmeasurementasastandard.Suchaquantityiscalledameasurementstandard.Theunitofmeasurementisafixedquantitywithacleardefinitionandnameanditsvalueis1,suchasalengthunitof1meter(m),atimeunitof1second(s),etc.Theunitofmeasurementmustbedefinedonthebasisofstrictscientifictheories.Thelegalunitofmeasurementisaunitofmeasurementprescribedbythestateintheformoflawsandregulations.Itisthebasisandbasisforaunifiedsystemofmeasurementunitsandunitvalues,andthushasuniformity,authorityandlegality.
OnFebruary27,1984,whentheStateCouncilissuedthe"OrderontheUnifiedImplementationofLegalUnitsofMeasurementinmycountry",itpointedoutthat:"ThePeople'sRepublicofChina'sLegalUnitsofMeasurement"shallbeadoptedforallunitsofmeasurementinmycountry.ThelegalunitofmeasurementinmycountryisbasedontheInternationalSystemofUnits(SI)andincludes10non-SIunitsselectedbyourcountry,suchastime(minutes,hours,days),planeangles(seconds,minutes,degrees),length(Nauticalmiles),mass(tons)andvolume(liters),etc.IntheInternationalSystemofUnits,itisdividedintobasicunits,derivedunitsandauxiliaryunits.Thebasicunitsarethosephysicalquantityunitsthatcanbespecifiedindependentlyofeachother.Thereare7unitsintotal.Theyarelengthunitmeters(m),timeunitseconds(s),massunitkilogram(kg),currentunitampere(A),andthermodynamictemperature.TheunitofKelvin(K),theunitofluminousintensitycandela(cd),andtheunitofsubstanceinmoles(mol).Unitsderivedfrombasicunitsthroughdefinitions,laws,andotherfunctionalrelationshipsarecalledderivedunits.Forexample,theunitofforce,Newton(N),isdefinedas"abodywithamassof1kilogramproducesaforcewithanaccelerationof1meterpersecondtothepowerof2",thatis,1N=1kg·m/s2.Inelectricalquantities,exceptforcurrent,theunitsofotherphysicalquantitiesarederivedunits.Forexample,theunitoffrequencyisHertz(Hz),whichisdefinedas"thefrequencyofaperiodicphenomenonwithaperiodof1second",thatis,1Hz=1/s.Internationally,theunitthatcanbeusedasaderivedpotentialisseparatelyclassifiedasacategorycalledauxiliaryunit.TheInternationalSystemofUnitsincludestwoauxiliaryunits,whicharetheunitradians(rad)oftheplaneangleandtheunitsphericalangle(sr)ofthesolidangle.
Thecompletesystemconsistingofbasicunits,auxiliaryunitsandderivedunitsiscalledtheunitsystem.Theunitsystemvarieswiththechoiceofbasicunit.Forexample,afterdeterminingcentimeters,grams,andsecondsasthebasicunits,theunitofspeediscentimeterspersecond(cm/s);theunitofdensityisgramscubiccentimeters(g/cm3);theunitofforceisDyn(dyn)andsoonconstituteasystemcalledthecentimeter-gram-secondsystem.TheInternationalSystemofUnitsisaunitsystemcomposedofthe7basicunits,2auxiliaryunitsand19derivedunitswithspecialnameslistedabove.TheLatinletterSIisinternationallystipulatedastheabbreviationoftheInternationalSystemofUnits.
Metrologybenchmark
Thebenchmarkreferstothemostadvancedscienceandtechnologyandthehighestlevelofscienceandtechnology,establishedwiththehighestaccuracyandstability,andisspecificallyusedtospecify,maintainandreproduceSpecialappliancesorinstruments,etc.whichareunitsofphysicalquantitymeasurement.Accordingtothestatus,natureandpurposeofbenchmarks,benchmarksareusuallydividedintoprimarybenchmarks,secondarybenchmarks,andworkingbenchmarks,whicharealsocalledprimary,secondary,andtertiarybenchmarks,respectively.
Maindatum
Themaindatumisalsocalledtheoriginaldatum.Itisusedtoreproduceandsavethemeasurementunit.Ithasthehighestaccuracymeasurementinstrumentthatcanbeachievedbymodernscienceandtechnology.Thenationalappraisalstandardservesasthehighestbasisforunifyingthevalueofthenationalunitofmeasurement.Therefore,themainbenchmarkisalsocalledthenationalbenchmark.
Sub-standard
Ameasuringinstrumentwhosevalueisdeterminedbycomparingdirectlyorindirectlywiththenationalstandardandapprovedbythecountry.Itisusedasasecondarybenchmarkforrecurringmeasurementunitsthroughoutthecountry,anditsstatusissecondonlytothenationalbenchmark.Itisusuallyusedtoreplacethenationalbenchmarkortoverifythechangeofthenationalbenchmark.
Workingbenchmark
Afterbeingcalibratedorcomparedwiththemainbenchmarkorsecondarybenchmark,andapprovedbythestate,itisactuallyusedtoverifythemeasurementinstrumentsofthesubordinatemeasurementstandards.Itsstatusasarecurringmeasurementunitinthecountryisonlyundertheprimarybenchmarkandthesecondarybenchmark.Thepurposeofsettingtheworkingreferenceistopreventtheprimaryreferenceorthesecondaryreferencefromlosingitsoriginalaccuracyduetofrequentuse.Itshouldbeunderstoodthatthebenchmarkitselfdoesnotnecessarilyequalexactlyoneunitofmeasurement.Forexample,thetimevaluereproducedbythecesium-133atomicfrequencyreferenceisnot1s,but(919261770)-1s.Thereproducedvoltagevalueofthestandardbatteryis1.0186V,not1V,etc.
Relatedconcepts
Severalrelatedconceptsinvolvedinthetransferandtrackingofthevalue
Thetransferandtrackingofthevalue
Thetransferandtrackingofthevalueistoaccuratelytransferaphysicalquantityunittothemeasuringinstrumentsandmeasuringtoolsusedindailyworkthroughvariouslevelsofbenchmarks,standardsandcorrespondingauxiliarymeanstoensurethewholeprocessoftheunityofthevalue.
Measuringequipment
Reproducedvalueormeasuringtools,instruments,anddevicesthatcanbemeasuredandconvertedintodirectlyobservableindicationvaluesorequivalentinformation.
Measuringstandardinstruments
Measuringinstrumentswhoseaccuracyislowerthanthemeasurementstandardandusedtoverifymeasurementstandardsorworkingmeasurementinstruments.Itcanbeclassifiedaccordingtoitsaccuracylevel,suchaslevel1,level2,level3,level4,andlevel5standardweights.Standardinstrumentscanbedividedintothreecategoriesaccordingtotheirlegalstatus:
(1)Socialpublicmeasurementstandardsrefertothoseestablishedbythemeasurementdepartmentsoflocalgovernmentsatorabovethecountylevelasthebasisforunifyingthemeasurementvaluesintheregion,andtoimplementmeasurementforthesocietySupervisevariousmeasurementstandardswithanotarizationfunction.
(2)Themeasurementstandardsusedbythedepartmentarethevariousmeasurementstandardsestablishedbytherelevantcompetentdepartmentsofthegovernmentatorabovetheprovincialleveltounifythevalueofthedepartment.
(3)Themeasurementstandardsusedbyenterprisesandinstitutionsarevariousmeasurementstandardsestablishedbyenterprisesandinstitutionsasthebasisforthevalueoftheunit.
Workingmeasuringinstrument
Itisameasuringinstrumentusedintheworkplacenottotransferthevaluebutdirectlytomeasurethevalueofthemeasuredobject.
Comparison
Underspecifiedconditions,comparethemeasurementvaluesbetweensimilarbenchmarks,standardsorworkingmeasuringinstrumentsofthesameaccuracylevel,thepurposeofwhichistoassessthemeasurementvalueconsistency.
Verification
Verificationreferstocomparingmeasuringinstrumentswithahigherlevelofaccuracytomeasuringinstrumentswithalowerleveltoachieveacomprehensiveassessmentofwhetherthemeasurementperformanceofthetestedmeasuringinstrumentsisqualifiedthegoalof.Generally,theaccuracyofthemeasurementstandardisrequiredtobe1/10to1/3ofthatoftheexaminee.
Calibration
Calibrationreferstothecomparisonbetweenthecalibratedmeasuringinstrumentandtheone-levelmeasurementstandardtodeterminetheindicationerrorofthecalibratedmeasuringinstrument(sometimesincludingdeterminingthecalibrationOthermeasurementperformanceoftheappliance).Generallyspeaking,thecontentoftheverificationismoreaccurateandcoversawiderrange.