>> P.546
9mm(9graduationlines)(1)0.1mm0.1mmDiviedinto10equaldivisionsAB(2)AlignedCalipersVernierScaleThisisashortauxiliaryscalethatenablesaccurateinterpolationbetweenthedivisionsofalongerscalewithoutusingmechanicalmagnication.Specically,ndivisionsonavernierscalearethesamelengthasn-1divisionsonthemainscaleitworkswith,andndenesthedivision(orinterpolation)ratio.Theexamplebelowisforn=10.Themainscaleisgraduatedinmm,andsothevernierscaleis9mm(10divisions)long,thesameas9mm(9divisions)onthemainscale.Thisproducesadifferenceinlengthof0.1mm(1)asshowningureA(the1stverniergraduationisalignedwiththerstmainscalegraduation).Ifthevernierscaleisslid0.1mmtotherightasshowningureB,the2ndgraduationlineonthevernierscalemovesintoalignmentwiththe2ndlineonthemainscale(2),andsoenableseasyreadingofthe0.1mmdisplacement.SmallHoleMeasurementwithanM-typeCaliperAstructuralerrordoccurswhenyoumeasuretheinternaldiameterofasmallhole.●Trueinternaldiameter(øD:5mm)Unitmmt1+t2+C0.30.50.7Δd0.0090.0260.047øD:Trueinternaldiameterød:Measureddiametert1,t2:ThicknessoftheinsidejawC:DistancebetweentheinsidejawsΔd:Measurementerror(øD–ød)øD-ødCt2t1ødøDfacesandthemeasuringInsideMeasurementwithaCM-typeCaliperBecausetheinsidemeasuringfacesofaCM-typecaliperareatthetipsofthejaws,attentionmustbegiventomeasuringforce.Additionally,theparallelismofjawsareproblematic.Theradiusofcurvatureofthemeasuringfacesmustbelessthan1/2ofthecombineddimensionsoftheinsidemeasurementsection.IncontrasttoanM-typecaliper,aCM-typecalipercannotmeasuresmallholesbelowthecombinedmeasurementsize.MitutoyoCM-typecalipersareprovidedwithanextrascaleonthesliderforinsidemeasurementssotheycanbereaddirectlywithouttheneedforcalculation.Theeliminationofcalculationsreducesmeasurementerrors.stepdifferencesoftheSomeearlycalipersdivided19divisionsonthemainscaleby20vernierdivisionstoprovide0.05mmresolution.However,thecloselyspacedlinesproveddifficulttoreadandso,sincethe1970s,alongvernierscalethatuses39mainscaledivisionstospreadthelinesisgenerallyusedinstead,asshownbelow.•19mmVernierscale(longvernierscale)Vernierscale•39mmvernierscale30405030405000101020203030404060607070AboutLongCalipersSteelrulesarecommonlyusedwhenmeasuringtoalimitedaccuracy.LongCalipersareusedthanaSteelRule,butlessthanaMicrometer.Alongcaliperisveryconvenientforitsuserfriendlinessbutdoesrequiresomecareinuse.•Minimumreadingandindicationerrordiffer(seeMitutoyo’scatalogfurtheraccuracyforvaluesfordetails)•Payattentiontohowthecalipersaresupported,asmeasurementerrorsduetodeflectiontendtooccur.•Whenusingtheinsidemeasuringfaces,payattentiontomeasuringforceasthefacesarefurthestawayfromthereferencesurface.•Whenusingalong-jawcaliper,payattentiontomeasuringforceevenwhenusingtheoutsidemeasuringfaces.13-19ødøDForoutsideonlyGeneralNotesonUseofCaliper1.PotentialcausesoferrorThemainfactorsbehindcalipererrorsare:•Excessivemeasuringforce•Differentialthermalexpansionduetoatemperaturedifferencebetweenthecaliperandworkpiece•Effectofthethicknessoftheknife-edgejawsandtheclearancebetweenthesejawsduringmeasurementofthediameterofasmallhole•Graduationaccuracy•Referenceedgestraightness•Mainscaleatnessonthebeam•SquarenessofthejawsThereisnoproblemwiththecaliperiftheseerrorfactorsarewithintheindicationerror.HandlingnoteshavebeenaddedtotheJISsothatconsumerscanappreciatetheerrorfactorscausedbythestructureofthecaliperbeforeuse.Thesenotesrelatetothemeasuringforceandstipulatethat“asthecaliperdoesnothaveaconstant-forcedevice,youmustmeasureaworkpiecewithanappropriateevenmeasuringforce.Takeextracarewhenyoumeasureitwiththerootortipofthejawbecausealargeerrorcouldoccurinsuchcases.”Calipers0246486108100102132456789810100.05mm0.5mmForinsideonly1919Reading:1.45mm3939Reading:30.35mmthatgaveCalipersweremade0.02mm.Theserequireda49-divisionvernierscaledividing50mainscaledivisions.However,theyweredifficulttoreadandarenowhardtofindsinceDigitalcaliperswithaneasilyreaddisplayandresolutionof0.01mmappeared.resolutionevenfineranof
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