>> P.256
willvarygreatlydependingonthemethodusedforsupportingthecaliperatthetime.Also,becarefulnottousetoomuchmeasuringforcewhenusingtheoutsidemeasuringfacesastheyarefurthestawayfromthemainbeamsoerrorswillbeatamaximumhere.Thisprecautionisalsonecessarywhenusingthetipsoftheoutsidemeasuringfacesofalong-jawcaliper.SmallholemeasurementwithastandardtypecaliperAstructuralerrordoccurswhenyoumeasuretheinternaldiameterofasmallhole.øD:Trueinternaldiameterød:Measureddiametert1,t2:ThicknessoftheinsidejawC:Distancebetweentheinsidejawsd:Measurementerror(øD–ød)Trueinternaldiameter(øD:5mm)Unit:mmt1+t2+Cd0.30.0090.50.0260.70.047Ct2t1ødøDInsideMeasurementwithacaliperwithNibStyleJawsandFineAdjustmentBecausetheinsidemeasuringfacesofacaliperwithNibStyleJawsandFineAdjustmentareatthetipsofthejawsthemeasuringfaceparallelismisheavilyaffectedbymeasuringforce,andthisbecomesalargefactorinthemeasurementaccuracyattainable.IncontrasttoanM-typecaliper,aCM-typecalipercannotmeasureaverysmallholediameterbecauseitislimitedtothesizeofthesteppedjaws,althoughnormallythisisnoinconvenienceasitwouldbeunusualtohavetomeasureaverysmallholewiththistypeofcaliper.Ofcourse,theradiusofcurvatureontheinsidemeasuringfacesisalwayssmallenoughtoallowcorrectholediametermeasurementsrightdowntothelowestlimit(jawclosure).MitutoyoCM-typecalipersareprovidedwithanextrascaleonthesliderforinsidemeasurementssotheycanbereaddirectlywithouttheneedforcalculation,justasforanoutsidemeasurement.Thisusefulfeatureeliminatesthepossibilityoferrorthatoccurswhenhavingtoaddtheinside-jaw-thicknesscorrectiononasingle-scalecaliper.ForinsideonlyForoutsideonlyødøDVernierscaleThisisashortauxiliaryscalethatenablesaccurateinterpolationbetweenthedivisionsofalongerscalewithoutusingmechanicalmagnication.Theprincipleofoperationisthateachvernierscaledivisionisslightlysmallerthanamainscaledivision,sothatsuccessiveverniergraduationssuccessivelycoincidewithmainscalegraduationsasoneismovedrelativetotheother.Specically,ndivisionsonavernierscalearethesamelengthasn-1divisionsonthemainscaleitworkswith,andndenesthedivision(orinterpolation)ratio.Althoughnmaybeanynumber,inpracticeitistypically10,20,25,etc.,sothatthedivisionisausefuldecimalfraction.Theexamplebelowisforn=10.Themainscaleisgraduatedinmm,andsothevernierscaleis9mm(10divisions)long,thesameas9mm(9divisions)onthemainscale.Thisproducesadifferenceinlengthof0.1mm(1)asshowningureA(the1stverniergraduationisalignedwiththerstmainscalegraduation).Ifthevernierscaleisslid0.1mmtotherightasshowningureB,the2ndgraduationlineonthevernierscalemovesintoalignmentwiththe2ndlineonthemainscale(2),andsoenableseasyreadingofthe0.1mmdisplacement.Someearlycalipersdivided19divisionsonthemainscaleby20vernierdivisionstoprovide0.05mmresolution.However,thecloselyspacedlinesproveddifficulttoreadandso,sincethe1970s,alongvernierscalethatuses39mainscaledivisionstospreadthelinesisgenerallyusedinstead,asshownbelow.•19mmVernierscale•39mmvernierscale(longvernierscale)010203040304050607002468100123456789100.05mm19mm39mmScalereading1.45mmScalereading30.35mmCalipersweremadethatgaveanevenfinerresolutionof0.02mm.Theserequireda49-divisionvernierscaledividing50mainscaledivisions.However,theyweredifficulttoreadandarenowhardtofindsinceDigitalcaliperswithaneasilyreaddisplayandresolutionof0.01mmappeared.LongCalipersSteelrulesarecommonlyusedtoroughlymeasurelargeworkpiecesbutifalittlemoreaccuracyisneededthenalongcaliperissuitableforthejob.Alongcaliperisveryconvenientforitsuserfriendlinessbutdoesrequiresomecareinuse.Intherstplaceitisimportanttorealizethereisnorelationshipbetweenresolutionandaccuracy.Fordetails,refertothevaluesinourcatalog.Resolutionisconstantwhereastheaccuracyobtainablevariesdramaticallyaccordingtohowthecaliperisused.Themeasuringmethodwiththisinstrumentisaconcernsincedistortionofthemainbeamcausesalargeamountofthemeasurementerror,soaccuracy04-43
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