>> P.257
Generalnotesonuseofthecaliper1.PotentialcausesoferrorAvarietyoffactorscancauseerrorswhenmeasuringwithacaliper.Majorfactorsincludeparallaxeffects,excessivemeasuringforceduetothefactthatacaliperdoesnotconformtoAbbe'sPrinciple,differentialthermalexpansionduetoatemperaturedifferencebetweenthecaliperandworkpiece,andtheeffectofthethicknessoftheknife-edgejawsandtheclearancebetweenthesejawsduringmeasurementofthediameterofasmallhole.Althoughtherearealsoothererrorfactorssuchasgraduationaccuracy,referenceedgestraightness,mainscaleatnessonthemainblade,andsquarenessofthejaws,thesefactorsareincludedwithintheEMPEerrortolerances.Therefore,thesefactorsdonotcauseproblemsaslongasthecalipersatisestheEMPEerrortolerances.HandlingnoteshavebeenaddedtotheJISsothatconsumerscanappreciatetheerrorfactorscausedbythestructureofthecaliperbeforeuse.Thesenotesrelatetothemeasuringforceandstipulatethat“asthecaliperdoesnothaveaconstant-forcedevice,youmustmeasureaworkpiecewithanappropriateevenmeasuringforce.Takeextracarewhenyoumeasureitwiththerootortipofthejawbecausealargeerrorcouldoccurinsuchcases.”LøDL<øD2.InsidemeasurementInserttheinsidejawasdeeplyaspossiblebeforemeasurement.Readthemaximumindicatedvalueduringinsidemeasurement.Readtheminimumindicatedvalueduringgroovewidthmeasurement.3.DepthmeasurementReadtheminimumindicatedvalueduringdepthmeasurement.4.ParallaxerrorwhenreadingthescalesLookstraightattheverniergraduationlinewhencheckingthealignmentofverniergraduationlinestothemainscalegraduationlines.Ifyoulookataverniergraduationlinefromanobliquedirection(A),theapparentalignmentpositionisdistortedbyXasshowninthegurebelowduetoaparallaxeffectcausedbythestepheight(H)betweentheplanesoftheverniergraduationsandthemainscalegraduations,resultinginareadingerrorofthemeasuredvalue.Toavoidthiserror,theJISstipulatesthatthestepheightshouldbenomorethan0.3mm.AHΔX5.MovingJawTiltErrorIfthemovingjawbecomestiltedoutofparallelwiththexedjaw,eitherthroughexcessiveforcebeingusedonthesliderorlackofstraightnessinthereferenceedgeofthebeam,ameasurementerrorwilloccurasshowninthegure.ThiserrormaybesubstantialduetothefactthatacaliperdoesnotconformtoAbbe’sPrinciple.f=h=h·a/ℓθahhfExample:Assumethattheerrorslopeofthejawsduetotiltoftheslideris0.01mmin50mmandtheoutsidemeasuringjawsare40mmdeep,thentheerror(atthejawtip)iscalculatedas(40/50)×0.01mm=0.008mm.Iftheguidefaceiswornthenanerrormaybepresentevenusingthecorrectmeasuringforce.6.RelationshipbetweenmeasurementandtemperatureThemainscaleofacaliperisengraved(ormountedon)stainlesssteel,andalthoughthelinearthermalexpansioncoefcientisequaltothatofthemostcommonworkpiecematerial,steel,i.e.(10.2±1)×10-6/K,notethatotherworkpiecematerials,theroomtemperatureandtheworkpiecetemperaturemayaffectmeasurementaccuracy.jawsaresharp,andthereforethe7.HandlingCalipercaretoavoidpersonalinjury.Avoiddamagingthescaleofadigitalcaliperanddonotengraveanidentificationnumberorotherinformationonitwithanelectricmarkerpen.Avoiddamagingacaliperbysubjectingittoimpactwithhardobjectsorbydroppingitonabenchorthefloor.instrumentmustbehandledwith8.MaintenanceofbeamslidingsurfacesandmeasuringfacesWipeawaydustanddirtfromtheslidingsurfacesandmeasuringfaceswithadrysoftclothbeforeusingthecaliper.9.CheckingandsettingtheoriginbeforeuseCleanthemeasuringsurfacesbygrippingasheetofcleanpaperbetweentheoutsidejawsandensurethatthevernierscale(ordisplay)readszerobeforeusingthecaliper.WhenusingaDigimaticcaliper,resettheorigin(ORIGINbutton)afterreplacingthebattery.jawsandthenslowlypullingitout.ClosetheORIGINbuttonsetsdisplaytozeroBatteryClosejawscompletely10.HandlingafteruseAfterusingapplyanti-corrosionoilandletitdrybeforestorage.Wipeoffwaterfromawaterproofcaliperaswellbecauseitmayalsorust.thecaliper,completelywipeoffanywaterandoil.Then,lightly11.NotesonstorageAvoiddirectsunlight,hightemperatures,lowtemperatures,andhighhumidityduringstorage.Ifadigitalcaliperwillnotbeusedformorethanthreemonths,removethebatterybeforestorage.Donotleavethejawsofacalipercompletelyclosedduringstorage.04-44
| < 
| 
> | 
>>
