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TechnicalInformationExplanationoftermsLinearscaleaccuracy1)LinearscaleindicationaccuracyAsshowninFigure1,theaccuracyofalinearscaleisdeterminedbycomparingthepositionalvalueindicatedbythelinearscalewiththereferencevaluefromalaserlengthmeasuringmachineatregularintervalsusingtheaccuracyinspectionsystem.Theinspectionenvironmenttemperatureis20°C,sotheaccuracyisatthistemperature.TheinspectionsareperformedwithotherinspectionconditionsandstandardvaluesthatcomplywithMitutoyo'sinternalstandards.LaserlengthmeasuringmachinecounterPCDigitalcounterLasersourceInterferometerOpticalaxisoflaserbeamCubecornerFixtureScaleunitMovabletable[Figure1]Linearscaleaccuracyinspectiondevice,overviewTheaccuracy(error)ateachmeasuredpointisdeterminedaccordingtothefollowingformula.Error=referencevalueindicatedbythelaserlengthmeasuringmachine–CorrespondingvalueindicatedbythelinearscaleHere,thewords"accuracy"and"error"havethesamemeaning.Werefertotheplotonagraphoftheerrorateachmeasuredpointintheeffectiverangeasanaccuracychart.Basedonthisaccuracychart,theaccuracyofthelinearscaleisnotedastherangebetweenthemaximumerrorandminimumerror.Therearethefollowingtwonotationmethods.(1)Notethesizeoftherangebetweenthemaximumerrorandminimumerroras'a'.Thevalue'a'showninFigure2-1indicatestheaccuracy.Thisstandardvalueisindicatedusingtheconversionformula(eachmodel.Forexample,foralinearscalewithanaccuracystandardvalueof(3+3L/1000)µmandaneffectiverangeLof1000mm,'a'is6µm.L)µm.Here,Listheeffectiverange(inmm)and+andarecoefficientsthatareseton(2)Notethesizeoftherangebetweenthemaximumerrorandminimumerroras'±a/2'.Thecentervaluebetweenthemaximumerrorandminimumerroris0,themaximumvalueisnotedas'+a/2',theminimumvalueisnotedas'-a/2',andthesizeoftheerrorrangeisnotedas'±a/2'.ThisnotationismainlyappliedtoSTscales.Innotations(1)and(2),'a'in(1)and'±a/2'in(2)arethesameaccuracystandardvalue.Linearscalesuseastraight-linescalethathasfixed-pitchgraduationsasthereferencetodetecttheamountofmovementandtheamountofchangeinposition.Bydetectinggraduations,alinearscaleobtains2-phasesinusoidalsignalsthathavethesamepitchasthegraduations.Thelinearscaleisdesignedsothatitcanperformreadingswithgreaterdetailthanthestraight-linescalebyinterpolatingthissinewavesignalwithanelectroniccircuit.Interpolationmeansthatthese2-phasesinusoidalsignalsareinterpolated,andtheresultisdividedintopulsesignalscorrespondingtotheresolution.Forexample,ifthegraduationpitchis20µm,readingscanbeperformedwitharesolutionof1µm.Here,errorwithinthegraduationpitchrangewilloccuraccordingtotheaccuracyofthisinterpolationprocessing.Thisiscalledinterpolationaccuracy.Theaccuracystandardvalueofalinearscaleincludestheaforementionederrorsinspectedatfixedintervalsandinterpolationaccuracy.Accuracychart(errorplot)Accuracy:a(µm)aEffectiverangeX:Measurementposition[Figure2-1]Accuracynotationmethod(1)Accuracy:±a/2(µm)a2±EffectiverangeX:Measurementposition[Figure2-1]Accuracynotationmethod(2)εError0εError07-55
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