>> P.337
Detectionprincipleofelectromagneticinductionscale(ABSST700,ABSAT1100)BasicoperationprincipleofelectromagneticinductionsystemL1CoilA～V2VI1I2L2CoilB[Figure1]ElectromagneticinductionsystemencoderprincipleWhenacurrent(I1)thatchangesovertimeispassedthroughcoilA,amagneticfluxiscreatedinthevicinityofcoilA.Thiscausesaninductivecurrent(I2)toflowincoilB,inadirectionthatcancelsoutthemagneticfield.Magneticpermeabilitybetweencoilsislargelyidenticalinair,water,oroil.Electromagneticinductiontypesensorhasexcellentwaterresistanceandoilresistance.PVoltage(V)DetectingcoilDisplce-mentExcitercoiPSensorsectionScalcoilDisplcementmagnitudeMulti-trackdesignallowsconfigurationofabsoluteencoderCoilsarrangedatconstantpitchonscale[Figure2]DetectionprincipleofelectromagneticinductionscaleElectromagneticinductionisaphenomenonthatoccurs,forexample,whentwocoilsarearrangedfacingeachother,asshowninFigure1,andatime-varyingcurrent(I1)ispassedthroughcoilA.Thiswillcauseaninducedcurrent(I2)toflowincoilB,inadirectionthatcancelsoutthemagneticfield.Theelectromagneticinductiontypelinearscaleusesthisphenomenontoconvertadisplacementmagnitudeintoanelectricalsignal.TheoperationalprincipleofthesensorsectionisshowninFigure2.Anumberofscalecoilsarearrangedwithprecisespacingonthemainscale.Themoveablesensorsectionthatdetectsdisplacementcarriesanexcitercoilandacorrespondingdetectorcoil.Acurrentissentthroughtheexcitercoil,therebycreatingamagneticfluxthatinducesacurrentinthefacingscalecoil.Themagneticfluxcreatedinturnbythatcurrentinducesacurrentinthefacingdetectorcoil.Thedegreeofinductivecouplingbetweenthecoilschangesaccordingtothedisplacementmagnitudeofthesensorsection,allowingasinusoidalsignalwithacyclethatcorrespondstothepitchofthescalecoilstobeobtained.Byusinganelectricalcircuitthatperformsinterpolation(division)ofthissinusoidalsignal,displacementcanbemeasuredwithfineresolution.7-60
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