6.电子感测器new

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1、Slide1ElectronicSensorsElectronicsensorscanbedesignedtodetectavarietyofquantitativeaspectsofagivenphysicalsystem.Suchquantitiesinclude:•Temperatures•Light(Optoelectronics)•MagneticFields•Strain•Pressure•DisplacementandRotation•Acceleration6.071ElectronicSensorsSli

2、de2ThermistorsSymbol:•Consistofasemiconductor,withenergygapEg(~1eV)attachedbetweentwoleads.•Temperaturedependencegivenby:bbR=R0×exp-TT0where,Egb=.2kbistypicallybetween3000and4000K.6.071ElectronicSensorsSlide3Thermistors2•Oneproblem:thermistorshaveanon-linear

3、temperatureresponse.Thiscanbehandledbymicro-computerinterpolationorparallellinearization.RRRR=0=0TotalR0+R11R1+exp-b-0TT0R1bDT»0»R-11024T20R2-b-TT0whereDT=T-T0isassumedtobesmall.•Tradeoffislinearizationreducesbsensitivitybyafactoroffour.6.0

4、71ElectronicSensorsSlide4ResistanceTemperatureDetectors•RTDsareresistorsfabricatedfromanearlypuremetal.•Duetoelectronscatteringoffthemetallatice,electronmobility,m,decreasesasTemperatureincreases.Conductivityofthedeviceiss(T)=n×q·m(T),whereniselectronconcentration

5、.•Linearoveralargetemperaturerange,butabout10timeslesssensitivethanthermistors.6.071ElectronicSensorsSlide5Thermocouples•WorkviatheSeebeckeffect,whichstatesthatcurrentwillcirculateinaloopformedbyjoiningtwosegmentsofdissimilarwiresifthetwojoiningpointsareatdifferen

6、ttemperatures.Thisisshowninthefigurebelow.metalAT1IT2metalBemfT1T26.071ElectronicSensorsSlide6ThermocoupleClassificationsThermocouplesareclassifiedbytypeasinthefollowingtable:TypeMetalA-MetalBTemperatureRange(°C)TypeEChromel-Constantan-200to+900TypeJIron-Constanta

7、n0to+750TypeKCromel-Alumel-200to+1250TypeTCopper-Constantan-200to+3506.071ElectronicSensorsSlide7MagneticFieldSensors-IntroductionSimplewire:currentB=m×n×I00#ofturnsB=B+m×Mpermeabilityof00freespaceMagnetization(dipolesalignalongB0)BB0ºHmagneticintensitym06.071Ele

8、ctronicSensorsSlide8MagneticFieldSensors-FluxgateMagnetometers•FigureshowsVacquier-typefluxgateconfiguration.•Centralcoilsaredrivenbyatime-varyingcurren