RESISTIVE SENSORS 传感与检测技术ppt课件.ppt

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1、2RESISTIVESENSORS2.1POTENTIOMETERSTheresistancebetweenthatcontactandthebottomterminal(接线端)isApotentiometerisazero-ordersystem.(2.1)2.1POTENTIOMETERSEquation(2.1)implies(意味)thefollowingsimplifications:1.theresistanceisuniform(相同的)alongthelength.2.theslidingcontactgivesasmooth

2、resistancevariation.For(2.1)tobevalid(正确)1.inductance(电感)andcapacitance(电容)canbeignoredwhensuppliedbyAC2.resistancechangesduetotemperatureareuniform3.Friction(摩擦)andinertia(惯性)ofwiper4.noiseassociationwiththewipercontactlimitsresolution.2.1POTENTIOMETERSAdvantages:SimpleRobu

3、st(结实)High-levelvoltagewithhighaccuracyrelativetoitscost.2.1POTENTIOMETERSDualpotentiometerswithasinglecontrolstick:moveinfourquadrants(象限)tolocate(定位)apointinaplane.Outputvoltage:2.1POTENTIOMETERSLiquidPotentiometer–fortilt(倾斜)measurementStructure:ahermetic(密封的),curvedvial(

4、小瓶)partiallyfilledwithaconductive(导电的)liquid,threemetalelectrodes(电极).Range:±0.5°~±60°Resolution:upto10-82.1POTENTIOMETERSRollingBallPotentiometer2.1POTENTIOMETERSLevelSensor2.1POTENTIOMETERSHydrocarbon(碳氢化合物)Sensor2.2STRAINGAGES2.2.1Fundamentals:PiezoresistiveEffectBasedont

5、hevariationofresistanceofaconductororsemiconductorwhensubjectedto(受到)amechanicalstress.Whenthewireisstressedlongitudinally(纵向的)2.2STRAINGAGESThechangeinlengthisgivenbyHooke’slaw:2.2STRAINGAGESForawirethatinadditiontoalengthlhasatransverse(横断的)dimensiont,alongitudinalstressch

6、angesbothlandt.ByPoisson’slaw,wehave2.2STRAINGAGESForawireofcircularcrosssectionofdiameterD,wehavePiezoresistiveeffect:thechangeinresistivityasaresultofamechanicalstress.2.2STRAINGAGESP.W.Bridgmanshowedthatthepercentofresistivityandvolumeareproportionalformetal:WhereCistheBr

7、idgmanconstant.Forusualalloys,1.13

8、GAGESUnlikemetal,whensemiconductorisstressed,inadditiontoitsdimensionalchan