会计学二、TheapplicationofHallsensor1.HallmicrodisplacementsensorBecausethemagneticinductionintensityinthemiddleofthemagnetisB=0,theHallpotentialUHoutputfromHallelementisalsozero.ThenthedisplacementisΔx=0.IftheHallelementhasarelativedisplacementinthetwomagnets,themagneticfluxdensityoftheHallelementalsowillchange.ThentheUHisnotzero,whichsizewillreflecttherelativepositionchangesbetweentheHallelementandthemagnet.Thisstructuresensorhasthedynamicrangeupto5mm,andtheresolutionis0.001mm.UH∝KxFig.(b)showsasimplestructureHalldisplacementsensor,whichisasensorconsistofapermanentmagnetmagneticcircuit.WhenΔx=0,theHallvoltageisnotzero.Fig.(c)isaHalldisplacementsensorcomposedoftwosamestructuremagneticcircuits.Inordertoobtainabetterlineardistribution,themagneticpoleendiswiththepoleshoe.AdjustingtheinitialpositionoftheHallelements,HallvoltageisUH=0.Thissensorhasahighsensitivity,butthedetectingamountofdisplacementissmall.Itissuitableformeasuringmicro-displacementandvibration.2.HallrotatespeedsensorFig.7-13isseveraldifferentstructureHallrotatespeedsensors.Theinputshaftandthemeasuredshaftofmagneticwheelareconnected.Whenthemeasuredshaftisrotating,themagneticwheelisrotatingtherewith.TheHallsensorwhichisfixednearthemagneticwheelcangenerateacorrespondingpulsebythetimeeachofthesmallmagnetpassing.Measuringthenumberofpulsesperunitoftime,themeasuredspeedwillbeobtained.Thenumberofthesmallmagnetonthemagneticwheeldeterminesrotatespeedmeasurementresolutionofthesensor.1-Inputshaft;2-Rotarytable;3-magnet;4-HallsensorFig.7-13severalstructuresofHallrotatespeedsensor3.HallCountingAssemblyHallswitchsensorSL3501isanintegratedHallelementwhichhasahighsensitivity.Itcanfeelasmallmagneticfieldchange.Thus,itcanbeusedtocountthemeasuredblackmetalparts.Fig.7-14isaworkschematicdiagramandcircuitdiagramofcountingball.WhenthesteelballpassestheHallswitchsensor,thesensorwilloutputpulsevoltageofpeak20mV.AfterthevoltagemagnifiesthroughtheoperationalamplifierA(μA741),thesemiconductortriodeVT(2N5812)isdriventowork.T