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招惠玲1,周美娟2,胡远忠1(1.,524088;2.,524088):,,ADC0809,8031,2764,8155LED,:,:;;:TP212:A:1000-9787(2004)03-0040-03DesignofcapacitivesystemforliquidlevelmeasurementZHAOHu-iling1,ZHOUMe-ijuan2,HUYuan-zhong1(1.DeptofMach,ZhanjiangOceanUniversity,Zhanjiang524088,China;2.DeptofElctandInfoEngin,ZhanjiangOceanUniversity,Zhanjiang524088,China)Abstract:Capacitivesystemforliquidlevelmeasurementcanmeasuretheliquidlevelaccordingtotheprinciplewhichcapacitancevalueischangedwiththedielectricconstant.Thesystemwhichconsistsofcapacitivesensorandsinglechipprocessorof8031,ADC0809,2764and8155,andlightemittingdiode(LED)isusedtomeasuretheliquidlevelofcoaloil.Itcanenacttheliquidlevel,showthepresentliquidlevelandgiveanalarmwithvoiceandlight.Theexperimentshowsasfollows.Itcanmeasuretheliquidlevelofconductiveliquid,anditsstructureissimple,itspriceislower,itsperformanceisstable.Keywords:capacitivesensor;liquidlevel;measuresystem0,,,,[1],,,-,;,:2003-10-09,,1,[2]11Fig1Liquidlevelmeasurementofconductiveliquid40(JournalofTransducerTechnology)20042331H=0,,[3],C0=20Lln(D0/d),(1)C0,F;0,F/m;L,m;D0,m;d,mH,CHCH=20(L-H)ln(D0/d)-2Hln(D0/d),(2),F/m;D,m,H,CC=2Hln(D/d)-20Hln(D0/d).(3)D0D,0,,,C2Hln(D/d).(4),,,Dd,2,[4],22Fig2Circuitofliquidlevelmeasurementusingcapacitivesensor,,,,E1,E2,f;Cd,Cx,A/(A),U00,Cd0H,U0,U0=AfC(E2-E1)Af(E2-E1)2H/ln(D/d).(8)8031[5,6],3,A/D3Fig3Structuraldiagramofmeasuresystem,ADC08098031P2.7WR(START)ALT,ADC0809ADDA,ADDB,ADDC,ADC0809IN07FF8H,IN0ADC08098031ALEA/D,8031LED,74LS37327648155I/O,2764CE,,LS7406ADC0809OE27648000H~FFFFH150~9,5,11Tab1Sheetofkeyboardvalues/0AH0BH0CHODH0EH,,:LED;LED,,,,,,,8031P1.0,,,P1.27406413:,31,d=10mm,D=20mm,L=3m,r=2.0OPA128FET/,QW1630[7],10Hz,2.5V,0.5V22(25)Tab2Voltagevaluesindifferentliquidlevel(25)H(m)U0(V)U1(V)0.41.28351.28340.82.56702.56491.23.85053.85011.65.13405.13392.06.41756.41692.47.70107.70022.88.98458.9838,0.08%4,0.001%[8],,,:(1);(2),,,:[1],.[M].:,2002.93.[2],,,.[M].:,2000.168-198.[3].[M].:,1999.148.[4].[M].:,2002.548.[5],,,.[J].,2001,8:12-14.[6].[M].:,1999.119-129.[7].[M].:,1988.357.[8].[M].:,2001.291.:(1964-),,,,(39)1R,G,B,1CMUcamTab1MeasuringtestresultofCMUcamvsionboardRGBRGB24935105250101627248510814253134210,,:(1),;(2);(3)4,,,,[2]CMUcam,,:[1],,.[J].,2002,33(4):12-14.[2],.[J].,2002,23(3):20-23.:(1963-),,,.4223