射频导纳仪表基本原理和操作课件

RFAdmittanceBasicsTheoryofOperation射频导纳仪表基本原理和操作WhatisPointLevel?什么是点位控制?PointlevelorOn/Offmeasurementindicatestheabsenceorpresenceofmaterialatacertainpointinthevessel,pit,pipe,etc…点位控制或开关量测量指示的是在容器或深井或管道里某一点被测介质的有无Pointlevelmeasurementsareusedfor点位控制主要应用于HighLevel高液位测量SpillPrevention溢出保护StopFill停止溢出LowLevel低液位测量StopEmpty防止空罐RefillIndication填充指示PumpProtection泵保护A=4.4sqIn2.1”2.1”D=1”pFTypicalValues介电常数值MaterialBetweenPlatesKCapacitanceinpFVacuum 1.0000 1.000Air 1.0006 1.0006Polyeth.Chips 1.3 1.3SoapPowder 1.55 1.55Kerosene 1.8 1.8Sand 4.8 4.8Alcohol 33 33D.I.Water 78 78DielectricConstant(K)介电常数(K)TheTankandProbeformaCapacitor

罐壁和探头形成一个电容C=kAdC=CapacitanceinpF电容pFk=DielectricConstantofmaterial介电常数A=Areaoftheplates探头测量区域d=Distancebetweenplates探头与罐壁距离kkair=1AdCkoil=2AffectsofDielectricandConductivity介电常数和电导率对电容值的影响VerticalInsulatedProbes垂直的绝缘探头InchesofLevel液位高度Cp(pF)0102030绝缘探头InsulatedProbe油Oil水WaterAffectsofDielectricandConductivity

介电常数和电导率对电容值的影响VerticalBareProbes垂直的非绝缘探头InchesofLevel液位高度Cp(pF)0102030油Oil水WaterBareProbe探头PropertiesofMaterial

物质的特性AMaterial’sphysicalpropertydoesnotaffectRFAdmittancemeasurements.物质的物理特性不会影响RFAdmittance测量.RFAdmittanceusestheproduct’selectricalpropertiestomakethemeasurement.RFAdmittance利用的是物质的导电特性来进行测量的.Physical物理特性Density密度Viscosity黏度Electrical导电特性Dielectric介电常数Conductivity导电率Conductivity(g)Scale

导电率uS1.00110K50-500Kerosene煤油MethylAlcohol甲醇OrangeJuice

果汁TapWater自来水Beer啤酒1250D.I.Water除盐水30%H2SO430%硫酸21MSeaWater海水80K90%H2SO490%硫酸2TheRFAdvantage:

射频导纳的优势:NotAffectedbyConductiveCoatings抗挂料RFAdmittance射频导纳Currentflowisnotmeasured电流未被测量Nocurrentflow没有电流Cote-ShieldNormalNormal正常CoteShieldDemonstration

CoteShield演示PointLevelTuningFork点位测量音叉TuningForkOperation

音叉的操作原理Tuningforkusespiezoelectriccrystalstodrivetheforkandmakeitvibrateatapproximately1200Hz.音叉是利用压电晶体产生振动频率(1200赫兹)来进行工作的Whenthetuningforkiscoveredintheproductthefrequencychanges当音叉被物体覆盖时振动频率发生改变.Thefrequencychangeisdetectedbytheinternaloscillatorandconvertedtoaswitchingcommand频率的改变会被内部的震荡器检测出来并把它转换成开关输出TuningFork

音叉TheTF-100seriestuningforkistobeusedoncleanliquidsonlyTF-100系列音叉仅仅是用于纯净液体的测量的Liquidapplicationsthatcontainairarenotaproblemforthetuningfork.液体中含有气泡对音叉无影响.Tuningforksshouldnotbeusedonliquidsthatcoatorcrystallize.音叉不能被用于产生黏附和结晶的液体测量TuningFork

音叉Independentofelectricalcharacteristics不受被测介质介电常数的影响Trippointrepeatability2mm重复精度2mmShortInsertionLengths可以截断插入深度Measuretotallevelinnon-dedicatedvessels可以测量液体液位Cleanliquids纯净的液体Willmeasureliquidlevelunderfoam可以测量泡沫以下的液位IgnoresFoam忽略泡沫影响Theoryof“GapSwitch”Operation

超声波测量开关的原理PiezoelectriccrystalononesideofthegaptransmitsacousticenergyPiezoelectriccrystalontheothersideofthegapactsasareceiverforthisenergy超声波测量开关有两个极板一个极板的压电晶体产生能量并且传送能量,另一个极板接收能量。Withairorgasinthegaptheenergyisnotsufficienttocrossthegaptothereceivecrystal在空气或气体中能量不足以在两个极板间传送Theoryof“GapSwitch”Operation

超声波测量开关的原理Liquidstransmitacousticenergymoreeffectivelythanairoranyothergas液体的声波能量传导性好于气体Whenliquidfillsthegap,theacousticsignalsignaltravelsthoughtheliquidtothereceivecrystalcausingtheoutputtogotothealarmcondition(highlevel当液体充满在两个极板间的时候,声波传导能量增大因此产生报警GapSwitch

超声波测量开关Independentofelectricalcharacteristics不受被测介质的介电常数的影响Trippointrepeatability1/16”重复精度1/16”ShortInsertionLengths可以截断插入长度Measuretotallevelinnon-dedicatedvessels可以测量液体液位Cleanliquids纯净的液体Willmeasureliquidlevelunderfoam可以测量泡沫以下的液位IgnoresFoam忽略泡沫影响CommonPointLevelTerminology

点位测量技术的共同点FailSafe安全保护HighLevelFail-Safe高液位安全报警Relaysde-energizewhenmaterialstouchessensingelement当介质接触到探头时,继电器会翻转LowLevelFail-Safe低液为安全报警Relaysde-energizewhenmaterialleavesthesensingelement当介质离开探头时,继电器会翻转InstallationOrientation安装方向VerticalApplication垂直安装HorizontalApplication水平安装C=KADTimeDelay时间延迟Agitator搅拌器Linepowervs.2-Wire

供电模式与.2-线制比较2-WireCurrentOutput

两线制电流输出

Intellipoint™andThePoint™OrFieldChangeabletooWhatisVerify?

校验是什么?Atestwhichmimicsahighlevelconditionwithoutactuallyraisingthelevelinthetank模拟高物位状态进行仪表测试.Availableon主要用于:HighLevelOnly高液位报警测试RFIntellipoint(TwoWireorLinePower)射频导纳RFIntellipoint两线或线路供电产品UltrasoniclinepoweredandtwowireVeriGAP超声波线路供电和两线VeriGAP产品IdealforOverfillandSpillPrevention用于溢出保护是很理想的HowRFVerifyworks

射频导纳是如何完成校验工作的IntellipointTheIntellipointproductrunsanAuto-Verifycheck3timesasecondIntellipoint产品运行自动检测功能每秒三次Thetestcomparesthecurrentcapacitancetotheaircapacitanceandindicatesafaultduetolossofsensingelementordisconnectedwiring自动测试是通过比较空气中的电容值并且指示报警由于传感器磨损或错误连线ThemanualCertifybuttonaddscapacitancethroughsoftwaretomimicahighlevelcondition