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P.O.Box2509•112FlintRoad•OakRidge,TN37831-2509Phone:[phone]•Fax:[phone]E-mail:[e-mail]rumentsTheAMIfamilyofliquidheliumlevelinstrumentsofferawiderangeofsolutions.AllinstrumentspassaconstantcurrentthroughasuperconductingNiobiumTitanium(NbTi)filamentandmeasuretheresistance.Theportionofthefilamentinliquidheliumbecomessuperconducting(i.e.noresistance).Theresultingresistanceofthewireabovetheliquidisconvertedtoalevelsignal.Advancedcircuitdesignsofferourcustomersmanyadvantages.Yearsoftroublefreeservicearetheresultofruggedconstructionbothinsideandout.Allourinstrumentsandsensorsfrom1”to36”arestockitemsforquickdelivery.Ourexperiencedstaffofferspromptrepairservicewhenneeded.OEMinstrumentdesignandmanufacturingpartnershipsarealwayswelcomedifourstandardproductsdonotmeetyourneeds.APPLICATIONS•MagneticResonanceImagingSystems•ScientificLaboratories•UniversityResearchGroups•IndustrialGasProducers/DistributorsLIQUIDHELIUMSENSOROPTIONS•Spray-proofsensorsforturbulentliquefierreturnchambers•Vacuum-tightmountingconnections•Highradiationenvironmentsensors•StainlesssteeltubesensorsOUTPUTOPTIONSAMI’sLiquidHeliuminstruments(Models135,135-2K,and136)maybeconfiguredwithupto(1)Analogand(1)Digitaloutput•Analog0-10VRecorderoutput•Analog4-20mAoutput•DigitalRS-232,RS-422,orIEEE-488(GPIB)output•LabViewdriversaresuppliedwithalldigitaloutputoptionsModel135&135-2KLiquidHeliumLevelMonitor........TheModels135&135-2KareadvancedliquidheliumlevelmonitorswhichincorporateAMI'spatentedsample-and-holddesignwithautomaticheliumlevelsensorvacuumburnoutprotection.TheModel135isidealforoperationinsystemswhereitisimportanttomonitortheliquidheliumlevelwhilealsominimizingtheheliumlosses.The135-2Khastheadditionalabilitytoprovideuninterruptedlevelreadingsoveratemperaterangeof1.8to4.2K.TheModel135-2KisidealforoperationinsystemswhereitisimportanttomonitortheliquidheliumlevelwheretransitionsthroughtheLambdaPointareneeded.AMIhighlyrecommendsusingthespeciallydesigned2Kheliumlevelsensorwiththe135-2Kinstrumentforbestresults.FEATURES:MinimalLiquidHeliumLosses(Sample-and-HoldSensing)Inordertominimizeliquidheliumloss,theseinstrumentsautomaticallyenergizetheliquidheliumlevelsensoratusersettimeintervalsandmonitorthenormal(resistive)zoneasitprogressesfromthetopofthesensortowardtheliquidsurface.Assoonasthenormalzonereachestheliquidsurface,thelevelreadingissavedandthecurrentinthesensoristurnedoffuntilthenextsampleintervaloccurs.AnLEDsensorcurrentindicatorisilluminatedduringeachsample.Sampleintervalsareusersetfromthefrontpanelbetween0.0(continuousreading)to600.0minutesorhours.Amanualupdateswitchprovidedonthefrontpanelcanalsobesettoobtaincontinuousreadingsduringaheliumtransferperiodortomanuallyforceanimmediatemeasurement.HighandLowAlarmFunctionsThesemodelsaddHighandLowalarmsetpointswhichactivatefrontpanelLEDwarningindicatorsandrearpanelrelayoutputsintheeventofanoverfillorliquidlosscondition.Thealarmsalsoenergizeanaudiblewarningwhichcanbesilencedfromthefrontpanel.HighandLowsetpointsareusersetfrom0to100percentofsensoractivelength.SensorBurnoutProtectionTheseinstrumentsprovideautomaticheliumlevelsensorvacuumburnoutprotection.Aliquidheliumlevelsensorenergizedinavacuumenvironmentwillself-heattothepointofburnoutwithinseconds.AMI’sinnovativemicroprocessor-basedcircuitrydetectsincipientsensorburnoutandde-energizesthesensorbeforedamagecanoccur.A5%increaseinsensorresistancewilltriggerthisprotection,causingthecurrenttobeswitchedofffor6secondsbeforeattemptingtoresumenormaloperation.IceBuildupPreventionThede-icing/dirtysensorfeaturegivestheuseranoptiontoincreasethesensorcurrentforashorttimeatthebeginningofeachsample.Thisfeatureissometimesusefulforremovingiceorotherdepositsfromasensorthatmaycausefalsereadings.SensorLengthStandardsensorsupto80inlengthareavailable.Customconfigurationsareavailableupto98inlength.Theseinstrumentsareeasilyreconfiguredfordifferentsensorlengthsfromthefrontpanelwithouttheneedtorecalibratetheinstrument.LowExcitationCurrentAMIliquidheliumlevelmonitorsuselowexcitationcurrents(100mA)whichresultsinlowerheliumconsumption.Model136LiquidHeliumLevelController.........................AMIoffersafulllineof4-wireliquidheliumlevelsensors.4-wiresensorsinsureaccuracybyeliminatingdifferingleadwireresistance;acommoncauseoffalsesignalswith3-wiresensors.AMIsensorsareconstructedofG-10tubingwithsizesof3/16,1/4,and3/8.Flexiblesensorsof3/32or5/16diametertubingareavailableforapplicationswherethesensormustconformtothecurvatureofahorizontalaxisdewarsuchasMRsystems.Standardleadwiresare28AWGTefloninsulatedcopperwire.Otherleadwiresavailable.ThisinnovativedesignincorporatesastandardAMIliquidheliumlevel-sensorintothelower22inchesofthesupplysidetransferleg.Thisallowstheusertomonitorthedecreasingheliumlevelinthesupplydewarandstopthetransferbeforehotgasisblownintothetargetdewar.AnyAMIliquidheliumlevelinstrumentcanbeusedtomonitorthelevelviathesignalcableattachedtoa4-pinelectricalconnectoronthetransferline.Thetransferlineisvacuumjacketedwithsuper-insulati