User Manual

Auto‐Ohm200S3/DMOM‐200S3/DMOM‐600USER’SMANUAL REV2
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1.2 DMOM-200 S3 General Description and Features
TheDMOM‐200S3isVanguard’sfourthgeneration,microprocessor‐based,trueDCmicro‐
ohmmeter.ItisdesignedfortestingEHVcircuit‐breakercontactresistances,bushingcontact
joints,weldingjoints,orforanylow‐resistancemeasuringapplication.Thishighcurrentand
verylightweight(19.8lbs/8.9Kg)micro‐ohmmeteris
designedtomeettheIEEEC57.09‐1999
(5.15)requirementfortestingcircuitbreakercontactresistance.
TheDMOM‐200S3canaccuratelymeasureresistancevaluesfrom1micro‐ohmto5ohms.A
0.1micro‐ohmresolutionispossiblewithcurrentgreaterthan5A.TheDMOM‐200S3appliesa
selectabletrue
DCtestcurrentfrom1Ato200Atotheresistanceloadtobetested.The
DMOM‐200S3controlsthetestcurrent’sriseandfallrates.Thetestcurrentriseandfallrate
canbeselectedfrom5secondsto10seconds.An“AutoTest”modeisalsoavailableandcanbe
initiatedsimplybyapplyingthesensecables’leadsacrossthetwopointsofinterestinthe
currentpath.Thisfeatureisveryconvenientwhenmeasuringasequenceofseveralresistance
valuesinacircuitbreakercontact.TheDMOM‐200S3canalsocomparetestresultsagainst
presetlimitsanddetermineifatestpassedorfailed,anda“Pass”or“Fail”flagisdisplayed
accordingly.
SinceatrueDCcurrent(withcontrolledrise/falltime)ispassedthroughthecircuitbreaker
contact,nomagnetictransientisinducedintothebreaker’scurrenttransformers.Thisfeature
greatlyreducestheriskofinductivelytrippingabreakercontrol(busdifferentialrelay).
WiththeDualGroundoption,theDMOM‐200S3canalsomeasurethecircuitbreakercontact
resistancewithbothsidesofthebreakerbushingbeinggrounded.Whenatestcurrentis
appliedtoacircuitbreakerwithbothsidesgrounded,someofthetestcurrentflowsthrough
thesafetygroundcables.Usinganexternalcurrentsensor,theDMOM‐200S3measuresand
eliminatesthiscurrentfromthetotaltestcurrent.TheDMOM‐200S3thencalculatestheactual
resistancevalueofthecircuitbreaker.
TheDMOM‐200S3featuresaback‐lit128x64pixelLCDscreenthatisviewableinbothdirect
sunlightandlowlightlevels.TheresistancereadingsaredisplayedontheLCDscreeninmicro‐
ohmsormilliohms.Theunitisoperatedviaaconvenient44‐key“QWERTY”keypadonthefront
panel.TheDMOM‐200S3canstore128recordsof64readingsinternally,andup999test
recordsonanexternalUSBFlashdrive.Testheaderinformation(Company,Substation,circuit
breakerID’s)canalsobeenteredusingthe44‐keykeypadandisstoredwitheachtestrecord.
TheDMOM‐200S3alsofeaturesabuilt‐in2.5”widethermalprinterthatcanbeusedtoprint
testreportsinthefield.
Windows®based(XP/Vista/7)analysissoftwareisprovidedwitheachunitandcanbeusedto
remotelycontroltheDMOM‐200S3viatheRS‐232Cport.Usingthissoftware,theusercan
retrievetestrecords(fromthe
unit’smemoryoraUSBFlashdrive),analyzetestresults,and
printtestresultsonadesktopprinter.TestresultscanalsobeexportedtoPDF,Excel,andXML
formats.