User Manual

Auto‐Ohm200S3/DMOM‐200S3/DMOM‐600USER’SMANUAL REV2
2
1.0 INTRODUCTION
1.1 Auto-Ohm 200 S3 General Description and Features
TheAuto‐Ohm‐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(16.8lbs/7.6Kg)micro‐ohmmeteris
designedtomeettheIEEE
C57.09‐1999(5.15)requirementfortestingcircuitbreakercontactresistance.
TheAuto‐Ohm‐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Auto‐Ohm‐200S3
appliesa
selectabletrueDCtestcurrentfrom1Ato200Atotheresistanceloadtobetested.
TheAuto‐Ohm‐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Auto‐Ohm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trip‐pingabreakercontrol(busdifferentialrelay).
WiththeDualGroundoption,theAuto‐Ohm‐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Auto‐Ohm‐200S3measuresand
eliminatesthiscurrentfromthetotaltestcurrent.TheAuto‐Ohmthencalculatestheactual
resistancevalueofthecircuitbreaker.
TheAuto‐Ohm‐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Auto‐Ohm200S3canstore128recordsof64readingsinternally,andupto
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.
Windows®based(XP/Vista/7)analysissoftwareisprovidedwitheachunitandcanbeusedto
remotelycontroltheAuto‐Ohm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recordscanalsobeexportedtoPDF,Excel,andXML
formats.