Extech Instruments 382357-NIST User manual

USERMANUAL

GroundResistanceClamp‐OnTester
MODEL382357

382357‐EU‐ENV2.42/13
2
Introduction
CongratulationsonyourpurchaseofExtech’s382357GroundResistanceTester.ThisClamp‐on
deviceallowstheusertomeasuregroundresistancewithouttheuseofauxiliarygroundrods.
Thisdevicecanonlybeusedonmulti‐groundedsystems.Itisnotnecessarytodisconnectthe
groundundertest.Thismeterisshippedfullytestedandcalibratedand,withproperuse,will
provideyearsofreliableservice.Pleasevisitourwebsite(www.extech.com)tocheckforthe
latestversionofthisUserGuide,ProductUpdates,andCustomerSupport.

Safety
Onlyqualifiedtechniciansshouldoperatethismeter.
Useextremecautionwhenoperatingthemeternearenergizedelectricalequipment.
Donotattempttousethismetertotwistorprythegroundelectrodeorgroundwireaway
fromgroundedequipment.
Allmetalobjectsorwiresconnectedtotheelectricalsystemundertestshouldbeassumed
tobelethaluntiltested.Groundedsystemsarenoexception.
Ensurethatthebatteriesareinsertedcorrectlyinthebatterycompartment.
Removethebatteriesfromthemeterifthemeteristobestoredforlongperiods.
WARNING:Ifthemeterisusedinamannernotspecifiedbythemanufacturer,thebuiltin
protectionsprovidedbythemetermaybeimpaired.

InternationalSafetySymbols
Thissymbol,adjacenttoanothersymbolorterminal,indicatestheusermust
refertothemanualforfurtherinformation.

Thissymbol,adjacenttoaterminal,indicatesthat,undernormaluse,hazardous
voltagesmaybepresent


382357‐EU‐ENV2.42/13
3
Description
1. JawAssembly
2. HoldButton
3. RotarySelectorSwitch
4. LCDDisplay
5. RecordButton
6. ▼(decrement)Button
7. ▲(increment)Button
8. FunctionButton
9. MeasurementTrigger




DisplaySymbols
1. REC:Indicatesdatalogginginprogress
2. NO.IndicatestheREADfunction
3.  :Clampjawsarenotfullyclosed
4. NOISE:Excessivenoiseontheground
conductororrod
5. ))):HiLoalarmposition
6. FunctionorRecorddisplay
7. Ω:Ohms(resistancemeasurement)
8. mA:milli‐amperes,Amperes(currentmeasurements)
9. H:Holdfunctionactivated
10. Maindisplay
11. :LowBattery
12. AutoPowerOff
1
2
3
4
5
6
7
8
9

382357‐EU‐ENV2.42/13
4
Operation
Note:Ensurethatthejawsarefullyclosedbeforetesting.

Note:DONOTclampontoanyconductororopentheclampjawsduringthestart‐upself‐
calibration(self‐calisidentifiedbytheLCDcountingdownfromCAL7toCAL1).
GroundResistanceMeasurements
1. Opentheclampjawsandcheckthatallsurfacesare
cleanandfreeofdust,dirt,oranyforeign
substances.Cleanifnecessary.
2. Forcefullysnaptheclampjawsopenandclosed
severaltimes.
3. Turnthemeteronbymovingtherotaryswitchto
theohmsposition.DONOTinterruptthestartup
procedurebyopeningtheclampjawsorclamping
aroundaconductor.Duringself‐calibration,the
meterwilldisplayCAL5,CAL4,CAL3,CAL2and
CAL1.
4. Oncethestart‐upcalibrationprocedureiscompleted,themeterwillsoundabeep.Clamp
ontoanelectrodeorgroundrodandreadthevalueofgroundresistanceonthedisplay.
Ground/LeakageCurrentMeasurement
1. Turnthemeteronbymovingtherotaryswitchtothe
mAorAposition.
2. Clampontotheelectrodeorconductor
3. Readthevalueofleakagecurrentdisplayedonthe
LCD.



HOLD
PresstheHOLDbuttontofreezethereadinginthedisplay.Hwillappearinthedisplay.Press
HOLDagaintoexitthefunction.

382357‐EU‐ENV2.42/13
5
HighandLowAlarm
1. Turnthemeteronbymovingtherotaryswitchtothe)))position.
2. PresstheFUNCbuttontoviewandadjustthe“HI”alarmvalue.
3. Press▲orthe▼buttontoincreaseordecreasethevalue.Holddownthebuttonto
increasethespeedofadjustment.Thevaluecanbeincrementedfrom0to1500ohmsand
thenOL(overload).Thevaluewillrolloverto0afterOLisdisplayed.
4. Oncethedesiredvalueisset,presstheFUNCbuttonasecondtimetoviewandadjustthe
“LO”alarmvalue.
5. PresstheFUNCbuttonthreemoretimestoexitthesettingmode.
6. Themeterwillnowcomparethemeasuredresistancevaluewiththehighandlowlimits
whenthemeterissettothe)))position.IfthereadingislargerthantheHIvalue,the
meterwillbeepanddisplay“HI”ontheLCD.IfthereadingislowerthantheLOvalue,the
meterwillbeepanddisplay“LO”ontheLCD.

DataLogging
SettingtheSamplingTime
1. PresstheFUNCbuttonthreetimesuntilthe“SEC”symbolappearsintheLCDdisplay.
2. Thesamplingrateisnowdisplayedinseconds.
3. Pressthe▲orthe▼buttontoincreaseordecreasethevalue.Thevaluecanbe
incrementedfrom0to255seconds.
4. Oncethedesiredvalueisset,presstheFUNCbuttonseveraltimesuntilthecharactersin
theupperrowoftheLCDdisappear.
RecordingData
1. PresstheRECbuttontostartrecordingdataatthespecifiedsamplingrate.The“REC”
symbolwillappearonthetopoftheLCDdisplay.Tostoprecording,presstheRECbutton.
The“REC”symbolwillnolongerbedisplayedontheLCD.
NOTE:Dataloggingwillautomaticallystopifthememoryisfilled(116records),orifthemeter
detectsalowbatterycondition.
NOTE:Ifthesamplingintervalissetto0,onlyonesamplewillberecorded.Torecordanother
sample,pressRECagain.

382357‐EU‐ENV2.42/13
6
RecallingStoredData
1. PresstheFUNCbuttonfourtimesuntilthe“NO.”symbolisdisplayedontheLCD.The
currentrecordnumberwillbedisplayedinthetoprowandthedatawillbedisplayedbelow
it.
2. Pressthe▲orthe▼buttontostepthroughandreadthedatainthenextmemory
location.Holdingdownthebuttonwillincreasethespeedoftheincrementingvalue.
ClearingDataMemory
1. Withthemeterpoweredoff,pressandholddowntheRECbuttonwhileturningthemeter
on.The“CL”symbolwillappearonthedisplayindicatingthatmemoryhasbeencleared.

382357‐EU‐ENV2.42/13
7
MeasurementPrinciples
Typicalmulti‐groundeddistributionsystem









Iftheparallelgroundresistances,
R1,R2,R3,etc,uptoRnarecombined
asReq,thenonlyRgandReqare
leftinthecircuit



Ifaconstantvoltageisappliedtothecircuit,thefollowingequationapplies:
eqg RR
I
V where: ni
R
R
i
eq ,...2,1,
1
1


IfRgandR1,R2,R3…Rn,areapproximatelythesame,andnislarge(200,forexample),thenReq
willbemuchlessthenRgandmaypossiblyapproachzero.
Example:
IfRgandR1,R2,R3…Rnareall10respectivelyandn=200,thenReqbycalculationequals:


05.0
10
1
...
10
1
10
1
1
eq
R
geqg RRR
I
V 05.1005.010 
V
I
Req
Rg

382357‐EU‐ENV2.42/13
8
Applications
Telephone‐ElectricalGroundRods
1. Removeanyprotectivecoveringfromthegroundconductor
2. TurnthemeterswitchtotheOhmfunction.
3. Oncethestart‐upcalibrationprocedureiscompletedclampontoanelectrodeorground
rod.
4. Allowseveralsecondsforthemetertosettleandthennotethereading.

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CellularTransmissionTowers
WARNING:Useextremecarewhenmakingmeasurementsaroundtransmissiontowers;High
Voltagemaybepresent.
Thegroundconductorshouldbelocatedatthebaseofthetower,butyourconfigurationmay
bedifferent.
1. Locatethegroundconductor
2. Clamparoundthegroundconductor.Youshouldplacetheclampbeforeanysplices,bonds
orothersplitsinthegroundsystem.
3. Readthemeasuredreading.








Transmission
Tower
Primary
Ground Conductor
Branch
Ground Conductors
Cement Pad

382357‐EU‐ENV2.42/13
9
ServiceEntrance
Note:Multiplegroundrods,multiplegroundsi.e.groundrod(s)andwaterpipegrounds,ora
combinationmaybepresentdependingontheparticularsituation.Inthesesituationsitis
necessarytomakeyourmeasurementsbetweentheservice‐entranceneutralandall
subsequentgroundpoints.



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
Troubleshooting
1. Snapthejawsopenandclosedtwoorthreetimesbeforeturningthemeteron
2. Donotclampontoanydeviceduringthepower‐upinitializationsequence.
3. Snapthejawstwoorthreetimesafterclampingontothegroundelectrodeorrod.
4. Slightamountsofdriftmayoccurathighresistancemeasurements;thisisnormaland
shouldnotbecauseforconcern.
Blankdisplayoranyfailuremode
Replacethebatterybeforeproceeding.
Start‐upInitializationFailure
Thestart‐upcalibrationwillcontinueindefinitelyifthejawsareopenordirty.Checkthatthe
jaws’matingsurfacesareclean.Donotopenthejawswhiletheinitializationsequenceis
running.
NoiseontheGroundElectrodeorRod
Ifnoiseispresent(over3Aor30V)onthegroundelectrodeorrod,theword“NOISE“will
appearonthedisplayandreadingscannolongerbeconsideredaccurate.Beforethemetercan
beusedaccurately,thenoiseproblemmustbeaddressed.
Distribution
Panel
Ground
Rod
Water
Pipe

382357‐EU‐ENV2.42/13
10
ReferenceTestLoop
Thereferencetestloopisasetofresistorsthatprovidesameanstochecktheperformanceof
themeter.
1. Openthemeasurementjawsandcheckthatthematingsurfacesarecleanandfreeofdust,
dirt,oranyforeignsubstances.Cleanifnecessary.
2. Clampthemeteraroundthereferenceloopasshowninthediagram.
3. Givethemeterafewsecondstosettleandreadthemeasurement.Themetershould
displayapproximatelythesamevalueasmarkedonthereferenceloop,takinginto
considerationtheaccuracylistedinthespecificationchart.Ifthereadingsarenotsimilarto
whatismarkedonthereferenceloop,consulttheTroubleShootingandMaintenance
sectionsofthismanual.
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382357‐EU‐ENV2.42/13
11
Maintenance
GeneralCare
Storethegroundresistancetesterandreferenceloopinitscasewhennotinuse.Adamp
clothmaybeusedtocleananysurfacedirtfromthemeter.Neveruseharshdetergents,
abrasives,solvents,orcleanersonthemeter.
BatteryReplacement
Whenthelowbatterysymbolappearsonthedisplay,replacethemeter’s9Vbattery.Usea
highqualityalkalinebatterywheneverreplacementbecomesnecessary.
1. Removethetworearscrewsandopenthemeterhousing.
2. Replacethebattery,closethemeterhousing,andaffixthetworearscrews.

Neverdisposeofusedbatteriesorrechargeablebatteriesinhouseholdwaste.
Asconsumers,usersarelegallyrequiredtotakeusedbatteriestoappropriate
collectionsites,theretailstorewherethebatterieswerepurchased,orwherever
batteriesaresold.
Disposal:Donotdisposeofthisinstrumentinhouseholdwaste.Theuseris
obligatedtotakeend‐of‐lifedevicestoadesignatedcollectionpointforthedisposal
ofelectricalandelectronicequipment.

OtherBatterySafetyReminders
oNeverdisposeofbatteriesinafire.Batteriesmayexplodeorleak.
oNevermixbatterytypes.Alwaysinstallnewbatteriesofthesametype.

ClampJawMaintenance
Thejawsmaybebrushedcleanwithatoothbrushorsimilarsoft‐bristledbrush.Caremustbe
takentoensurethatthecontactfinsarenotbentordeformed,asthiswillaffecttheoperation
ofthemeter.

382357‐EU‐ENV2.42/13
12
Specifications
GeneralSpecifications
ResistanceTestFrequency: 3.333kHz(15mVrmsapprox.)
MaxConductorsize23mm(0.9”)
Display4‐digit(9999count)display
Samplingrate0.5seconds
Memory116records
Dataloggingsamplerate1to255seconds
PowersupplyOne(1)9Vbattery
Powerconsumption40mADC
BatteryLife3000measurements
Temp.Coefficient 0.15timesthespecifiedaccuracyperoCfrom4to18oC(39to
64ºF)and28to50oC(82to122ºF)
CurrentOverload Protectedto100AContinuous;200Aforlessthan5seconds
(50/60Hz)
RangeselectionAutomaticranging
SafetyMeetstherequirementsforIEC1010‐1CategoryIII300Vand
CategoryII600V
Operatingconditions0to50oC(32to122oF)with<85%RH
Storageconditions‐20to60oC(‐4to140oF)with<75%RH
Dimensions257x100x47mm(10.1x3.9x1.9”)
Weight1.4lbs(640g)
AccessoriesResistancecheckplate,9Vbattery,&carryingcase

382357‐EU‐ENV2.42/13
13
GroundResistance(Autorange)Specifications
RangeResolutionAccuracy(ofreading)
0.025to0.2500.002±(1.5%+0.05
0.250to1.0000.02±(1.5%+0.05
1.001to9.9990.02±(1.5%+0.1
10.00to50.000.04±(2.0%+0.3
50.01to99.990.04±(2.0%+0.5
100.0to200.00.4±(3.0%+1.0
200.1to400.02±(5.0%+5
400.0to600.05±(10%+10
600.1to150020±20%
AccuracyNote:Loopresistancenon‐inductive,externalfield<50A/m,externalelectricalfield
<1V/m,conductorcentered
Ground/LeakageCurrentSpecifications
RangeAccuracy(%ofreading)
0.300to1.000mA±(2.0%±0.05mA)
1.00to10.00mA±(2.0%±0.03mA)
10.0to100.0mA±(2.0%±0.3mA)
100to1000mA±(2.0%±0.3mA)
Autoranging
0.20to4.00A±(2.0%±0.03A)
4.00to30.00A±(3.0%±0.03A)
Manualrange
Notes:50/60Hzbandwidth,TrueRMSsensing,CrestFactor<3.0
HighandLowAlarm(programmable)
RangeResolution
HighAlarm0‐15101
LowAlarm0‐15101

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