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.







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.












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.






