Extech Instruments 382357-NIST User manual

USERMANUAL



GroundResistanceClamp‐OnTester

MODEL382357

382357‐EU‐ENV2.42/13

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

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

382357‐EU‐ENV2.42/13

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

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

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

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

V where: ni

eq ,...2,1,

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

...

R

geqg RRR

V 05.1005.010 

Req

382357‐EU‐ENV2.42/13

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

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

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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