ENGLISH User Manual - Test & Measurement … GROUND RESISTANCE TESTERS ENGLISH User Manual 3640 4610...
Transcript of ENGLISH User Manual - Test & Measurement … GROUND RESISTANCE TESTERS ENGLISH User Manual 3640 4610...
DIGITAL GROUND RESISTANCE TESTERS
E N G L I S H User Manual
36404610
ΩPress ToMeasure
X-Z
Xv-Y
Xv-Y
ZYXC1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTERMODEL 3640
AUTORANGINGREFER TO USER MANUALFOR FAULT WARNING LIGHTEXPLANATIONS
!
®
I N S T R U M E N T S
ΩPress ToMeasure
X-Z
Xv-Y
Xv-Y
ZYX XvC1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTERMODEL 4610
AUTORANGINGREFER TO USER MANUALFOR FAULT WARNING LIGHTEXPLANATIONS
!
®
I N S T R U M E N T S
Statement of Compliance
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments certifies that this instrument has been calibrated using standards and instruments traceable to international standards.
We guarantee that at the time of shipping your instrument has met its published specifications.
An NIST traceable certificate may be requested at the time of purchase, or obtained by returning the instrument to our repair and calibration facility, for a nominal charge.
The recommended calibration interval for this instrument is 12 months and begins on the date of receipt by the customer. For recalibration, please use our calibration services. Refer to our repair and calibration section at www.aemc.com.
Serial #: ________________________________
Catalog #: ______________________________
Model #: 3640 / 4610
Please fill in the appropriate date as indicated:
Date Received: _________________________________
Date Calibration Due: _______________________
Chauvin Arnoux®, Inc.d.b.a AEMC® Instrumentswww.aemc.com
Digital Ground Resistance Tester Model 3640 and 4610 1
Table of Contents
1. INTRODUCTION ................................................................................. 31.1 International Electrical Symbols ................................................31.2 DefinitionofMeasurementCategories .....................................41.3 ReceivingYourShipment ..........................................................41.4 OrderingInformation .................................................................4
1.4.1 Kits,AccessoriesandReplacementParts ....................5
2. PRODUCT FEATURES ......................................................................... 62.1 3640ControlandConnectorIdentification ...............................62.2 4610ControlandConnectorIdentification ...............................72.3 FaultIndicatorLEDs .................................................................8
2.3.1 X-ZFault .......................................................................82.3.2 X-YHighResist.(3640)-Xv-YHighResist. ....................... 82.3.3 X-YHighNoise(3640)-Xv-YHighNoise(4610) ...........8
2.4 Over-rangeIndication ...............................................................92.5 FaultLEDIndication–TipsandSolutions ................................9
3. SPECIFICATIONS ............................................................................. 103.1 Electrical .................................................................................103.2 Mechanical ..............................................................................113.3 Environmental .........................................................................113.4 SafetySpecifications ..............................................................113.5 Auto-ranging ...........................................................................12
4. OPERATION ..................................................................................... 134.1 GroundingElectrodeResistance ............................................13
4.1.1 EffectofGroundElectrodeSize/DepthonResist. ......154.1.2 EffectsofSoilResistivityonElectrodeResistance .....164.1.3 FactorsAffectingSoilResistivity .................................164.1.4 EffectofGroundRodDepthonResistance ................19
4.2 GroundResistanceValues .....................................................204.3 GroundResistanceTestingPrinciple .....................................22
4.3.1 PositionofAuxiliaryElectrodesinMeasurements ......234.4 MeasuringResistanceofGroundElectrodes .........................24
2 Digital Ground Resistance Tester Model 3640 and 4610
4.4.1 AuxiliaryElectrodeSpacing ........................................274.5 GroundResistanceMeasurementProcedure ........................284.6 MultipleElectrodeSystem ......................................................294.7 2-PointMeasurement(SimplifiedMeasurement) ............. 314.8 ContinuityMeasurement .........................................................324.9 SoilResistivityMeasurements(Model4610Only) .................334.10SoilResistivityMeasurementProcedure(4-Point) .................344.11HowtoUse25ΩCalibrationChecker .....................................36
5. MAINTENANCE ................................................................................ 375.1 Warning...................................................................................375.2 Cleaning ..................................................................................375.3 ReplacingtheBattery .............................................................375.4 ReplacingtheSafetyFuse ......................................................38RepairandCalibration ....................................................................39TechnicalandSalesAssistance ......................................................39Limited Warranty .............................................................................40WarrantyRepairs ............................................................................40
Digital Ground Resistance Tester Model 3640 and 4610 3
CHAPTER 1
INTRODUCTION
WARNING “It should be impressed on all personnel that a lethal potential can exist between the station ground and a remote ground if a system fault involving the station ground occurs while tests are being made. Since one of the objects of tests on a station ground is the establishment of the location of an effectively remote point for both current and potential electrodes, the leads to the electrodes must be treated as though a possible potential could exist between these test leads and any point on the station ground grid.”
- excerpted from IEEE Std. 81-1962
Thesesafetywarningsareprovidedtoensurethesafetyofpersonnelandproperoperationoftheinstrument.• The instrument must not be operated beyond its specified operatingrange.
• Safetyistheresponsibilityoftheoperator.• Allmetalobjectsorwiresconnectedtotheelectricalsystemshouldbeassumedtobelethaluntiltested.Groundingsystemsarenoexception.
• Use extreme caution when using the instrument around energizedelectricalequipment.
• Neverattempttousetheinstrumenttotwistorprythegroundelectrodeorgroundwireawayfromtheequipmentbeinggrounded.
• The use of rubber gloves is an excellent safety practice even if theequipmentisproperlyoperatedandcorrectlygrounded.
• Always inspect the instrument and leads prior to use. Replace anydefectivepartsimmediately.
1.1 International Electrical SymbolsThis symbol signifies that the instrument is protected by double or reinforced insulation.This symbol on the instrument indicates a WARNING and that the operator must refer to the user manual for instructions before operating the instrument. In this manual, the symbol preceding instructions indicates that if the instructions are not followed, bodily injury, installation/sample and product damage may result.Risk of electric shock. The voltage at the parts marked with this symbol may be dangerous.
In conformity with WEEE 2002/96/EC
4 Digital Ground Resistance Tester Model 3640 and 4610
1.2 Definition of Measurement CategoriesCAT II: Formeasurements performed on circuits directly connected to
theelectricaldistributionsystem.Examplesaremeasurementsonhouseholdappliancesorportabletools.
CAT III: For measurements performed in the building installation atthe distribution level such as on hardwired equipment in fixedinstallationandcircuitbreakers.
CAT IV: For measurements performed at the primary electrical supply(<1000V) such as on primary overcurrent protection devices,ripplecontrolunits,ormeters.
1.3 Receiving Your ShipmentUponreceivingyourshipment,makesurethatthecontentsareconsistentwith the packing list. Notify your distributor of anymissing items. If theequipmentappearstobedamaged,fileaclaimimmediatelywiththecar-rierandnotifyyourdistributoratonce,givingadetaileddescriptionofanydamage.Savethedamagedpackingcontainertosubstantiateyourclaim.
1.4 Ordering InformationGround Resistance Tester Model 3640 ............................ Cat. #2114.92Includes soft carrying case, batteries and a user manual.
Ground Resistance Tester Model 3640 Kit (150 ft) .........Cat. #2135.13Includes ground tester, two 150 ft color-coded leads on spools (red/blue), one 30 ft lead (green), two T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, batteries, carrying bag and user manual.
Ground Resistance Tester Model 3640 Kit (300 ft) .........Cat. #2135.14Includes ground tester, two 300 ft color-coded leads on spools (red/blue), two 100 ft color-coded leads (hand-tied, green/black), four T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, batteries, carrying bag and user manual.
Ground Resistance Tester Model 3640 Kit (500 ft) .........Cat. #2135.15Includes ground tester, two 500 ft color-coded leads on spools (red/blue), two 100 ft color-coded leads (hand-tied, green/black), one 30 ft lead (green), four T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, batteries, carrying bag, and user manual.
Ground Resistance Tester Model 4610 ............................ Cat. #2114.94Includes soft carrying case, batteries and a user manual.
Ground Resistance Tester Model 4610 Kit (150 ft) .........Cat. #2135.16Includes ground tester, two 150 ft color-coded leads on spools (red/blue), one 30 ft lead (green), two T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, batteries, carrying bag and user manual.
Digital Ground Resistance Tester Model 3640 and 4610 5
Ground Resistance Tester Model 4610 Kit (300 ft) .........Cat. #2135.17Includes ground tester, two 300 ft color-coded leads on spools (red/blue), two 100 ft color-coded leads (hand-tied, green/black), four T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, batteries, carrying bag and user manual.
Ground Resistance Tester Model 4610 Kit (500 ft) .........Cat. #2135.18Includes ground tester, two 500 ft color-coded leads on spools (red/blue), two 100 ft color-coded leads (hand-tied, green/black), one 30 ft lead (green), four T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, batteries, carrying bag and user manual.
1.4.1 Kits, Accessories and Replacement Parts
Test Kit for 3-Point Testing ...............................................Cat. #2135.35Includes two 150 ft color-coded leads on spools (red/blue), one 30 ft lead (green), two T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, carrying bag.
Test Kit for 4-Point Testing ...............................................Cat. #2135.36Includes two 300 ft color-coded leads on spools (red/blue), two 100 ft color-coded leads (hand-tied, green/black), four T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, carrying bag.
Test Kit for 4-Point Testing ...............................................Cat. #2135.37Includes two 500 ft color-coded leads on spools (red/blue), two 100 ft color-coded leads (hand-tied, green/black), one 30 ft lead (green), four T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, carrying bag.
Test Kit for 3-Point Testing (Supplementalfor4-PointTesting) ...Cat. #2135.38Includes two 100 ft color-coded leads (hand-tied, green/black), one 30 ft lead (green), two T-shaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure, carrying bag.
Set of 2, T-Shaped Auxiliary Ground Electrodes ............Cat. #2135.39Ground Tester Video/Workbook Set ................................Cat. #2130.6425Ω Calibration Checker ...................................................Cat. #2130.59Tape Measure – AEMC 100 ft ............................................Cat. #2130.60Fuse – Set of 5, 0.1A, >250V, 0.25 x 1.25" ........................Cat. #2970.12
Order Accessories and Replacement Parts Directly OnlineCheck our Storefront at www.aemc.com/store for availability
6 Digital Ground Resistance Tester Model 3640 and 4610
CHAPTER 2
PRODUCT FEATURES
2.1 3640 Control and Connector Identification
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYXC1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 3640
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
2 3 4 5
6
78910
1
Figure 1
1. Press-to-Measurebutton
2. InputterminalX(C1)
3. InputterminalY(P2)
4. Groundresistanceshortinglink
5. InputterminalZ(C2)
6.Display
7. Lowbatteryindicator
8.Xv-Yhighnoiseindicator
9.Xv-Yhighresistanceindicator
10.X-Zfaultindicator
Digital Ground Resistance Tester Model 3640 and 4610 7
2.2 4610 Control and Connector Identification
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYX Xv
C1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 4610
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
2 3 4 5 6
7
891011
1
Figure 2
1. Press-to-Measurebutton
2. InputterminalX(C1)
3. InputterminalXv(P1)
4. InputterminalY(P2)
5. Groundresistanceshortinglink
6. InputterminalZ(C2)
7.Display
8. Lowbatteryindicator
9.Xv-Yhighnoiseindicator
10.Xv-Yhighresistanceindicator
11. X-Zfaultindicator
8 Digital Ground Resistance Tester Model 3640 and 4610
2.3 Fault Indicator LEDsThe three indicators describedbelowconfirm the correctmeasurementbeingtakenifnoneofthemarelit.
2.3.1 X-Z Fault
ThisLEDsignalsthatvoltagebetweenterminalsXandZexceeds30Vpeak.
Therearefourpossiblecauses:• theresistanceofthecurrentcircuitbetweenXandZistoohigh• interferencevoltageinthecurrentcircuitistoohigh• thefuseisblown• thecircuitisopen(leadnotconnected)
2.3.2 X-Y High Resistance (3640) - Xv-Y High Resistance (4610)
ThisLEDsignalsthattheresistanceinthevoltagecircuit(betweenXvandYorXandY)istoohigh(approx50kΩ)orthatthecircuitmaybeopen.
• Flashingwill continue throughout themeasurement,even if theresistancedropsbelowthethreshold(e.g.afterreconnectingorloweringauxiliaryrodresistance).
• In thiscase,youmustreleasethepush-buttonandpressagainafterthefaulthasbeencorrected.
• Occasionally, a stray voltageabove6VDCmayalso set off thislight.
• Checktheleadsforapossiblesolution.
2.3.3 X-Y High Noise (3640) - Xv-Y High Noise (4610)
ThisLEDsignalsthepresenceofexcessivenoise(approx13Vpeak)inthevoltagecircuit(betweenXvandYorXandY).
• Oneremedyistouseshieldedleadsfromtheinstrumenttotheauxiliaryelectrodes.
• Connectalltheshieldstotherodundertest.
Digital Ground Resistance Tester Model 3640 and 4610 9
2.4 Over-range IndicationOver-rangeisindicatedwhenthedisplayreads1,orwhenthedisplayisblinkingandtheindicatorislit.
2.5 Fault LED Indication – Tips and SolutionsTheLEDindicatorsshowexcessiveelectroderesistanceandexcessivetransientnoiseand/orstraycurrent.Intheeventofanincorrectmeasurementindication:
• ImprovethequalityoftheconnectiontoearthofauxiliarygroundelectrodesYandZ.Zisthemostlikelysourceofproblemscausedbyexcessiveelectroderesistance.
• Checkconnectionsforcontinuitybetweenleadsandelectrodes.• Be sure that electrodes are properly inserted; they should be
buriedasmuchaspossible.• Ifhighelectroderesistancestillexistsafterproperlyinsertingaux-
iliaryelectrodesintotheearth,trypouringwateronandaroundtheauxiliaryelectrodes.Thiswillimprovetheirelectricalconnec-tiontoearth.
• Ifstraycurrentsaresuspected,onesolutiontoreducetheirinflu-enceistomovebothYandZelectrodesinanarcrelativetotheXelectrode(try,e.g.,a90°shift),andtestagain.
• Displayof0.00:XvandYareshort-circuited.• Displayof<0:XandZorXvandYrodsarereversed.
NOTE: Accuracy may be affected by auxiliary ground rod (Ry, Rz) resistance levels and by stray signal levels (earth currents).
10 Digital Ground Resistance Tester Model 3640 and 4610
CHAPTER 3
SPECIFICATIONS
3.1 ElectricalMeasurement Ranges:Auto-ranging0to2000Ω
Range 20Ω 200Ω 2000ΩMeasurement 0 to 19.99Ω 20 to 199.9Ω 200 to 1999ΩResolution 10mΩ 100mΩ 1ΩTest Current 10mA 1mA 0.1mAAccuracy ± 2% of Reading ± 1ct ± 5% of Reading ± 3ctsOpen Voltage <42V peak
Operating Frequency:128Hzsquarewave
Max. Auxiliary Rod Resistance:Range 20Ω 200Ω 2000ΩCurrent Circuit 3kΩ 30kΩ 50kΩVoltage Circuit 50kΩ
Response Time: Approximately6secondsforastabilizedmeasurement
Interference: Models3640&4610aredesignedtorejecthighlevelsofinterferencevoltage(DC,50/60Hz,harmonics)
• DCvoltageinserieswithX:20V• ACvoltageinserieswithY:13Vpeak• ACvoltageinserieswithZ:32Vpeak
Accuracies and specifications are given for an ambient temperature of 23°C ± 3°, RH of 45 to 55%, battery power at 8V, auxiliary resistance at the measurement terminals <200Ω, no stray voltage and a magnetic field from 0 to 40A/m.
Power Source: Eight1.5V“AA”batteries;Alkalinerecommended.
Battery Life: 180015-secondmeasurements
Low Battery Indicator: Ifthe“LoBat”indicatorlightsup,thebatteriesarelosingpower.Theavailableoperatingtimeremainingis10015-secondmeasurements(approx).
Fuse Protection: Highbreakingcapacity-0.1A,>250V,0.25x1.25"
Digital Ground Resistance Tester Model 3640 and 4610 11
3.2 MechanicalConnection:Color-codedterminalsacceptspadelugswithminimumgapof6mmorstandard4mmbananajacks
Display:7segmentLCD,.71"(18mm)high(3-1/2digit);2000ctsLCDalsoindicatesoverrange,testleadshortsandleadreversals.
Dimensions:8.7x5.4x5.9"(220x136x150mm)
Weight: 2.9lbs(1.3kg)
Case: Heavy-duty,ABS
Colors: Case-safetyyellow;Frontpanel-gray
Mechanical Shock: IEC 68-2-27
Vibration: IEC 68-2-6
Drop Test: IEC 68-2-32
Case Material: UL94
Environmental: O-ringsealedagainstdustandwatertoIP50
3.3 EnvironmentalOperating Temperature: 14°to131°F(-10°to55°C);0to90%RH
Storage Temperature:-40°to158°F(-40°to70°C); 0to90%RHwithbatteriesremoved
3.4 Safety Specifications
Electrical: EN61010-1,CATlII,PollutionDegree2,42V
Electromagnetic Compatibility: Emission:EN61326-1 Immunity:EN61326-1
*Specifications are subject to change without notice.
12 Digital Ground Resistance Tester Model 3640 and 4610
3.5 Auto-rangingTheselectionofthemeasurementcurrentisdependingontheresistancetomeasure.
WhentheinstrumentisturnedON,themeasurementstartsonthesmallestcurrentrange(100µA).Ifthemeasurementisbetween185and1950cts,therangestaysthesame(100µA).Ifthemeasurementisunder185cts,thecurrentismultipliedby10(within10mAmax).Ifitisabove1950cts,thecurrentisdividedby10(withoutgoingunder100µA).
Thisisdonetoavoidswitchingbackandforthbetweenrangeswhenyouaremeasuring190Ω.Itispossibletodisplay190.0or190Ωdependingontheautomaticrangeselection.
Digital Ground Resistance Tester Model 3640 and 4610 13
CHAPTER 4
OPERATION
4.1 Grounding Electrode ResistanceFigure3illustratesagroundingrod.Theresistanceoftheelectrodehasthefollowingcomponents:
• theresistanceofthemetalandthatoftheconnectiontoit• thecontactresistanceofthesurroundingearthtotheelectrode• theresistanceinthesurroundingearth
Morespecifically:A) Groundingelectrodesareusuallymadeofaveryconductivemetal
(copper)withadequatecrosssectionssothatoverallresistanceisnegligible.
B) TheNationalInstituteofStandardandTechnology(N.I.S.T.)hasdemonstratedthattheresistancebetweentheelectrodeandthesurrounding earth is negligible if the electrode is free of paint,greaseorothercoating,andiftheearthisfirmlypacked.
Ground Rodand Clamp
Contact ResistanceBetween Rod and Soil
ConcentricShells of Earth
Figure 3
14 Digital Ground Resistance Tester Model 3640 and 4610
C) The only component remaining is the resistance of the surround-ing earth. The electrode can be thought of as being surrounded by concentric shells of earth or soil, all of the same thickness. The closer the shell to the electrode, the smaller its surface; hence, the greater its resistance. The farther away the shells are from the electrode, the greater the surface of the shell; hence, the lower the resistance. Eventually, adding shells at a distance from the grounding electrode will no longer noticeably affect the overall earth resistance surrounding the electrode. The distance at which this effect occurs is referred to as the effective resistance area and is directly dependent on the depth of the grounding electrode.
In theory, the ground resistance may be derived from the general formula:
R = ρ Resistance = Resistivity xLA
LengthArea
This formula clearly illustrates why the shells of concentric earth decrease in resistance the farther they are from the ground rod:
R = Resistivity of Soil x Thickness of ShellArea
In the case of ground resistance, uniform earth (or soil) resistivity through-out the volume is assumed, although this is seldom the case in nature. The equations for systems of electrodes are very complex and often expressed only as approximations. The most commonly used formula for single ground electrode systems, developed by Professor H. R. Dwight of the Massachusetts Institute of Technology, follows:
4Lr
R =ρ
2πLIn -1
R = resistance in ohms of the ground rod to the earth (or soil)
L = grounding electrode length
r = grounding electrode radius
ρ = average resistivity in ohms-cm
Digital Ground Resistance Tester Model 3640 and 4610 15
4.1.1 Effect of Ground Electrode Size and Depth on Resistance
Size: Increasing thediameter of the roddoesnotmaterially reduce itsresistance.Doublingthediameterreducesresistancebylessthan10%.
0255075
100
1/2 5/8 3/4 1 1 1/4 1 1/2 1 3/4
Rod Diameter (inches)
Res
ista
nce
in %
Figure 4
Depth: As a ground rod is driven deeper into the earth, its resistanceissubstantiallyreduced.Ingeneral,doublingtherodlengthreducestheresistancebyanadditional40%.
5 15 25 35 40 50 60 701
2
34568
10
20
3040
6080
100
200
Driven Depth in FeetGround Resistance Versus Ground Rod Depth
Res
ista
nce
in O
hms
1/2" dia.1" dia.
Figure 5
16 Digital Ground Resistance Tester Model 3640 and 4610
NEC®2014250.52(A)(5)requiresaminimumof8ft(2.4m)oftheelec-trodetobe incontactwith thesoil.Themostcommonofelectrode isa10ft(3m)cylindricalrodwhichmeetstheNEC®code,whichrequiresaminimumdiameterof5/8"(1.59cm).
4.1.2 Effects of Soil Resistivity on Ground Electrode ResistanceDwight’s formula,citedpreviously,showsthat theresistance toearthofgroundingelectrodesdependsnotonlyonthedepthandsurfaceareaofgroundingelectrodesbutonsoilresistivityaswell.Soilresistivity isthekeyfactorthatdetermineswhattheresistanceofagroundingelectrodewillbe,andtowhatdepthitmustbedriventoobtainlowgroundresistance.Theresistivityofthesoilvarieswidelythroughouttheworldandchangesseasonally.Soilresistivityisdeterminedlargelybyitscontentofelectro-lytes,consistingofmoisture,mineralsanddissolvedsalts.Adrysoilhashighresistivityifitcontainsnosolublesalts.
SoilAshes, cinders, brine, waste
Clay, shale, gumbo, loamSame, with varying proportionsof sand and gravelGravel, sand, stones withlittle clay or loam
590
340
1,020
59,000
2,370
4,060
15,800
94,000
7,000
16,300
135,000
458,000
Resistivity, Ω-cm
Minimum Average Maximum
Table 1
4.1.3 Factors Affecting Soil Resistivity
Twosamplesofsoil,whenthoroughlydried,maybecomeinfactverygoodinsulators, having a resistivity in excess of 109 ohm-centimeters. Theresistivityofthesoilsampleisseentochangequiterapidlyuntilapproxi-matelytwentypercentorgreatermoisturecontentisreached.
Digital Ground Resistance Tester Model 3640 and 4610 17
02.55
10152030
> 109250,000165,00053,00019,00012,0006,400
> 109150,00043,00018,50010,5006,3004,200
Resistivity, Ω-cmMoisture content,% by weight Top Soil Sandy Loam
Table 2
Theresistivityofthesoilisalsoinfluencedbytemperature.Table3showsthevariationoftheresistivityofsandyloam,containing15.2%moisture,withtemperaturechangesfrom20°to-15°C.Inthistemperaturerangetheresistivityisseentovaryfrom7,200to330,000ohm-centimeters.
201000-5-15
6850
32 (water)32 (ice)
2314
7,2009,90013,80030,00079,000330,000
ResistivityΩ-cm
Temperature
°C °F
Table 3
Becausesoil resistivitydirectly relates tomoisturecontentand temper-ature, it is reasonable to assume that the resistance of any groundingsystemwillvarythroughoutthedifferentseasonsoftheyear.Suchvaria-tionsareshowninFigure6below.Since both temperature and moisture content become more stable atgreaterdistancesbelowthesurfaceoftheearth,itfollowsthatagroundingsystem(tobemosteffectiveatalltimes)shouldbeconstructedwiththegroundroddrivendownaconsiderabledistancebelowthesurfaceoftheearth.Bestresultsareobtainedifthegroundrodreachesthewatertable.
18 Digital Ground Resistance Tester Model 3640 and 4610
0
20
40
60
80
Jan.
Mar
.
May
July
Sep
t.
Nov
.
Jan.
Mar
.
May
July
Curve 1
Curve 2
Figure 6
Seasonal variation of earth resistance with an electrode of 3/4" pipe in rather stony clay soil. Depth of electrode in earth is 3 ft for Curve 1, and 10 ft for Curve 2.
Insomelocations,theresistivityoftheearthissohighthatlow-resistancegroundingcanbeobtainedonlyatconsiderableexpenseandwithanelab-orategroundingsystem.Insuchsituations, itmaybeeconomical touseagroundrodsystemoflimitedsizeandtoreducethegroundresistivitybyperiodicallyincreasingthesolublechemicalcontentofthesoil.Table4showsthesubstantialreductioninresistivityofsandyloambroughtaboutbyanincreaseinchemicalsaltcontent.
00.11.05
1020
10,7001,800460190130100
The Effect of Salt* Content on the Resistivity of Soil(sandy loam, moisture content, 15% by weight, temperature 17°C)
Added Salt% by weight of moisture
Resistivity(Ohm-centimeters)
Table 4
Chemicallytreatedsoilisalsosubjecttoconsiderablevariationofresistiv-itywithchangesintemperature,asshowninTable5.Ifsalttreatmentisemployed,itis,ofcourse,necessarytousegroundrodswhichwillresistchemicalcorrosion.
Digital Ground Resistance Tester Model 3640 and 4610 19
20100-5
-13
110142190312
1440
The Effect of Temperature on the Resistivity of Soil Contining Salt*(sandy loam, 20% moisture; salt 5% of weight of moisture)
Temperature °C Resistivity (Ohm-centimeters)
Table 5
*Suchascoppersulfate,sodiumcarbonateandothers.SaltsmustbeEPAorlocalordinanceapprovedpriortouse.
4.1.4 Effect of Ground Rod Depth on ResistanceToassisttheengineerindeterminingtheapproximategroundroddepthrequired to obtain a desired resistance, a device called theGroundingNomographmaybeused.TheNomograph,shownonthefollowingpage,indicatesthattoobtainagroundingresistanceof20ohmsinasoilwitharesistivityof10,000ohm-centimeters,a5/8"ODrodmustbedriven20ft.Note that the values indicated on theNomograph are based on theassumption that the soil is homogeneous and, therefore, has uniformresistivity(Figure7).TheNomographvalueisanapproximation.
20 Digital Ground Resistance Tester Model 3640 and 4610
Grounding Nomograph
Ground Rod
Resistance-Ohms
Soil Resistivity
(Ohm-centimeters)
Rod Depth
Feet
Rod Diameter
Inches
R
P
D
DIA
20
3040
90
5060
7080
100
15
10
1
5
2
4
3
5/8
1/4
1/2
3/4
1
1.5
87
65
43
2
10000
15000
10000050000
4000030000
20000
3000
500
1000
2000
40005000
20
30
10090
8070
6050
40
15
1
2
3
4
5
67
89
10
K
Figure 7
1. SelectrequiredresistanceonRscale.
2. SelectapparentresistivityonPscale.
3. Lay straightedge on R and P scale, and allow to intersect with Kscale.
4. MarkKscalepoint.
5. LaystraightedgeonKscalepointandDIAscale,andallowtointersectwithDscale.
6. PointonDscalewillberoddepthrequiredforresistanceonRscale.
4.2 Ground Resistance ValuesNEC®2008article250.56regardingtheresistanceofrod,pipeandplateelectrodesstatesthatiftherod,pipe,orplatedoesnothavearesistanceof25Ωorlesstogroundshallbeaugmentedbyoneadditionalelectrodeofanyofthetypesspecifiedby250.52(A)(4)through(A)(8).Wheremultiplerod,pipeorplateelectrodesareinstalledtomeettherequirementsofthesection,theyshallnotbelessthan6feetapart.
Digital Ground Resistance Tester Model 3640 and 4610 21
FPN:Theparallelingefficiencyofrodslongerthan8feetisimprovedbyspacinggreaterthan6feetapart.
TheNationalElectricalCode® (NEC®)statesthattheresistancetogroundshallnotexceed25Ω.This isanupper limitandguideline,sincemuchlowerresistanceisrequiredinmanyinstances.
“How low in resistance should a ground be?”Anarbitraryanswertothisinohmsisdifficult.Thelowerthegroundresis-tance,thesafer,andforpositiveprotectionofpersonnelandequipment,itisworththeefforttoaimforlessthanoneohm.Itisgenerallyimpracticaltoreachsuchalowresistancealongadistributionsystemoratransmis-sionlineorinsmallsubstations.Insomeregions,resistancesof5Ω or less maybeobtainedwithoutmuchtrouble.Inothers,itmaybedifficulttobringresistanceofdrivengroundsbelow100Ω.
Acceptedindustrystandardsstipulatethattransmissionsubstationsshouldbedesignednottoexceedoneohmresistance.Indistributionsubstations,themaximumrecommendedresistanceis5Ω.Inmostcases,theburiedgridsystemofanysubstationwillprovidethedesiredresistance.
Inlightindustrialorintelecommunicationscentraloffices,5Ωisoftentheacceptedvalue.Forlightningprotection,thearrestersshouldbecoupledwithamaximumgroundresistanceof1Ω.
Theseparameterscanusuallybemetwiththeproperapplicationofbasicgroundingtheory.Therewillalwaysexistcircumstanceswhichwillmakeit difficult to obtain the ground resistance required by theNEC®.Whenthesesituationsdevelop,severalmethodsof loweringthegroundresis-tancecanbeemployed.Theseincludeparallelrodsystems,deepdrivenrod systemsutilizing sectional rods and chemical treatment of the soil.Additionalmethods,discussedinotherpublisheddata,areburiedplates,buried conductors (counterpoise), electrically connected building steel,andelectricallyconnectedconcretereinforcedsteel.
Electricallyconnectingtoexistingwaterandgasdistributionsystemswasoftenconsideredtoyieldlowgroundresistance;however,recentdesignchangesutilizingnon-metallicpipesandinsulatingjointshavemadethismethodofobtaininga lowresistancegroundquestionableand inmanyinstancesunreliable.
Groundrods,ofcourse,willberequiredinhighvoltagetransmissionlines,wheremaximumresistanceof15ohmsisrecommended;andindistribu-tionlines,wheremaximumresistanceof25ohmsispreferred.Allelectri-calsystemsconstructedinaccordancewiththeNationalElectricalCode®, shouldnotexceed25ohms.
22 Digital Ground Resistance Tester Model 3640 and 4610
The measurement of ground resistances may only be accomplishedwith specially designed test equipment. Most instruments use the Fallof Potential principle of alternating current (AC) circulating between anauxiliaryelectrodeandthegroundelectrodeunder test; thereadingwillbegiveninohmsandrepresentstheresistanceofthegroundelectrodetothesurroundingearth.AEMC®Instrumentshasalsorecentlyintroducedaclamp-ongroundresistancetester.
Note: The National Electrical Code® and NEC® are registered trademarks of the National Fire Protection Association.
4.3 Ground Resistance Testing Principle (Fall-of-Potential — 3-Point Measurement)
Three-point measurement is used to measure resistance to ground ofgroundrodsandgrids.ThepotentialdifferencebetweenrodsXandYismeasuredbyavoltmeter,andthecurrentflowbetweenrodsXandZismeasuredbyanammeter.
ByOhm’sLawE=RIorR=E/I,wemayobtain thegroundelectroderesistance R.IfE=20VandI=1A,then:
R===20ohmsEI
201
Itisnotnecessarytocarryoutallthemeasurementswhenusingagroundtester.Thegroundtesterwillmeasuredirectlybygeneratingitsowncur-rentanddisplayingtheresistanceofthegroundelectrode.
Digital Ground Resistance Tester Model 3640 and 4610 23
ZYX
VOLTMETER (E)
AUXILIARYPOTENTIAL
ELECTRODE
GROUNDELECTRODEUNDER TEST
AUXILIARYCURRENT
ELECTRODE
AMMETER (I)
CURRENTSUPPLY
R
EARTH
Figure 8
NOTE: Terminals X and Xv are shorted together in three-point measurement
4.3.1 Position of the Auxiliary Electrodes in MeasurementsThegoalinpreciselymeasuringtheresistancetogroundistoplacetheauxiliarycurrentelectrodeZfarenoughfromthegroundelectrodeundertestsothattheauxiliarypotentialelectrodeYwillbeoutsideoftheeffec-tiveresistanceareasofboththegroundelectrodeandtheauxiliarycurrentelectrode.ThebestwaytofindoutiftheauxiliarypotentialrodYisoutsidetheeffectiveresistanceareasistomoveitbetweenXandZandtotakeareadingateachlocation.IftheauxiliarypotentialrodYisinaneffectiveresistancearea(orinbothiftheyoverlap),bydisplacingit,thereadingstakenwillvarynoticeablyinvalue.Undertheseconditions,noexactvaluefortheresistancetogroundmaybedetermined.
24 Digital Ground Resistance Tester Model 3640 and 4610
X-Y Distance
Res
ista
nce
Reading Variation
Effective ResistanceAreas (Overlapping)
X Y' Y Y'' Z
Figure 9
On the other hand, if the auxiliary potential rodY is located outside oftheeffectiveresistanceareas,asYismovedbackandforththereadingvariationisminimal.Thereadingstakenshouldberelativelyclosetoeachother,andarethebestvaluesfortheresistancetogroundofthegroundX.Thereadingsshouldbeplottedtoensurethattheylieina“plateau”regionasshowninFigure10.
X-Y Distance
Res
ista
nce
Reading Variation
Effective ResistanceAreas (No Overlap)
X Y Y Y'' Z
Figure 10
4.4 Measuring Resistance of Ground Electrodes
(62% Method)
The 62%method has been adopted after graphical consideration andafteractualtest.Itisthemostaccuratemethodbutislimitedbythefactthatthegroundtestedisasingleunit.Thismethodappliesonlywhenallthreeelectrodesareinastraightlineandthegroundisasingleelectrode,pipe,orplate,etc.,asinFigures11and12.
Digital Ground Resistance Tester Model 3640 and 4610 25
Model 3640
Alligator Clips
Y ZX52% 62% 72%0% 100% of distance
between X and Z
Ground Rod Y Electrode Z Electrode
Ground Rod
Y Electrode Z Electrode
GroundStrip
-10% 3rdMeasurement
+10% 2ndMeasurement
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYX Xv
C1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 4610
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
46.9
Figure 11
Model 4610
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
Fault
Hi Resistance
Hi Noise
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
Alligator ClipsGround Rod
Y Electrode Z Electrode
GroundStrip
GROUND RESISTANCE TESTER
MODEL 4610
ZYX Xv
C1 P1 P2 C2
Figure 12
ConsiderFigure13,whichshowstheeffectiveresistanceareas(concentricshells)ofthegroundelectrodeXandoftheauxiliarycurrentelectrodeZ.Theresistanceareasoverlap.IfreadingsweretakenbymovingtheauxiliarypotentialelectrodeYtowardseitherXorZ,thereadingdifferentialswouldbegreat andone couldnot obtaina readingwithin a reasonablebandoftolerance.Thesensitiveareasoverlapandactconstantlyto increaseresistanceasYismovedawayfromX.
26 Digital Ground Resistance Tester Model 3640 and 4610
Distance from Y to Ground Electrode
Res
ista
nce
Overlapping EffectiveResistance Areas
X Y Z
GroundElectrode
Under Test
AuxiliaryPotentialElectrode
AuxiliaryCurrent
Electrode
Figure 13
NowconsiderFigure 14,where theXandZelectrodesare sufficientlyspacedsothattheareasofeffectiveresistancedonotoverlap.Ifweplottheresistance,measuredwefindthatthemeasurementsleveloffwhenYisplacedat62%ofthedistancefromXtoZ,andthatthereadingsoneithersideoftheinitialYsettingaremostlikelytobewithintheestablishedtoleranceband.Thistolerancebandisdefinedbytheuserandexpressedasapercentoftheinitialreading:±2%,±5%,±10%,etc.
Res
ista
nce
Distance from Y to Ground Electrode
Effective ResistanceAreas Do
Not Overlap
X Y Z
GroundElectrode
Under Test
AuxiliaryPotentialElectrode
AuxiliaryCurrent
Electrode
D62% of D 38% of D
Resistance ofAuxiliary CurrentElectrode
Resistance of Earth Electrode
Figure 14
Digital Ground Resistance Tester Model 3640 and 4610 27
4.4.1 Auxiliary Electrode SpacingNodefinitedistancebetweenXandZcanbegiven,sincethisdistanceisrelativetothediameteroftheelectrodetested,itslength,thehomogeneityof the soil tested, andparticularly, the effective resistanceareas.How-ever,anapproximatedistancemaybedeterminedfromthefollowingchartwhichisgivenforahomogeneoussoilandanelectrodeof1"indiameter.(Foradiameterof1/2",reducethedistanceby10%;foradiameterof2"increasethedistanceby10%.)
Depth Driven Distance to Y Distance to Z 6 ft 45 ft 72 ft 8 ft 50 ft 80 ft 10 ft 55 ft 88 ft 12 ft 60 ft 96 ft 18 ft 71 ft 115 ft 20 ft 74 ft 120 ft 30 ft 86 ft 140 ft
Approximate Distance to Auxiliary ElectrodesUsing the 62% Method
Table 6
28 Digital Ground Resistance Tester Model 3640 and 4610
4.5 Ground Resistance Measurement Procedure
(3-Point)
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYXC1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 3640
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
Alligator ClipsGround Rod
Y Electrode Z Electrode
GroundStrip
Figure 15
WARNING: Use extreme caution when disconnecting the ground connection from the rest of the circuit. Current may be flowing and a dangerous potential could exist between the disconnected wires.
• XandXv(C1,P1)areshorted• DisconnectshortinglinkbetweenYandZ(C2,P2)• ConnectXtothegroundrodtobetested• ConnectY(P2)tothecentralelectrode• ConnectZ(C2)totheouterelectrode• Depressthe“Measure”buttontomeasuregroundresistance
Digital Ground Resistance Tester Model 3640 and 4610 29
4.6 Multiple Electrode SystemAsingledrivengroundelectrodeisaneconomicalandsimplemeansofmakingagoodgroundsystem,butsometimesasinglerodwillnotprovidesufficientlowresistance,andseveralgroundelectrodeswillbedrivenandconnectedinparallelbyacable.Veryoftenwhentwo,threeorfourgroundelectrodesareused,theyaredriveninastraightline.Whenfourormoreareused,ahollowsquarecon-figurationisusedandthegroundelectrodesarestillconnectedinparallelandequallyspaced(Figure16).Inmultipleelectrodesystems,the62%methodelectrodespacingmaynolongerbeapplieddirectly.Thedistanceoftheauxiliaryelectrodesisnowbasedonthemaximumgriddistance(e.g.,inasquare,thediagonal;inaline,thetotallength).Asquarehavingasideof20 ftwillhaveadiagonalofapproximately28ft.
DIAGONAL
DIAG
ON
AL
a
a a
a
Figure 16
30 Digital Ground Resistance Tester Model 3640 and 4610
6 ft8 ft10 ft12 ft14 ft16 ft18 ft20 ft30 ft40 ft50 ft60 ft80 ft100 ft120 ft140 ft160 ft180 ft200 ft
78 ft87 ft100 ft105 ft118 ft124 ft130 ft136 ft161 ft186 ft211 ft230 ft273 ft310 ft341 ft372 ft390 ft434 ft453 ft
125 ft140 ft160 ft170 ft190 ft200 ft210 ft220 ft260 ft300 ft340 ft370 ft440 ft500 ft550 ft600 ft630 ft700 ft730 ft
Multiple Electrode SystemMax Grid Distance Distance to Y Distance to Z
Table 7
Digital Ground Resistance Tester Model 3640 and 4610 31
4.7 2-Point Measurement (Simplified Measurement)
Thisisanalternativemethodtothree-pointmeasurementwhen an excel-lent ground is already available.Incongestedareaswherefindingroomtodrivethetwoauxiliarygroundelectrodesmaybeaproblem, the two-pointmeasurementmethodmaybeapplied.Thereadingobtainedwillbethatofthetwogroundsinseries.Therefore,thewaterpipeorothergroundmustbeverylowinresistancesothatitwillbenegligibleinthefinalmeasurement.Theleadresistanceswillalsobemeasuredandshouldbededucted from thefinalmeasure-ment.Thismethodisnotasaccurateasthree-pointmethods(62%method),asitisparticularlyaffectedbythedistancebetweenthetestedelectrodeandthedeadgroundorwaterpipe.Thismethodshouldnotbeusedasastan-dardprocedure,butratherasabackupintightareas.SeeFigure17.
Procedure:
• ShortXandXv(C1,P1)
• ShortYandZ(P2,C2)
• ConnectXtogroundrodtobemeasured
• ConnectZtoanelectrode
• Measureasinthethree-pointmethod
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYX Xv
C1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 4610
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
25.4
Grounding conductor
Ground level
Ground rodButt plate
Utility pole
Terminals shortedAuxiliary rod(Y-Z shorted)
Figure 17
32 Digital Ground Resistance Tester Model 3640 and 4610
4.8 Continuity MeasurementConnecttheshortingstripsbetweenXandXv(C1,P1),andY(P2)andZ (C2).Continuitymeasurementismadewithtwoleads,onefromX–Xv,theotherfromY–Z(P2,C2);pushthe“Measure”buttontomeasure.
Model 3640
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYXC1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 3640
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
Figure 18
Model 4610
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYX Xv
C1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 4610
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
Figure 19
Digital Ground Resistance Tester Model 3640 and 4610 33
4.9 Soil Resistivity Measurements (Model 4610 Only)
Why make soil resistivity measurements?Soilresistivitymeasurementshaveathreefoldpurpose.First,suchdataareusedtomakesub-surfacegeophysicalsurveysasanaidinidentifyingorelocations,depthtobedrockandothergeologicalphenomena.Second,resistivityhasadirectimpactonthedegreeofcorrosioninundergroundpipelines.Adecreaseinresistivityrelatestoanincreaseincorrosiveactiv-ityandthereforedictatestheprotectivetreatmenttobeused.Third,soilresistivitydirectlyaffectsthedesignofagroundingsystem,anditistothattaskthatthisdiscussionisdirected.Whendesigninganextensiveground-ingsystem, it isadvisable to locate theareaof lowestsoil resistivity inordertoachievethemosteconomicalgroundinginstallation.Resistivitymeasurementsareoftwotypes,thetwopointandthefourpointmethod.Thetwopointmethodissimplytheresistancemeasuredbetweentwopoints.Formostapplications, themostaccuratemethod is thefourpoint method, which is used by the AEMC® Instruments Model 4610GroundTester.Thefourpointmethod,asthenameimplies,requirestheinsertionoffourequallyspaced,andin-line,electrodesintothetestarea.Aknowncurrentfromaconstantcurrentgeneratorispassedbetweentheoutermostelectrodes.Thepotentialdrop(afunctionoftheresistance)isthenmeasuredacrossthetwoinnermostelectrodes.TheModel4610iscalibratedtoreaddirectlyinohms.
b< a20 a a a
Z electrodeY electrodeXv electrodeX electrode
ΩPress ToMeasure
X-Z
Xv-Y
Xv-Y
ZYX XvC1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTERMODEL 4610
AUTORANGINGREFER TO USER MANUALFOR FAULT WARNING LIGHTEXPLANATIONS
!
®
I N S T R U M E N T S
225
Figure 20
34 Digital Ground Resistance Tester Model 3640 and 4610
4.10 Soil Resistivity Measurement Procedure (4-Point)
Assumingthattheobjectiveislowresistivity,preferenceshouldbegiventoanareacontainingmoistloamasopposedtoadrysandyarea.Consid-erationmustalsobegiventothedepthatwhichresistivityisrequired.• DisconnecttheshortingstripfromtheXandXvterminals.• Arrangetheelectrodesinastraightline.Besurethatdistancesbetween
electrodesare identical:e.g.3metersbetweeneachelectrode(SeeFigure20).
• Thedistancebetweenpolesisproportionaltotheaveragedepthofthesoilsampleyouwishtomake.
• Theelectrodesshouldbeplacedatadepthofapproximately6inches(0.15meters),sothatthedepthisapproximately1/20thofthedistancebetweenelectrodes.
• UseleadstoconnecttheX,Xv,Y,andZelectrodestotherespectiveterminalsontheDigitalGroundResistanceTester.
• Pressthe“Measure”button.• Readtheresistancelevel(R)indicatedonthedisplay.• In the event of difficulties in performingmeasurements, consult the
previousinstructionsconcerninggroundresistancemeasurements.• Applythefollowingformulainordertodetermineresistivity(ρ):
ρ = 2πxRxA A=distancebetweenelectrodesinmeters ρ = resistivity in Ω meters R=ohmsreadingobtainedonModel4610
Example 1: For measurement performed in soil with a high limestone content, the reading is R = 225Ω, with A = 3 meters.
ρ = 2πx225Ωx3m ρ = 4239Ωm
Example 2: After inspection, the area to be investigated has been narrowed down to a plot of ground approximately 75 square feet (22.5m2). Assume that you need to determine the resistivity at a depth of 15 feet (457cm). The distance “A” between the electrodes must then be equivalent to the depth at which average resistivity is to be determined (15 ft, or 450cm). Using the more simplified Wenner formula (ρ = 2πAR), the electrode depth must then be 1/20th of the electrode spacing or 8⅞" (22.5cm). If the electrode depth is greater than 1/20th of the electrode spacing, the following formula must be used:
Digital Ground Resistance Tester Model 3640 and 4610 35
ρ =4πAR
1 + 2A(A2 + 4B2)
2A(4A2 + 4B2)
Layout theelectrodes inagridpattern (Figure22)andconnect to theModel4610asshowninFigure21.Proceedasfollows:
• RemovetheshortingstripbetweenXandXv• Connectallfourauxiliarygroundelectrodes
Forexample,ifthereadingisR=15,ρ (resistivity) = 2πxRxAA(distancebetweenelectrodes)=450cmρ=6.28x15x450=42,390Ω-cm
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYX Xv
C1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 4610
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
R
B
X Xv Y Z
AA A
Figure 21
AAA
A
A
A
Figure 22
36 Digital Ground Resistance Tester Model 3640 and 4610
4.11 How to Use 25Ω Calibration CheckerThe calibration checker is good for both the 3640 and 4610. It has aresistance of 25Ω. The procedure to use the calibration checker is asfollows:
• LoosentheX,XV(4610only),YandZterminals.
• InserttheresistorasshowninFigure23.
• TightendowntheterminalsX,XV(4610only),YandZ.
• Pushdownthe“PresstoMeasure”button.
• Compare thereadingon thedisplay to themeasurement rangeprovidedonthelabel.
NOTE: For alignment purposes of the test resistor, it is recommended that the shorting links remain connected between X and XV for the Model 4610, and Y and Z for the Models 3640 and 4610.
Forexample,ifacheckwasperformedontheModel4610or3640,thedisplayshouldshowareadingbetween24.15Ω and 25.85Ω.Ifso(asinFigure23),theinstrumentisingoodworkingcondition.
LO BAT
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYX Xv
C1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 4610
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
3640/461024.15 Ω - 25.85 Ω
460024.05 Ω - 25.95 Ω
362018.75 Ω - 31.25 Ω
25Ω CALIBRATION CHECKER®
I N S T R U M E N T S
LO BAT
ΩPress To
Measure
X-Z
Xv-Y
Xv-Y
ZYXC1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 3640
AUTORANGINGREFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
I N S T R U M E N T S
3640/461024.15 Ω - 25.85 Ω
460024.05 Ω - 25.95 Ω
362018.75 Ω - 31.25 Ω
25Ω CALIBRATION CHECKER®
I N S T R U M E N T S
Figure 23
Digital Ground Resistance Tester Model 3640 and 4610 37
CHAPTER 5
MAINTENANCE
5.1 WarningPleasemakesure thatyouhavealready readand fullyunderstand theWARNINGsectiononpage3.
• Toavoidelectricalshock,donotattempttoperformanyservicingunlessyouarequalifiedtodoso.
• Toavoidelectricalshockand/ordamagetotheinstrument,donotgetwaterorother foreignagents into thecase.Turn the instru-mentOFFanddisconnecttheunitfromallcircuitsbeforeopeningthecase.
5.2 Cleaning
NOTE: Disconnect the instrument from any source of electricity.
• Useasoftclothlightlydampenedwithsoapywater.• Rinsewithadampclothandthendrywithadrycloth.
• Donotusealcohol,solventsorhydrocarbons.
5.3 Replacing the Battery• Loosenthetwofasteningscrewsonthebatterycompartmentcover,
whichislocatedonthebottomofthecase(SeeFigure24).
• Removethebatterycompartmentcovertogainaccesstotheeight1.5V“AA”batteries.
• Replacewithnewbatteriesandreassembletheinstrument.
38 Digital Ground Resistance Tester Model 3640 and 4610
5.4 Replacing the Safety Fuse
NOTE: Do not replace the fuse when the instrument is connected.
To replace the fuse:• Loosen the two fastening screws on the battery compartment
cover,whichislocatedonthebottomofthecase.• Removethebatterycompartmentcovertogainaccesstothefuse
holder.• Replacethefusewiththeappropriatereplacement(0.1A,>250V,
0.25x1.25")andreassembletheinstrument.
! ATTENTIONNE PAS OUVRIR LE BOITIER AVANT D'AVOIRDECONNECTE TOUTES LES ENTREES
! WARNINGDISCONNECT INSTRUMENT FROM ALLINPUTS BEFORE OPENING CASE
SpareFuse
Holders
FuseHolder
Battery CompartmentFastening
ScrewFastening
Screw
Figure 24
Digital Ground Resistance Tester Model 3640 and 4610 39
Repair and Calibration
Toensurethatyourinstrumentmeetsfactoryspecifications,werecommendthatitbescheduledbacktoourfactoryServiceCenteratone-yearintervalsforrecalibration,orasrequiredbyotherstandardsorinternalprocedures.
For instrument repair and calibration:Youmust contactourServiceCenter foraCustomerServiceAuthorizationNumber(CSA#).Thiswillensurethatwhenyourinstrumentarrives,itwillbetrackedandprocessedpromptly.PleasewritetheCSA#ontheoutsideoftheshipping container. If the instrument is returned for calibration,weneed toknowifyouwantastandardcalibration,oracalibrationtraceabletoN.I.S.T.(Includescalibrationcertificateplusrecordedcalibrationdata).
Ship To: ChauvinArnoux®,Inc.d.b.a.AEMC®Instruments 15 Faraday Drive Dover,NH03820USA Phone:(800)945-2362(Ext.360) (603)749-6434(Ext.360) Fax: (603)742-2346or(603)749-6309 E-mail:[email protected]
(Orcontactyourauthorizeddistributor)Costsforrepair,standardcalibration,andcalibrationtraceabletoN.I.S.T.areavailable.NOTE: You must obtain a CSA# before returning any instrument.
Technical and Sales Assistance
Ifyouareexperiencinganytechnicalproblems,orrequireanyassistancewiththeproperoperationorapplicationofyourinstrument,pleasecall,mail,faxore-mailourtechnicalsupportteam:
ChauvinArnoux®,Inc.d.b.a.AEMC®Instruments 200FoxboroughBoulevard Foxborough,MA02035USA Phone:(800)343-1391 (508) 698-2115 Fax: (508)698-2118 E-mail:[email protected] www.aemc.com
NOTE: Do not ship Instruments to our Foxborough, MA address.
40 Digital Ground Resistance Tester Model 3640 and 4610
Limited Warranty
TheGroundResistanceTestersModel3640and4610arewarrantedtotheownerforaperiodofoneyearfromthedateoforiginalpurchaseagainstde-fects inmanufacture.This limitedwarranty isgivenbyAEMC® Instruments,notbythedistributorfromwhomitwaspurchased.Thiswarrantyisvoidiftheunithasbeentamperedwith,abusedorifthedefectisrelatedtoservicenotperformedbyAEMC®Instruments.
Full warranty coverage and product registration is available on our website at www.aemc.com/warranty.html.
Please print the online Warranty Coverage Information for your records.
What AEMC® Instruments will do:Ifamalfunctionoccurswithintheone-yearperiod,youmayreturntheinstrumenttousforrepair,providedwehaveyourwarrantyregistrationinformationonfileoraproofofpurchase.AEMC®Instrumentswill,atitsoption,repairorreplacethefaultymaterial.
REGISTER ONLINE AT:www.aemc.com
Warranty Repairs
What you must do to return an Instrument for Warranty Repair: First, request aCustomerServiceAuthorizationNumber (CSA#) by phoneorbyfaxfromourServiceDepartment(seeaddressbelow),thenreturntheinstrumentalongwith thesignedCSAForm.Pleasewrite theCSA#on theoutsideoftheshippingcontainer.Returntheinstrument,postageorshipmentpre-paidto:
Ship To: ChauvinArnoux®,Inc.d.b.a.AEMC®Instruments 15FaradayDrive•Dover,NH03820USA Phone:(800)945-2362(Ext.360) (603)749-6434(Ext.360) Fax: (603)742-2346or(603)749-6309 E-mail:[email protected]
Caution:Toprotectyourselfagainstin-transitloss,werecommendyouinsureyourreturnedmaterial.
NOTE: You must obtain a CSA# before returning any instrument.
11/15
99-MAN100143v18
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments15FaradayDrive•Dover,NH03820USA•Phone:(603)749-6434•Fax:(603)742-2346
www.aemc.com