DIGITAL GROUND RESISTANCE AND SOIL

DIGITAL GROUND RESISTANCE AND SOIL

DIGITAL GROUND
RESISTANCE AND SOIL
RESISTIVITY TESTERS
ENGLISH
User Manual
4620
4630
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 #: 4620 / 4630
Please fill in the appropriate date as indicated:
Date Received: __________________________________
Date Calibration Due: ________________________
Chauvin Arnoux®, Inc.
d.b.a AEMC® Instruments
www.aemc.com
Table of Contents
1. INTRODUCTION.................................................................................. 3
1.1
1.2
1.3
1.4
International Electrical Symbols.................................................4
Definition of Measurement Categories......................................4
Receiving Your Shipment...........................................................4
Ordering Information..................................................................5
1.4.1 Kits, Accessories and Replacement Parts.....................6
2. PRODUCT FEATURES.......................................................................... 7
2.1 Control and Connector Features (Model 4620) ........................7
2.2 Control and Connector Features (Model 4630).........................8
2.3 Fault Indicator LEDs..................................................................9
2.3.1 X-Z Fault........................................................................9
2.3.2 Xv-Y High Resistance....................................................9
2.3.3 Xv-Y High Noise.............................................................9
2.4 Buzzer......................................................................................10
2.5 Over-range Indication..............................................................10
2.6 Fault LED Indication – Tips and Solutions...............................10
3. SPECIFICATIONS.............................................................................. 11
3.1Electrical.................................................................................. 11
3.2 Mechanical...............................................................................12
3.3Environmental..........................................................................13
3.4 Safety.......................................................................................13
3.5 Auto-ranging............................................................................13
4. GROUNDING THEORY........................................................................ 14
4.1 Grounding Electrode Resistance.............................................14
4.1.1 Effect of Electrode Size/Depth on Resistance.............16
4.1.2 Effects of Soil Resistivity on Electrode Resistance......17
4.1.3 Factors Affecting Soil Resistivity..................................17
4.1.4 Effect of Ground Rod Depth on Resistance.................20
4.2 Ground Resistance Values......................................................21
4.3 Ground Resistance Testing Principle ......................................23
4.3.1 Position of Auxiliary Electrodes in Measurements.......24
Digital Ground Resistance Tester Model 4620 and 4630
1
4.4 Measuring Resistance of Ground Electrodes .........................26
4.4.1 Auxiliary Electrode Spacing.........................................28
4.5 Multiple Electrode System.......................................................28
5. OPERATION...................................................................................... 30
5.1
5.2
5.3
5.4
Ground Resistance Measurement Procedure ........................30
2-Point Measurement (Simplified Measurement)....................31
Continuity Measurement..........................................................32
Soil Resistivity Measurements.................................................32
5.4.1 Purposes of Soil Resistivity.........................................32
5.4.2 Types of Resistivity Measurements.............................33
5.5 Soil Resistivity Measurement Procedure (4-Point)..................34
5.6 How to Use 25Ω Calibration Checker (accessory).................36
6. MAINTENANCE................................................................................. 37
6.1 Warning ..................................................................................37
6.2Disassembly............................................................................37
6.3 Power Supply...........................................................................38
6.3.1 Testing the Battery.......................................................38
6.3.2 Replacing the Battery (Model 4620)............................39
6.3.3 Recharging the Battery (Model 4630)..........................39
6.3.4 Replacing the Safety Fuse...........................................40
6.4 Cleaning...................................................................................40
6.5 Storage....................................................................................40
Repair and Calibration.....................................................................41
Technical and Sales Assistance.......................................................41
Limited Warranty..............................................................................42
Warranty Repairs.............................................................................42
2
Digital Ground Resistance Tester Model 4620 and 4630
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
These safety warnings are provided to ensure the safety of personnel and proper operation of the instrument.
• The instrument must not be operated beyond its specified
operating range.
• Safety is the responsibility of the operator.
• All metal objects or wires connected to the electrical system
should be assumed to be lethal until tested. Grounding systems are no exception.
• Use extreme caution when using the instrument around energized electrical equipment.
• Never attempt to use the instrument to twist or pry the ground
electrode or ground wire away from the equipment being
grounded.
• AEMC® Instruments considers the use of rubber gloves to be
an excellent safety practice even if the equipment is properly
operated and correctly grounded.
• Always inspect the instrument and leads prior to use. Replace
any defective parts immediately.
Digital Ground Resistance Tester Model 4620 and 4630
3
1.1
International Electrical Symbols
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/or 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
1.2
Definition of Measurement Categories
CAT II: For measurements performed on circuits directly connected to
the electrical distribution system. Examples are measurements
on household appliances or portable tools.
CAT III: For measurements performed in the building installation at
the distribution level such as on hardwired equipment in fixed
installation and circuit breakers.
CAT IV: For measurements performed at the primary electrical supply
(<1000V) such as on primary overcurrent protection devices,
ripple control units, or meters.
1.3
Receiving Your Shipment
Upon receiving your shipment, make sure that the contents are consistent
with the ordering information. Notify your distributor of any missing items.
If the equipment appears to be damaged, file a claim immediately with the
carrier and notify your distributor at once, giving a detailed description of
any damage. Save the damaged packing container to substantiate your
claim.
Do not use equipment which is damaged or appears to be damaged.
4
Digital Ground Resistance Tester Model 4620 and 4630
1.4
Ordering Information
Ground Resistance Tester Model 4620............................. Cat. #2130.43
Includes ground tester workbook on USB stick, 8 C cell batteries and user manual.
Ground Resistance Tester Model 4620 Kit (150 ft).......... Cat. #2135.19
Includes 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, ground tester workbook on USB stick, batteries, carrying bag and user manual.
Ground Resistance Tester Model 4620 Kit (300 ft).......... Cat. #2135.20
Includes ground tester, two 300 ft color-coded leads on spools (red/blue), two 100 ft colorcoded leads (hand-tied, green/black), four T-shaped auxiliary ground electrodes, set of
5 spaded lugs, one 100 ft AEMC® tape measure, ground tester workbook on USB stick,
batteries, carrying bag and user manual.
Ground Resistance Tester Model 4620 Kit (500 ft).......... Cat. #2135.21
Includes ground tester, two 500 ft color-coded leads on spools (red/blue), two 100 ft colorcoded 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, ground tester workbook
on USB stick, batteries, carrying bag and user manual.
Ground Resistance Tester Model 4630............................. Cat. #2130.44
Includes ground tester workbook on USB stick, rechargeable battery, AC power cord and
user manual.
Ground Resistance Tester Model 4630 Kit (150 ft).......... Cat. #2135.22
Includes 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, ground tester workbook on USB stick, batteries, carrying bag and user manual.
Ground Resistance Tester Model 4630 Kit (300 ft).......... Cat. #2135.23
Includes ground tester, two 300 ft color-coded leads on spools (red/blue), two 100 ft colorcoded leads (hand-tied, green/black), four T-shaped auxiliary ground electrodes, set of
5 spaded lugs, one 100 ft AEMC® tape measure, ground tester workbook on USB stick,
batteries, carrying bag and user manual.
Ground Resistance Tester Model 4630 Kit (500 ft).......... Cat. #2135.24
Includes ground tester, two 500 ft color-coded leads on spools (red/blue), two 100 ft colorcoded 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, ground tester workbook
on USB stick, batteries, carrying bag and user manual.
Digital Ground Resistance Tester Model 4620 and 4630
5
1.4.1 Kits, Accessories and Replacement Parts
Test Kit for 3-Point Testing (150 ft)................................... Cat. #2135.35
Includes two 150 ft color-coded leads on spools (red/blue), one 30 ft lead (green), two Tshaped auxiliary ground electrodes, set of 5 spaded lugs, one 100 ft AEMC® tape measure
and carrying bag.
Test Kit for 4-Point Testing (300 ft)................................... Cat. #2135.36
Includes 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 and carrying bag.
Test Kit for 4-Point Testing (500 ft)................................... Cat. #2135.37
Includes 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 and carrying bag.
Test Kit for 3-Point Testing (Supplemental for 4-Point Testing).... Cat. #2135.38
Includes 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
and carrying bag.
25Ω Calibration Checker...................................................... Cat. #2130.59
Tape Measure – AEMC 100 ft.............................................. Cat. #2130.60
Ground Tester Video/Workbook Set..................................... Cat. #2130.64
Set of 2, T-Shaped Auxiliary Ground Electrodes.................. Cat. #2135.39
Inverter – 12VDC to 120VAC 200 Watt for vehicle use ......... Cat. #2135.43
Fuse – Set of 5, 0.1A, >250V, 0.25 x 1.25".......................... Cat. #2970.12
Replacement 9.6V Rechargeable Battery Pack (4630)........ Cat. #2960.21
115V Power Cord................................................................. Cat. #5000.14
Order Accessories and Replacement Parts Directly Online
Check our Storefront at www.aemc.com/store for availability
6
Digital Ground Resistance Tester Model 4620 and 4630
CHAPTER 2
PRODUCT FEATURES
2.1
Control and Connector Features
(Model 4620)
1
9
2
Ω
3
4
10
11
5
6
7
8
Figure 1
1.
2.
3.
4.
5.
6.
Low battery indicator
Input terminal Z (H)
Input terminal Y (S)
Input terminal Xv (ES)
Input terminal X (E)
X-Z Fault indicator
7. Xv-Y High Resistance indicator
8. Xv-Y High Noise indicator
9. Display (with backlight - lights up when
the TEST button is pressed)
10. Fuse holder
11. TEST button
(when released, turns the unit OFF)
Digital Ground Resistance Tester Model 4620 and 4630
7
2.2
Control and Connector Features
(Model 4630)
1
2
10
3
11
Ω
4
5
12
6
7
8
9
Figure 2
1.
2.
3.
4.
5.
6.
8
Low battery indicator
AC power input
Input terminal Z (H)
Input terminal Y (S)
Input terminal Xv (ES)
Input terminal X (E)
7.
8.
9.
10.
11.
12.
X-Z Fault indicator
Xv-Y High Resistance indicator
Xv-Y High Noise indicator
Display (with backlight)
Fuse holder
Test button
Digital Ground Resistance Tester Model 4620 and 4630
2.3
Fault Indicator LEDs
The three indicators confirm that the correct measurement is being taken,
if none of them are lit.
2.3.1 X-Z Fault
This LED signals that the voltage between terminals X and Z exceeds 30V
peak.
There are four possible causes:
•
•
•
•
the resistance of the current circuit between X and Z is too high
interference voltage in the current circuit is too high
the fuse is blown
the circuit is open (lead not connected)
2.3.2 Xv-Y High Resistance
This LED signals that the resistance in the voltage circuit (between Xv and
Y or X and Y) is too high (approx 50kΩ) or that the circuit may be open.
• Flashing will continue throughout the measurement, even if the
resistance drops below the threshold (e.g. after reconnecting
or lowering auxiliary rod resistance). In this case, you must
release the push-button and press again after the fault has been
corrected.
• Occasionally, a stray voltage above 4.5V may also set off this
light.
• Check the leads for a possible solution.
2.3.3 Xv-Y High Noise
This LED signals the presence of excessive electrical noise (13V peak
approx) in the voltage circuit (between Xv and Y or X and Y).
• One remedy is to use shielded leads from the instrument to the
auxiliary electrodes.
• Connect all the shields to the rod under test.
Digital Ground Resistance Tester Model 4620 and 4630
9
2.4Buzzer
The Models 4620 and 4630 feature a buzzer, which will sound when the
terminals of the tester are connected to a voltage source. The sound
volume is proportional to the voltage up to 30V approximately, then
becomes stable.
2.5
Over-range Indication
Over-range is indicated when the display reads 1, or when the display is
blinking and the indicator is lit.
2.6
Fault LED Indication – Tips and Solutions
The LED indicators show excessive electrode resistance and excessive
transient noise and/or stray current.
In the event of an incorrect measurement indication:
• Improve the quality of the connection to earth of auxiliary ground
electrodes Y and Z. Z is the most likely source of problems caused
by excessive electrode resistance.
• Check connections for continuity between leads and electrodes.
• Be sure that electrodes are properly inserted; they should be
buried as much as possible.
• If high electrode resistance still exists after properly inserting auxiliary electrodes into the earth, try pouring water on and around
the auxiliary electrodes. This will improve their electrical connection to earth.
• If stray currents are suspected, one solution to reduce their influence is to move both Y and Z electrodes in an arc relative to the X
electrode (try, e.g. a 90° shift), and test again.
• Display of 0.00: Xv and Y are short-circuited.
• Display of <0: X and Z or Xv and Y rods are reversed.
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 4620 and 4630
CHAPTER 3
SPECIFICATIONS
3.1Electrical
Measurement Range: Auto-ranging 0 to 2000Ω
Range
Measurement
Resolution
Test Current
Accuracy
Open Voltage
20Ω
200Ω
0 to 19.99Ω
20 to 199.9Ω
10mΩ
100mΩ
10mA
1mA
2% of Reading ± 1ct
<42V peak
2000Ω
200 to 1999Ω
1Ω
0.1mA
± 5% of Reading ± 3cts
Operating Frequency: 128Hz square wave
Max. Auxiliary Rod Resistance:
Range
Current Circuit
Voltage Circuit
20Ω
3kΩ
200Ω
30kΩ
50kΩ
2000Ω
50kΩ
Response Time: 4 to 8 seconds approx for a stabilized measurement
Interference:
The Models 4620 & 4630 are designed to reject high levels of interference
voltage (DC, 50/60Hz, harmonics)
• DC voltage in series with X: 20V
• AC voltage in series with Y: 13V peak (@ 16.67, 50, 60, 400Hz)
• AC voltage in series with Z: 32V peak (@ 16.67, 50, 60, 400Hz)
Accuracies and specifications are given for an ambient temperature of 23°C ±3°K, RH of
45 to 55%, battery power at 9.5V, auxiliary resistance at the measurement terminals = 0, no
stray voltage, an electrical field < 1V/m, and a magnetic field from 0 to 40A/m.
Voltage Detection Range: 20 to 250VAC between the X and Z terminals
or between the Xv and Z terminals.
Frequency: DC at 450Hz
Voltage Withstanding: Both models are fuse protected. In the event of a
system fault, the units can withstand 250VAC or 100VDC.
Fuse Protection: High breaking capacity - 0.1A, >250V, 0.25 x 1.25"
Digital Ground Resistance Tester Model 4620 and 4630
11
Model 4620
Power Source: Eight 1.5V C cell batteries
Battery Life: 4500 measurements of 15 seconds each
Low Battery Indicator: If the
losing power.
indicator lights up, the batteries are
Model 4630
Power Source: NiMH rechargeable cell (4630)
Battery Life: 2000 measurements of 15 seconds each
Battery Charging:
External recharge - 120-230V /50-60Hz, 20VA
Charge time - 6 hrs to attain 80% of the battery capacity
Low Battery Indicator: If the “CHARGE” indicator turns on solid RED,
the battery needs to be charged.
3.2Mechanical
Connection:
Color-coded terminals accept spade lugs with minimum gap of 6mm or
standard 4mm banana jacks.
Display:
2000-count 7 segment LCD, approx 1" high (3-1/2 digit)
LCD also indicates overrange, test lead shorts and lead reversals.
Blue electroluminescent backlight.
Dimensions:
10.8 x 9.7 x 5.0" (273 x 247 x 127mm)
Weight:
Model 4620: 6.28 lbs (2.85kg)
Model 4630: 7.38 lbs (3.35kg)
Colors:
Case - safety yellow; Front panel - gray
Mechanical Protection:
The Models 4620 and 4630 have successfully undergone all the required
mechanical tests and therefore meet all the requirements of the standards
EN 61557 and EN 61010-1.
12
Digital Ground Resistance Tester Model 4620 and 4630
3.3Environmental
Operating Temperature:
14° to 131°F (-10° to 55°C), 0 to 90% RH
Storage Temperature:
-40° to 158°F (-40° to 70°C), 0 to 90% RH with batteries removed
3.4Safety
Electrical:
EN 61010-1 + A2 (ed. 95)
EN 61557 (ed. 97)
30Vrms, CAT III, Pollution Degree 2
Electromagnetic Compatibility:
EN 61326-1 (ed.98)
*Specifications are subject to change without notice
3.5Auto-ranging
The selection of the measurement current is depending on the resistance
to measure.
When the instrument is turned ON, the measurement starts on the smallest
current range (100µA). If the measurement is between 185 and 1950cts,
the range stays the same (100µA). If the measurement is under 185cts,
the current is multiplied by 10 (within 10mA max). If it is above 1950cts, the
current is divided by 10 (without going under 100µA).
This is done to avoid switching back and forth between ranges when you
are measuring 190W. It is possible to display 190.0 or 190W depending on
the automatic range selection.
Digital Ground Resistance Tester Model 4620 and 4630
13
CHAPTER 4
GROUNDING THEORY
4.1
Grounding Electrode Resistance
Figure 3 illustrates a grounding rod. The resistance of the electrode has
the following components:
• the resistance of the metal and that of the connection to it
• the contact resistance of the surrounding earth to the electrode
• the resistance in the surrounding earth
More specifically:
A) Grounding electrodes are usually made of a very conductive metal
(copper) with adequate cross sections so that overall resistance is
negligible.
B) The National Institute of Standard and Technology (N.I.S.T.) has
demonstrated that the resistance between the electrode and the
surrounding earth is negligible if the electrode is free of paint,
grease or other coating, and if the earth is firmly packed.
Ground Rod
and Clamp
Contact
Resistance
Between Rod
and Soil
Concentric
Shells of
Earth
Figure 3
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Digital Ground Resistance Tester Model 4620 and 4630
C) The only component remaining is the resistance of the surrounding 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 L
A
Resistance = Resistivity x
Length
Area
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 Shell
Area
In the case of ground resistance, uniform earth (or soil) resistivity throughout 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:
R =
ρ
2πL
In
4L
-1
r
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 4620 and 4630
15
4.1.1 Effect of Ground Electrode Size and Depth on Resistance
Resistance in %
Size: Increasing the diameter of the rod does not materially reduce its
resistance. Doubling the diameter reduces resistance by less than 10%.
100
75
50
25
0
1/2
5/8
3/4
1
1 1/4
1 1/2
1 3/4
Rod Diameter (inches)
Figure 4
Depth: As a ground rod is driven deeper into the earth, its resistance
is substantially reduced. In general, doubling the rod length reduces the
resistance by an additional 40%.
200
100
Resistance in Ohms
80
60
40
30
20
1" dia.
1/2" dia.
10
8
6
5
4
3
2
1
5
15
25
35 40
50
60
70
Driven Depth in Feet
Ground Resistance Versus Ground Rod Depth
Figure 5
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Digital Ground Resistance Tester Model 4620 and 4630
NEC® 2014 250.52 (A)(5) requires a minimum of 8 ft (2.4m) of the electrode to be in contact with the soil. The most common of electrode is a
10 ft (3m) cylindrical rod which meets the NEC® code, which requires a
minimum diameter of 5/8” (1.59cm).
4.1.2 Effects of Soil Resistivity on Ground Electrode Resistance
Dwight’s formula, cited previously, shows that the resistance to earth of
grounding electrodes depends not only on the depth and surface area of
grounding electrodes but on soil resistivity as well.
Soil resistivity is the key factor that determines what the resistance of a
grounding electrode will be, and to what depth it must be driven to obtain
low ground resistance.
The resistivity of the soil varies widely throughout the world and changes
seasonally. Soil resistivity is determined largely by its content of electrolytes, consisting of moisture, minerals and dissolved salts. A dry soil has
high resistivity if it contains no soluble salts.
Resistivity, Ω-cm
Soil
Minimum
Average
Maximum
Ashes, cinders, brine, waste
590
2370
7000
Clay, shale, gumbo, loam
340
4060
16,300
1020
15,800
135,000
59,000
94,000
458,000
Same, with varying proportions
of sand and gravel
Gravel, sand, stones with
little clay or loam
Table 1
4.1.3 Factors Affecting Soil Resistivity
Two samples of soil, when thoroughly dried, may become in fact very good
insulators, having a resistivity in excess of 109 ohm-centimeters. The resistivity of the soil sample is seen to change quite rapidly until approximately
twenty percent or greater moisture content is reached.
Digital Ground Resistance Tester Model 4620 and 4630
17
Moisture content,
% by weight
Resistivity, Ω-cm
Top Soil
Sandy Loam
9
> 109
0
> 10
2.5
250,000
150,000
5
165,000
43,000
10
53,000
18,500
15
19,000
10,500
20
12,000
6300
30
6400
4200
Table 2
The resistivity of the soil is also influenced by temperature. Table 3 shows
the variation of the resistivity of sandy loam, containing 15.2% moisture,
with temperature changes from 20° to -15°C. In this temperature range the
resistivity is seen to vary from 7200 to 330,000 ohm-centimeters.
Temperature
°C
°F
Resistivity
Ω-cm
20
68
7200
10
50
9900
0
32 (water)
13,800
0
32 (ice)
30,000
-5
23
79,000
-15
14
330,000
Table 3
Because soil resistivity directly relates to moisture content and temperature, it is reasonable to assume that the resistance of any grounding
system will vary throughout the different seasons of the year. Such variations are shown in Figure 6 below.
18
Digital Ground Resistance Tester Model 4620 and 4630
Since both temperature and moisture content become more stable at
greater distances below the surface of the earth, it follows that a grounding
system (to be most effective at all times) should be constructed with the
ground rod driven down a considerable distance below the surface of the
earth. Best results are obtained if the ground rod reaches the water table.
80
60
Curve 1
40
20
July
May
Mar.
Jan.
Nov.
Sept.
July
May
Mar.
Curve 2
Jan.
0
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.
In some locations, the resistivity of the earth is so high that low-resistance
grounding can be obtained only at considerable expense and with an elaborate grounding system.
In such situations, it may be economical to use a ground rod system of
limited size and to reduce the ground resistivity by periodically increasing
the soluble chemical content of the soil.
Table 4 shows the substantial reduction in resistivity of sandy loam brought
about by an increase in chemical salt content.
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)
0
0.1
1.0
5
10
20
10,700
1800
460
190
130
100
Table 4
Digital Ground Resistance Tester Model 4620 and 4630
19
Chemically treated soil is also subject to considerable variation of resistivity
with changes in temperature, as shown in Table 5.
If salt treatment is employed, it is necessary to use auxiliary ground
electrodes, which will resist chemical corrosion.
The Effect of Temperature on the Resistivity of Soil Contining Salt*
(sandy loam, 20% moisture; salt 5% of weight of moisture)
Temperature ˚C
20
10
0
-5
-13
Resistivity (Ohm-centimeters)
110
142
190
312
1440
Table 5
*Such as copper sulfate, sodium carbonate and others. Salts must be EPA or local ordinance
approved prior to use.
4.1.4 Effect of Ground Rod Depth on Resistance
To assist the engineer in determining the approximate ground rod depth
required to obtain a desired resistance, a device called the Grounding
Nomograph may be used. The Nomograph, shown in Figure 7, indicates
that to obtain a grounding resistance of 20 ohms in a soil with a resistivity
of 10,000 ohm-centimeters, a 5/8" OD rod must be driven 20 ft. Note that
the values indicated on the Nomograph are based on the assumption that
the soil is homogeneous and, therefore, has uniform resistivity. The Nomograph value is an approximation.
20
Digital Ground Resistance Tester Model 4620 and 4630
Grounding Nomograph
Ground Rod
Resistance-Ohms
Soil Resistivity
(Ohm-centimeters)
R
100
90
P
80
70
100000
50000
60
50
40000
Rod Depth
Feet
D
K
100
90
80
70
60
50
40
30
Rod Diameter
Inches
DIA
8
7
6
5
4
3
30000
40
30
20000
20
15000
10000
20
2
15
1.5
15
5000
10
10
1
4000
3/4
3000
9
2000
8
5
7
5/8
1/2
1000
6
4
5
500
3
2
4
1/4
3
1
2
1
Figure 7
1. Select required resistance on R scale.
2. Select apparent resistivity on P scale.
3. Lay straightedge on R and P scale, and allow to intersect with K
scale.
4. Mark K scale point.
5. Lay straightedge on K scale point and DIA scale, and allow to intersect
with D scale.
6. Point on D scale will be rod depth required for resistance on R scale.
4.2
Ground Resistance Values
NEC® 2008 article 250.56 regarding the resistance of rod, pipe and plate
electrodes states that if the rod, pipe, or plate does not have a resistance
of 25Ω or less to ground shall be augmented by one additional electrode of
any of the types specified by 250.52 (A)(4) through (A)(8). Where multiple
rod, pipe or plate electrodes are installed to meet the requirements of the
section, they shall not be less than 6 feet apart.
Digital Ground Resistance Tester Model 4620 and 4630
21
FPN: The paralleling efficiency of rods longer than 8 feet is improved by
spacing greater than 6 feet apart.
The National Electrical Code® (NEC®) states that the resistance to ground
shall not exceed 25Ω. This is an upper limit and guideline, since much
lower resistance is required in many instances.
“How low in resistance should a ground be?”
An arbitrary answer to this in ohms is difficult. The lower the ground resistance, the safer, and for positive protection of personnel and equipment, it
is worth the effort to aim for less than one ohm. It is generally impractical
to reach such a low resistance along a distribution system or a transmission line or in small substations. In some regions, resistances of 5Ω or less
may be obtained without much trouble. In others, it may be difficult to bring
resistance of driven grounds below 100Ω.
Accepted industry standards stipulate that transmission substations
should be designed not to exceed one ohm resistance. In distribution substations, the maximum recommended resistance is 5Ω. In most cases, the
buried grid system of any substation will provide the desired resistance.
In light industrial or in telecommunications central offices, 5Ω is often the
accepted value. For lightning protection, the arresters should be coupled
with a maximum ground resistance of 1Ω.
These parameters can usually be met with the proper application of basic
grounding theory. There will always exist circumstances which will make
it difficult to obtain the ground resistance required by the NEC®. When
these situations develop, several methods of lowering the ground resistance can be employed. These include parallel rod systems, deep driven
rod systems utilizing sectional rods and chemical treatment of the soil.
Additional methods, discussed in other published data, are buried plates,
buried conductors (counterpoise), electrically connected building steel,
and electrically connected concrete reinforced steel.
Electrically connecting to existing water and gas distribution systems was
often considered to yield low ground resistance; however, recent design
changes utilizing non-metallic pipes and insulating joints have made this
method of obtaining a low resistance ground questionable and in many
instances unreliable.
Auxiliary ground electrodes will be required in high voltage transmission
lines, where maximum resistance of 15 ohms is recommended, and in
distribution lines, where maximum resistance of 25 ohms is preferred. All
electrical systems constructed in accordance with the National Electrical
Code®, should not exceed 25 ohms.
22
Digital Ground Resistance Tester Model 4620 and 4630
The measurement of ground resistances may only be accomplished with
specially designed test equipment. Most instruments use the Fall of Potential principle of alternating current (AC) circulating between an auxiliary
electrode and the ground electrode under test; the reading will be given
in ohms and represents the resistance of the ground electrode to the surrounding earth. AEMC® Instruments has also recently introduced a clampon ground resistance tester.
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)
3-Point measurement is used to measure resistance to ground of auxiliary
ground electrodes and grids. The potential difference between rods X and
Y is measured by a voltmeter, and the current flow between rods X and Z
is measured by an ammeter.
By Ohm’s Law E = RI or R = E/I, we may obtain the ground electrode
resistance R.
If E = 20V and I = 1 A, then:
E
20
R = = = 20 ohms
I
1
It is not necessary to carry out all the measurements when using a ground
tester. The ground tester will measure directly by generating its own current and displaying the resistance of the ground electrode.
Digital Ground Resistance Tester Model 4620 and 4630
23
CURRENT
SUPPLY
AMMETER (I)
VOLTMETER (E)
GROUND
ELECTRODE
UNDER TEST
X (E)
AUXILIARY
POTENTIAL
ELECTRODE
Y (S)
AUXILIARY
CURRENT
ELECTRODE
Z (H)
R
EARTH
Figure 8
NOTE: Terminals X and Xv are shorted together in 3-Point measurement.
4.3.1 Position of the Auxiliary Electrodes in Measurements
The goal in precisely measuring the resistance to ground is to place the
auxiliary current electrode Z far enough from the ground electrode under
test so that the auxiliary potential electrode Y will be outside of the effective resistance areas of both the ground electrode and the auxiliary current
electrode. The best way to find out if the auxiliary potential rod Y is outside
the effective resistance areas is to move it between X and Z and to take
a reading at each location. If the auxiliary potential rod Y is in an effective
resistance area (or in both if they overlap), by displacing it, the readings
taken will vary noticeably in value. Under these conditions, no exact value
for the resistance to ground may be determined.
24
Digital Ground Resistance Tester Model 4620 and 4630
X
Y' Y Y''
Z
Resistance
Effective Resistance
Areas (Overlapping)
Reading Variation
X-Y Distance
Figure 9
On the other hand, if the auxiliary potential rod Y is located outside of
the effective resistance areas, as Y is moved back and forth the reading
variation is minimal. The readings taken should be relatively close to each
other, and are the best values for the resistance to ground of the ground X.
The readings should be plotted to ensure that they lie in a “plateau” region
as shown in Figure 10.
Y Y Y''
Z
Effective Resistance
Areas (No Overlap)
Resistance
X
Reading Variation
X-Y Distance
Figure 10
Digital Ground Resistance Tester Model 4620 and 4630
25
4.4
Measuring Resistance of Ground Electrodes
(62% Method)
The 62% method has been adopted after graphical consideration and
after actual test. It is the most accurate method but is limited by the fact
that the ground tested is a single unit.
This method applies only when all three electrodes are in a straight line
and the ground is a single electrode, pipe, or plate, etc., as in Figure 11.
Ω
Ground
Strip
Z Electrode
Y Electrode
Ground Rod
Alligator Clips
-10% 3rd
Measurement
Ground Rod
X
0%
+10% 2nd
Measurement
Y Electrode
Y
52% 62% 72%
Z Electrode
Z
100% of distance
between X and Z
Figure 11
Consider Figure 12, which shows the effective resistance areas (concentric
shells) of the ground electrode X and of the auxiliary current electrode Z.
The resistance areas overlap.
If readings were taken by moving the auxiliary potential electrode Y
towards either X or Z, the reading differentials would be great and one
could not obtain a reading within a reasonable band of tolerance. The
sensitive areas overlap and act constantly to increase resistance as Y is
moved away from X.
26
Digital Ground Resistance Tester Model 4620 and 4630
Ground
Electrode
Under Test
Auxiliary
Potential
Electrode
X
Y
Auxiliary
Current
Electrode
Z
Resistance
Overlapping Effective
Resistance Areas
Distance from Y to Ground Electrode
Figure 12
Now consider Figure 13, where the X and Z electrodes are sufficiently
spaced so that the areas of effective resistance do not overlap. If we plot
the resistance, measured we find that the measurements level off when
Y is placed at 62% of the distance from X to Z, and that the readings on
either side of the initial Y setting are most likely to be within the established
tolerance band. This tolerance band is defined by the user and expressed
as a percent of the initial reading: ±2%, ±5%, ±10%, etc.
Auxiliary
Potential
Electrode
Ground
Electrode
Under Test
X
Auxiliary
Current
Electrode
Y
Z
D
Resistance
62% of D
38% of D
Resistance of
Auxiliary Current
Electrode
Effective
Resistance
Areas Do
Not Overlap
Resistance of Earth Electrode
Distance from Y to Ground Electrode
Figure 13
Digital Ground Resistance Tester Model 4620 and 4630
27
4.4.1 Auxiliary Electrode Spacing
No definite distance between X and Z can be given, since this distance is
relative to the diameter of the electrode tested, its length, the homogeneity
of the soil tested, and particularly, the effective resistance areas. However, an approximate distance may be determined from the following chart
which is given for a homogeneous soil and an electrode of 1" in diameter.
(For a diameter of 1/2", reduce the distance by 10%; for a diameter of 2"
increase the distance by 10%.)
Approximate Distance to Auxiliary Electrodes
Using the 62% Method
Depth Driven
6 ft
8 ft
10 ft
12 ft
18 ft
20 ft
30 ft
Distance to Y
45 ft
50 ft
55 ft
60 ft
71 ft
74 ft
86 ft
Distance to Z
72 ft
80 ft
88 ft
96 ft
115 ft
120 ft
140 ft
Table 6
4.5
Multiple Electrode System
A single driven ground electrode is an economical and simple means of
making a good ground system, but sometimes a single rod will not provide
sufficient low resistance, and several ground electrodes will be driven and
connected in parallel by a cable.
Very often when two, three or four ground electrodes are used, they are
driven in a straight line. When four or more are used, a hollow square configuration is used and the ground electrodes are still connected in parallel
and equally spaced (Figure 14).
In multiple electrode systems, the 62% method electrode spacing may no
longer be applied directly. The distance of the auxiliary electrodes is now
based on the maximum grid distance (e.g. in a square, the diagonal; in a
line, the total length). A square having a side of 20 ft will have a diagonal
of approximately 28 ft.
28
Digital Ground Resistance Tester Model 4620 and 4630
a
a
a
a
DIAGONAL
DIAGONAL
Figure 14
Multiple Electrode System
Max Grid Distance
6 ft
8 ft
10 ft
12 ft
14 ft
16 ft
18 ft
20 ft
30 ft
40 ft
50 ft
60 ft
80 ft
100 ft
120 ft
140 ft
160 ft
180 ft
200 ft
Distance to Y
78 ft
87 ft
100 ft
105 ft
118 ft
124 ft
130 ft
136 ft
161 ft
186 ft
211 ft
230 ft
273 ft
310 ft
341 ft
372 ft
390 ft
434 ft
453 ft
Distance to Z
125 ft
140 ft
160 ft
170 ft
190 ft
200 ft
210 ft
220 ft
260 ft
300 ft
340 ft
370 ft
440 ft
500 ft
550 ft
600 ft
630 ft
700 ft
730 ft
Table 7
Digital Ground Resistance Tester Model 4620 and 4630
29
CHAPTER 5
OPERATION
5.1
Ground Resistance Measurement Procedure
(3-Point)
Ω
Ground
Strip
Y Electrode
X
Ground Rod
Z Electrode
Alligator Clips
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.
• X and Xv (E, ES) are shorted
• Disconnect shorting link between Y and Z (S, H)
• Connect X to the ground rod to be tested
• Connect Y (S) to the center electrode
• Connect Z (H) to the outer electrode
• Depress the “Test” button to measure ground resistance
30
Digital Ground Resistance Tester Model 4620 and 4630
5.2
2-Point Measurement (Simplified Measurement)
This is an alternative method to 3-Point measurement when an excellent
ground is already available.
In congested areas where finding room to drive the two auxiliary ground
electrodes may be a problem, the 2-Point measurement method may be
applied. The reading obtained will be that of the two grounds in series.
Therefore, the water pipe or other ground must be very low in resistance
so that it will be negligible in the final measurement. The lead resistances
will also be measured and should be deducted from the final measurement.
This method is not as accurate as 3-Point method (62% method), as it is
particularly affected by the distance between the tested electrode and the
dead ground or water pipe. This method should not be used as a standard
procedure, but rather as a backup in tight areas.
Procedure:
• Short X and Xv (E, ES)
• Short Y and Z (S, H)
• Connect X to ground rod to be measured
• Connect Z to an electrode
• Measure as in the 3-Point method
Grounding conductor
Metallic Water Pipe
(Y-Z shorted)
Ground
level
Utility
pole
Ω
Butt plate
Ground
rod
Terminals shorted
Figure 16
Digital Ground Resistance Tester Model 4620 and 4630
31
5.3
Continuity Measurement
Connect the shorting link, supplied with the instrument, between X and Xv
(E and Es).
Connect a short wire or jumper cable between Y and Z (H and S) as shown
in Figure 17.
Continuity measurement is made with two leads, one from X-Xv and the
other from Y-Z.
Push the “Test” button to measure continuity. This is a good test to verify
bonding between grounding electrode and the ground wire.
Ω
Figure 17
5.4
Soil Resistivity Measurements
5.4.1 Purposes of Soil Resistivity
Soil resistivity measurements have three purposes:
1. Such data is used to make sub-surface geophysical surveys as an
aid in identifying ore locations, depth to bedrock and other geological
phenomena.
2. Resistivity has a direct impact on the degree of corrosion in underground pipelines. A decrease in resistivity relates to an increase in
corrosive activity and therefore dictates the protective treatment to be
used.
32
Digital Ground Resistance Tester Model 4620 and 4630
3. Soil resistivity directly affects the design of a grounding system, and
it is to that task that this discussion is directed. When designing an
extensive grounding system, it is advisable to locate the area of lowest
soil resistivity in order to achieve the most economical grounding
installation.
5.4.2 Types of Resistivity Measurements
There are two types of resistivity measurements:
• 2-Point method
The 2-Point method is simply the resistance measured between
two points.
• 4-Point method
For most applications, the most accurate method is the 4-Point
method, which is used by the AEMC® Instruments Model 4620
and 4630 Ground Testers. The 4-Point method, as the name
implies, requires the insertion of four equally spaced, in-line electrodes into the test area. A known current from a constant current
generator is passed between the outermost electrodes (X and Z).
The potential drop (a function of the resistance) is then measured
across the two innermost electrodes (Xv and Y). The Models 4620
and 4630 are calibrated to read directly in ohms.
Ω
X electrode
b<
A
20
A
Xv electrode
A
Y electrode
Z electrode
A
Figure 18
Digital Ground Resistance Tester Model 4620 and 4630
33
5.5 Soil Resistivity Measurement Procedure
(4-Point)
Given a sizeable tract of land in which to determine the optimum soil resistivity, some intuition is in order. Assuming that the objective is low resistivity, preference should be given to an area containing moist loam as
opposed to a dry sandy area. Consideration must also be given to the
depth at which resistivity is required.
• Disconnect the shorting link from the X and Xv terminals.
• Arrange the electrodes in a straight line. Be sure that distances
between electrodes are identical.
Example: 10 ft between each electrode for auxiliary ground electrodes that will be driven 10 ft deep (See Figure 18).
• The distance between poles is proportional to the average depth
of the soil sample you wish to make.
• The electrodes should be placed at a depth of approximately 6"
(0.15m), so that the depth is approximately 1/20th of the distance
between electrodes.
• Use leads to connect the X, Xv, Y, and Z electrodes to the respective terminals on the Digital Ground Resistance Tester.
• Press the “Test” button.
• Read the resistance level (R) indicated on the display.
• In the event of difficulties in performing measurements,
consult the previous instructions concerning ground resistance
measurements.
• Apply the following formula in order to determine resistivity (ρ):
ρ = 2π x R x A
A = distance between electrodes in cm
ρ = resistivity in Ωcm
R = ohms reading obtained on Model 4620/4630
Example 1: For measurement performed in soil with a high limestone content, the
reading is R = 225Ω, with A = 300cm (3m).
ρ = 2π x 225Ω x 300cm
ρ = 423,900Ωcm
34
Digital Ground Resistance Tester Model 4620 and 4630
Example 2: After inspection, the area to be investigated has been narrowed down
to a plot of ground approximately 75 square feet (22.5 m2). Assume that you need
to determine the resistivity at a depth of 15 ft (457cm). The distance “A” between
the electrodes must then be equivalent to the depth at which average resistivity is
to be determined (15ft or 450 cm). Using the more simplified Wenner formula (ρ =
2πAR), the electrode depth must then be 1/20th of the electrode spacing or 8-7/8"
(22.5cm). If the electrode spacing is greater than 1/20th of the electrode spacing,
the following formula must be used:
ρ =
4πaR
1+
2a
a2 + 4b2
a
a2 + b2
Lay out the electrodes in a grid pattern (Figure 20) and connect to the
Model 4630 as shown in Figure 19. Proceed as follows:
• Remove the shorting link between X and Xv
• Connect all four auxiliary ground electrodes
Example 3: If the reading is R = 15:
ρ (resistivity) = 2π x R x A
A (distance between electrodes) = 450 cm
ρ = 6.28 x 15 x 450 = 42,390Ωcm
Ω
A
X
Xv
A
Y
A
Z
B
R
Figure 19
Digital Ground Resistance Tester Model 4620 and 4630
35
A
A
A
A
A
A
Figure 20
5.6
How to Use 25Ω Calibration Checker (optional accessory)
The calibration checker is good for both the 4620 and 4630. It has a
resistance of 25Ω. The procedure to use the calibration checker is as
follows:
• Loosen the X, Xv, Y and Z terminals.
• Insert the calibration checker as shown in Figure 21.
• Tighten down the terminals X, Xv, Y and Z.
• Push down the “Test” button.
• Compare the reading on the display to the measurement range
provided below.
NOTE: For alignment purposes of the calibration checker, it is recommended
that the shorting links remain connected.
Ω
INSTRUMENTS
®
25Ω CALIBRATION CHECKER
If a check performed on the Model 4630 or 4620 displays a reading
between 24.1Ω and 25.9Ω (as in Figure 21), the instrument is in good
working condition. The readings are for an ambient temperature between
68° and 79°F (25°C ±3°C).
Figure 21
36
Digital Ground Resistance Tester Model 4620 and 4630
CHAPTER 6
MAINTENANCE
6.1Warning
Please make sure that you have already read and fully understand the WARN ING section on page 3.
• To avoid electrical shock, do not attempt to perform any servicing
unless you are qualified to do so.
• To avoid electrical shock and/or damage to the instrument, do not
get water or other foreign agents into the case.
• Turn the instrument OFF and disconnect the unit from all circuits
before opening the case.
• Use specified spare parts only.
6.2Disassembly
Necessary equipment:
• A Torx ACX.10 screwdriver or similar
• A Phillips screwdriver
With the Phillips screwdriver, remove the 4 screws (1) at the back of the
case and free the internal unit (2) from the yellow case (3).
Digital Ground Resistance Tester Model 4620 and 4630
37
To open the internal unit:
• Set the unit upside-down on the table and open the battery compartment (4) by removing the 2 Phillips screws holding the latch. Then, free
the battery (5) or the batteries (depending on the type of instrument).
• Remove the 2 Torx screws (6) in the bottom of the battery compartment.
• To get access to the two connectors (9) linking the power supply and
display boards together, lift up the cover of the internal unit. Once these
connectors are free, it is possible to completely pull away the bottom
part from the cover.
• The display board (7) is connected to the front plate.
• The power supply board (8) is connected to the bottom of the body.
To free the display board from the cover:
• Remove the 3 Phillips screws and unsolder all the wires connecting to the terminals and to the fuse.
To free the power supply board from the bottom of the body:
• Remove the 6 Phillips screws at the back of the body and disconnect the connector coming from the battery.
6.3
Power Supply
6.3.1 Testing the Battery
• Short-circuit the X and Z terminals.
• Press the “TEST” button.
• If the low battery or charge indicator lights up on the display you
will need to replace or recharge the batteries.
38
Digital Ground Resistance Tester Model 4620 and 4630
6.3.2 Replacing the Battery (Model 4620)
• Detach the four screws on the bottom of the yellow case.
• Remove the shell and front panel assembly.
• Unscrew the two fastening screws on the battery compartment,
then remove the cover.
• Remove the 8 batteries and replace them.
To replace the batteries with rechargeable cells (1.2V - 2 Ah or above,
NiCd or NiMH of the same size):
• Remove the plug under the batteries.
• Set the switch to the position: NiCd/NiMH
• Replace the plug.
• Insert the 8 rechargeable cells.
NOTE: The Model 4620 does not have a built-in battery charger. The
rechargeable cells will need to be charged outside the instrument.
6.3.3 Recharging the Battery (Model 4630)
• Connect the battery charge connector to the mains.
• The CHARGE indicator light will turn red.
• When the battery is charged, the CHARGE indicator will become
green.
• The charge time is approximately 6 hrs for 80% of the battery
capacity.
To achieve maximum charge capacity:
• Disconnect the power cord (the green LED will go out in approximately 20 sec).
• Reconnect the power cord. The charge will resume where the first
charge left off, and continue until maximum capacity is achieved.
NOTE: If the unit has been stored for a long period of time, recharge the bat-
tery before use.
NOTE: 1/2 hr charge provides enough power for one day of measurements
(approx 135 measurements lasting 15 sec).
Digital Ground Resistance Tester Model 4620 and 4630
39
6.3.4 Replacing the Safety Fuse
To check the fuse continuity, short circuit the X and Z terminals and make
a measurement. If the FAULT indicator light flashes, it means that the fuse
is blown.
To replace the fuse:
NOTE: Do not replace the fuse when the instrument is connected.
• The fuse is located on the front of the faceplate.
• Using a screwdriver, turn the screw a quarter of a turn.
• Take out the support containing the fuse.
• Replace the fuse (0.1A, >250V, 0.25 x 1.25").
• Replace the support and screw it back in.
6.4Cleaning
NOTE: Disconnect the instrument from any source of electricity.
• Use a soft cloth lightly dampened with soapy water.
• Rinse with a damp cloth and then dry with a dry cloth.
• Do not use alcohol, solvents or hydrocarbons.
6.5Storage
If the Model 4620 is not used for a long period of time (two months or
more), remove the batteries and store them separately.
If the Model 4630 is not used for a long period of time (two months or
more), it is recommended to charge the battery for a few hours.
40
Digital Ground Resistance Tester Model 4620 and 4630
Repair and Calibration
To ensure that your instrument meets factory specifications, we recommend
that it be scheduled back to our factory Service Center at one-year intervals
for recalibration, or as required by other standards or internal procedures.
For instrument repair and calibration:
You must contact our Service Center for a Customer Service Authorization
Number (CSA#). This will ensure that when your instrument arrives, it will be
tracked and processed promptly. Please write the CSA# on the outside of the
shipping container. If the instrument is returned for calibration, we need to
know if you want a standard calibration, or a calibration traceable to N.I.S.T.
(Includes calibration certificate plus recorded calibration data).
Ship To:
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
15 Faraday Drive
Dover, NH 03820 USA
Phone:(800) 945-2362 (Ext. 360)
(603) 749-6434 (Ext. 360)
Fax: (603) 742-2346 or (603) 749-6309
E-mail:repair@aemc.com
(Or contact your authorized distributor)
Costs for repair, standard calibration, and calibration traceable to N.I.S.T. are
available.
NOTE: You must obtain a CSA# before returning any instrument.
Technical and Sales Assistance
If you are experiencing any technical problems, or require any assistance with
the proper operation or application of your instrument, please call, mail, fax or
e-mail our technical support team:
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
200 Foxborough Boulevard
Foxborough, MA 02035 USA
Phone:(800) 343-1391
(508) 698-2115
Fax: (508) 698-2118
E-mail:techsupport@aemc.com
www.aemc.com
NOTE: Do not ship Instruments to our Foxborough, MA address.
Digital Ground Resistance Tester Model 4620 and 4630
41
Limited Warranty
The Models 4620 and 4630 are warranted to the owner for a period of one
year from the date of original purchase against defects in manufacture. This
limited warranty is given by AEMC® Instruments, not by the distributor from
whom it was purchased. This warranty is void if the unit has been tampered
with, abused or if the defect is related to service not performed by AEMC®
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:
If a malfunction occurs within the one-year period, you may return the instrument
to us for repair, provided we have your warranty registration information on file
or a proof of purchase. AEMC® Instruments will, at its option, repair or replace
the faulty material.
REGISTER ONLINE AT:
www.aemc.com
Warranty Repairs
What you must do to return an Instrument for Warranty Repair:
First, request a Customer Service Authorization Number (CSA#) by phone
or by fax from our Service Department (see address below), then return the
instrument along with the signed CSA Form. Please write the CSA# on the
outside of the shipping container. Return the instrument, postage or shipment
pre-paid to:
Ship To:
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
15 Faraday Drive • Dover, NH 03820 USA
Phone:(800) 945-2362 (Ext. 360)
(603) 749-6434 (Ext. 360)
Fax: (603) 742-2346 or (603) 749-6309
E-mail:repair@aemc.com
Caution: To protect yourself against in-transit loss, we recommend you insure
your returned material.
NOTE: You must obtain a CSA# before returning any instrument.
42
Digital Ground Resistance Tester Model 4620 and 4630
Notes:
Digital Ground Resistance Tester Model 4620 and 4630
43
10/16
99-MAN 100259 v18
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
15 Faraday Drive • Dover, NH 03820 USA • Phone: (603) 749-6434 • Fax: (603) 742-2346
www.aemc.com
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