AEMC 4620 User manual

4620 & 4630
User Manual
ENGLISH
GROUND TESTERS
WITH AEMC
®
INSTRUMENTS

Copyright © Chauvin Arnoux®, Inc. d.b.a. AEMC®Instruments. All rights reserved.
No part of this documentation may be reproduced in any form or by any means (including electronic
storage and retrieval or translation into any other language) without prior agreement and written consent
from Chauvin Arnoux®, Inc., as governed by United States and International copyright laws.
Chauvin Arnoux®, Inc. d.b.a. AEMC®Instruments
15 Faraday Drive • Dover, NH 03820 USA
Tel: [phone] or [phone] • Fax: [phone]
This documentation is provided “as is,” without warranty of any kind, express, implied, or otherwise.
Chauvin Arnoux®󰀨
but does not warrant the accuracy or completeness of the text, graphics, or other information contained
in this documentation. Chauvin Arnoux®, Inc. shall not be liable for any damages, special, indirect,


user of the documentation has been advised of the possibility of such damages.

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 ................................................................................ 6
1.1 PRECAUTIONS FOR USE .................................................. 7
1.2 RECEIVING YOUR SHIPMENT................................................ 7
1.4 ORDERING INFORMATION ..................................................... 8
1.4.1 Kits, Accessories, and Replacement Parts .................................... 9
2. PRODUCT FEATURES.................................................................... 10
2.1 CONTROL AND CONNECTOR FEATURES (4620) .............. 10
2.2 CONTROL AND CONNECTOR FEATURES (4630) .............. 11
2.3 FAULT INDICATOR LEDS ....................................................... 12
2.3.1 X-Z Fault ......................................................................................12
2.3.2 Xv-Y High Resistance ..................................................................12
2.3.3 Xv-Y High Noise...........................................................................12
2.4 BUZZER.................................................................................... 12
2.5 OVER-RANGE INDICATION................................................... 12
2.6 FAULT LED INDICATION – TIPS AND SOLUTIONS ............ 13
3. OPERATION ..................................................................................... 14
3.1 GROUND RESISTANCE MEASUREMENT PROCEDURE
(3-POINT)..............................................................................................14
3.2 2-POINT MEASUREMENT (SIMPLIFIED MEASUREMENT) .....14
3.3 CONTINUITY MEASUREMENT.............................................. 16
3.4 SOIL RESISTIVITY MEASUREMENTS ................................. 16
3.4.1 Purposes of Soil Resistivity..........................................................16
3.4.2 Types of Resistivity Measurements..............................................17
3.5 SOIL RESISTIVITY MEASUREMENT PROCEDURE
(4-POINT).................................................................................... 18

(OPTIONAL ACCESSORY).................................................................20
4. GROUNDING THEORY ................................................................... 21
4.1 GROUNDING ELECTRODE RESISTANCE .......................... 21
󰀨 .........23
󰀨 .........24
󰀨 ..................................................25
󰀨 .................................27

Digital Ground Resistance Tester Models 4620 & 4630 5
4.2 GROUND RESISTANCE VALUES.......................................... 28
4.3 GROUND RESISTANCE TESTING PRINCIPLE
(FALL-OF-POTENTIAL—3-POINT MEASUREMENT) ......................30
4.3.1 Position of the Auxiliary Electrodes in Measurements .................31
4.4 MEASURING RESISTANCE OF GROUND ELECTRODES
(62% METHOD) ........................................................................ 32
4.4.1 Auxiliary Electrode Spacing..........................................................34
4.5 MULTIPLE ELECTRODE SYSTEM........................................ 34
5. SPECIFICATIONS............................................................................ 36
5.1 ELECTRICAL............................................................................ 36
5.2 MECHANICAL .......................................................................... 37
5.3 ENVIRONMENTAL................................................................... 38
3.4 SAFETY .................................................................................... 38
5.5 AUTO-RANGING...................................................................... 38
6. MAINTENANCE................................................................................ 39
6.1 WARNING................................................................................. 39
6.2 DISASSEMBLY......................................................................... 39
6.3 POWER SUPPLY ..................................................................... 40
6.3.1 Testing the Battery .......................................................................40
6.3.2 Replacing the Battery (Model 4620).............................................40
6.3.3 Recharging the Battery (Model 4630) ..........................................41
6.3.4 Replacing the Safety Fuse...........................................................41
6.4 CLEANING................................................................................ 42
6.5 STORAGE................................................................................. 42
6.6 REPAIR AND CALIBRATION .................................................. 42
6.7 TECHNICAL AND SALES ASSISTANCE ............................... 43
6.8 LIMITED WARRANTY.............................................................. 43
6.9 WARRANTY REPAIRS ............................................................ 43

6 Digital Ground Resistance Tester Models 4620 & 4630
1. INTRODUCTION
Thank you for purchasing a Digital Ground Resistance Tester Model 4620 or
Model 4630.
For best results from your instrument and for your safety, read the enclosed
operating instructions carefully and comply with the precautions for use. These

Symbols
Instrument is protected by double or reinforced insulation.
CAUTION - DANGER! Read the User Manual.
Risk of electric shock. The voltage at the parts marked with this
symbol may be dangerous.
The trash can with a line through it means that in the European
Union, the product must undergo selective disposal for the recycling
of electric and electronic material in compliance with Directive
WEEE 2002/96/EC.
Denition of Measurement Categories (CAT)
CAT IV corresponds to measurements taken at the primary electrical supply
(<1000 V).
Example: primary overcurrent protection devices, ripple control units, and meters.
CAT III corresponds to measurements taken in building installations at the
distribution level.
Example: distribution panel, circuit-breakers, machines, and xed industrial
devices.
CAT II corresponds to measurements taken on circuits directly connected to low-
voltage installations.
Example: power supple to domestic electrical appliances and portable tools

Digital Ground Resistance Tester Models 4620 & 4630 7
1.1 PRECAUTIONS FOR USE
“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 eectively 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.”
- excerpt from IEEE Std. 81-1962
These safety warnings are provided to ensure the safety of personnel and proper
operation of the instrument.
■
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.
■
equipment.
■Never attempt to use the instrument to twist or pry the ground electrode or
wire away from the grounded equipment
■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.
1.2 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

notify your distributor at once with a detailed description of any damage. Save
the damaged packing container to substantiate your claim.
NOTE: Do not use equipment that appears to be damaged.

8 Digital Ground Resistance Tester Models 4620 & 4630
1.4 ORDERING INFORMATION
Ground Resistance Tester Model 4620......................................... Cat. #2130.43
Includes 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 two 5 ft color-
coded (red/blue) leads, set of 5 spaded lugs, one 100 ft AEMC®tape measure, 8
C cell 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 color-coded leads (hand-tied, green/black), four T-shaped auxiliary ground
electrodes, set of two 5 ft color-coded (red/blue) leads, set of 5 spaded lugs, one
100 ft AEMC®tape measure, 8 C cell 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 color-coded leads (hand-tied, green/black), one 30 ft lead (green), four
T-shaped auxiliary ground electrodes, set of two 5 ft color-coded (red/blue) leads,
set of 5 spaded lugs, one 100 ft AEMC®tape measure, 8 C cell batteries, carrying
bag, and user manual.
Ground Resistance Tester Model 4630......................................... Cat. #2130.44
Includes 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 two 5 ft color-
coded (red/blue) leads, set of 5 spaded lugs, one 100 ft AEMC®tape measure,
rechargeable battery, 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 color-coded leads (hand-tied, green/black), four T-shaped auxiliary ground
electrodes, set of two 5 ft color-coded (red/blue) leads, set of 5 spaded lugs,
one 100 ft AEMC®tape measure, rechargeable battery, 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 color-coded leads (hand-tied, green/black), one 30 ft lead (green), four
T-shaped auxiliary ground electrodes, set of two 5 ft color-coded (red/blue) leads,
set of 5 spaded lugs, one 100 ft AEMC®tape measure, rechargeable battery,
carrying bag, and user manual.

Digital Ground Resistance Tester Models 4620 & 4630 9
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 T-shaped auxiliary ground electrodes, set of two 5 ft color-coded (red/blue)
leads, 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 two 5 ft color-coded (red/blue) leads, 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 two 5 ft color-coded (red/blue) leads, 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.
 ................................................................. Cat. #2130.59
Tape Measure – AEMC 100 ft........................................................... Cat. #2130.60
Set of 2, T-Shaped Auxiliary Ground Electrodes .............................. Cat. #2135.39
Inverter – 12 V to 120 V 200 Watt for vehicle use.................... Cat. #2135.43
Ground Rod – Set of 2, 17” Stainless Steel T-shaped
Auxiliary Ground Electrodes............................................................. Cat. #2135.44
Replacement 9.6 V Rechargeable Battery Pack (4630)................... Cat. #2960.21
Fuse – Set of 5, 0.1 A, >250 V, 0.25 x 1.25”..................................... Cat. #2970.12
115 V Power Cord ............................................................................ Cat. #5000.14
Lead – Replacement set of 2, 5 ft color-coded for use with
ground tester reels incorporating banana jack input......................... Cat. #5000.34
Download the Ground Tester Workbook at www.aemc.com.
Order Accessories and Replacement Parts Directly Online
Check our Storefront at www.aemc.com/store for availability

10 Digital Ground Resistance Tester Models 4620 & 4630
2. PRODUCT FEATURES
2.1 CONTROL AND CONNECTOR FEATURES (4620)
Ω
1. Low battery indicator
2. Input terminal Z (H)
3. Input terminal Y (S)
4. Input terminal Xv (ES)
5. Input terminal X (E)
6. X-Z Fault indicator
Figure 1
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)
2
1
3
4
5
11
10
9
867

Digital Ground Resistance Tester Models 4620 & 4630 11
2.2 CONTROL AND CONNECTOR FEATURES (4630)
Ω
1. Low battery indicator
2. AC power input
3. Input terminal Z (H)
4. Input terminal Y (S)
5. Input terminal Xv (ES)
6. Input terminal X (E)
Figure 2
7. X-Z Fault indicator
8. Xv-Y High Resistance indicator
9. Xv-Y High Noise indicator
10. Display (with backlight)
11. Fuse holder
12. Test button
3
2
1
4
5
6
12
11
10
978

12 Digital Ground Resistance Tester Models 4620 & 4630
2.3 FAULT INDICATOR LEDS
If none of the three indicators are lit, the correct measurement is being taken.
2.3.1 X-Z Fault
This LED signals that the voltage between terminals X and Z exceeds 30 V.
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

■
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.
■󰀨
■To verify a lead’s continuity, perform a continuity check with a multimeter. You
can also perform a continuity measurement using the instrument as shown in
§3.3 by performing the test on the lead instead of an electrode.
2.3.3 Xv-Y High Noise
This LED signals the presence of excessive electrical noise (13 V approx)
in the voltage circuit (between Xv and Y or X and Y). One solution to reduce the
electrical noise in the voltage circuit is below.
■Use shielded leads from the instrument to the auxiliary electrodes.
■Connect all the shields to the rod under test.
2.4 BUZZER

terminals are connected to a voltage source. The sound volume is proportional to

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.

Digital Ground Resistance Tester Models 4620 & 4630 13
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, the following tips and
solutions could help.
■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.
■
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.
■
move both Y and Z electrodes in an arc relative to the X electrode (try, e.g. a
90° shift), and test again.
■A display of 0.00 indicates that Xv and Y are short-circuited.
■A display of < 0 indicates that X and Z or Xv and Y rods are reversed.
NOTE: 󰀨
resistance levels and by stray signal levels (earth currents).

14 Digital Ground Resistance Tester Models 4620 & 4630
3. OPERATION
3.1 GROUND RESISTANCE MEASUREMENT PROCEDURE
(3-POINT)
Figure 15
WARNING: Use extreme caution when disconnecting the ground

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.
3.2 2-POINT MEASUREMENT (SIMPLIFIED MEASUREMENT)
This is an alternative method to 3-Point measurement when an excellent ground
is already available.
In congested areas without room to drive the two auxiliary ground electrodes, the
2-Point measurement method may be applied. Since the two auxiliary ground
rods are not used, the reading will show two grounds in series. Therefore, the
water pipe or other ground must be very low in resistance so that it will be


Alligator Clips
Ground Rod
X
Y Electrode Z Electrode
Groun
d
Strip
Ω

Digital Ground Resistance Tester Models 4620 & 4630 15
This method is not as accurate as 3-Point method (62% method) because it is
󰀨
ground or water pipe. This method should not be used as a standard procedure
but as a backup in congested 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.
Figure 16
Grounding conductor
Ground
level
Ground
rod
Butt plat
e
Utility
pole
Terminals shorted
Metallic Water Pipe
(Y-Z shorted)
Ω

16 Digital Ground Resistance Tester Models 4620 & 4630
3.3 CONTINUITY MEASUREMENT
■Connect the supplied shorting link 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.
Figure 17
3.4 SOIL RESISTIVITY MEASUREMENTS
3.4.1 Purposes of Soil Resistivity
Soil resistivity measurements have three purposes:
1. The data is used to make sub-surface geophysical surveys to help identify
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, determines the necessary protective treatment to use.
3. 󰀨
designing an extensive grounding system, the most economical grounding
installation requires locating the area with the lowest soil resistivity.
Ω

Digital Ground Resistance Tester Models 4620 & 4630 17
3.4.2 Types of Resistivity Measurements
There are two types of resistivity measurements:
■2-Point method
The 2-Point method is 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 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.
Figure 18
b<
A
20 AAA
Z electrodeY electrodeXv electrodeX electrode
Ω

18 Digital Ground Resistance Tester Models 4620 & 4630
3.5 SOIL RESISTIVITY MEASUREMENT PROCEDURE
(4-POINT)
To locate the lowest soil resistivity in a large area, the best locations to test would
󰀨
the soil resistivity.
■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: 20 ft (609.6 cm) between each electrode for auxiliary ground
electrodes that will be driven 10 ft deep (See Figure 18).
■The distance between electrodes 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” (0.15 m), so
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.
■󰀩
instructions concerning ground resistance measurements.
■
• 
• 
• 
• 
Example 1: For measurement performed in soil with a high limestone content,

• 
• 

Digital Ground Resistance Tester Models 4620 & 4630 19
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 ft (457 cm). The distance “A”
between the electrodes must then be equivalent to the depth at which average


electrode spacing or 8-7/8” (22.5 cm). If the electrode spacing is greater than
1/20th of the electrode spacing, the following formula must be used:
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:
• 
• 
• 
Figure 19
ρ
=
4πaR
1 +2a
a
2
+ 4b
2
a
a
2
+ b
2
R
B
XXvYZ
AAA
Ω

20 Digital Ground Resistance Tester Models 4620 & 4630
Figure 20
3.6 HOW TO USE 25 Ω CALIBRATION CHECKER
(OPTIONAL ACCESSORY)
The calibration checker is good for both the 4620 and 4630. It has a resistance of

■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.
If a check performed on the Model 4630 or 4620 displays a reading between 24.1

readings are for an ambient temperature between 68° and 79°F (25°C ±3°C).
Figure 21
AAA
A
A
A
25
Ω
CALIBRATION CHECKER
®
INSTRUMENTS
Ω