Clamp-On Ground Resistance Tester Models 3711 and 3731

Clamp-On
Ground Resistance Tester
Models 3711 and 3731
USER MANUAL
®
®
A
Ω
ON
OFF
MEM
AL
A
Ω
ON
OFF
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 #: 2117.60/2117.61
Model #:
3711/3731
Please fill in the appropriate date as indicated:
Date Received:
Date Calibration Due:
Chauvin Arnoux®, Inc.
d.b.a AEMC® Instruments
www.aemc.com
Limited Warranty
The Models 3711 and 3731 are warranted to the owner for a period of
two years 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.
For full and detailed warranty coverage, please read the Warranty
Coverage Information, which is attached to the Warranty
Registration Card (if enclosed) or is available at www.aemc.com.
Please keep the Warranty Coverage Information with your records.
What AEMC® Instruments will do:
If a malfunction occurs within the warranty 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.
YOU CAN NOW 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:
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
15 Faraday Drive • Dover, NH 03820 USA
Tel:
(800) 945-2362 (Ext. 360)
(603) 749-6434 (Ext. 360)
Fax:
(603) 742-2346 or (603) 749-6309
repair@aemc.com
Caution: To protect yourself against in-transit loss, we recommend you
insure your returned material.
NOTE: All customers must obtain a CSA# before returning any
instrument.
Table of Contents
Warning ..................................................................................................... 4
International Electrical Symbols ................................................................ 4
Definition of Measurement Categories ...................................................... 5
Receiving Your Shipment.......................................................................... 5
Packaging.................................................................................................. 5
Accessories ............................................................................................... 5
Important Information - Proper Operation ................................................. 5
Description ................................................................................................ 6
Product Construction ............................................................................. 6
Jaw Design ............................................................................................ 7
Body Design .......................................................................................... 7
Electrical Specifications ............................................................................ 8
Ground Resistance ................................................................................ 8
Ground or Leakage Current................................................................... 8
Mechanical Specifications ......................................................................... 8
Safety Specifications ................................................................................. 9
Model 3711 Controls ............................................................................... 10
Model 3731 Controls ............................................................................... 11
Digital Display Features .......................................................................... 12
Additional Features of the Model 3731................................................ 13
Function Controls .................................................................................... 14
On/Off .................................................................................................. 14
Auto-Off ............................................................................................... 15
Hold ..................................................................................................... 15
Beeper Disable .................................................................................... 15
Resistance ........................................................................................... 15
Resistance ........................................................................................... 16
Current ................................................................................................. 17
Alarm ................................................................................................... 18
Programming the Alarm Setpoint ........................................................ 18
Changing the Alarm Trigger ................................................................ 19
Memory ................................................................................................ 19
Memory ................................................................................................ 20
Memory Recall ..................................................................................... 20
Clear Memory ...................................................................................... 20
Function Access Summary ..................................................................... 21
Programming Summary .......................................................................... 21
Principle of Operation .............................................................................. 22
Field Applications .................................................................................... 24
Pole Ground Rods ............................................................................... 24
Service Entrance or Meter ................................................................... 25
Pad Mounted Transformer................................................................... 25
Pad Mounted Transformer................................................................... 26
Transmission Towers .......................................................................... 27
Central Office Locations ...................................................................... 27
Service Panel ...................................................................................... 28
Phone Pedestal ................................................................................... 29
Above Telephone Space ..................................................................... 31
General Measurement Notes .............................................................. 31
Operating Reference Card ...................................................................... 32
Field Test Loop........................................................................................ 32
Commonly Asked Questions for.............................................................. 33
Clamp-on Ground Resistance Measurements ........................................ 33
Maintenance ............................................................................................ 34
Battery Replacement Procedure ............................................................. 35
Troubleshooting ...................................................................................... 35
Repair and Calibration ............................................................................ 36
Technical and Sales Assistance ............................................................. 36
Ground Resistance Tester Models 3711 and 3731
Warning
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.
 Open and close the clamp-on jaws slowly ensuring proper
alignment.
 AEMC® Instruments considers the use of rubber gloves to be
an excellent safety practice even if the equipment is properly
operated and correctly grounded.
International Electrical Symbols
This symbol signifies that the instrument is protected by double
or reinforced insulation. Use only specified replacement parts
when servicing the instrument.
This symbol signifies CAUTION! and requests that the user refer
to the user manual before using the instrument.
Risk of electric shock. The voltage at the parts marked with this
symbol may be dangerous.
This is a type A current sensor. This symbol signifies that
application around and removal from HAZARDOUS LIVE
conductors is permitted.
-4-
Ground Resistance Tester Models 3711 and 3731
Definition of Measurement Categories
CAT IV: For measurements performed at the primary electrical supply
(<1000V) such as on primary overcurrent protection devices,
ripple control units, or meters
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 II: For measurements performed on circuits directly connected to
the electrical distribution system. Examples are measurements
on household appliances or portable tools.
Receiving Your Shipment
Upon receiving your shipment, be sure that the contents are consistent
with the packing list. 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.
Packaging
The Model 3711 (Cat. #2117.60) and Model 3731 (Cat. #2117.61) are
shipped with a hard carrying case, one 9V battery (not installed), a user
manual with warranty registration and a field test loop. The manual,
warranty card, and test loop are located behind the “egg crate” foam on
the inside of the carrying case cover.
Accessories
5 Field Test Loop ............................................................... Cat. #2141.51
Important Information - Proper Operation
The proper operation and measurement accuracy depends on the proper
jaw closing. For any measurement make sure that the jaw mating
surfaces are clean and that no foreign matter obstructs their closing.
-5-
Ground Resistance Tester Models 3711 and 3731
Description
The Ground Resistance Tester, Models 3711 and 3731, measure ground
rod and small grid resistance through any season, without the use of
auxiliary ground rods. Clamp-on ground resistance testers are used in
multi-grounded systems without disconnecting the ground under test.
The Models 3711 and 3731 simply clamp around the ground conductor
or rod and measure the resistance to ground. By performing
measurements on intact ground systems, the user also verifies the
quality of the grounding connections and bonds. Resistance and
continuity of grounding loops around pads and buildings may also be
measured.
Both models include a current measurement function. The probe’s high
sensitivity enables measurement of leakage current flowing to ground or
circulating in ground loops down to 1mA and neutral currents to 30Arms.
This feature provides additional information which is becoming vital as
distribution ground networks carry higher levels of noise and harmonics
which affect power quality.
Both models offer battery life information at power-up and Auto-Off for
power management. Additional features are also displayed on the large
LCD to ensure precise measurements. The Buzzer and Auto-Off features
may be disabled from the push-buttons at any time.
The Model 3731 offers an Alarm function and a Memory (logging)
function. In the Alarm mode, the probe will audibly and visually indicate if
the reading is beyond an input set point. The user may also have the
Alarm initiated above or below the set point. This Alarm feature permits
quick field checks where only “pass” or “fail” readings will suffice.
The Memory function logs up to 99 measurements (Ohms or Amperes).
This enables the user to conduct field surveys, and to retrieve and
analyze the readings at a later time. The alarm settings and stored
memory information are saved when the ground tester is turned off.
Product Construction
The Models 3711 and 3731 body cases are built of Lexan® for rugged
use. The probe heads are encapsulated in a double-walled Lexan® shell
(or equivalent polycarbonate) for extra strength and are reinforced at the
body interfaces for enhanced field reliability. Overall construction and
mechanical design ratings such as drop test, shock and vibration,
weatherproofing against water projections, meet or exceed IEC
(International Electrotechnical Commission) standards. The products
have also been designed to meet EN 61010.
-6-
Ground Resistance Tester Models 3711 and 3731
Jaw Design
The probe head, or jaw, is a key component in the measurement and
overall product performance. Considerable research and development
were dedicated to ensuring its performance, reliability and versatility.
The large jaw has an inner opening diameter of 1.25" (32mm) permitting
use on tight ground conductors on poles and in manholes. The large
opening accommodates not only ground rods, but larger ground
conductors (up to 1000 kcmil) typically found in telecommunication or
railroad applications.
The inner jaw is composed of two independent and individually shielded
magnetic cores permitting the injection of a test signal and accurate
return signal measurement without noise interference or cross talk
common to separate probe instruments.
Thorough mechanical design, including small winglets, ensures repetitive
jaw alignment for accuracy and prevents undesirable insertions into the
jaw spring assembly.
Body Design
The ergonomic body design permits one-handed operation. The guard
provides additional strength, and prevents the hand from slipping or
coming into contact with conductors under test. The Lexan® (or
equivalent polycarbonate) body construction provides strength. The LCD
lens cover may be easily replaced if scratched. The sealed push-buttons
directly access all test functions and are easily operated even with
gloved hands.
®
Lexan is a registered trademark of General Electric Corporation.
-7-
Ground Resistance Tester Models 3711 and 3731
Electrical Specifications
Ground Resistance
Measurement Range
Autoranging
0.01 to 1200
Range
Resolution
Accuracy*
0.1 to 1.00
0.01
± (2% R ± 0.02)
1.0 to 50.0
0.1
± (1.5% R ± 0.1)
50.0 to 100.0
0.5
± (2.0% R ± 0.5)
100 to 200
1
± (3.0% R ± 1)
200 to 400
5
± (6.0% R ± 5)
400 to 600
10
± (10% R ± 10)
600 to 1200
50
Approx. 25% ± 50
Ground or Leakage Current
Measurement Range
Autoranging
1mA to 30.00Arms
Range
Resolution
Accuracy*
1 to 299mA
1mA
± (2.5% R + 2mA)
0.300A to 2.999A
0.001A
± (2.5% R + 2mA)
3.00A to 29.99A
0.01A
± (2.5% R + 20mA)
R = Reading
* Reference conditions: 23°C ± 3K, 50% RH ± 10%, battery at 8V ± 0.2V, external magnetic
field < 40A/m, external electrical field < 1V/m, conductor centered, loop resistance noninductive. Accuracy % of Reading, Frequency: 50/60Hz.
Resistance Measurement Frequency: 2403Hz
Voltage Generated into the Loop: Approx. 60mVrms
Alarm Range (Model 3731 Only): 0 to 199
Resistance Overload: OL displayed above 1200
Current Measurement Frequency: 47 to 800Hz
Influence of Frequency: Add 7.5% to the reference specification
Current Overload: OL displayed above 29.99Arms
Mechanical Specifications
Dimensions: 9.25 x 3.94 x 2.17" (235 x 100 x 55mm)
Weight: 2.2lbs. (1kg)
-8-
Ground Resistance Tester Models 3711 and 3731
Case Material: Lexan® 920A (UL94V2) or equivalent
Jaw Cover Material:
Lexan® with 10% fiberglass charge (UL94V0) or equivalent
LCD Cover Material: Clear Lexan® (UL94V1) or equivalent
Color: Gray body, red jaws
Jaw Window Diameter: 1.25” (32mm)
Jaw Opening: 1.38” (35mm)
Operating Temperature: 14° to 131°F (-10° to 55°C)
Operating Humidity:
10 to 90% RH @ 14° to 104°F (-10° to 40°C), 75% RH @ 131°F (55°C)
Storage Temperature: -22° to 158°F (-30° to 70°C)
Altitude: Operational - 2000m; Storage - 12000m
Power Supply: 9V Alkaline (IEC 6LF22 or NEDA 1604A)
Battery Life: Typical: 8 hours or approx. 1000 measurements of 30 s
LCD: 3-3/4 digit, 1.73 x 1.10” (44 x 28mm)
US Design Patent: No. 362,639
Safety Specifications
E192383
EN 61010-1 (Class 2), Double Insulation
Working Voltage: 150V, CAT III - Pollution Degree 2
300V, CAT II - Pollution Degree 2
Environmental: IP30 (Protection Index) EN 60529 Ed. 92
IK04, EN 50102 Ed. 95
Vibration Test: IEC 68-2-6
Shock Test: IEC 68-2-27
Drop Test (1m): IEC 68-2-32
Max A Overload: 100A continuous, 200A (< 5s) 50/60Hz
OL displayed above 29.99Arms
Electromagnetic Compatibility:
EN 61326-1+A1 (industrial environment)
EM Field: IEC 61000-4-3, criteria B
-9-
Ground Resistance Tester Models 3711 and 3731
Model 3711 Controls
A
ON
OFF
Ω
Figure 1
1. Head Assembly: Consists of
two individually shielded
magnetic cores.
4. ON/OFF: Power ON or OFF,
activates display self-test at
power-up.
2. Hold: Freezes last measured
value on the display.
5. : Resistance measurement.
3. Display: 3000 count LCD,
function indicators.
6. A: Current measurement.
7. Lever: Opens or closes jaws.
- 10 -
Ground Resistance Tester Models 3711 and 3731
Model 3731 Controls
1. Head Assembly: Consists of two
individually shielded magnetic
cores.
2. Hold: Freezes last measured
value on the display.
1
3. Display: 3000 count LCD,
function indicators.
4. ON/OFF: Power ON or OFF,
activates display self test at
power-up.
5. : Resistance Measurement
9
®
Increment the Alarm setpoint,
increment Memory position in
program mode.
6. A: Current Measurement
2
HOLD
Model 3731
GROUND TESTER
INSTRUMENTS
HOLD
NOISE
R 1
mA
MEM
MR
MEM
AL
A
Ω
ON
OFF
8
Decrement the Alarm setpoint,
decrement the Memory in
program mode.
3
+
–
4
7
6
5
7. AL: Activates/deactivates the Alarm function, access the value of the
Alarm setpoint in program mode.
8. MEM: Stores the reading into memory, reads Memory Recall (MR)
values and clears the memory in recall mode.
9. Lever: Opens or closes jaws.
- 11 -
Ground Resistance Tester Models 3711 and 3731
Digital Display Features
HOLD
MEM
MR
NOISE
R .1
mA
+
–
Figure 3
Displayed when the beeper is active. To turn the beeper On/Off,
push ON &  together at power-up. The beeper is active when
displayed.
HOLD
Displayed when the HOLD function is activated. This function
locks the present displayed value. During HOLD: A, , and
Alarm functions are deactivated. The Memory function may still
be used.
Indicates that the jaws of the instrument are not properly closed.
The Open Jaw indication is present only in the  Mode. Check
for foreign matter in the jaw mating surface.
In the  function, this symbol indicates the presence of
excessive stray noise in the ground electrode under test. This
NOISE symbol will be present if noise signals reach an amplitude of
approx. 5A or 50V. Resistance measurement values are no
longer valid. The beeper is also activated.
R .1
Displayed when measured resistance is below 0.1. This may
indicate that grounding electrode you are clamped onto is
continuous with itself (the instrument is measuring a metallic
loop and not the ground electrode resistance). In this situation,
electrode resistance measurements may not be valid. The main
display can measure between 0.7 to 0.07, but without any
specified accuracy.
mA, A Current measurement mode.
Ground resistance measurement mode.
- 12 -
Ground Resistance Tester Models 3711 and 3731
Indicates the Auto-Off feature is deactivated and the instrument
stays on permanently (until turned off by the user). With no
symbol displayed, after 5 minutes of non-use the instrument will
automatically shut itself off. The Auto-Off feature is turned
On/Off by pressing Hold at power-up.
Display flashes this symbol (1/second) during a low battery
condition. Measurements are still possible. When this symbol is
displayed continuously, measurements are no longer possible.
Battery replacement is necessary.
Indicates the approximate percentage of useful battery life
remaining (0-100%). This function is displayed only upon initial
power-up when the ON push-button is held down for more than
2 seconds.
The overload symbol will illuminate when the measurement
reading is beyond the limits of the instrument:
Resistance > 1200
Current > 30.00A rms
The beeper is activated in current overload.
Additional Features of the Model 3731
Indicates that an alarm set point is set in memory. Alarm set
points may be set from 1 to 199. Arrows indicate whether the
measured value is above or below alarm setpoint.
MEM
MR
Memory function is activated. Ninety-nine (99) separate values
may be logged for either resistance (), current (A) or a
combination thereof. At the 99th value, display number will blink
indicating that memory is full.
Memory recall register. Displays the numbered value being
recalled from memory (1-99).
Note: Models 3711 and 3731 share the same LCD and display all
segments at power-up. Functions not available on the 3711 are
displayed at power-up.
- 13 -
Ground Resistance Tester Models 3711 and 3731
Function Controls
Model 3711 and 3731 share common functions (On/Off, A, , Auto-off,
Buzzer disable, Hold). Even though the Model 3711 is shown in the
examples for these functions, the controls will respond identically for the
Model 3731.
On/Off
The ON/OFF push-button, when pushed actuates power on or power off
with an audible control tone. Upon initial power-up, the instrument will be
in the Ohms function () and will go to OL until clamped on. When the
ON push-button is pushed and held down, after three seconds the
instrument will beep and provide a self test featuring a full function
display (Fig. 4) followed by status indications for:
a. Status of remaining battery life
(battery symbol blinks, 0-100%) (Fig. 5)
b. Number of stored values in memory
(MEM blinks, 0-99) (Model 3731 only)
Release the ON/OFF push-button to initialize the instrument.
A
Ω
ON
OFF
A
Figure 4
Figure 5
- 14 -
Ω
ON
OFF
Ground Resistance Tester Models 3711 and 3731
Auto-Off
The instrument will shut off automatically after five minutes of non-use.
The instrument will issue a short beep 15 seconds prior to shutting down
and the LCD flashes once per second. The
Auto-Off may be disabled by turning on the
meter while holding down the HOLD pushbutton. The
indicator will appear on the
display to indicate the Auto-Off feature has
been disabled. (Fig. 6).
A
ON
OFF
Ω
Hold
The HOLD push-button freezes the last
measured value onto the display. When the
HOLD function is enabled, HOLD is
displayed on the LCD. (Fig. 7)
Figure 6
When the HOLD function is enabled, other control
functions are disabled (except the memory
function).
To exit HOLD, press the HOLD push-button and
normal operation is resumed.
A
Ω
Note: When HOLD is pressed during power-up,
the auto-off feature is disabled and
is
displayed on the LCD. See Auto-Off.
ON
OFF
Figure 7
Beeper Disable
To disable the beeper, press the ON and 
together at power-up. The
indicator will
disappear from the LCD. (Fig. 8).
This setting is saved indefinitely. To reset the
beeper, press the ON and  together at power
up.
A
Figure 8
- 15 -
Ω
ON
OFF
Ground Resistance Tester Models 3711 and 3731
Resistance
The  function provides resistance measurements from 0.1 to 1200 in
seven autoranges. (Fig. 9).
Range
Resolution
0.07 to 1
1.0 to 50.0
50 to 100
100 to 200
200 to 400
400 to 600
600 to 1200
0.01
0.1
0.5
1
5
10
50
ON
OFF
A
Figure 9
Upon initial power-on, the  function is chosen by default.
The Models 3711 and 3731 will track down to
0.07 and indicate R .1 below 0.1 (Fig. 10).
Accuracy is not defined below 0.1.
Measurements below 0.1 typically (or even
1) indicate the ground tester is clamped onto
a closed loop and that the signal is not flowing
through the ground under test.
A
Ω
ON
OFF
Figure 10
A
Ω
If the resistance readings are above 1200, OL
will be displayed on the LCD (Fig. 11). This may
indicate high ground resistance but may also be
caused by a disconnected or poorly bonded
ground.
ON
OFF
Figure 11
- 16 -
Ground Resistance Tester Models 3711 and 3731
Current
Press A to enter the current function. True RMS current measurements
are possible up to 30.00A (Fig. 12).
Above 30Arms, OL will be displayed and the test must be discontinued.
The beeper is also activated during OL.
Range
Resolution
1 to 299mA
1mA
0.300 to 2.999A
0.001A (1mA)
3.00A to 29.99A
0.01A (10mA)
A
Ω
Figure 12
- 17 -
ON
OFF
Ground Resistance Tester Models 3711 and 3731
Alarm
Turn the Alarm on/off by pressing the AL
button. The alarm feature provides a
continuous audible warning (when beeper is
active) and visual indications when a
setpoint has been reached (Fig. 13, 14) (e.g.
alarm indication when ground electrode
resistance is above the NEC limit of 25.) If
will be
the alarm is not triggered, only
displayed indicating that the alarm is active.
MEM
AL
A
Ω
ON
OFF
Figure 13
Programming the Alarm Setpoint
To program the alarm setpoint, push ON and AL together at power-up.
The alarm setpoint value will blink. To program the proper setpoint value
(1 to 199), use the cursor arrows ( down, up).
MEM
AL
When the setpoint is reached, turn the
instrument off. This will put the setpoint into
memory. Turn the instrument back on (you
may need to press AL to activate the alarm
feature).
ON
OFF
Note: The alarm setpoint is preset at 25.
The alarm will be triggered when the
setpoint is exceeded.
A
Ω
Figure 14
The user has the option of having the alarm
triggered when a reading is below the
programmed setpoint. This is accomplished
with an internal switch and outlined in the
following section.
- 18 -
Ground Resistance Tester Models 3711 and 3731
Changing the Alarm Trigger
The Model 3731 alarm may be set to trigger above or below a setpoint.
Follow the procedure below for setting the alarm trigger.
1. The instrument must be OFF and disconnected from any conductor.
2. Place the meter face down and remove the two phillips screws on the
back of the instrument.
3. Remove the back cover by pulling down and away from the
instrument.
4. To set the alarm to trigger above a setpoint, slide the alarm setpoint
switch #1 up. To set the alarm to trigger below a setpoint, slide the
alarm setpoint switch #1 down.
5. Replace the back cover while
ensuring that it slips beneath the holddown lip and fits securely into position.
Use caution not to pinch the battery
leads.
6. Install and tighten screws.
Alarm Setpoint Switch
IMEJ?D IMEJ?D
Switch 1 Up - Alarm above the setpoint
Switch 1 Down - Alarm below the setpoint
Figure 15
- 19 -
Ground Resistance Tester Models 3711 and 3731
Memory
To activate the Memory feature, press the A
and ON buttons together at power-up (Fig.
16). MEM will be displayed.
The Memory feature allows the user to log
into memory 1 to 99 measured values
(including OL). Measured values can now be
ON
logged for both resistance () and amps (A)
OFF
MEM AL
A
Ω
by pushing the MEM button during
measurement and during “HOLD”. A long
beep indicates the measurement was stored.
After the 99th value is entered (MEM 99) will
blink indicating memory is now full.
Figure 16
Measurements may still be made but no
longer logged. Stored values are retained when the instrument is turned
off.
Pressing the A and ON buttons again at power-up will de-activate the
Memory feature.
Memory Recall
MEM
AL
A
Ω
ON
OFF
To recall memory values, push ON and
MEM together at power-up. MR will be
displayed with the memory number (Fig.
17). Memorized value will be displayed. To
select stored values use the cursor arrows
down,
up). For rapid access of
(
memory recall values, press the cursor
push-button continuously.
Turn the instrument off to exit the Memory
Recall mode.
Figure 17
Clear Memory
To clear the memory, push ON & MEM together at power-up and hold
them down. After a three second interval the “clear” message will be
displayed (Fig. 18) along with four repetitive beeps and a fifth long tone.
The memory is now cleared (Fig. 19).
Once cleared, releasing the ON & MEM buttons returns the instrument to
Resistance measurement mode.
- 20 -
Ground Resistance Tester Models 3711 and 3731
MEM
AL
A
Ω
ON
OFF
MEM
Figure 18
AL
A
Ω
ON
OFF
Figure 19
Function Access Summary
Function
Push Button(s)
Used
Function Setting
Saved @ Power Down
On/Off
ON/OFF
 Function

Default Setting
A Function
A
No
Alarm Function ()
AL
Yes
Display Hold
HOLD
No
Auto-Off On/Off
ON + HOLD
No
Beeper On/Off
ON + 
No (3711), Yes (3731)
Programming Summary
Function
Push Buttons
Used
Function Setting
Saved @ Power Down
Memory On/Off
ON + A
Yes
Memory Recall (MR)
ON + MEM (< 2 sec)
No
Clear Memory
ON + MEM (> 6 sec)
No
Program Alarm Setpoint
ON + AL
No
- 21 -
Ground Resistance Tester Models 3711 and 3731
Principle of Operation
Typically grounded distribution system may be simulated by the basic
circuit shown in Fig. 20 or an equivalent circuit, shown in Fig. 21. If
voltage (V) is applied to any measured grounding electrode Rx through a
special transformer, current (I) flows through the circuit, thereby
establishing the following equation:
V = Rx +
I
Σ
1
n
i=1
1
Ri
where, usually
Rx »
1
Σi=1 Ri1
n
Therefore, V/I = Rx is established. If I is detected and measured with V
kept constant, the measured grounding electrode resistance Rx can be
obtained. A signal is fed to a special transformer via a power amplifier
from a 2403Hz constant voltage oscillator. The resulting current is then
sensed by a detection CT. An active filter is used to dampen earth
current at commercial frequency and high-frequency noise.
Example: If we clamp around any grounding electrode in a multigrounded system, the measured value of the electrode under test will be
the resistance of that particular rod in series with the equivalent parallel
resistance value that the rest of the multi-grounded system represents. If
we had an electrical system that had 101 grounding electrodes and each
had a resistance value of 25, and we were to clamp around any
electrode in the system, the measured value would be 25 in series with
the equivalent parallel resistance or 0.25. The displayed value would
be 25.2 (instrument resolution to 0.1).
V/I = 25 + 0.25
Rx = 25.2
In most field applications, the number of electrodes that make up a multigrounded system would be higher, therefore the equivalent parallel
resistance is negligible with respect to the rod under test.
- 22 -
Ground Resistance Tester Models 3711 and 3731
I
V
Rx
R1
R2
Rn-1
Rn
Figure 20
Rx
R1
Rn-1
Figure 21
- 23 -
Rn
Ground Resistance Tester Models 3711 and 3731
Field Applications
Pole Ground Rods
Remove any molding covering the ground conductor, and provide
sufficient room for the jaws of the clamp-on. The jaws must be able to
close easily around the conductor. The jaws can be placed around the
ground rod itself.
Note: The instrument must be placed so that the jaws close around an
electrical path from the system neutral or ground wire to the ground rod
or rods as the circuit provides.
Select the current range “A.” Clamp onto the ground conductor and
measure the ground current. The maximum range is 30.00A Trms.
However, if the ground current exceeds 5A or noise exceeds 50V,
ground resistance measurements are not possible. Do not proceed
further with the measurement. Remove the instrument from the circuit
noting the location for maintenance and continue to the next test
location.
After noting the ground current, select the ground resistance range ()
and measure the resistance directly. The reading you measure with the
clamp-on tester indicates not just the resistance of the rod, but of the
connection to the system neutral and all bonding connections between
the neutral and the rod.
Note that in Fig. 22 there is both a butt plate and a ground rod. In this
type of circuit, it is necessary to place the instrument above the bond so
that both grounds are included in the test. For future reference, note the
date, ohms reading, current reading and pole number. Replace any
molding you may have removed from the conductor.
Figure 22
- 24 -
Ground Resistance Tester Models 3711 and 3731
Note: A high reading or OL indicates one or more of the following:
A. Poor ground rod
B. Open ground conductor
C. High resistance bonds on the rod or splices on the conductor; watch
for buried split butts, clamps, and hammer-on connections.
Service Entrance or Meter
Follow the same procedure as for Pole Ground Rods. Notice that Fig. 24
shows multiple ground rods and in Fig. 23 the ground rods have been
replaced with a water
pipe ground. You may
also have both types
acting as a ground. In
these cases, it is
necessary to make the
measurements between
the service neutral and
both grounded points.
Figure 23
Building wall
Pole-mounted
transformer
Service box
Service meter
Figure 24
Water pipe
- 25 -
Ground Resistance Tester Models 3711 and 3731
Pad Mounted Transformer
Observe all safety requirements - High voltage may be present!
Locate and number all rods (usually only a single rod is present). If the
ground rods are inside the enclosure, refer to Fig. 25 and if they are
outside the enclosure, refer to Fig. 26. If a single rod is found within the
enclosure, the measurement should be taken on the conductor just
before the bond on the ground rod. Often, more than one ground
conductor is tied to this clamp, looping back to the enclosure or neutral.
Figure 25
In many cases, the best reading can be obtained by clamping the
instrument onto the ground rod itself, below the point when the ground
conductors are attached to the rod, so that you are measuring the
ground circuit. Care must be taken to find the conductor with only one
return path to the neutral.
Generally < 0.7 R .1 indicates that you are on a closed loop. In Fig.
26, the ground rod is located outside the enclosure. Clamp at the
indicated measuring point to obtain the correct reading. If more than one
rod exists at different corners of the enclosure, it is necessary to
determine how they are connected to properly measure the ground
resistance.
Figure 26
- 26 -
Ground Resistance Tester Models 3711 and 3731
Transmission Towers
Observe all safety requirements - Dangerously high voltage may
be present!
Locate the ground conductor at the base of the tower. Many different
configurations exist. Care should be taken when searching for the
ground conductor. Fig. 27 shows a single leg mounted on a concrete pad
with an external ground conductor. The point at which you clamp the
instrument should be above all splices and connections which allow for
multiple rods, butt wraps, or butt plates.
Note: Current flowing to ground may be high.
Figure 27
Central Office Locations
The main ground conductor from a ground window or a ground plane is
usually the location to clamp the tester. Due to the wiring practices within
the central office, there are many locations at which you can look at the
water pipe or counterpoise from within the building. An effective location
is usually at the ground buss in the power room, or near the backup
generator.
By measuring current and resistance at several points and comparing
the readings, you will be able to identify neutral loops, utility grounds and
central office grounds. The test is effective and accurate when the
ground window is connected to the utility ground at only one point.
- 27 -
Ground Resistance Tester Models 3711 and 3731
Service Panel
If we clamp-on the grounding electrode conductor in Fig. 28, the multigrounded system required to complete the circuit may be from different
sources. These sources may include the following: Electric Neutral,
Phone, CATV, and Water.
The Electric Utility Neutral should be the principle conductor of the lowimpedance signal return path required to test the resistance of this
ground electrode with the Model 3711/3731. This can be verified by
removing other ground connections, noting if any changes appear in the
readings. If by removing one of these signal return paths a much higher
reading is noted, it could mean that the primary signal return path (the
Electric Neutral) is defective or open.
Warning: For safety reasons do not remove any ground source
without first de-energizing the service panel.
Figure 28
- 28 -
Ground Resistance Tester Models 3711 and 3731
Phone Pedestal
Provide sufficient room for the Model 3711/3731 jaws, which must be
able to close easily around the conductor (Fig. 29). The jaws can be
placed around the ground rod itself.
Note: If not enough room is available for this task refer to Fig. 30 and
continue with this example. The clamp must be placed so that the jaws
are in an electrical path from the sheath bond(s) or ground bar to the
ground rod(s) as the circuit provides.
Select the current range “A.” Clamp onto the ground conductor and
measure the ground current. The maximum current range is 30A. If the
ground current exceeds 5A, ground resistance measurements are not
possible. Do not proceed further with the measurement. Remove the
clamp-on tester from the circuit, noting the location for maintenance, and
continue to the next test location.
After noting the ground current, select the ground resistance range “”
and measure the resistance directly. The reading you measure with the
3711/3731 indicates the resistance of not just the rod, but also the
connection to the sheath ground and all bonding connections between
the sheath bond and the rod.
A high reading indicates one or more of the following:
A. Poor ground rod
B. Open ground conductor
C. High resistance bonds on the rod or splices on the conductor. Also
look for bad connections on the ground bar to the sheath(s).
Note: This same test can be done using the TIP instead of the sheath
ground. However keep in mind that this is intended to be grounded only
back at the central office.
- 29 -
Ground Resistance Tester Models 3711 and 3731
Figure 29
Figure 30
- 30 -
Ground Resistance Tester Models 3711 and 3731
Above Telephone Space
Select the current range “A.” Clamp onto the ground wire and measure
the current (Fig. 31). The maximum current range is 30A. If the ground
current exceeds 5A, resistance measurements are not possible. Do not
proceed further with the measurement. Remove the clamp-on tester from
the circuit, noting the location for attention, and continue to the next test
location.
After noting the current, select the ground resistance range “” and
measure the resistance directly.
The reading you measure with
the 3711/3731 indicates the
bonding connections between the
Telephone ground and the Power
company ground. One of the
following two scenarios should be
observed:
A. If “OL” or a high resistance
reading is displayed this
would indicate no bond has
been established or a poor
connection exists between
the Telephone and Power
grounds.
B. If 4 and/or a very low
reading is displayed then the
bond between these two
grounds has been verified.
Figure 31
General Measurement Notes
A reading of OL is most likely a cable which is not connected to the
ground at both ends. It may be there is no ground rod at all, or that there
is no path back to the system neutral.
A reading which is < 0.1 R .1 generally indicates that the cable where
you are clamped is continuous with itself. You may have located a
ground loop, which can usually be confirmed by comparatively high
current readings also obtained when readings are taken at multiple
locations. A good low resistance ground may also have very high AC
current flowing, depending upon the type of equipment being grounded.
- 31 -
Ground Resistance Tester Models 3711 and 3731
Operating Reference Card
Included with the Model 3711 and 3731 you will find an operating
reference card like the one shown here.
This card summarizes all the features of the Model 3711 and 3731.
Ω Ω
!" #!$
Ω % &!
'
% &!
#(
& ! " ) *
$
% + ! ,
-
. ( -#
) % * '
# $ !! /
) % '
# 0" !
$ /
% &!
$ #!$ Figure 32
Field Test Loop
The test loop of 5 (Fig. 33) is provided to perform a quick check of the
instrument. Check the clamp-on ground resistance tester by clamping
around the loop; the 3711 or 3731 should read between 4.9 and 5.1.
* Value is for ambient temperature between 68° and 78°F. Value may differ a few counts
under or above this temperature.
®
INSTRUMENTS
CALIBRATION LOOP 5Ω
Figure 33
- 32 -
Ground Resistance Tester Models 3711 and 3731
Commonly Asked Questions for
Clamp-on Ground Resistance Measurements
Q. Can the Clamp-on method be used effectively on high tension towers
despite the distance or spacing between them?
A. Yes. Extended distances will not adversely affect the measurement
results. The important factor is that it be a multiple electrode system.
Q. Does the grounding electrode have to be disconnected and isolated
as is required when using the “Fall-Of-Potential” test with auxiliary
electrodes?
A. No. Actually the electrode must be connected to the system to provide
the path for test signal injection as well as to provide the background
impedance necessary as the reference. Additionally, if the tested rod is
poorly bonded to the ground connector, a high reading will be present.
Q. Does this mean I am not able to test an independent electrode?
A. No, however as soon as the connection is made to a multiple
electrode system, usually provided by the connection to the system
neutral, you can clamp on and make a measurement.
Q. Must the instrument be clamped directly on the electrode?
A. No, the instrument will provide valid measurement results when
clamped on to the electrode or the conductor leading to the grounding
electrode. The reading through the conductor will also verify not only the
grounding electrode resistance, but connections of the ground wire to the
rest of the system.
Q. Does the system under test have to be energized or de-energized to
perform the test?
A. We are measuring the grounding network. The only requirements are
that ground connections be made to the system under test and that the
voltage-to-ground at the tested point not exceed the instrument rating.
- 33 -
Ground Resistance Tester Models 3711 and 3731
Q. Can the clamp-on method be used for substation grid resistance
testing?
A. It depends. It can be used as long as the instrument can be clamped
onto a point on the grounding system at a common point where it ties to
the system neutral. Testing a grid must be treated as if it were a single
electrode. Often, clamping on to points within the grid system will yield a
closed loop reading.
Q. How does clamp-on ground testing compare with the standard
“Fall-Of-Potential” test?
A. Empirical testing has validated that when performed correctly, both
methods will provide accurate and repeatable readings for ground
electrode resistance.
Q. How large a conductor can the jaw accommodate?
A. The inner diameter of the jaw is 1.25" and can accommodate cables
up to 1000 kcmil.
Maintenance
Warning
 To ensure optimum performance, it is important to keep the probe jaw
mating surfaces clean at all times. Failure to do so may result in error
in readings. To clean the probe jaws, use a lint free clean cloth, or if
the jaws are pitted use a very fine sand paper (fine 600 grit) to avoid
scratching the jaw, then gently clean with a soft cloth. Do not leave
any residue.
 For maintenance use only specified factory replacement parts.
 Avoid electrical shock: do not attempt to perform any servicing unless
you are qualified to do so.
 Avoid electrical shock and/or damage to the instrument: do not allow
water or other foreign substances into the case. Disconnect the unit
from all circuits and test cables before opening the case. Use caution
with metallic tools that may short battery packs, power supplies, etc.
- 34 -
Ground Resistance Tester Models 3711 and 3731
Battery Replacement Procedure
The Clamp-On Ground Resistance Testers are powered by a single 9V
battery. The battery replacement indicator will display continuously when
battery replacement is required.
Recommended replacement type is Alkaline (IEC 6LF22, 6LR61 or
NEDA 1604A). Ni-Cad batteries may also be used. To change the
battery, refer to Figure 15, page 18 and follow this procedure.
1. The instrument must be OFF and disconnected from any conductor.
2. Place the meter face down and remove the two Phillips screws on
the back of the instrument.
3. Remove back cover by pulling it down and away from the instrument.
4. Lift the battery away from the case and disconnect the battery.
5. Connect the new battery and position the leads so that they won’t get
pinched when the cover is replaced.
6. Replace the back cover noting that it slips beneath the hold down lip
and fits securely into position.
7. Install and tighten screws.
Typical battery life is approximately 8 hours of use or about 1000
separate 30-second measurements.
Troubleshooting
Symptom
Indication/Recommended Action
Instrument will not turn ON
Low Battery
Replacement required
Continuous audible tone
Alarm setpoint tripped
Deactivate Alarm or
Change Setpoint Trigger mode
Display is erratic
Foreign matter in jaws
Clean jaw mating surfaces
Function controls inoperative
Hold button on
Turn HOLD off
Light pulsing audible beep
Normal operation
Battery power management feature
- 35 -
Ground Resistance Tester Models 3711 and 3731
Repair and Calibration
To ensure that your instrument meets factory specifications, we recommend
that it be submitted 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).
Chauvin Arnoux®, Inc.
d.b.a. AEMC® Instruments
15 Faraday Drive
Dover, NH 03820 USA
Tel:
(800) 945-2362 (Ext. 360)
(603) 749-6434 (Ext. 360)
Fax:
(603) 742-2346 or (603) 749-6309
repair@aemc.com
(Or contact your authorized distributor)
Costs for repair, standard calibration, and calibration traceable to N.I.S.T. are
available.
NOTE: All customers 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, fax or e-mail our technical support hotline:
Chauvin Arnoux®, Inc.
d.b.a. AEMC® Instruments
Tel.
(800) 945-2362 (Ext. 351)
(603) 749-6434 (Ext. 351)
Fax:
(603) 742-2346
techsupport@aemc.com
- 36 -
Chauvin Arnoux®, Inc. d.b.a AEMC® Instruments
15 Faraday Drive • Dover, NH 03820 USA
www.aemc.com
99-MAN 100218 v15 02/18