Megger DET3T, DET4 Operating Manual
DET Series
EARTH GROUND ELECTRODE TESTERS
M
USER GUIDE
CONTENTS
CONTENTS 2
INTRODUCTION 3
G SAFETY WARNINGS 4
G LIVE EARTH SAFETY PRECAUTIONS 5
G BATTERY INSTALLATION 5
GBATTERY CHARGING (DET4TCR2 and DET4TR2 ONLY) 5
GENERAL DESCRIPTION 6
PREPARATIONS FOR USE 9
GENERAL OPERATING INSTRUCTIONS 10
INSTRUMENT ILLUSTRATIONS 12
BATTERY 18
DESCRIPTION OF TESTS 23
PREVENTIVE INSTRUMENT MAINTENANCE 60
TECHNICAL SPECIFICATION 61
REPAIR AND WARRANTY 64
Symbols used on the instrument are:
G Caution: refer to accompanying notes
t Equipment protected throughout by Double Insulation
c Equipment complies with current EU directives
Equipment complies with “C tick” requirements
Do not dispose of in normal waste stream
Note: The safety warnings provided in this document are indicative of safe practice and shall not be
considered exhaustive. Additionally, they are not intended to replace local safety procedures where the
instrument is being used.
Note: This user guide uses the terms ‘earth’ and ‘ground’ interchangeably.
2
INTRODUCTION
Thank you for purchasing the Megger Earth Ground Tester.
For your own safety and to get the maximum benefit from your instrument, please ensure that you read
and understand the following safety warnings and instructions before attempting to use the instruments.
This user manual describes the operation and functions of the DET series of Earth Ground Testers:
DET3TA
DET3TC
DET3TD
DET4TD2
DET4TR2
DET4TC2
DET4TCR2
ICLAMP
VCLAMP
CALIBRATION ADAPTOR
TWO-CLAMP CALIBRATION ADAPTOR
These instruments are designed and manufactured by:
Megger Limited
Archcliffe Road
Dover
Kent
CT17 9EN
England
Megger Limited reserves the right to change the specification of these instruments at any time without
prior notice.
3
G
Safety Warnings and Precautions must be read and understood before the instrument is used.
Do not leave the instrument connected to the system under test when not in use.
Do not touch circuit connections and exposed metalwork of an installation or equipment under test.
Do not touch the earth stakes, test leads and their terminations (including connections to the
Do not touch the earth stakes, test leads and their terminations (including connections to the
Do not operate the instrument or connect it to any external system if it shows any visible signs of
Do not operate the instrument or connect it to any external system if the battery compartment or
Special precautions are necessary when operating in situations where "live" earths may be
Special precautions are necessary when working near high tension systems (MV and HV): rubber
Special precautions are necessary when working in wet conditions or in agricultural areas: observe
SAFETY WARNINGS
They must be observed during use.
earthing system under test) if an installation earth fault can arise unless adequate precautions are
taken.
earthing system under test) while the instrument is switched on.
damage or if it has been stored for prolonged periods in unfavourable conditions.
casing is open or any parts of the case (including keypad, selector switch, display window, etc.) are
missing.
encountered: isolation switches and fuses (not supplied with this instrument) must be used.
gloves and shoes (not supplied with this instrument) should be worn.
the local safety standards and take all necessary special precautions applicable to the particular
location and do not touch the test leads with bare hands.
Always disconnect the instrument from the earthing system under test while batteries are being
changed or the fuse replaced.
Always replace batteries and fuses with parts of the correct type and rating.
Do not replace the rechargeable cells in the DET4TR2 and DET4TCR2 with non-rechargeable “dry”
cells.
Do not use any other charging equipment other than that supplied by Megger for use with the
DET4TR2 and DET4TCR2.
Do not operate the charging equipment supplied with the DET4TR2 and DET4TCR2 in damp or wet
environments or outside.
NOTE: THE INSTRUMENT MUST ONLY BE USED BY SUITABLY TRAINED
AND COMPETENT PERSONS.
Users of this equipment and/or their employers are reminded that National Health and Safety Legislation
requires them to carry out valid risk assessments of all electrical work so as to identify potential sources of
electrical danger and risk of electrical injury such as inadvertent short circuits. Where the assessments
show that the risk is significant then the use of fused test leads may be appropriate.
4
G
LIVE EARTH SAFETY PRECAUTIONS
A 'Live' earth is one that carries current from the mains supply, or could do so under fault conditions. The
following warnings apply in addition to those listed previously.
All persons involved must be trained and competent in isolation and safety procedures for the system
to be worked on. They must be clearly instructed not to touch the earth electrode, test stakes, test
leads, or their terminations if any 'Live' earths may be encountered. It is recommended that they wear
appropriate rubber gloves, rubber soled shoes, and stand on a rubber mat.
The earth electrode under test should be isolated from the circuit it is protecting before testing
commences. If this is not possible, ART may be used to measure electrode resistance.
The instrument terminals should be connected to the system under test through isolation switches
that are rated to handle the likely maximum fault voltages and currents that could be encountered at
the installation. The isolation switch must be open whilst any personal contact is made with the
remote test stakes, or the connecting leads, e.g. when changing their position.
The instrument terminals should be connected to the system under test through fuses that are rated
to handle the likely maximum fault voltages and currents that could be encountered at the
installation.
G
Warning: Whenever battery cells are being fitted or replaced, there should be no connections to the
instrument terminals and the instrument should be switched off.
Warning: To avoid damage by leaking electrolyte or deep discharge, do not leave cells fitted in an
instrument which will remain unused for extended periods of time.
Warning: Incorrect battery cell polarity can cause electrolyte leakage, resulting in damage to the
instrument. If the battery condition indicator does not show a full charge when battery cells are new, a cell
may be reversed.
DET4TR2 and DET4TCR2 ONLY Warning: Only use the cells recommended by Megger, part number
25985-031.
G
BATTERY INSTALLATION
BATTERY CHARGING (DET4TR2 and DET4TCR2 ONLY)
Warning: Whenever battery cells are being recharged, there should be no connections to the instrument
terminals and the instrument should be switched off.
Warning: Do not attempt to recharge non-rechargeable (dry) cells in the DET4TR2 and DET4TCR2.
Doing so will result in instrument damage and may cause personal injury.
Warning: Only use the charging equipment provided by Megger for use with this instrument.
5
GENERAL DESCRIPTION
The Megger DET family of test instruments offers a unique solution to the measurement of earth or
ground electrode (rod) resistance and soil resistivity. The family has seven variants supporting 2, 3 and 4wire measurements:
The DET3TA provides 2 and 3-wire measurements and offers an analogue display.
The DET3TC and DET3TD provide 2 and 3-wire measurements and offer a digital display.
The DET4TD2, DET4TR2, DET4TC2 and DET4TCR2 provide 2, 3 and 4-wire measurement and offer a
digital display.
The DET4TR2 and DET4TCR2 provide a rechargeable battery power source.
The DET4TC2 and DET4TCR2 offer variable frequency testing (94 Hz, 105 Hz, 111 Hz and 128 Hz) and
measurement to 200 k).
The DET3TC, DET4TC2 and DET4TCR2 can use an optional current clamp (ICLAMP) to measure
conductor current and electrode (rod) resistance without disconnection, leaving the installation earthing
system intact (Attached Rod Technique, ART).
Additionally, the DET4TC2 and DET4TCR2 can drive an optional voltage-inducing clamp (VCLAMP) which,
in conjunction with the ICLAMP, can be used to make stakeless measurements of the earthing system.
6
The DET family have the following features:
Feature DET3TA DET3TD DET3TC DET4TD2 DET4TR2 DET4TC2 DET4TCR2
Automatic C
stake check
Automatic P
stake check
Manual P stake
check
Automatic noise
check
Manual noise
check
Noise rejection
(40 V pk-pk)
Variable
frequency test
2-wire test
3-wire test
4-wire test
2 k range
20 k range
200 k range
No disconnect
testing (ART)
Stakeless
measurement
Voltmeter
(ground noise
voltage
measurement)
Current meter
LCD display
Backlit display
Moving coil
meter
IP54 rated
EN61010-1 100V
CAT IV
Built-in battery
charger
7
Each instrument kit comprises the following:
DET instrument
Test leads (for 3-wire instruments, lead lengths are: 3m, 10m and 15m; for 4-wire instruments: 3m,
10m, 10m and 15m)
Test stakes (for 3-wire instruments: 2 stakes are supplied; for 4-wire instruments, 4 stakes are
supplied)
Batteries – 8x AA (LR6) alkaline (except DET4TR2 and DET4TCR2)
Batteries – 8x AA (LR6) 1800 mA hr NiMH (DET4TR2 and DET4TCR2 only)
Warranty card
Calibration certificate (not DET3TA)
Owners CD-ROM manual
Tough polypropylene carrying-case
External AC/DC adaptor (DET4TR2 and DET4TCR2 only)
8
PREPARATIONS FOR USE
Batteries
The Megger DET series instruments are supplied with batteries fitted. When batteries become exhausted,
refer to the section on battery replacement or recharging.
Warning: Do not switch the instrument on with the battery cover removed.
Inspection
Before each use of the instrument, visually inspect the instrument case, test leads, stakes and connectors
to confirm that their condition is good, with no damaged or broken insulation.
9
GENERAL OPERATING INSTRUCTIONS
OFF
Instrument output voltage selection
The maximum output voltage of the instrument is 50 V. It is possible to reduce this to 25 V for operation
in situations which require it. The most appropriate output voltage should be selected by the operator
based on local safety procedures.
The procedure for changing the output voltage is as follows:
DET3TA:
1. Press and hold the TEST button and switch instrument ON to the V setting using the selector
switch.
2. The needle will sweep across the scaleplate and return to the rest position. [On older DET3TC
and DET3TD instruments, the firmware version will be displayed followed by ‘tst’].
3. Release TEST button. The maximum output test voltage will be displayed, either ‘50 V’ or
‘25 V’.
4. To toggle between the maximum output test voltages, press the TEST button.
5. Switch off instrument when the desired maximum test voltage is displayed.
DET3TC, DET3TD, DET4TD2, DET4TR2, DET4TC2 and DET4TCR2:
1. Press the 25V/50V button after selecting the measurement mode; the display will indicate the
selected output voltage.
Note:
For ART mode, the output voltage is automatically set to 25 V and cannot be changed.
Note: Some older versions of the DET3TC and DET3TD do not have the the 25V/50V button. The
procedure for changing the output voltage is as per the DET3TA.
Auto power down
To extend battery life, the instrument will automatically switch off six minutes after the last operation.
The instrument can be switched back on by turning the selector switch to the O
selecting the desired mode of operation.
Display symbols (DET3TC, DET3TD, DET4TD2, DET4TR2, DET4TC2 and DET4TCR2)
Symbol Meaning
Warning triangle. (Refer to user guide)
Fuse blown.
Battery indicator.
position and then
ART
ART
Situation is suitable for making ART measurements [DET3TC, DET4TC2
and DET4TCR2 only].
Situation is not suitable for making ART measurements [DET3TC,
DET4TC2 and DET4TCR2 only].
10
>100V
Rp
Indicates that the ground noise voltage exceeds the instrument
measurement capability (test is inhibited).
Potential stake (P stake) is within range for accurate measurement.
Rp
Rc
Rc
V
V
I
I
Potential stake (P stake) resistance exceeds range for accurate
measurement.
Current stake (C stake) is within range for accurate
Measurement.
Current stake (C Stake) resistance exceeds range for accurate
measurement.
Ground noise voltage is within range for accurate measurement of
resistance.
Ground noise voltage exceeds range for accurate measurement of
resistance.
ICLAMP is connected; VCLAMP is connected [DET3TC, DET4TC2 and
DET4TCR2 only].
ICLAMP is not connected; VCLAMP is not connected [DET3TC, DET4TC2
and DET4TCR2 only].
Sufficient ICLAMP current [DET3TC, DET4TC and DET4TCR only].
I
Insufficient ICLAMP current [DET3TC, DET4TC2 and DET4TCR2 only].
Display symbols (DET3TA)
Symbol Meaning
Rc
Rc
Rc
Current stake (C Stake) resistance exceeds range for accurate
measurement.
OR Fuse blown.
Current stake (C stake) is within range for accurate measurement.
Instrument is performing pre-measurement checks.
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INSTRUMENT ILLUSTRATIONS
DET3TA
Multi-function
analogue display
Spike
button
Test button
Test lead
connections (at
rear)
Rc OK
Resistance
measurement
settings (2P and
3P)
Selector switch
Battery check setting
voltage setting
Resistance
Voltage scale
scale
Test lead connections (at rear of instrument)
Potential test
spike resistance
indicator
Battery charge
indicator
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DET3TC
LCD display
Test button
25 V/50 V output
voltage select button
Test lead
connections (at rear)
Resistance
measurement
settings (2P and 3P
and clamp)
Selector switch
Voltage and current
measurement settings
Output voltage
indicator
Over/under
range
indicator
Potential probe
resistance indicator
(OK/Not OK)
Ruptured fuse
indicator
Current probe
resistance (OK/Not
OK)
Warning – refer to
user manual
Ground noise voltage
indicator (OK/Not OK)
Battery charge
indicator
ART measurement
indicator
(Possible/Not
possible
Measuring range
Clamp
current/presence
indicator (OK/Not OK)
Test lead connections (at rear of instrument)
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DET3TD
LCD display
25 V/50 V output voltage select button
Test button
Test lead connections (at
rear)
Resistance measurement
settings (2P and 3P)
Selector switch
Voltage measurement settings
Output voltage
indicator
Over/
under
range
indicator
Ruptured fuse
indicator
Potential probe
Resistance indicator
(OK or high)
Warning – refer to
user manual
Current probe resistance
(OK or high)
Battery charge
indicator
Measuring range
Ground noise voltage
indicator (OK high)
Test lead connections (at rear of instrument)
14
DET4TD2
LCD display
Test button
Output voltage
indicator
25 V/50 V output
voltage select
button
Ruptured fuse
indicator
Test lead connections
(at rear)
Resistance measurement settings
(2P, 3P and 4P)
Selector switch
Voltage measurement
settings
Warning – refer to
user manual
Battery charge
indicator
Over/under
range
indicator
Potential probe
resistance indicator
(OK or high)
Current probe
resistance (OK or
high)
Measuring range
Ground noise voltage
indicator (OK high)
Test lead connections (at rear of instrument)
15
DET4TR2
LCD display
Test button
Output voltage
indicator
Test lead connection
(at rear)
25 V/50 V output
voltage select button
Ruptured fuse
indicator
Resistance measurement settings
(2P, 3P and 4P)
Selector switch
Voltage measurement
settings
Warning – refer to
user manual
Over/
under
range
indicator
Potential probe
Resistance indicator
(OK or high)
Current probe resistance
(OK or high)
Battery charge
indicator
Measuring range
Ground noise voltage
indicator (OK high)
Test lead connections (at rear of instrument)
16
DET4 TC2
LCD display
Test lead connections
(at rear)
Resistance measurement settings
Selector switch
Voltage and current
measurement settings
Test button
Output voltage
indicator
Over/under
range
indicator
Frequency select button
25 V/ 50 V output
voltage select button
Ruptured fuse
indicator
Backlight control button
Warning – refer to
user manual
Battery charge
indicator
ART measurement
indicator
(Possible/Not
possible
Measuring range
Potential probe
resistance indicator
(OK/Not OK)
Test lead connections (at rear of instrument)
Current probe
resistance (OK/Not
OK)
Ground noise voltage
indicator (OK/Not OK)
Clamp
current/presence
indicator (OK/Not OK)
17
DET4TCR2
LCD display
Test button
Output voltage
indicator
Over/under
range
indicator
25 V/ 50 V output
voltage select button
Ruptured fuse
indicator
Test lead
connections
(at rear)
Resistance measurement settings
Selector switch
Frequency select button
Warning – refer to
user manual
Voltage and current
measurement settings
Backlight control button
Battery charge
indicator
ART measurement
indicator
(Possible/Not
possible
Potential probe
resistance indicator
(OK/Not OK)
Current probe
resistance (OK/Not
OK)
Test lead connections (at rear of instrument)
Ground noise voltage
indicator (OK/Not OK)
Measuring range
Clamp
current/presence
indicator (OK/Not OK)
18
BATTERY
Battery status indication (DET3TC, DET3TD, DET4TD2 and DET4TC2)
The battery condition indicator is displayed whilst the instrument is switched on as shown:
100% battery charge remaining.
75% battery charge remaining.
50% battery charge remaining.
25% battery charge remaining.
Some charge remaining, but instrument may auto power
down at any time.
0% battery charge remaining – instrument will auto power
down.
Battery status indication (DET4TR2 and DET4TCR2)
The battery condition indicator is displayed whilst the instrument is switched on as shown:
Full battery charge – shown immediately after charging.
Nearly fully battery charge.
Some change remaining, but instrument may auto power
down at any time.
19
0% battery charge remaining – instrument will auto power
down.
Note: If the DET4TR2 and DET4TCR2’s rechargeable batteries are replaced with alkaline batteries the
instrument may automatically disable its charging circuit to prevent inadvertent charging of nonrechargeable cells. Follow the instructions ‘Re-enabling the DET4TR2 and DET4TCR2 charger circuit’ to
switch the charger back on when the NiMH cells are re-inserted.
Battery status indication (DET3TA)
1. Set the rotary selector switch to the position.
2. Press and hold the TEST button.
3. The battery charge level will be indicated on the scaleplate as shown in Figure 1.
Figure 1: battery charge level indicator
4. Release the TEST button.
Battery charging (DET4TR2 and DET4TCR2)
When the battery status indicator shows a nearly empty or exhausted battery, the instrument may be
recharged using the following procedure.
Warning: Do not attempt to operate the instrument whilst the external AC/DC adaptor is connected.
Warning: Do not attempt to recharge non-rechargeable (dry) cells in the DET4TR2 and DET4TCR2.
Doing so will result in instrument damage and may cause personal injury. Only use the cells
recommended by Megger.
Warning: Only use the external charging equipment provided by Megger.
1. To avoid the possibility of electric shock, switch instrument OFF and disconnect the instrument
from any electrical circuits.
2. Move the slide on the terminal panel until the external AC/DC adaptor socket is exposed.
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