ET3 Contractor Series
D
arth/Ground Resistance Testers
E
DET3 Contractor Series
3-Terminal Earth/Ground Resistance Testers
■
2 and 3 point testing
■
ART (Attached Rod Technique)
testing capability
■
User selectable test voltage (25/50 V)
■
Choice of digital or analog display
■
Warning indicators prevent test failure
■
IP54 rated
■
Complete with leads, stakes and
rugged carry case
■
Simple one button operation
DESCRIPTION
Megger’s already popular 3-terminal ground testing
instrument family includes the following models:
Model Description
DET3TD
DET3TC The revolutionary new model with the
Using ART method with the DET3TC
to test commercial ground without
disconnecting the system
start testing in one package. Optional terminal adapters
are available for acceptance of a variety of test leads.
For basic requirements it provides digital
ground testing and bond testing capabilities
capability of testing on-site grounds without
disconnecting the utility connection.
The DET3TC includes a
current measuring function
T (Attached Rod
for AR
Technique) testing
capabilities. With this
added function, on-site
ounds can be tested
gr
separately without having
to remove the utility
connection (as explained
further in this document).
The complete kit of
instrument, test leads,
stakes, batteries and
calibration certificate is
delivered in a tough
opylene carry case
polypr
– everything you need to
All models are rated to IP54, making them truly outdoor
instruments. They are designed to meet stringent safety
standards and are rated CAT IV 100V. The ground testers
have been designed to be easy to use – a large selector
switch makes selection of 2 or 3 pole tests easy with
gloved hands – and the design makes the fitting of
shorting links to perform 2-pole tests a thing of the past. A
large, clear, easy to read LCD and thumb-sized test button
also make the instruments particularly well suited to the
outdoor conditions of gr
ease of use feature, the ground tester automatically checks
the connection and conditions of the P spike, C spike, and
also the level of ground noise, indicating the status on the
display. The instruments also include a voltmeter to enable
ement of ground voltage. They can measure
measur
esistance fr
r
testing in noisy environments, the instruments are capable
of rejecting noise up to 40V peak to peak.
The Megger gr
batteries which are widely available and also give
excellent testing time – the status of these batteries is
given by a bar graph on the LCD, allowing the operator to
decide when to change the batteries before they expire.
By using the optional ICLAMP with the DET3TC, the user
can augment the traditional fall-of-potential measur
method with ART (Attached Rod Technique), which allows
electr
current measurements down to 0.5 mA.
om 0.01 ohms to 2 k
ound testers are powered by eight AA
ode testing without disconnection and also leakage
ound testing. In addition to this
. Also, to allow accurate
Ω
ement
ET3 Contractor Series
D
arth/Ground Resistance Testers
E
PPLICATIONS
A
Proper grounding provides many varied benefits to both
people and facilities. It lessens the chance of injury due to
faulty installation, reduces the likelihood of damage from
ightning strikes and induced voltages, improves the
l
performance of computer, communication and other
sensitive equipment and protects against static electricity
from friction. Over time, ground systems can degrade or
become ineffective.
Corrosion and weather influences exert mechanical strain
n ground rods and cause metallic corrosion. Catastrophic
o
events like lightning strikes or large fault currents can
cause instant degradation. In addition, facility expansion
can create different ground system needs.
The risks from ground system deterioration include
potentially deadly electrical shock situations, plant-wide
equipment damage, disruption in the performance of
sensitive equipment and heat build-up on a single piece of
electrical equipment.
The maintenance of an adequate low resistance ground
connection is essential to both the protection and
performance of any electrical system. Ground testing
should be performed both upon installation, to meet
design specification, and periodically thereafter in order to
maintain service. All models can also perform bonding
tests (using an ac signal), to determine that adequate
connection has been made from equipment to the
grounding system. Furthermore, the addition of a built-in
current clamp capability enables the testing of attached
grounds (ART) without lifting the utility connection.
Selection is easy. For basic requirements, DET3TD affords
ground testing and bond testing capabilities. Applications
to systems that have been connected to the utility feed are
simplified with model DET3TC, where a built-in clamp
input permits individual components of an expanded
system to be separately measured without extra
calculations.
Grounding electrodes from simple to complex systems can
be tested, including:
■
Primary and secondary electrical grounding systems
■
Utility pole gr
■
Lightning protection systems
■
Residential grounds
■
Machinery safety grounds
■
Computer and communication system gr
■
EMI/RFI system grounds
■
Antenna and pedestal grounds
■
CATV system grounds
ounds
ounds
FEATURES AND BENEFITS
■
Microprocessor control for improved error detection
■
Clear, unambiguous warnings and error indications
ensure the reliability of the reading and reduce test time
■
Simple to use, one touch operation improves efficiency
■
User selectable test voltage ensures that the units can be
used in agricultural environments
■
Rugged, weatherproof case to IP54 makes the units truly
outdoor instruments
■
arge, clear LCD that can be read in ambient lighting
L
■
oise rejection to 40 V pk to pk allows accurate testing
N
in noisy environments
■
Testing kits and certificates supplied — everything
needed to start testing immediately
■
Accuracy of 2% of reading enhances reliability of
measurements
■
Clamp model for Attached Rod Technique allows the
testing of the rod without the need for disconnection.
■
Voltmeter function included allows you to measure the
ground voltage and enhances operator safety
■
CAT IV 100V provides increased operator safety in
outdoor environments
Model DET3TC shown performing the classic fall-of-potential test method.
SPECIFICATIONS
Resistance range: 0.01 to 2000 autoranging
Resistance accuracy:
2P measurements 2% ±3 digits
3P measurements 2% ±3 digits
ART measurements5% ±3 digits
Maximum probe resistance
Rp limit:
Rc limit: 100kΩ (50V output voltage)
Limits reduced to 50kΩ for 25V output voltage
Limits reduced to 5kΩ for 0.01 Ω resolution
Earth voltage range: 0 – 100 V
Earth voltage accuracy: 2% ±2 V
2- and 3-wire test: Yes
ART (Attached Rod Technique): DET3TC
Ground current range (with current measuring clamp):
0.5 mA to 19.9 A
Ground current accuracy: 5% ±3 digits
Display: LCD
Test frequency: 128 Hz
Test voltage: 25 V or 50 V, user selectable (factory setting 50 V)
Test current: 450 micro-amps
Noise rejection: 40V pk to pk
Noise check: Automatic
C spike check: Automatic
P spike check: Automatic
Maximum current loop resistance: 100 k-ohms at 50V,
50 k-ohms at 25 V and 5 k-ohms for 0.01 ohm resolution for
readings below 19 ohms
Maximum voltage probe resistance: 100 k-ohms at 50V,
50 k-ohms at 25 V and 5 k-ohms for 0.01 ohm resolution for
readings below 19 ohms
Battery type: 8 1.5 V AA cells
Battery life: 3 hours, 700 consecutive tests
Safety: EN61010-1 CAT IV 100 V
Terminals: 4 mm plug type (test leads)
Ingress protection: IP54
EMC: Meets the requirements of EN61326-1:1998 for use in
heavy industrial areas
Dimensions: 8 x 5.7 x 3.2 in. (203 x 148 x 78 mm)
Weight: 2.2 lb (1 kg)
Operating temperature range: -5º to +131º F (-15º to +55º C)
Storage temperatur
Humidity: 95% RH
Standards Compliance
Complies with the requirements of KEMA K85B.
Complies with the following parts of EN61557, “Electrical safety in
low voltage distribution systems up to 1000 V a.c. and 1500 V
d.c. - Equipment for testing, measuring or monitoring of
protective measures”.
Part 1 - General requirements
Part 5 - Resistance to earth
100kΩ (50V output voltage)
e range:
-40º to +158º F (-40º to +70º C)
non-condensing at 104º F (40º C)
DET3 Contractor Series
arth/Ground Resistance Testers
E
Each instrument comes complete with three leads, two test spikes,
instruction manual CD, and a rugged carrying case, (current measuring
clamp, shown, is an optional accessory for performing the ART testing
capability using the DET3TC.)
Terminal Adapters are
optional accessories used
to allow the units’ terminals
to accept alternative cable
connections.
ART (ATTACHED ROD TECHNIQUE)
ESTING CAPABILITY
T
The DET3TC includes the additional testing capability that
we have termed
ART, for Attached Rod Technique. A
nagging problem with traditional ground testing has been
the requirement to “lift” (i.e., disconnect) the utility
onnection. Once the grounding conductor (the main
c
conductor that connects the facility to the ground rod or
grid) has been attached to the grounding electrode, the
utility ground becomes a parallel resistance. The utility
neutral is typically bonded to the ground bus at the
service entrance and this connection, during a ground
test, causes test current to flow back through the utility
ground as well as through the test electrode. Test current
divides according to Law of Parallel Resistance, but the
tester makes its measurement based on total current flow.
The reading is the combined parallel resistance of the onsite ground and the utility protection. This is a valid
measurement, but not of the test electrode exclusively.
This poses a considerable problem in many common
testing situations. If a commissioning test were required to
determine if design specifications had been met for a new
facility, such a reading would be insufficient. Lightning
protection requiring a short, straight path into the earth,
could also not be properly validated. But lifting the utility
connection poses several problems, not the least of which
is the breaking of what is often a welded bond, in
addition to the temporary loss of protection.
Clamp-on ground testers, which measure ground
resistance by clamping around the rod and inducing a test
current onto it, are only a limited solution. They can
accurately measure resistance of a single rod in a parallel
system by inducing the test current onto the clamped rod
and utilizing all the parallel grounds as the return.
Collectively, these returns, typically the multiple grounds
of the utility, contribute little to the loop measurement.
This is essentially the reverse of the operation of a
traditional tester, which uses the current probe as the
return while current “goes to ground” through all parallels
collectively. This technique solves the pr
oblem of
separately measuring an attached rod, but leaves the
problem that it cannot be proven.
A clamp-on measurement has to be accepted on faith and
its reliability is based squarely on the knowledge and
gin for
experience of the operator, leaving a lar
ge mar
“human error.” In complex, multiply connected grids and
other grounding schemes, return paths may exist that are
entirely metallic, not including earth at all. The clamp-on
test curr
r
ent will cir
eading, essentially a continuity reading of the grid
culate through such paths and give a
structure having nothing to do with soil resistance. Such
eadings will be low, and appear to the uninformed as
r
acceptable grounds. The responsibility for making these
determinations falls squar
ely on the operator
. But even
when properly addressed, there is no way of
demonstrating the competence of the readings to a third
party, such as a client. They must simply be accepted.
DET3 Contractor Series
Earth/Ground Resistance Testers
ART testing capability combines the advantages of
The
both of these technologies to produce a method that can
reliably measure an attached ground, and prove it! A
uilt-in clamp input, used in conjunction with the optional
b
ICLAMP accessory, connected below the point of
separation of the parallel test currents, measures only the
current flowing through the test ground, not that going
ack through the utility. This current value is then used by
b
the microprocessor to calculate ground resistance, strictly
in accordance with Fall of Potential or its derivative
procedures, supported by IEEE Standard 81 for proper
ground testing, and subject to the appropriate proofs.
ART method employs leads and probes just as does
The
any traditional tester. Ground resistance can be profiled
and graphed by moving the potential probe against the
position of the current probe, and a Fall of Potential
graph, Slope Method mathematical proof, or any of the
other proven methods utilized to demonstrate the
accuracy of the test. The only thing different from the
operation of a familiar, traditional ground tester is that the
clamp permits separation of the test currents in an
attached or otherwise parallel-grounded system. This
technique enables local grounds to be tested without
lifting the utility connection, yet with the ease, reliability
and confidence of a separate commissioning test.
Current measuring clamp (inset)
testing capability
T
for AR
OPTIONAL ACCESSORY KITS
DET3 Contractor Series
arth/Ground Resistance Testers
E
Standard Kit,
Cat. No. 250579
Three color-coded test
eads, 25, 50, 100 ft.
l
(8, 15, 30 m); two 20-in.
(51 cm) ground rods;
canvas accessory case for
eads and rods only
l
Deluxe Kit,
Cat. No. 250581
Set of three color-coded
est leads, 25, 50, 100 ft.
t
(8, 15, 30 m); two 20-in.
(51 cm) ground rods;
padded case to hold
instrument, leads and rods
Standard Kit
Cat. No. EV6310-755
Hammer, 2.5 lb (1.13 kg);
four galvanized steel
spikes, 0.5 in. (12 mm);
two spike extractors; four
eads in carrying case
l
Professional Kit
Cat. No. 6320-245
Red, black, yellow, green
cable reels (50 m); earth
lectrode leads (4 m
e
reen, 4 mm shrouded
g
plug and large croc clip);
4 auger-style spikes;
molded polyethylene
arrying case; fiberglass
c
measuring tape, 50 m
ORDERING INFORMATION
Item (Qty)
T capability
Digital ground tester
, AR
Digital ground tester DET3TD
Included Accessories
Hard carry case EV5410-409
Replacement 3-wire lead set
(15m red wire, 10m yellow wire, 4m green wire)
Ground test stakes (x2) (200mm, 8mm dia)
UK
Archcliffe Road, Dover
CT17 9EN England
T +44 (0) 1 304 502101
F +44 (0) 1 304 207342
UKsales@megger.com
UNITED STATES
4271 Bronze Way
Dallas, TX 75237-1019 USA
T 1 800 723 2861 (USA
T +1 214 333 3201
F +1 214 331 7399
USsales@megger.com
Cat. No.
DET3TC
6220-805
6220-804
only)
Item (Qty) Cat. No.
Optional Accessories
Current measuring clamp and connecting
lead for ART testing method ICLAMP
Calibration check box 6220-824
Right angled terminal adaptor set 6220-803
Standard accessory kit (leads, rods, canvas
accessory case for leads & rods) 250579
Deluxe accessory kit (leads, rods, padded case) 250581
Standard accessory kit (hammer
, spikes, leads) EV6310-755
Professional ground testing kit
(2 x 50m, 2 x 30m, 4 auger stakes, carry case) 6320-245
“Getting Down to Earth”
VTM25-T
.com
A
5410-429
en_V02
a Megger guide to earth testing
Replacement hard carry case
OTHER TECHNICAL SALES OFFICES
Täby SWEDEN, Norristown USA,
Sydney AUSTRALIA, T
Trappes FRANCE, Kingdom of BAHRAIN,
Mumbai INDIA, Johannesburg SOUTH
AFRICA, and Chonburi THAILAND
onto CANADA,
or
ISO STATEMENT
Registered to ISO 9001:2000 Reg no. Q 09250
Registered to ISO 14001 Reg no. EMS 61597
DET3SERIES_DS_US
.megger
www
Megger is a registered trademark
A
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