99 Washington Street

Melrose, MA 02176
Phone 781-665-1400
Toll Free 1-800-517-8431

Visit us at www.TestEquipmentDepot.com

DET3 Contractor Series

DET3 Contractor Series Earth/Ground Resistance Testers

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
■ Calibration test certificate included
(except DET3TA)

DESCRIPTION All models are rated to IP54, making them truly outdoor
Megger’s already popular 3-terminal ground testing instruments. They are designed to meet stringent safety
instrument family includes 3 models as shown below: standards and are rated CAT IV 100V. The ground testers
have been designed to be easy to use – a large selector
Model Description
switch makes selection of 2 or 3 pole tests easy with
DET3TD For basic requirements it provides digital gloved hands – and the design makes the fitting of
ground testing and bond testing capabilities shorting links to perform 2-pole tests a thing of the past. A
DET3TA For those who prefer an analog display large, clear, easy to read LCD or analog (DET3TA) display
DET3TC The revolutionary new model with the and thumb sized test button also make the instruments
capability of testing on-site grounds without particularly well suited to the outdoor conditions of
disconnecting the utility connection ground testing. In addition to this ease of use feature, the
ground tester automatically checks the connection and
The DET3TC includes a conditions of the P spike, C spike, and also the level of
current measuring function ground noise, indicating the status on the display. (The
for ART (Attached Rod analog model allows the operator to check the condition
Technique) testing of the spikes). The instruments also include a voltmeter to
capabilities. With this enable measurement of ground voltage. They can measure
added function, on-site resistance from 0.01 ohms to 2 kΩ. Also, to allow accurate
grounds can be tested testing in noisy environments, the instruments are capable
separately without having of rejecting noise up to 40V peak to peak.
to remove the utility
connection (as explained The Megger digital and analog ground testers are powered
further in this document). by eight AA batteries which are widely available and also
give excellent testing time – the status of these batteries is
The complete kit of given by a bar graph on the LCD display, allowing the
instrument, test leads, operator to decide when to change the batteries before
stakes, batteries and they expire. (On the analog model, battery status is
Using ART method with the DET3TC calibration certificate is indicated by selecting the function on the selector switch).
to test commercial ground without delivered in a tough
disconnecting the system By using the optional ICLAMP with the DET3TC, the user
polypropylene carry case –
everything you need to start testing in one package. can augment the traditional fall-of-potential measurement
(Certificate not included with analog model). Optional method with ART (Attached Rod Technique), which allows
terminal adapters are available for acceptance of a variety electrode testing without disconnection and also leakage
of test leads. current measurements down to 0.5 mA.
 DET3 Contractor Series
Earth/Ground Resistance Testers

SELECTION GUIDE DET3TD DET3TA DET3TC

2-wire Resistance ■ ■ ■

3-wire Resistance ■ ■ ■

ART (Attached Rod Technique) Resistance Measurement ■

Resistance Range 0.01 to 2000 0.01 to 2000 0.01 to 2000

2% ± 3d 2.5% of scale length 2% ± 3d
Ground Voltage Range 0 to 100V 0 to 100V 0 to 100V
Ground Current Range (with optional current measuring clamp) 0.5mA to 19.9A
Display Digital Analog Digital

APPLICATIONS Grounding electrodes from simple to complex systems can

Proper grounding provides many varied benefits to both be tested, including:
people and facilities. It lessens the chance of injury due to ■ Primary and secondary electrical grounding systems
faulty installation, reduces the likelihood of damage from ■ Utility pole grounds
lightning strikes and induced voltages, improves the
■ Lightning protection systems
performance of computer, communication and other
■ Residential grounds
sensitive equipment and protects against static electricity
from friction. Over time, ground systems can degrade or ■ Machinery safety grounds

become ineffective. ■ Computer and communication system grounds

■ EMI/RFI system grounds

Corrosion and weather influences exert mechanical strain
on ground rods and cause metallic corrosion. Catastrophic ■ Antenna and pedestal grounds
events like lightning strikes or large fault currents can ■ CATV system grounds
cause instant degradation. In addition, facility expansion
can create different ground system needs.
FEATURES AND BENEFITS
The risks from ground system deterioration include ■ Microprocessor control for improved error detection
potentially deadly electrical shock situations, plant-wide ■ Clear, unambiguous warnings and error indications
equipment damage, disruption in the performance of ensure the reliability of the reading and reduce test time
sensitive equipment and heat build-up on a single piece of
■ Simple to use, one touch operation improves efficiency
electrical equipment.
■ User selectable test voltage ensures that the units can be
The maintenance of an adequate low resistance ground used in agricultural environments
connection is essential to both the protection and ■ Rugged, weatherproof case to IP54 makes the units truly
performance of any electrical system. Ground testing
outdoor instruments
should be performed both upon installation, to meet
■ Large, clear LCD that can be read in ambient lighting
design specification, and periodically thereafter in order to
maintain service. All models can also perform bonding ■ Noise rejection to 40 V pk to pk allows accurate testing

tests (using an ac signal), to determine that adequate in noisy environments

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 among the three-model family is easy. For basic
requirements, DET3TD affords ground testing and bond
testing capabilities. For those who prefer an analog tester,
DET3TA affords the same testing capabilities with a
mechanical movement. The model’s prime advantage is
reliable performance in extremes of weather, either heat
or cold, that stress the limits of digital 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.

Model DET3TC shown performing the classic fall-of-potential test method.

 DET3 Contractor Series
Earth/Ground Resistance Testers

■ 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

SPECIFICATIONS
Resistance range: 0.01 to 2000 autoranging
Resistance accuracy:
Analog model:
2.5% of scale length
Each instrument comes complete with three leads, two test spikes,
Digital models: instruction manual CD, and a rugged carrying case, (current measuring
2P measurements 2% ±3 digits clamp, shown, is an optional accessory for performing the ART testing
3P measurements 2% ±3 digits capability using the DET3TC.)
ART measurements 5% ±3 digits
Maximum probe resistance
Rp limit: 100kΩ (50V output voltage)
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, all models
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 Terminal Adapters are
Display: LCD (moving coil meter for analog model) optional accessories used
Test frequency: 128 Hz to allow the units’ terminals
to accept alternative cable
Test voltage: 25 V or 50 V, user selectable (factory setting 50 V) connections.
Test current: 450 micro-amps
Noise rejection: 40V pk to pk
Noise check: Automatic (by selector switch DET3TA)
C spike check: Automatic (by pushbutton DET3TA)
P spike check: Automatic (by pushbutton DET3TA)
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);
DET3TA: -4º to +122º F (-20º to +50º C)
Storage temperature range: -40º to +158º F (-40º to +70º C)
Humidity: 95% RH non-condensing at 104º F (40º C)
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”.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX 781.665.0780 - TestEquipmentDepot.com
 DET3 Contractor Series
Earth/Ground Resistance Testers

Part 1 - General requirements demonstrating the competence of the readings to a third

Part 5 - Resistance to earth party, such as a client. They must simply be accepted.

ART (ATTACHED ROD TECHNIQUE) The ART testing capability combines the advantages of
TESTING CAPABILITY both of these technologies to produce a method that can
The DET3TC includes the additional testing capability that reliably measure an attached ground, and prove it! A
we have termed ART, for Attached Rod Technique. A built-in clamp input, used in conjunction with the optional
nagging problem with traditional ground testing has been ICLAMP accessory, connected below the point of
the requirement to “lift” (i.e., disconnect) the utility separation of the parallel test currents, measures only the
connection. Once the grounding conductor (the main current flowing through the test ground, not that going
conductor that connects the facility to the ground rod or back through the utility. This current value is then used by
grid) has been attached to the grounding electrode, the the microprocessor to calculate ground resistance, strictly
utility ground becomes a parallel resistance. The utility in accordance with Fall of Potential or its derivative
neutral is typically bonded to the ground bus at the procedures, supported by IEEE Standard 81 for proper
service entrance and this connection, during a ground ground testing, and subject to the appropriate proofs.
test, causes test current to flow back through the utility The ART method employs leads and probes just as does
ground as well as through the test electrode. Test current any traditional tester. Ground resistance can be profiled
divides according to Law of Parallel Resistance, but the and graphed by moving the potential probe against the
tester makes its measurement based on total current flow. position of the current probe, and a Fall of Potential
The reading is the combined parallel resistance of the on- graph, Slope Method mathematical proof, or any of the
site ground and the utility protection. This is a valid other proven methods utilized to demonstrate the
measurement, but not of the test electrode exclusively. accuracy of the test. The only thing different from the
This poses a considerable problem in many common operation of a familiar, traditional ground tester is that the
testing situations. If a commissioning test were required to clamp permits separation of the test currents in an
determine if design specifications had been met for a new attached or otherwise parallel-grounded system. This
facility, such a reading would be insufficient. Lightning technique enables local grounds to be tested without
protection requiring a short, straight path into the earth, lifting the utility connection, yet with the ease, reliability
could also not be properly validated. But lifting the utility and confidence of a separate commissioning test.
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. Current measuring clamp (inset)
for ART testing capability
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 problem 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
experience of the operator, leaving a large margin for
“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 current will circulate through such paths and give a
reading, essentially a continuity reading of the grid
structure having nothing to do with soil resistance. Such
readings will be low, and appear to the uninformed as
acceptable grounds. The responsibility for making these
determinations falls squarely on the operator. But even
when properly addressed, there is no way of
 DET3 Contractor Series
Earth/Ground Resistance Testers

OPTIONAL ACCESSORY KITS

Standard Kit, Deluxe Kit, Standard Kit Professional Kit

Cat. No. 250579 Cat. No. 250581 Cat. No. EV6310-755 Cat. No. 6320-245
Three color-coded test Set of three color-coded Hammer, 2.5 lb (1.13 kg); Red, black, yellow, green
leads, 25, 50, 100 ft. test leads, 25, 50, 100 ft. four galvanized steel cable reels (50 m); earth
(8, 15, 30 m); two 20-in. (8, 15, 30 m); two 20-in. spikes, 0.5 in. (12 mm); electrode leads (4 m
(51 cm) ground rods; (51 cm) ground rods; two spike extractors; four green, 4 mm shrouded
canvas accessory case for padded case to hold leads in carrying case plug and large croc clip);
leads and rods only instrument, leads and rods 4 auger-style spikes;
molded polyethylene
carrying case; fiberglass
measuring tape, 50 m

ORDERING INFORMATION
Item (Qty) Cat. No. Item (Qty) Cat. No.
Analog ground tester DET3TA “Getting Down to Earth”
a Megger guide to earth testing AVTM25-TA
Digital ground tester, ART capability DET3TC
Replacement hard carry case 5410-429
Digital ground tester DET3TD
Replacement ground test stakes (x2)
Included Accessories for included kit (200mm, 8mm dia) 6220-804
Hard carry case EV5410-409 Replacement ground test leads (x4)
Replacement 3-wire lead set for included kit (15m, 10m, 10m, 3m) 6220-806
(15m red wire, 10m yellow wire, 4m green wire) 6220-805 Replacement auger stakes (x2)
Ground test stakes (x2) (200mm, 8mm dia) 6220-804 for professional kit 6220-839
Optional Accessories Replacement cable reel (50m, red cable)
for professional kit 6220-840
Current measuring clamp and connecting
lead for ART testing method ICLAMP Replacement cable reel (50m, black cable)
for professional kit 6220-841
Calibration check box 6220-824
Replacement cable reel (30m, yellow cable)
Right angled terminal adaptor set 6220-803
for professional kit 6220-842
Standard accessory kit (leads, rods, canvas
Replacement cable reel (30m, green cable)
accessory case for leads & rods) 250579
for professional kit 6220-843
Deluxe accessory kit (leads, rods, padded case) 250581
Standard accessory kit (hammer, spikes, leads) EV6310-755
Professional ground testing kit Visit us at www.TestEquipmentDepot.com
(2 x 50m, 2 x 30m, 4 auger stakes, carry case) 6320-245