DET4TDR2 and DET4TCCR2 Earth Testers

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DET4TD/R2 and DET4TC/CR2 Earth Testers Product
Sales Guide

• Selected Key Features Benefits
• Stakeless (clamp-on) Testing Capability
  (DET4TC/CR2)
• Can be used like a clamp-on tester (saving time)
  in appropriate applications.
• Two test methods (clamp-on and fall-of-potential)
  in once box.
• Allows testing in areas where driving spikes is
  impossible.
• Attached Rod Technique (ART) Capability
  (DET4TC/CR2)
• Can make fall-of-potential tests without
  disconnecting the ground rod.
• No need to shut down the supply to ensure safety.
• 40 V Peak-to-Peak Noise Rejection
• Make accurate readings with up to 40 V pk-to-pk
  between potential terminals.
• Allows testing in noisy environments like
  substations.
• Variable Test Frequency (DET4TC/CR2)
• Can select a test frequency away from any ground
  noise experienced at 128 Hz.
• Allows testing in noisy environments like
  substations.
• 200 kOhm (kO) Range (DET4TC/CR2)
• Can measure resistivity in any type of soil.
• Increased spike resistance tolerance (for more
  reliable lazy spike testing).
• User Selectable Output Voltage (25/50 V)
• Can test in agricultural locations as per
  IEC61557-5 (25 V requirement).

Overview The DET4TD2, DET4TR2, DET4TC2 and
DET4TCR2 are 4-terminal earth testers designed to
make 2-pole, 3-pole (fall-of-potential) and
4-pole (soil resistivity) measurements by simply
turning the selector switch. The DET4TD/R2 units
provide basic test capability at a moderate
price, while the DET4TC/CR2 units include many
additional features that both extend the testing
capability of the units and allow them to operate
under a wider range of conditions. These models
can make both ART tests and stakeless (clamp-on)
tests. All models have industry best noise
rejection.
General Applications and Uses The DET4TD/R2 and
DET4TC/CR2 are used to test the quality of
ground/earth electrodes and to make soil
resistivity measurements allowing the grounding
requirements to be designed. Good grounding
reduces the chance of injury due to faulty
insulation, lowers the likelihood of damage from
lightning strikes and induced voltages, protects
against static electricity and improves the
performance of computer, communication and other
sensitive equipment. Ground system performance
deteriorates over time due to a wide range of
factors, including corrosion, weather,
catastrophic electrical events and changes in
soil resistivity.

• Typical Ground Electrodes Tested
• Primary and secondary electrical grounding
  systems.
• Utility pole grounds.
• Lightning protection systems.
• Residential grounds.
• Machinery safety grounds.
• Computer and communication system grounds.
• EMI/RFI system grounds.
• Antenna and pedestal grounds.
• Facility ground grids/systems.
• CATV ground systems.

• Typical End Users
• Power utilities.
• Electrical contractors/electricians.
• Industrial plant maintenance personnel.
• Telecom and datacom companies.
• Electrical testing companies.
• Field service and maintenance personnel.
• Petrochemical companies.
• Specialist grounding companies and consultants.
• Railroads.

Competitive Instruments The DET4TD/R2 and
DET4TC/CR2 compete with the Fluke/LEM 1623 and
1625, the AEMC 6470 and 6472 and the Megabras
MDT-20KWe and EM-4055. While the Fluke and AEMC
units have good features, the Megger units have
the best capabilities for real-life (outdoor)
testing environments, including the best noise
rejection, the best CAT rating, the best humidity
specs and the best IP rating. While Fluke claims
IP56, they acknowledge that the battery door on
their units is only IP40 (meaning they have no
protection against liquids). The Megabras units
come up far short of the Megger units in a number
of key areas. AEMC and Megabras indicate good IP
ratings, but only with the instrument lid closed
(cant test this way).
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Competitive Comparison
Clarifying Questions for Customers In what types
of environments might they be testing? The Megger
units have the best IP rating, best humidity
specs and best safety (CAT) rating. Earth testing
is normally done outdoors, meaning that the IP
rating is critical. The Fluke IP rating of IP40
for the battery compartment is extremely poor and
the Megabras and AEMC ratings are only for when
the lid is closed (you cannot test with the lid
closed). Megabras does not even provide safety
ratings and AEMC and Fluke do not publish
humidity specs. How important is operator
safety? The Megger units have the best safety
rating (CAT IV 100 V) of any available units. By
comparison, Flukes units are only CAT II 300
V. How important is testing time to the end
user? The DET4TC2 and DET4TCR2 include both
stakeless (clamp-on) testing capability and
attached rod testing (ART) capability, making
them the most versatile units available. When
conditions permit, the units can be used as
clamp-on earth testers. If a fall-of-potential
measurement is required, it can be made using the
ART method in many situations, which means the
ground rod does not have to be disconnected. Is
the end user testing in noisy environments? Noise
rejection and variable frequency are critical
factors in allowing testing in noisy
environments. The Megger units have exceptional
noise rejection capability.
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• General Applications and Uses
• Soil resistivity testing. (4 pole)
• Used to locate the optimum position for a new
  earth system.
• Obtain earth resistance measurements required to
  design the earth system
• Earth Electrode testing (2, 3 pole)
• Lightning strike protection testing
• Noise level reducing earth testing.
• Static electricity dissipation.
• Fault or high load conditions protection testing
• ART Attached Rod Technique (TC models only)
• Testing an electrode resistance without the
  requirement to disconnect it.
• Stakeless Test (TC models only)
• Electrode testing in inner city concrete jungles,
  and locations such as cable cellars beneath sub
  stations.
• Measuring electrode resistance on lightning
  protection system on buildings.

Explaining the output specification of the
DET4TC/R2 to the customer Instruments such as
the Fluke 1625 specify 250mA, so why is the
DET4TC/R2 specified output only 4.5mA at 50V?
The Fluke specification is the maximum short
circuit current, Megger specify the actual test
current used. There are good reasons why Megger
do this. The safety standard IEC 61010-1 states
that for test voltage above 33V rms the current
is limited to 0.5mA.. The DET4TC/R/2 uses a
constant regulated test current of 0.45mA, which
demonstrates our compliance with IEC 60101-1. In
effect competitors are not telling you their true
test current only the short circuit capability of
their current source. Note If a competitor is
using higher test current at 50V they do not
comply with IEC 61010-1. Note 50V / 0.45mA gives
a maximum loop resistance of 111k? (would include
spike and lead resistance), a lower test current
is actually used by the DET4TC/R4 to test at
200k?. Why does the Megger DET4TC/R2 have a 25V
range? The maximum test voltage permitted in IEC
61557-5 (defines instrument requirements for
earth testing) is 25V when used under normal
conditions in agricultural locations. Why then
is the test current on the DET4TC/R2 on the 25V
range only limited to 4.5mA max.? Remember this
is test current not short circuit current. 4.5mA
gives adequate volt drop across the earth ground
resistance being measured to accurately measure
with 0.01 O resolution. Higher test currents are
used on some instruments to allow readings of
0.001? resolution, or to allow the use of less
accurate voltage measurement circuits. Note 25V
/ 4.5mA gives a maximum loop resistance of 5.5k?
(and enough voltage drop to accurately resolve to
0.01?), a lower test current is actually used by
the DET4TC/R4 to test at 100k?.
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Detailed Competitive Specification Comparison
Note The Megger DET4T units are supplied with a
complete set of PowerDB Lite earth testing forms.
These forms allow the user to automate the
calculations for all test methods, including Full
Fall of Potential, Simplified Fall of Potential,
Slope Method, Four Potential Method, Star-Delta
Method and the Intersecting Curves Method. The
forms will also calculate Soil Resistivity.