Extech Instruments 382356 User manual
User’s Manual
Ground Resistance Clamp On Tester
MODEL 382356
382356 V2.0 5/03
2
WARRANTY
EXTECH INSTRUMENTS CORPORATION warrants the basic instrument to be free of
defects in parts and workmanship for one year from date of shipment (a six month limited
warranty applies on sensors and cables). If it should become necessary to return the
instrument for service during or beyond the warranty period, contact the Customer Service
Department at (781) 890-7440 for authorization. A Return Authorization (RA) number
must be issued before any product is returned to Extech. The sender is responsible for
shipping charges, freight, insurance and proper packaging to prevent damage in transit.
This warranty does not apply to defects resulting from action of the user such as misuse,
improper wiring, operation outside of specification, improper maintenance or repair, or
unauthorized modification. Extech specifically disclaims any implied warranties or
merchantability or fitness for a specific purpose and will not be liable for any direct, indirect,
incidental or consequential damages. Extech's total liability is limited to repair or
replacement of the product. The warranty set forth above is inclusive and no other
warranty, whether written or oral, is expressed or implied.
Introduction
Congratulations on your purchase of Extech’s 382356 Ground Resistance Tester. This
Clamp-on device allows the user to measure the ground resistance of a ground rod without
the use of auxiliary ground rods. This device can only be used on multi-grounded systems.
It is not necessary to disconnect the ground under test. Proper use and care of this meter
will yield years of reliable service.
Safety
Safety is the responsibility of the operator. Only qualified technicians should operate this
meter.
Use extreme caution when operating the meter near energized electrical equipment.
Do not attempt to use this meter to twist or pry the ground electrode or ground wire away
from grounded equipment.
All metal objects or wires connected to the electrical system under test should be assumed
to be lethal until tested. Grounded systems are no exception.
Ensure that the batteries are inserted correctly in the battery compartment.
Remove the batteries from the meter if the meter is to be stored for long periods.
WARNING: If the meter is used in a manner not specified by the manufacturer, the built in
protections provided by the meter may be impaired.
382356 V2.0 5/03
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International Safety Symbols
This symbol, adjacent to another symbol or terminal, indicates the user
must refer to the manual for further information.
This symbol, adjacent to a terminal, indicates that, under normal use,
hazardous voltages may be present
Meter Description
1. Jaw Assembly
2. Hold Button
3. Rotary Selector Switch
4. LCD Display
5. Measurement Trigger
Display Symbols
ΩOhms.
mA, A milliamps, Amps.
•))) Continuity.
NOISE Annunciator for excessive noise on the ground conductor or rod.
Indicates that the clamp jaws are not fully closed.
Low Battery.
382356 V2.0 5/03
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Specifications
General Specifications
Resistance Test Frequency: 1.667KHz (15mV rms approx.)
Max Conductor size 0.9” (23mm)
Display 4-digit (9999 count) display
Sampling rate 0.4 seconds
Power supply One 9V battery
Power consumption 40mA
Temp. Coefficient 0.15 times the specified accuracy per degree
centigrade (from 39 to 64ºF (4 to 18oC) and 82 to
122ºF (28 to 50oC))
Current Overload Protected to 100A Continuous; 200A for less than 60
seconds (50/60Hz)
Continuity check Audible tone if reading is less than approx. 40Ω
Range selection Automatic ranging
Safety Meets the requirements for IEC1010-1 Category III 300V
and Category II 600 V
Operating conditions 4 to 122oF (-20 to 50oC) with < 85% RH
Storage conditions -20 to 140oF (-28 to 60oC) with < 75% RH
Dimensions 10.2 x 4.4 x 1.9” (258 x 110 x 47mm)
Weight 24.7oz (700g)
Accessories Resistance check plate, 9V battery, carrying case
Ground Resistance (Autorange) Specifications
Range Resolution Accuracy (of reading)
0.03 to 9.99Ω0.02 Ω ± (1.5% + 0.1 Ω)
10.0 to 99.9 Ω 0.1 Ω ± (2.0% + 0.3 Ω)
100.0 to 199.9 Ω 0.4 Ω ± (3.0% + 1 Ω) typical
200.0 to 399.9 Ω 2 Ω ± (5.0% + 5 Ω) typical
400.0 to 599.9 Ω 5 Ω ± (10% + 10 Ω) typical
600.0 to 999.9 Ω 10 Ω Not specified
1000 to 1500 Ω 30 Ω Not specified
Accuracy Note: Loop resistance non-inductive, external field < 50A/m, external electrical
field <1 V/m, conductor centered
382356 V2.0 5/03
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Ground / Leakage mA Current Specifications
Range Accuracy (% of reading)
0.200 to 0.999mA ± (2.5% ± 0.05mA)
1.00 to 9.99mA ± (2.5% ± 0.05mA)
10.0 to 99.99mA ± (2.0% ± 0.3mA)
100.0 to 750.0mA ± (2.5% ± 3mA)
(Autorange, 50/60Hz, True RMS, Crest Factor <3.0)
Ground/Leakage A Current Specifications
Range Accuracy (% of reading)
0.20 to 15A ±(2.0% ±0.05A)
Max Current 100A Continuous; 200A for less than 60 seconds
(50/60Hz, True RMS, Crest Factor <2.0)
382356 V2.0 5/03
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Operating Instructions
Note: The accuracy of measured readings will be affected if the clamp jaws are not fully
closed. Pay special attention to ensure that the jaws are fully closed before testing
begins.
Note: DO NOT clamp on to any conductor or open the clamp jaws during the start-up
self-calibration (display counts down from CAL 7 to CAL 0).
Ground Resistance Measurements
1. Open the clamp jaws and check that all surfaces are clean and free of dust, dirt, or
any foreign substances. Clean if necessary.
2. Snap the Jaws open and closed a
few times so that they seat
properly.
3. Turn the meter on by moving the
rotary switch to the ohms Ω
position. DO NOT interrupt the
start up procedure by opening the
clamp jaws or clamping around a
conductor.
4. Once the start-up calibration
procedure is completed, clamp on
to an electrode or ground rod and
read the value of ground
resistance on the display.
Continuity Loop Test
The testing procedures are the same as for
Ground Resistance measurements except that the
rotary switch is set to the •))) position and an
audible tone will sound if the measured resistance
is below approximately 40Ω.
Ground / Leakage Current Measurement
1. Turn the meter on by moving the rotary switch to
the mA or Aposition.
2. Clamp on to the electrode or conductor
3. Read the value of leakage current displayed on
the display.
RLOOP
Typical application
382356 V2.0 5/03
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Principle of Operation
Typical multi-grounded distribution system.
If the parallel ground resistances,
R1, R2, R3,etc, up to Rnare combined
as Req, then only Rgand Req are
left in the circuit
If a constant voltage is applied to the circuit, the following equation applies:
eqg RR
I
V+= where: ni
R
R
i
eq ,...2,1,
1
1=
∑
=
If Rgand R1, R2, R3…Rn, are approximately the same, and n is large (200, for example),
then Req will be much less then Rgand may possibly approach zero.
Example:
If Rgand R1, R2, R3…Rnare all 10Ωrespectively and n = 200, then Req by calculation
equals:
Ω=
++
=05.0
10
1
...
10
1
10
1
1
eq
R
Rn R
2
R
1
R
g
V
I
Req
Rg
382356 V2.0 5/03
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geqg RRR
I
V→=+=+= 05.1005.010
382356 V2.0 5/03
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Applications
Telephone/Electrical Ground Rods
1. Remove any protective coverings from the ground conductor
2. Turn the meter to the Ohm Ωfunction.
3. Once the start-up calibration procedure is completed clamp on to an electrode or
ground rod.
4. Allow several seconds for the meter to settle and note the reading.
Cellular Transmission Towers
WARNING: Use extreme care when making measurements around transmission towers.
High Voltage may be present.
The ground conductor should be located at the base of the tower, but your configuration
may be different.
1. Locate the ground conductor
2. Clamp around the ground conductor. You should place the clamp before any
splices, bonds or other splits in the ground system.
3. Read the measured reading.
Transmission
Tower
Primary
Ground Conductor
Branch
Ground Conductors
Cement Pad
382356 V2.0 5/03
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