Megger DLRO User manual

AVTM24-1J
Rev A
April 2006
Instruction Manual
DLRO®
Digital Low Resistance Ohmmeters
Catalog No. 247000 Series
M
Valley Forge Corporate Center
2621 Van Buren Avenue
Norristown, PA 19403-2329
U.S.A.
610-676-8500
www.megger.com
Advanced Test Equipment Rentals
www.atecorp.com 800-404-ATEC (2832)
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DLRO®
Digital Low Resistance Ohmmeters
Catalog No. 247000 Series

Copyright© 2006by Megger. All rights reserved.
The information presented in this manual is believed to be adequate for the
intended use of the product. If the product or its individual instruments are
used for purposes other than those specified herein, confirmation of their
validity and suitability must be obtained from Megger. Refer to the warranty
information below. Specifications are subject to change without notice.
WARRANTY
Products supplied by Megger are warranted against defects in material and
workmanship for a period of one year following shipment. Our liability is
specifically limited to replacing or repairing, at our option, defective
equipment. Equipment returned to the factory for repair must be shipped
prepaid and insured. Contact your MEGGER representative for instructions
and a return authorization (RA) number. Please indicate all pertinent
information, including problem symptoms. Also specify the serial number and
the catalog number of the unit. This warranty does not include batteries, lamps
or other expendable items, where the original manufacturer’s warranty shall
apply. We make no other warranty. The warranty is void in the event of abuse
(failure to follow recommended operating procedures) or failure by the
customer to perform specific maintenance as indicated in this manual.
M
Valley Forge Corporate Center
2621 Van Buren Ave
Norristown, PA 19403-2329
610-676-8500 (Telephone)
610-676-8610 (Fax)
www.megger.com

AVTM24-1J Rev AApril 2006 i
Table of Contents
1.0 10 Ampere Systems .....................................................................................1
Section A INTRODUCTION............................................................1
Section B SAFETY PRECAUTIONS .............................................3
Section C RECEIVING INSTRUCTIONS ..................................5
Section D SPECIFICATIONS...........................................................7
Section E CIRCUIT DESCRIPTION...........................................15
Section F CONTROLS AND CONNECTIONS.....................19
Section G OPERATING PROCEDURE....................................23
Section H APPLICATIONS.............................................................27
Section I MAINTENANCE.............................................................31
Section J FIELD REPLACEABLE PARTS LIST.....................33
Section K WARRANTY & REPAIR.............................................35
2.0 100 Ampere System..................................................................................37
Section A INTRODUCTION..........................................................37
Section B SAFETY...............................................................................41
Section C DESCRIPTION & SPECIFICATIONS..................43
Section D OPERATING PROCEDURE....................................47
Section E MAINTENANCE............................................................51
Section G RECOMMENDED TEST LEADS..........................53
Section H WARRANTY and REPAIR..........................................55
Section J FIELD REPLACEABLE PARTS LIST.....................57
-11 OPTION INPUT PROTECTION...................................................... 59

AVTM24-1J RevA April 2006 ii
List of Figures
Figure 1: Cat.No. 247000 DLRO instrument without charger ...iii
Figure 2: Various DLRO Unit Combinations.....................................6
Figure 3: Controls & Connections........................................................21
Figure 4: Typical Connections to a Test Sample............................25
Figure 5: Cat. No. 247101 DLRO consists of three elements:
Left: 100A Current Source Center: Measuring Module Right:
Charger Module for Measuring Module...................................36
Figure 6: Arrangement for Making Measurements in the 100-
Ampere Range...................................................................................49

AVTM24-1J Rev AApril 2006 iii
Figure 1: Catalog No. 247000 DLRO instrument without charger

AVTM24-1J RevA April 2006 iv
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AVTM24-1J Rev AApril 2006 1
1.0
10 Ampere Systems
Section A
INTRODUCTION
Part 1.0 of this manual applies to a series of instruments;
the principal models are Catalog Numbers 247000,
247001, 247002. Part 2.0 describes the 100 Ampere
systems including catalog numbers 247100, 247101 and
247120.
The Catalog No. 247000 Digital Low Resistance
Ohmmeter is a portable, rugged instrument that provides a
direct-reading digital display of resistance in five ranges. It
is powered by self-contained rechargeable batteries. A
battery charger, operating from J1SV 50/60 Hz, is
furnished in a separate package.
The Catalog No.247001 is similar to Catalog No. 247000
except that it has a built-in, line-operated charger.

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AVTM24-1J REV AApril 2006 2
The Catalog No. 247100 is a 100 Ampere Test System
composed of a Catalog No. 247000 Measuring Module,
and a Cat. No. 247120 100-amp power supply. The
Catalog No. 24701 is also a 100 ampere test system.
The ohmmeter has four terminals for a Kelvin connection
to the sample under test, and it is recommended that
Biddle test leads shown in Bulletin 24-1be used with this
instrument.
Panel features include a two-position on-off switch that
allows continuous or momentary operation, and on the
rechargeable battery models a meter to indicate relative
state of charge of the internal batteries.
A prop is provided to keep the lid in a partly open position
so that it can be used as a sunshade when reading the
digital display in bright sunlight.
The Catalog No. 247002 is similar to Catalog No. 247001
except that it has an extra 600 µΩrange.

AVTM24-1J REV AApril 2006 3
Section B
SAFETY PRECAUTIONS
SAFETY IS THE RESPONSIBILITY OF THE USER
La seguridad es la responsabilidad del operador
F
WARNING
Do NOT connect this instrument to energized
circuits.
The Digital Low Resistance Ohmmeters have been
designed and constructed to meet the requirements of
ANSI/ISDA S82.01-1994. There is no shock hazard from
the instrument itself and it may be used freely in wet or
outdoor environments. The line-operated battery charger
and the A.C. supply, however, should be used and
maintained by trained personnel who are familiar with the
usual precautions for handling line-operated equipment.
F
DO NOT USE IN EXPLOSIVE ATMOSPHERE (This
includes poorly ventilated battery rooms and
enclosures.)

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AVTM24-1J REV AApril 2006 4
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AVTM24-1J REV AApril 2006 5
Section C
RECEIVING INSTRUCTIONS
READ COMPLETELY BEFORE OPERATING
Your Digital Low Resistance Ohmmeter has been
thoroughly tested and inspected to rigid specifications
before being shipped and is ready for use. Check the
equipment received against the packing list. Notify
Megger, Norristown, PA 19403 of any shortage of
materials. The instrument should be examined for damage
received in transit. If any damage is found, file a claim with
the carrier at once and notify Megger or its nearest
representative giving a detailed description of the damages
observed.
Charge batteries overnight before initial use of instrument.
Refer to Section G for charging procedure. Check for
correct operation of the instrument by connecting it to a
resistor of known value. See Section G, Operating
Procedure.

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AVTM24-1J REV AApril 2006 6
Catalog No. 247000 with Charger Catalog No. 247001
Catalog No. 247101with Charger
Figure 2: Various DLRO Unit Combinations

AVTM24-1J REV AApril 2006 7
Section D
SPECIFICATIONS
Ranges, Resolution, Accuracy
& Test Current
LIMIT OF ERROR
RANGE
TEST
CURRENT
AMPERES
(±20%)
RESOLUTION 1 year
15-35°C 1 year 0-50°C
0.000 -5.999 mO10 1 µO ¼ % Rdg + 1 lsd*½ % Rdg + 1lsd*
00.00 -59.99 mO110 µO ¼ % Rdg + 1 lsd*½ % Rdg + 1lsd*
000.0 -599.9 mO0.1 100 µO ¼ % Rdg + 1 lsd*½ % Rdg + 1lsd*
0.000 -5.999 O0.01 1 µO ¼ % Rdg + 1 lsd*½ % Rdg + 1lsd*
00.00 -59.99 O0.001 10 µO ¼ % Rdg + 1 lsd*½ % Rdg + 1lsd*
*(Least Significant Digit)
Zero Offset: Typically 0-1 count over 15-35°C.
Full accuracy can be realized by using
the Forward-Reverse switch to
average the readings. An internal zero
adjustment is also provided.
On-Off
Control: Toggle switch energizes all circuits. Has momentary and lock positions.
Response
Time (after On-Off switch is closed): 2 seconds to final reading.

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AVTM24-1J REV AApril 2006 8
Interference
Effects: Error in item under test caused by line-frequency current of 0.1X test
current: ±l lsd
Error caused by 5-gauss line-
frequency
magnetic field: ±2 lsd
Error caused by connection to
ground or voltage to ground
(assuming battery operation): None
Input
Protection: One volt peak may be applied between any two of the Rx terminals.
Effect of
Inductive Test
Item:
None except time constant delay. No
damage caused by inductive kick, but
see precautions in Section H.
Temperature
Range: Operating: 0-50°C (line supply, 0-40°C)
Storage: -40°C to + 60°C
Display: Red LED, 4 digits 0.5” high, decimal
point, and negative (-) sign. Upper
right hand segments of digits flash on
overrange input

Specifications
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Calibration
Adjustments: Internal zero and span adjustments for all ranges.
Test Lead
Resistance
Requirements:
Potential Leads (P1. P2):
No limitations.
Current Leads (C1, C2): each lead 20
milliohms nominal. Deviations affect
test current but do not affect accuracy
unless they are large compared to the
measuring range.
Power Supply, Rechargeable System:
Battery
Complement: (internal batteries, nickel cadmium type):
Display circuit, 4 cells size “D”
(Eveready CH4 or Gould 4.0 SCB or
G.E. #GCW 3.5 SB.)
Measuring circuit, 2 cells, size “F”.
(Gould 7.0 SCB).
Battery
Condition
Meter:
Shows state of charge of batteries.
Switch selects either battery for test.

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AVTM24-1J REV AApril 2006 10
Battery
Charger: Separate charger unit plugs into receptacle on measuring unit. Full
charge in 14 hours. Charging may be
continued while instrument is
operating. Fused, with UL listed 3-
wire line cord and plug. Power
requirements, 0.22 amps at 115 volts,
50/60 Hz; or 0.165 amps at 230 volts,
50/60 Hz.
Fuse ratings:
115V-0.2A Slow Blow
230V-0.1A Slow Blow
CONTINUOUS OPERATING
TIME BETWEEN CHARGES CONTINUOUS OPERATING TIME WHILE ON CHARGE
RANGE MEASURING
CIRCUIT
BATTERY
DISPLAY
BATTERY MEASURING CIRCUIT BATTERY DISPLAY BATTERY
6 mO1 Hour 15 Hours 1 Hour No Limit
60 mO10 Hours 15 Hours No Limit No Limit
600 mO100 Hours 15 Hours No Limit No Limit
6 O1000 Hours 15 Hours No Limit No Limit
60 O1000 Hours 15 Hours No Limit No Limit
Battery Life: Approximately 300 full charge-
discharge cycles.

Specifications
AVTM24-1J REV AApril 2006 11
Safety: Meets all applicable requirements
of ANSI/ISA S82.01-1994.
Highest voltage existing (except in
charger primary and line supply
primary) is 6 volts.
Case: The measuring unit and charger
have rugged molded case with
handles and removable hinged
lids. The measuring unit lid can be
used as a sun shield. The charger
case has similar construction with
additional space for storing test
leads.
Test Lead
Terminals:5/16” diameter studs with wing nuts for spade or ring lugs.
Dimensions and Weights:
Cat. No. Weight Dimensions
lbs kg inches
cm
247000 11 5.01 8-7/8W x 8-1/8D x 8-1/8H
22.4 x 20.6 x 20.6(Instrument)
247000-47 --8-1/8W x 8-1/8D x 7-3/8H
22.4 x 20.6 x 18.8 (Charger)
247001 12.1 5.5 12W x 9 5/8D x 6 3/8H
30 x 24.5 x 16.2
247002 12.2 5.5 12W x 9 5/8D x 6 3/8H
30 x 24.5 x 16.2

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AVTM24-1J REV AApril 2006 12
Catalog Numbers and Unit Combinations
for 10-Ampere Systems
CATALOG
No. DESCRIPTION
247000 Instrument with Internal Rechargeable
Batteries and separate 115V 50/60 Hz
Charger Unit. Range: 0 to 60 Ohms in
5 ranges, 0 to 5.999 Milliohms lowest
range (Note 1).
247000-3Same as Cat. No. 247000 except with
100A adapter plug.
247000-47 Same as Cat. No. 247000 except with
230V-50/60 Hz charger.
247000-3-47 Same as Cat. No. 247000-47 except with
100A adapter plug.
247001 Same as Cat. No. 247000 except in single
case.
247002 Same as Cat. No. 247001 except with an
extra 600 µΩrange.