Megger DLRO2 Operating Manual
DLRO2
Ducter™ Low Resistance Ohmmeter 2 A
User Guide
This document is copyright of:
Megger Limited, Archcliffe Road, Dover, Kent CT17 9EN. ENGLAND
T +44 (0)1304 502101 F +44 (0)1304 207342 www.megger.com
Megger Ltd reserves the right to alter the specification of its products from time to time without
notice. Although every effort is made to ensure the accuracy of the information contained within
this document it is not warranted or represented by Megger Ltd. to be a complete and up - to - date
description.
For Patent information about this instrument refer to the following web site:
megger.com/patents
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This manual supersedes all previous issues of this manual. Please ensure that you are using the most recent issue of this
document. Destroy any copies that are of an older issue.
Declaration of Conformity
Hereby, Megger Instruments Limited declares that radio equipment manufactured by Megger Instruments Limited
described in this user guide is in compliance with Directive 2014/53/EU. Other equipment manufactured by Megger
Instruments Limited described in this user guide is in compliance with Directives 2014/30/EU and 2014/35/EU where they
apply.
The full text of Megger Instruments EU declarations of conformity are available at the following internet address:
megger.com/company/about-us/eu-dofc
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Contents
Contents
1. Introduction ................................................................................................................................... 2
1.1 Product Description ................................................................................................................................. 2
1.2 Features .................................................................................................................................................... 2
1.2.1 Difference Meter .................................................................................................................................... 2
1.3 Applications ............................................................................................................................................. 3
1.4 Company web site ................................................................................................................................... 4
2. Safety Warnings ............................................................................................................................ 5
2.1 Warnings, Cautions and Notes ............................................................................................................... 5
2.1.1 Warnings ............................................................................................................................................... 5
2.1.2 Cautions ................................................................................................................................................ 5
2.1.3 Notes ..................................................................................................................................................... 5
2.2 Safety warnings ....................................................................................................................................... 5
2.3 Test lead safety warnings ....................................................................................................................... 6
2.4 Installation Category Definitions............................................................................................................ 6
2.5 Safety, Hazard and Warning Symbols on the Instrument ..................................................................... 7
2.5.1 Warning Icons ........................................................................................................................................ 7
3. Instrument Controls ..................................................................................................................... 8
3.1 Instrument Layout ................................................................................................................................... 8
3.2 Instrument Display .................................................................................................................................. 9
3.3 Instrument Rotary Control ...................................................................................................................... 10
3.4 Instrument connections and leads.......................................................................................................... 11
3.4.1 External electrical connections of DLRO2 ................................................................................................ 11
3.5 The Difference Meter .............................................................................................................................. 12
3.5.1 Difference Meter example of operation .................................................................................................. 13
4. Setting up the DLRO2 ................................................................................................................... 15
4.1 Warnings and exception conditions ....................................................................................................... 15
4.2 Power ....................................................................................................................................................... 15
4.2.1 First use ................................................................................................................................................ 15
4.2.2 Turn the instrument on and off .............................................................................................................. 15
4.2.3 Battery options ....................................................................................................................................... 15
5. Tests, Inductive mode ................................................................................................................... 16
5.1 Manual stop ............................................................................................................................................. 16
5.1.1 First test ................................................................................................................................................. 16
5.1.2 Second test ............................................................................................................................................ 17
5.2 Auto stop ................................................................................................................................................. 18
5.2.1 First test ................................................................................................................................................ 18
5.2.2 Second test ............................................................................................................................................ 19
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6. Tests, Resistance mode .................................................................................................................. 20
6.1 Auto-start, bidirectional / unidirectional resistance mode ................................................................... 20
6.1.1 Post auto-start, unidirectional test .......................................................................................................... 21
6.1.2 Post auto-start, bidirectional test ............................................................................................................ 21
6.2 Manual, bidirectional / unidirectional resistance mode........................................................................ 22
6.2.1 For a unidirectional test .......................................................................................................................... 23
6.2.2 For a bidirectional test ............................................................................................................................ 23
6.2.3 After the test ......................................................................................................................................... 23
7. Tests, Long leads mode ................................................................................................................. 24
7.1 Long leads mode – auto and manual start ............................................................................................ 24
7.1.1 For manual mode ................................................................................................................................... 25
7.1.2 For auto mode ....................................................................................................................................... 25
8. Error and Warning Conditions...................................................................................................... 27
8.1 Error code categorization ....................................................................................................................... 27
8.2 On screen error messages ....................................................................................................................... 27
8.2.1 Error screen A ........................................................................................................................................ 27
8.2.2 Fuse fail screen ....................................................................................................................................... 27
8.2.3 Error screen B ......................................................................................................................................... 27
9. Settings .......................................................................................................................................... 28
9.1 General settings ....................................................................................................................................... 28
9.2 Language settings ................................................................................................................................... 29
9.3 Instrument Information .......................................................................................................................... 29
9.4 Firmware update ..................................................................................................................................... 29
10. Maintenance ................................................................................................................................ 31
10.1 General Maintenance ............................................................................................................................ 31
10.2 Cleaning ................................................................................................................................................. 31
10.3 Battery .................................................................................................................................................... 31
10.3.1 Battery status ....................................................................................................................................... 31
10.3.2 12 V supply .......................................................................................................................................... 32
10.3.3 Battery Charging .................................................................................................................................. 32
10.3.4 Battery error screens ............................................................................................................................. 32
10.4 Battery Replacement ............................................................................................................................. 33
10.4.1 Replace batteries and remove isolation tab ........................................................................................... 34
11. Specifications ............................................................................................................................... 35
12. Accessories and Equipment ........................................................................................................ 37
12.1 Included Accessories .............................................................................................................................. 37
12.2 Optional Accessories.............................................................................................................................. 37
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13. Calibration, Repair and Warranty .............................................................................................. 38
13.1 Return procedure .................................................................................................................................. 38
14. Decommissioning ........................................................................................................................ 39
14.1 WEEE Directive ...................................................................................................................................... 39
14.2 Battery disposal ..................................................................................................................................... 39
15. Notes ............................................................................................................................................ 40
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Introduction
1. Introduction
This user guide details the operational and functional details of the Megger DLRO2 Ducter Low Resistance
Ohmmeter 2 A.
Please read this user guide fully before attempting to use the DLRO2.
1.1 Product Description
The DLRO2 is a tough and truly hand held 2 A low resistance ohmmeter, designed to provide fast, accurate and
repeatable measurements even in electrically noisy environments.
The DLRO2 is designed for ease of use, it can be operated by non-technical users with minimal training.
There are three main measurement modes:
Normal resistance (µΩ).
Fast / long test lead (mΩ).
Inductive resistance (µΩ).
The DLRO2 is supplied with six HR6 rechargeable NiMH cells which can be charged in the instrument using the
supplied external power supply. Non-rechargeable Alkaline AA cells can also be used.
For personal safety and to get the maximum benefit from this instrument, make sure that the safety warnings and
instructions are read and understood before the instrument is used. Refer to 2. Safety warnings on page 5.
Note: This user guide includes instructions for all DLOR2 variants. Some facilities may not be available on your
model of this equipment.
1.2 Features
New ‘Difference Meter’ for quick comparison of results. Refer to 3.5 The Difference Meter on page 12.
Rotary dial test function selection.
Unidirectional or bidirectional test options on normal resistance test mode.
Secondary display field showing either forward and reverse measurement results or previous two test results,
allowing three test results to be on display at any time for easy comparison.
Current reversal capability to cancel standing EMF.
Noisy connection warning, showing when electrical noise or noise from poor clip / probe connections is present.
Test currents selectable from 1 mA to 2 A
Capable of 500 measurements from a single charge.
Supplied with compact CATIII 600 V / CATIV 300 V rated kelvin clip test leads.
1.2.1 Difference Meter
The Difference Meter allows repetitive measurements to be easily compared with an initial reference measurement.
The Difference Meter translates percentage difference to a needle / pointer movement making it easy to see changes
in value.
A new reference measurement can be set at any time at the push of a button.
Refer to 3.5 The Difference Meter on page 12 for further information.
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1.3 Applications
The DLRO2 measures low resistance values in applications ranging from railways and aircraft to resistance of
components in industry.
Any metallic joint can be measured but users must be aware of measurement limitations depending on application.
For example, if a cable manufacturer plans to make resistive measurements on a thin wire, a low test current should
be selected to prevent heating the wire thereby changing its resistance.
This instrument is suited to measuring thick conductors, bonds and quality of welding.
Measurements on electric motors and generators will be inductive and require the user to understand the inductive
mode and charging process before a correct result is achieved.
Electromagnetic noise induced into the leads can interfere with a reading. A noise icon alerts the user, but does not
prevent a measurement.
When dissimilar metals are joined a galvanic effect is created. Users should select a bidirectional mode to make sure
this effect is cancelled. The instrument measures with current flowing in both directions and averages the result.
Aviation – Lightning protection testing measuring mΩ resistance between receptors. Wing tip to wing tip etc.,
using long test leads. Optional long cable reel test leads are available, can be used for assembly of components,
interconnection of equipment, repair and maintenance.
Wind turbines – Lightning protection, measuring mΩ resistance between wing tip to ground connection at base
using long test leads. Optional long cable reel test leads are available.
Rail – Tram and Underground - rolling stock and infrastructure, track high current joints, signalling systems.
Marine - Power wiring systems, protection systems, ship to shore bonding, cathode protection system testing.
Cable laying applications.
Oil and gas pipelines - Bonding between welded joints, grounding systems.
Automotive and EV - Battery connections, weld quality, quality of crimped connections, assembly robot welding
cables.
Cable manufacturers - Quality control, cable length.
Component manufacturers - Quality control.
Space exploration and engineering - structural metal to metal, ground network metal to metal, carbon fibre to
metal, carbon fibre to carbon fibre.
Data Centres - During electrical installation of main panel, generator and UPS systems. Verification of protective
device contact resistance, busbar parallel feeds, busbar lapped joints, optimum resistance over torque and cable
lug to busbar connections. During maintenance using trending data for all aspects of the above, verification
after repair.
Medical hand held opportunity - earthing and bonding systems for protection against microshock and
macroshock.
Panel / Switchgear Manufacturers - End of production line testing, site commissioning, maintenance and fault
finding.
Robotics - Wiring systems and connections which are subject to stress / movement / vibration, bonding of
component parts to minimise static, grounding of machine, welding leads of robot spot welder.
Electrical infrastructure - Cable resistance from one end, cable length, identification of parallel supplies while
connected, cable to lug to connection fault finding, checking assembled connections main supply cables and
panels, switch gear and protective devices, ups and changeover panels, interlinking busbars, interlinking cables,
distribution and PDU boards, lightning protection systems, final circuits.
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Introduction
1.4 Company web site
Occasionally an information bulletin may be issued via the Megger web site. This may concern new accessories, new
usage instructions or a software update. Please occasionally check on the Megger web site for anything applicable
to your Megger instruments.
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Safety Warnings
2. Safety Warnings
The safety instructions given in this document are indicative of safe practice and are not to be considered exhaustive.
Additionally, they are not intended to replace local safety procedures in the region where the instrument is used. If
the equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may
be impaired.
There are no user replaceable parts within the DLRO2.
2.1 Warnings, Cautions and Notes
This user guide follows the internationally recognized definition of warnings, cautions and notes. These instructions
must be adhered to at all times.
2.1.1 Warnings
Warnings alert the reader to hazardous situations where injury to personnel can occur. They are set in red type
to make them stand out. They are placed before the item to which they relate and repeated at each applicable
occasion.
2.1.2 Cautions
Cautions alert the reader to situations where equipment damage may result if a process is not followed properly.
They are set in bold type. They are placed before the item to which they relate and repeated at each applicable
occasion.
2.1.3 Notes
Notes give additional important information that will help the reader. They are not used when a Warning or Caution
is applicable. They are not safety related and may be placed either before or after the associated text as required.
2.2 Safety warnings
These safety warnings must be read and understood before the instrument is used. Retain for future reference.
Warning: This instrument must be operated only by suitably trained and competent people.
Protection provided by the instrument may be impaired if it is not used in a manner specified by the
manufacturer.
Local Health and Safety Legislation requires users of this equipment and their employers to carry out valid risk
assessments of all electrical work to identify potential sources of electrical danger and risk of electrical injury such
as inadvertent short circuits. Where the assessments show that the risk is significant the use of fused test leads
may be appropriate.
If battery power is lost during the test, then the user will no longer be warned that the load is being discharged.
The user must check by independent means that the load is discharged before breaking connection.
Disconnect all test leads and switch the instrument OFF before opening the battery cover. Covers must be in
place before reconnecting the test leads.
Ensure every cell in the battery compartment is of identical type. Never mix rechargeable and non-chargeable
cells.
This product is not intrinsically safe. Do not use it in an explosive atmosphere.
Protection provided by the instrument may be impaired if it is not used in a manner specified by the
manufacturer.
The voltage warning function will operate only if the instrument is switched on and working correctly.
In the absence of an indication do not assume that there are no hazardous voltages.
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Safety Warnings
The voltage indicator and current discharge features must be regarded as additional safety features and MUST
not substitute the normal safe working practice which MUST be followed.
The instrument must not be used if any part of it is damaged or if the terminal shutter is missing.
The circuit under test must be switched off, de-energized, securely isolated and proved dead before test
connections are made.
Circuit connections, exposed conductive parts and other metalwork of an installation or equipment under test
must not be touched during testing.
Only Megger approved test leads with right-angled instrument connectors must be used with this instrument.
Test leads must be at least 1 m in length and provide a total loop impedance ≥ 26 mΩ.
When inductive loads are measured it is essential that the current carrying leads are securely clamped to the item
being tested and that they are not removed before any stored charge has been discharged at the end of the test.
Failure to comply with these instructions might result in an arc being produced which might be dangerous for
the instrument and the operator.
All test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation.
Verify the integrity of the test leads before use.
The safe maximum limit of a measurement connection is that of the lowest rated component in the
measurement circuit formed by the instrument, test leads and any accessories.
Ensure that hands remain behind finger guards of probes and clips.
2.3 Test lead safety warnings:
Test leads, including crocodile clips, must be in good condition, clean, dry, and free of broken or cracked
insulation. The lead set or its components must not be used if any part of it is damaged.
The safe maximum limit of a measurement connection is that of the lowest rated component in the
measurement circuit formed by the instrument, test leads and any accessories.
2.4 Installation category definitions:
CAT IV - Measurement category IV: Equipment connected between the origin of the low-voltage mains supply and
distribution panel.
CAT III -Measurement category III: Equipment connected between the distribution panel and electrical outlets.
CAT II - Measurement category II: Equipment connected between the electrical outlets and user’s equipment.
Measurement equipment may be safely connected to circuits at the marked rating or lower. The connection rating is
that of the lowest rated component in the measurement circuit.
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2.5 Safety, Hazard and Warning Symbols on the Instrument
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This paragraph details the various safety and hazard icons on the instrument’s outer case.
Icon Description
Warning: High Voltage, risk of electric shock
Caution: Refer to User Guide.
Equipment complies with current EU directives.
Equipment complies with current ‘C tick’ requirements.
Do not dispose of in the normal waste stream.
Equipment protected throughout by double insulation.
Safety Warnings
IP54 IP rating
2.5.1 Warning Icons
This paragraph details the warning icons that can show on the display.
Icon Warning Description
External Voltage Warning If an external voltage is applied between the terminals and the
instrument is set to ON, the external voltage warning will flash
on the display. This is a warning that the item under test is live,
it might be dangerous so testing is disabled. The external voltage
warning message will flash if more than 5 V potential difference
is applied between the voltage terminals and the current
terminals. This warning will not show if all terminals are at the
same external voltage.
NOTE: The warning will not operate if the instrument is set to OFF.
Internal Error Warning Internal Error Warning. To clear the error, switch the instrument
OFF and then back ON. Contact Megger if this does not clear
the error.
Read the User Guide Refer to the user guide if this message shows.
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Instrument Controls
3. Instrument Controls
3.1 Instrument Layout
Front View Rear View
1
2
3
10
6
7
9
Item Description Item Description
1 External electrical connections.
Refer to 3.4.1 External electrical
connections of DLRO2 on page 11
2 Display 11 Battery cover
3 Soft keys (multifunction) 12 Stand
4 Has no function on this model
5 Back-light control
6 Has no fucntion on this model
7 Test
8 TICK button
9 Rotary selection switch
4
5
8
10 Attachment point for strap
11
12
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3.2 Instrument Display
Instrument Controls
1
16
15
14
13
12
3 4
52
6
7
8
9
10
Item Description Item Description
1 Difference Meter. Refer to 3.5 The
Difference Meter on page 12
2 Operating mode 10 P continuity indicator
3 Primary field 11 Soft keys functions (dependant on rotary
4 Latest result 12 Secondary field
5 Battery condition indicator 13 C continuity indicator
6 Noise indicator 14 Forward measurement result
7 Units of measure (for latest result) 15 Unidirectional or bidirectional selection
8 Reverse measurement result 16 Inductive charge warning
9 Selected test current
selection switch position)
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