Megger DLRO10HD User manual

DLRO10HD and DLRO10HDX
10 A Digital Low Resistance Ohmmeter
User Guide

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DLRO10HD and DLRO10HDX i
Contents
Instrument Safety 1
Measurement Connection ...............................................................................................................................2
Voltage .........................................................................................................................................................2
CAT IV ..........................................................................................................................................................2
CAT III ...........................................................................................................................................................2
CAT II ...........................................................................................................................................................2
Safety and Hazard Icons ..................................................................................................................................2
Warning Icons..................................................................................................................................................3
Description 4
Key Features ....................................................................................................................................................4
Applications 5
Overview 6
Controls and Connections................................................................................................................................6
Display Icons....................................................................................................................................................7
Secondary Display..........................................................................................................................................7
Test Mode Rotary Switch .................................................................................................................................8
Range Rotary Switch........................................................................................................................................9
Resolution and Accuracy..............................................................................................................................10
Test Leads 11
Connection to the Instrument........................................................................................................................11
Test Lead Connection.....................................................................................................................................11
Connection to a Test Piece ...........................................................................................................................12
DH4-C Duplex Hand-spikes ...........................................................................................................................12
Tests with the DH4-C Duplex Hand-spikes or Individual Leads ........................................................................12
Tests 13
Inductive Test ................................................................................................................................................13
Manual Bi-directional Test ..............................................................................................................................14
Automatic Bi-directional Test..........................................................................................................................15
Automatic Uni-directional Test .......................................................................................................................16
Continuous Test.............................................................................................................................................17
Tests with Automatic Save (DLROHD10X) 18
Automatic Bi-directional Test..........................................................................................................................18
Automatic Uni-directional Test .......................................................................................................................19
Continuous Test ............................................................................................................................................20

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DLRO10HD and DLRO10HDX
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Memory Features (DLRO10HDX) 21
Date and Time Setup .....................................................................................................................................21
Recall Test Result Records ..............................................................................................................................22
Download Test Result Records........................................................................................................................23
Delete Test Result Records..............................................................................................................................24
Maintenance 25
Routine Inspection ........................................................................................................................................25
Cleaning........................................................................................................................................................25
Instrument Care.............................................................................................................................................25
Test Leads .....................................................................................................................................................25
Mains Power Fuse..........................................................................................................................................25
Battery Care ..................................................................................................................................................25
Battery Charge .............................................................................................................................................25
Specifications 26
Power Lead ...................................................................................................................................................27
Power Lead Connection Table .....................................................................................................................27
Accessories 28
General Accessories .......................................................................................................................................28
Test Leads (No In-line connector)....................................................................................................................28
Duplex Leads ...............................................................................................................................................28
Individual leads ............................................................................................................................................29
Test leads (In-line Connector) .........................................................................................................................29
Repair and Warranty 30
Calibration, Service and Spare Parts ..............................................................................................................30
Approved Repair Companies .........................................................................................................................31
Return an Instrument for Repair ....................................................................................................................31
End of Life Disposal 32
WEEE Directive ..............................................................................................................................................32
Batteries .......................................................................................................................................................32
Declaration of Conformity 33

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DLRO10HD and DLRO10HDX 1
Instrument Safety
Instrument Safety
If the equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment
may be impaired
The instrument must be operated only by suitably trained and competent persons
Users of this equipment and their employers are required by National Health and Safety Legislation to carry
out valid risk assessments of all electrical work so as to identify potential sources of electrical danger and risk
of electrical injury
The instrument must NOT be used if any part of it is damaged
Damaged test leads must NOT be used. Test leads, connectors and mechanical guards must be in good order,
clean and have no broken or cracked insulation
If the test subject to which the instrument is connected is energised while the instrument is turned off,
protection devices may not prevent the instrument from overheating. In which case, parts of the case may
become very hot and damage may occur
Set the instrument to ON before connecting to the test subject
The test subject must be set to OFF, de-energised and checked before test connections are made. Make
sure that the test subject cannot be re-energised whilst the instrument is connected
Do not leave the equipment unattended when connected to the test subject
Do not leave the equipment connected to the test subject after the test is completed
The user must exercise caution when connecting to and disconnecting from the test subject
Always connect test leads to the instrument before attaching to test subject
Keep hands behind any tactile barriers on probe clips and clamps when making or breaking connections.
High current connections between the instrument and test subject must be secured against accidental
detachment and must not be disengaged whilst test current is flowing
Circuit terminals must not be touched during test
Do not disconnect the instrument from the test subject until the test current has stopped and the TEST
warning indicator is extinguished
Test leads and connections may become hot during use. Exercise caution when handling
Disconnect from the test subject before switching the instrument OFF
There are no user-serviceable parts inside the instrument; all servicing, including battery and fuse
replacement, must be referred a Megger approved service centre
When used on hazardous voltages the Megger terminal cover (part number 1002-390) must be used
This product is not intrinsically safe. Do not use in an explosive atmosphere

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DLRO10HD and DLRO10HDX
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Instrument Safety
Measurement Connection
Only Megger supplied test leads designed for this instrument provide the full safety rating.
Voltage
The rated measurement connection voltage is the maximum line to earth voltage at which it is safe to connect.
CAT IV
Measurement category IV: Equipment connected between the origin of the low-voltage Mains Power supply and
the distribution panel.
CAT III
Measurement category III: Equipment connected between the distribution panel and the electrical outlets.
CAT II
Measurement category II: Equipment connected between the electrical outlets and the 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.
Safety and Hazard Icons
This section details the various safety and hazard icons on the instruments outer case.
Icon Description
GCaution: refer to User Guide
tEquipment protected throughout by Double Insulation
Equipment complies with current EU directives
Equipment complies with current “C tick” requirements
Do not dispose of in the normal Waste stream
fFuse

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DLRO10HD and DLRO10HDX 3
Instrument Safety
Warning Icons
This section details the warning icons that can show on the display.
Icon Warning Description
FExternal Voltage Warning If an external voltage is applied between the terminals and the
instrument is set to On, the High Voltage warning will flash on the
display. This is a warning that the item under test is live and might be
dangerous and testing is disabled. The High Voltage warning message
will flash if more than 50 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 high voltage.
Note: The warning will not operate if the instrument is set to Off.
FDischarge Voltage /
Current Warning
The High Voltage warning and the red High Voltage LED on the panel
will flash if a current greater than 1 mA is still flowing after an inductive
test is completed. This suggests that the inductive load has been
tested and is discharging. Do not disconnect the current loop while the
discharge warning is showing.

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DLRO10HD and DLRO10HDX
4
Description
Description
This User Guide details the DLRO10HD and the DLRO10HDX.
Both the DLRO10HD and the DLRO10HDX measure the same tests and parameters, in addition the DLRO10HDX
can save, recall and download test results to PowerDB.
The DLRO10 range of digital low resistance ohm meters measure resistance in a range of 0.1 µΩ to 2 k. These
instruments provide a maximum test current of 10 Amps. The DLRO10 range consist of four versions:
DLRO10
DLRO10X
DLRO10HD
DLRO10HDX
Key Features
Simple operation
High power ranges
Simultaneous testing and battery charging
Rugged case construction designed for use in demanding environments or the lab
IP65 with the lid closed and IP54 with the lid open for protection against ingress during operation
Multiple lead set options (Megger connect leads - see the lead set data-sheet)
10 A while measuring up to 250 mΩ and 1 A while measuring up to 2.5 Ω
Monitors test lead contact, which reduces the chance of erroneous readings
Rechargeable battery: Capacity <1000 10A test
Auto power off
Large, clear LCD for all light conditions
Time and Date stamped memory for recording of results (DLRO10HDX only)
Memory storage and USB download capability (DLRO10HDX only)
CAT III 300 V: Protected against accidental connection to external voltages up to 600 V DC applied between
any pair of the four terminals for up to 10 seconds

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DLRO10HD and DLRO10HDX 5
Applications
Applications
The DLRO10HD and DLRO10HDX measure 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.
Both instruments are well suited to measuring thick conductors, bonds and quality of welding because of their 10
A range for resistance values up to 250 mΩ. 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 Bi-directional mode to make
sure this effect is cancelled. The instrument measures with current flowing in both directions and averages the
result.
Typical applications include DC resistance measurements of:
Switch and contact breaker resistance
Transformer and motor winding resistance
Busbar and cable joints
Rail and pipe bonds
Aircraft frame bonds and static control circuits
Metal alloys, welds and fuse resistance
Integrity of welded joints
Graphite electrodes and other composites
Inter-cell connections on battery systems
Wire and cable resistance
300 V peak
Transmitter aerial and lightning conductor bonding
Quality control of resistive components

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DLRO10HD and DLRO10HDX
6
Overview
Overview
This section details an over view of the instrument:
Controls and Connections
DLRO10HDX 3
1 2
4
6
5
7
89
1011
12
13
14
15
16
DLRO10HD 1 2
4
7
16
9811
14
12
13
15
3
Item Description Item Description
1 Current Terminals 9 Test button (Start and stop tests)
2 Potential Terminals 10 Navigation keypad (setup and stored results)
3 Test Lead LED Cable 11 Test modes and Off rotary switch
4 Display 12 Mains Power On LED
5 Save Button 13 Fuse
6 USB socket (download records) 14 Contrast button
7 Hazard warning LED during test 15 Mains Power Socket
8 Range Rotary Switch 16 Back-light

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DLRO10HD and DLRO10HDX 7
Overview
Display Icons
DLRO10HDX
15
71 2 3 4 56 8
10
9
11
12
13
14
DLRO10HD 7 8
10
9
11
12
13
14
Item Description Item Description
1 Delete 9 Noise (over 100 mV 50 / 60 Hz)
2 Test Result Download mode 10 Over Temperature
3 Recall Test Result Mode 11 Refer to User Guide
4 Date and Time mode 12 High Voltage Warning
5 Save mode 13 Secondary Display
6 USB connected 14 Primary Display
7 Mains Power connected 15 Direction of Current flow in a test
8 Battery Status
Secondary Display
Directional arrow to show current flow above C indicator
Directional arrow to show current flow above P indicator
15

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DLRO10HD and DLRO10HDX
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Overview
Test Mode Rotary Switch
Test modes and instrument Off are selected with the Test Mode rotary switch.
AUTO
3s
25
1 6
3 4
Available test modes are:
Item Mode Description
1Off Instrument is Off. Rotate the switch to any mode to start the instrument
2Manual Bi-directional Test current applied in both directions current flow. Continuity of all four
connections is checked. Current is applied in both forward and reverse
direction.
See Manual Bi-directional Test (page 14)
3Automatic
Bi-directional
Test current applied in both directions current flow
See Automatic Bi-directional Test (page 15)
See Automatic Bi-directional Test (page 18): Automatic save (DLRO10HDX)
4Automatic
Uni-directional
Current is applied in one direction only, to speed up the measurement process.
Standing EMF’s setup during the test are ignored so lower accuracy can result
See Automatic Uni-directional Test (page 16)
See Automatic Uni-directional Test (page 19): Automatic save (DLRO10HDX)
5Continuous Test current is applied in both directions. The test repeats at three seconds
intervals
See Continuous Test (page 17)
See Continuous Test (page 20): Automatic save (DLRO10HDX)
6Inductive Test current applied in only one direction.
See Inductive Test (page 13)
Warning: When inductive loads are measured the current carrying leads must be securely clamped to
the item being tested.
Warning: Do not remove the current carrying leads before any stored charge has been discharged at
the end of the test.
Warning: Failure to comply with these instructions might result in an arc being produced, which might
be dangerous for the instrument and the operator.
Note: When inductive loads are measured it is necessary to wait for the voltage to stabilise, so the measurement
process can take a few seconds or several minutes.

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DLRO10HD and DLRO10HDX 9
Overview
Range Rotary Switch
The instruments test range of resistance and current is selected with the Range rotary switch.
DLRO10HDX DLRO10HD
2.5
Ω
250
mΩ
µA
100
2.5
kΩ
1mA 10mA
100
mA
1A
1A
10A
10A
250
Ω
25
Ω 2.5
Ω 250
mΩ
25
mΩ
2.5
mΩ
1
5
4
3
2
2
Green resistance ranges: Low output power (<0.25 W) outputs
Red resistance ranges: Higher 2.5 W (1 A) and 25 W (10 A) power outputs (
G
shows)
Item Description
1Date and Time Setup (page 21)
2Resolution and Accuracy (page 10)
3Delete Test Result Records (page 24)
4Download Test Result Records (page 23)
5Recall Test Result Records (page 22)

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DLRO10HD and DLRO10HDX
10
Overview
Resolution and Accuracy
Test current accuracy ±10%
Voltmeter input impedance >200 kΩ
Maximum lead resistance at 10 A <100 mΩ
Test Current Resistance Range Resolution
(as shown)
Basic Accuracy* Full Scale
Voltage
Max. Power
Output
100 µA 0 to 2.5 kΩ 0.1 Ω ±0.2% ±200 mΩ 25 mV 25 µW
100 µA 0 to 250 Ω 0.01 Ω ±0.2% ±20 mΩ 25 mV 2.5 µW
1 mA 0 to 25 Ω 1 mΩ ±0.2% ±2 mΩ 25 mV 25 µW
10 mA 0 to 2.5 Ω 0.1 mΩ ±0.2% ±200 µΩ 25 mV 250 µW
100 mA 0 to 250 mΩ 0.01 mΩ ±0.2% ±20 µΩ 25 mV 2.5 mW
1 A 0 to 25 mΩ 1 µΩ ±0.2% ±2 µΩ 25 mV 25 mW
10 A 0 to 2.5 mΩ 0.1 µΩ ±0.2% ±0.2 µΩ 25 mV 0.25 W
1 A** 0 to 2.5 Ω 0.1 mΩ ±0.2% ±200 µΩ 2.5 V 2.5 W
10 A** 0 to 250 mΩ 0.01 mΩ ±0.2% ±50 µΩ 2.5 V 25 W
* Basic accuracy stated assumes forward and reverse measurements.
** Higher 2.5 W (1 A) and 25 W (10 A) power outputs (
G
shows).
Inductive or Uni-directional mode can introduce an undefined error if an external EMF is present.
Basic accuracy at reference conditions.

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DLRO10HD and DLRO10HDX 11
Test Leads
Test Leads
The test leads can be used with either:
Hand-spikes or
Clamps
See Accessories (page 28).
Connection to the Instrument
Connect the supplied test leads to the instrument as show below:
OK
2.5
Ω
250
mΩ
µA
100
2.5
kΩ
1mA 10mA
100
mA
1A
1A
10A
10A
250
Ω
25
Ω2.5
Ω250
mΩ
25
mΩ
2.5
mΩ
DIGITAL LOW RESISTANCE OHMMETER
DLRO
TEST
AUTO
3s
Tip: To help connect the test leads remove the instrument lid. Open the lid to approximately 45º and slide it to
the right.
Test Lead Connection
A good test measurement requires both the Current carrying circuit and the Voltage detection circuit to be
completed by the unit under test. The Instrument checks for continuity in both C and P circuits.
A test will not start until there is a good connection to the test piece by the test leads.
Confirmation of successful continuity:
If C 1----2 and P 1----2 are constant the connectivity is good
If either C 1----2 and P 1----2 flash there is no connectivity, and the test will not start
Successful Connection Unsuccessful connection
The resistance result is shown on the display in either Ω, mΩ or µΩ ranging from 2500.0 Ω to 0.1 µΩ.
The result in Bi-directional modes is the average of two readings shown by the two secondary displays, with
arrows to show the direction of current flow. The large arrow at the top of the display between C1 and C2 shows
the measurement current flow.

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DLRO10HD and DLRO10HDX
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Test Leads
Connection to a Test Piece
Connect the test leads to the test piece in the Kelvin arrangement as shown:
P
G
<30V AC WITHOUT
TERMINAL COVER
CATRATED WHEN
USED WITH MEGGER
TERMINAL COVER
The image shows the correct test lead connection of the current (C1, C2) and potential probes (P1, P2) to a test
piece. To make sure test readings are accurate, the current terminals (C1 and C2) must be connected outside of
the potential terminals (P1 and P2).
DH4-C Duplex Hand-spikes
Each hand-spike is marked with the letter P (potential terminals). These should always be the inside contacts
when a test measurement is taken.
One of the test lead connectors has two LEDs (L1 and L2) and an LED driver cable. The LED driver cable plugs into
the terminal next to terminal P2 (see Connection to the Instrument (page 11)).
LEDs L1 and L2, give information to the User that would otherwise only be available on the display:
Lamp L1 Lamp L2 Description
On (red) Off Inadequate continuity at C or P contacts
Flashing (red) Off Voltage present between contacts
Off On (green) Current, 1mA, test complete
Off On (red) Measurement fail
For example, when the test leads are used in an Auto test mode:
1. Press
TEST
.
2. L1 shows a steady red to show there is a contact failure.
3. When all four contacts are connected, L1 goes Off.
4. No LEDs show in a test, unless contact fails.
5. To signal end of test, L2 shows a steady green when the current flow has decayed to less than 1 mA.
6. When the test leads are removed from the test piece, L2 goes Off (end of test) and L1 shows red (no contact).
When the DH4-C Duplex Hand-spikes are used, the instrument always makes sure that there is a good contact
before the full test current is applied, so there should be no erosion of the contact tips. However, if the tips
become worn or blunted, they can be replaced. Pull out the worn tips and install new ones.
Tests with the DH4-C Duplex Hand-spikes or Individual Leads
Connect the four leads as shown. In all cases make sure that the potential probes (P1 and P2) are inside the
current (C1 and C2) probes.

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DLRO10HD and DLRO10HDX 13
Tests
Tests
This section details the instruments test procedures, which also can be manually saved (DLRO10HDX only).
For information on test lead connection to a test piece, see Test Lead Connection (page 11).
Inductive Test
Warning: When inductive loads are measured the current carrying leads must be securely clamped to
the item being tested.
Warning: Do not remove the current carrying leads before any stored charge has been discharged at
the end of the test.
Warning: Failure to comply with these instructions might result in an arc being produced, which might
be dangerous for the instrument and the operator.
Note: When inductive loads are measured it is necessary to wait for the voltage to stabilise, so the measurement
process can take a few seconds or several minutes.
AUTO
3s
2.5
Ω
250
mΩ
µA
100
2.5
kΩ
1mA 10mA
100
mA
1A
1A
10A
10A
250
Ω
25
Ω 2.5
Ω 250
mΩ
25
mΩ
2.5
mΩ
Tip: Use Clamp test leads (optional accessory).
1. Press
TEST
.
Test starts (LED shows red).
Arrow direction animated (based on current direction)
and plateau.
2. Continuous measurements are taken on the connected
test piece.
The last three test records show (new test result shows
on the Primary display (rolling display)).
Last test record is shown while the next test is in
progress.
TEST
3. Press
TEST
to stop the test.
The last complete three test results are shown.
TEST
4. DLRO10HDX only: Save test results (if required).
Press . The test result is saved and the memory slot
number is shown.
The Save screen is shown for three seconds.

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DLRO10HD and DLRO10HDX
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Tests
Manual Bi-directional Test
AUTO
3s
2.5
Ω
250
mΩ
µA
100
2.5
kΩ
1mA 10mA
100
mA
1A
1A
10A
10A
250
Ω
25
Ω 2.5
Ω 250
mΩ
25
mΩ
2.5
mΩ
Tip: Use Clamp test leads (optional accessory).
Note: In Manual test mode both the Current and Voltage test leads must be connected across the test piece
before
TEST
is pressed.
1. Press
TEST
(acknowledged by a beep sound).
Test starts (LED shows red).
TEST
Arrow direction animated (based on current direction)
and plateau.
Test result for the currently connected test piece is
shown.
2. DLRO10HDX only: Save test results (if required).
Press . The test result is saved and the memory slot
number is shown.
The Save screen is shown for three seconds.
3. If the test piece is still connected, press
TEST
to do
another test.
4. DLRO10HDX only: Press as required.

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DLRO10HD and DLRO10HDX 15
Tests
Automatic Bi-directional Test
AUTO
3s
2.5
Ω
250
mΩ
µA
100
2.5
kΩ
1mA 10mA
100
mA
1A
1A
10A
10A
250
Ω
25
Ω 2.5
Ω 250
mΩ
25
mΩ
2.5
mΩ
1. Connect the test leads to the test piece.
Test starts (LED shows red).
TEST
Arrow direction animated (based on current direction)
and plateau.
2. Test results for the currently connected test piece are
shown.
3. DLRO10HDX only: Save test results (if required).
Press . The test result is saved and the memory slot
number is shown.
The Save screen is shown for three seconds.
4. The test automatically continues for subsequent
connected test piece.
5. DLRO10HDX only: Press as required.
6. Press
TEST
to stop the test.

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DLRO10HD and DLRO10HDX
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Tests
Automatic Uni-directional Test
AUTO
3s
2.5
Ω
250
mΩ
µA
100
2.5
kΩ
1mA 10mA
100
mA
1A
1A
10A
10A
250
Ω
25
Ω 2.5
Ω 250
mΩ
25
mΩ
2.5
mΩ
1. Connect the test leads to the test piece.
Test starts (LED shows red).
TEST
Arrow direction animated (based on current direction)
and plateau.
2. Test results for the currently connected test piece are
shown.
3. DLRO10HDX only: Save test results (if required).
Press . The test result is saved and the memory slot
number is shown.
The Save screen is shown for three seconds.
4. The test automatically continues for subsequent
connected test piece.
5. DLRO10HDX only: Press as required.
6. Press
TEST
to stop the test.