Megger DLRO 200 User manual

DLRO®200
High Current, Low Resistance Ohmmeter
User Guide

This document is copyright of:
Megger Limited, Archcliffe Road, Dover, Kent CT17 9EN. ENGLAND
T [phone] F [phone] www.megger.com
Megger Limited 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 Limited 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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DLRO®200
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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/eu-dofc
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.
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Contents
1. Safety warnings ............................................................................................................................ 6
1.1 Installation category definitions.............................................................................................................6
1.2 Warnings, Cautions and Notes ...............................................................................................................7
1.3 Safety, Hazard and Warning symbols on the instrument.....................................................................7
2. Instrument Overview....................................................................................................................8
2.1 Instrument layout....................................................................................................................................8
3. General description....................................................................................................................... 9
3.1 Principle of operation .............................................................................................................................9
4. Operation.......................................................................................................................................10
4.1 Main menu screen ...................................................................................................................................10
4.2 TEST menu ...............................................................................................................................................11
4.3 Normal mode...........................................................................................................................................11
4.4 Continuous mode ....................................................................................................................................11
4.5 Overheating.............................................................................................................................................11
4.6 Automatic mode......................................................................................................................................11
4.7 OPTIONS menu ........................................................................................................................................12
4.8 Retrieve ....................................................................................................................................................12
4.8.1 Display ...................................................................................................................................................12
4.8.2 Download ..............................................................................................................................................12
4.9 Passbands .................................................................................................................................................13
4.10 Set clock .................................................................................................................................................13
4.11 Delete data ............................................................................................................................................13
4.12 Storage...................................................................................................................................................13
4.13 CURRENT menu .....................................................................................................................................14
4.13.1 SET ......................................................................................................................................................14
4.13.2 LIMIT....................................................................................................................................................14
4.14 Warning messages.................................................................................................................................14
4.15 Test circuit continuity ............................................................................................................................14
4.16 External voltage warning......................................................................................................................14
4.17 Discharge current warning ...................................................................................................................14
4.18 Entering notes in the memo screen .....................................................................................................15
4.19 Test result storage ................................................................................................................................. 15
4.20 Real time downloading of test data. ...................................................................................................15
5. Test techniques and applications .................................................................................................16
5.1 Cleaning ...................................................................................................................................................16
5.2 Test Sequence ..........................................................................................................................................16
5.3 Lead Resistance........................................................................................................................................16
5.4 Interference And Grounding The Sample.............................................................................................. 16

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6. Download PowerDB...................................................................................................................... 17
7. Specifications................................................................................................................................. 18
8. Accessories and Equipment.......................................................................................................... 20
9. Calibration, Repair and Warranty ................................................................................................ 21
9.1 Return procedure ....................................................................................................................................21
10. Decommissioning ........................................................................................................................22
10.1 WEEE Directive ......................................................................................................................................22
10.2 Battery disposal .....................................................................................................................................22
11. Worldwide Sales Offices............................................................................................................. 23

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Safety warnings
1. Safety warnings
THESE SAFETY WARNINGS MUST BE READ AND UNDERSTOOD BEFORE THE INSTRUMENT IS USED.
DLRO200 is supplied without a plug terminating the supply lead.
An appropriate plug must be fitted prior to use.
The DLRO200 must be grounded (earthed) when in use.
The instruments need a ground connection for two reasons.
As a safety ground.
To provide the internal voltmeter with a ground reference, so that it can alert the user if a dangerous voltage
is connected to the terminals.
At switch on, an interanl test circuit checks that the ground wire is connected. A single-phase supply normally
has one live wire one neutral wire and a ground. The neutral is connected to ground at some point, so that
neutral and ground are both at approximately the same voltage. At switch-on there is a continuity check from
ground to neutral. (There is also a check from ground to live in case the power leads are reversed). If there is
no continuity the instrument will refuse to start and the screen will remain blank.
This system works well when power is taken from a supply where there is one live phase wire and a neutral
which is at ground potential. A problem arises when power is obtained from a portable generator where the
two supply wires are floating. Connecting the DLRO ground to real ground makes it safe but the internal test
circuit does not work because there is no connection between ground and the power wires.
The solution to the problem:
Connect the ground terminal to real ground (for safety).
Connect one of the power wires to ground (to enable the ground test circuit).
It is a good idea to also connect the generator chassis to ground (for safety).
Circuits must be de-energised before testing.
The DLRO200 must only be used on dead systems. If the item under test has a voltage upon it greater than 10
volts ac peak or dc with reference to ground the DLRO200 will indicate the presence of the voltage and prevent
any tests being carried out.
Testing inductive circuits can be hazardous:
The DLRO200 is a high power instrument, designed for testing resistive loads. It must NOT be used to test
inductive loads.
During use the DLRO200, its current leads and the sample being tested can become hot.
This is normal and is caused by the passage of high currents. Take care when touching the instrument, current
leads, clips and the test sample.
This product is not intrinsically safe. Do not use in an explosive atmosphere.
Ensure that the power switch is always accessible so that power can be disconnected in an emergency.
If this equipment is used in a manner not specified by the manufacturer, the protection provided by the
equipment may be impaired.
1.1 Installation category definitions
CAT II
Measurement category II: Equipment connected between the electrical outlets and the user’s equipment.
CAT III
Measurement category III: Equipment connected between the distribution panel and the electrical outlets.
CAT IV
Measurement category IV: Equipment connected between the origin of the low-voltage mains supply and the
distribution panel.

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Safety warnings
1.2 Warnings, Cautions and Notes
This user guide follows the internationally recognised definition. These instructions must be adhered to at all times.
Description
DANGER :DANGER : Indicates a dangerous situation which, if ignored, could lead to death, serious
injury or health problems.
WARNING : Indicates a potentially dangerous situation which, if ignored, could lead to death, serious
injury or health problems.
ATTENTION : Indicates a dangerous situation which, if ignored, could lead to injuries or health
problems.
CAUTION : Indicates a situation which could lead to damage of the equipment or environment
NOTE : Indicates important instructions to be followed to perform the relevant process safely and
efficiently.
1.3 Safety, Hazard and Warning symbols on the instrument
This paragraph details the various safety and hazard icons on the instrument’s outer case.
Icon Description
FWarning: High Voltage, risk of electric shock
GCaution: Refer to user guide.
UK conformity. This equipment complies with current UK legislation
cEU conformity. Equipment complies with current EU directives.
Equipment complies with current ‘C tick’ requirements.
Do not dispose of by landfill, sewage systems or by fire.
uProtective Conductor Terminal
sHot Terminals
1Power on
0Power off

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Instrument Overview
2. Instrument Overview
2.1 Instrument layout
1 3 4 5 6 7 82
912 11 1013
Item Description Item Description
1 RS232 port 8 Delete button
2 Power on LED 9 TEST button
3 Alphanumeric Keyboard 10 Status lamp
4 ESC button 11 ENTER key
5 Reduce contrast 12 Two-axis paddle
6 Increase contrast 13 Display
7 Display backlight

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General description
3. General description
The Megger®DLRO®200 is an AC powered low resistance ohmmeter deigned to measure DC resistances in the
low milliohms or microhms using a maximum test current of 200 Amps DC The maximum test current available is
dependent upon the power supply, the resistance of the test leads and the resistance of the item being tested. Full
details are available in the SPECIFICATIONS section later in this book.
The power lead entry is located on the left-hand side panel and marked “100-265 V AC, 10 A max., 50/60Hz” for
the DLRO200, or ‘115 V AC 10 A max. 50/60Hz’ for the DLRO200-115. The main On/Off switch is located next to
the power lead entry. All other controls are mounted on the front panel. Should the supply earth be inadequate the
instrument will refuse to switch on, the display will remain blank. An additional earth terminal is provided on the left
ahd side of the instrument.
3.1 Principle of operation
The required current is set before the test starts. When the TEST button is pressed, after a short delay the current
increases to the set current, the voltage detected across the “P” leads is measured, and the current then reduces to
zero.
Operation is controlled using the two-axis paddle and the menu system, which appears on the backlit liquid crystal
display. The keyboard is used to set the desired test current and to add notes, which may be stored with test results in
on board memory for later download via the RS232 socket provided. The measured resistance, the actual test current
and measured voltage are clearly presented on the display after the test is complete.
The use of a four terminal measurement technique removes the test lead resistance from the measured value
although the use of lightweight current leads may prevent the DLRO200 from producing the full requested current.
In this case the instrument will produce the highest current possible taking into account the resistance of the current
leads and the item being tested.
Before a test may be started the potential test lead contact is monitored to ensure good contact is present.
This reduces the chance of erroneous readings and prevents arcing at the contact point, which would otherwise
damage the item under test and the test lead contacts. A resistance measurement takes approximately 10 seconds.
DLRO200 is supplied complete with a pair of 5 metre (16 feet) current leads terminated with large clamps, and
smaller, lighter potential leads. Other lengths and terminations are available if required.
The large terminals C1 and C2 supply a low voltage (from zero to 5 volts) which is adjusted automatically to produce
the desired current (from 10 A to 200 A). C1 is the positive terminal. This DC voltage is half wave rectified and
unsmoothed in the DLRO200, the inductance of the test leads providing sufficient smoothing for the current.
The DLRO200-115 has additional smoothing within the instrument.
P1 and P2 are voltage measuring terminals. P1 is nominally positive, but connections can be reversed without
affecting the measurement. All four terminals are floating.
A warning will be given if dangerous voltages are connected to any terminal (C or P) with respect to ground.

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Operation
4. Operation
Terminate the supply lead with a plug suitable for your circumstances.
Plug the instrument supply lead into a socket outlet and switch the instrument on using the On/Off switch situated
on the left side of the instrument. The POWER lamp will illuminate, the instrument will display the firmware version
number and perform a calibration check. If this is successful the display will show “CALIBRATED”. If the check fails
the display will show “NOT CALIBRATED”.
DLRO 200 V1.00
COPYRIGHT
MEGGER LIMITED
2002
INITIALISING HARDWARE
CALIBRATED
After a slight pause the display will change to the Main Menu screen.
TEST OPTIONS
CURRENT
SET CURRENT 150
CURRENT LIMIT 200
23 TESTS STORED
21/03/02 15:13
4.1 Main menu screen
This screen provides access to the menuing system, through which you set up your instrument and choose the
desired test parameters. Navigation of this menuing system is by means of the cursor control and Enter key.
At the top of the screen are the three main menu choices; “TEST”, “OPTIONS” and “CURRENT”.
Below this are details of the test current selected (SET CURRENT), maximum current to be allowed (CURRENT LIMIT),
the number of stored tests and the current date and time.
To perform a measurement is straightforward.
1. Use the Left and Right arrows of the two-axis cursor control to highlight the TEST menu. Use the down arrow to
select the required test type. Press Enter.
2. Use the Left and Right arrows of the two-axis cursor control to highlight the CURRENT menu. Use the down
arrow to select SET and press Enter. Type in the desired current using the numeric keys on the keypad. When
finished press Enter.
If the current you have set is greater than the current limit, DLRO200 will beep and clear the SET CURRENT field.
Re-enter the desired current, if necessary increasing the current limit to a value equal to or greater than the
desired level. (See separate topic for setting the current limit).
3. Connect the sample to be tested to the instrument terminals and press the TEST button. The different test types
have slightly different connection requirements, which are detailed, in the sections below.
Please note that if your DLRO200 is inadequately grounded / earthed it will not be possible to start a test.