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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DLRO®200
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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.

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Operation
4.2 TEST menu
The TEST menu allows the selection of one of three test modes - Normal, Automatic or Continuous. Only one mode
can be active at a time and the active mode is displayed below the heading TEST when you return to the MAIN MENU
screen.
4.3 Normal mode
Normal mode makes a single measurement of the resistance of the sample under test.
Please note that in this mode both the current and voltage leads must be connected across the test sample before the
Test button is pressed. When the TEST button is pressed DLRO200 will check for good contact in the P circuit. If the P
circuit continuity is faulty the display will show “POTENTIAL FAIL”. Press the ENTER key to remove this message and
adjust the contact of the P probes to ensure good contact is achieved. Press the TEST button again. P circuit continuity
will be checked and if satisfactory DLRO200 will proceed to carry out a test. After a short period of time, if there is
inadequate contact in the C circuit the instrument will display “CURRENT LOOP FAIL”. Press Enter to remove this
message, make good the connection and press the TEST button to start the test. A sequence of bars will appear across
the display while the test is being completed.
To make another measurement, ensure the test leads are connected and press the Test button.
NORMAL mode is abbreviated to NORM under the TEST heading in the main menu screen.
4.4 Continuous mode
Continuous mode requires the current leads and the voltage leads to be securely connected to the item under test before
pressing the Test button. The DLRO200 checks voltage and current loop continuity as in Normal Mode and, if adequate,
passes a continuous DC current, repeating resistance measurements at approximately 2-second intervals until the test is
terminated by pressing the Test button (or until the DLRO200 overheats if particularly high currents are used).
CONTINUOUS mode is abbreviated to CONT under the TEST heading in the main menu screen.
4.5 Overheating
When operating continuously at 200 A, overheating will occur after approximately 15 minutes (assuming a starting
temperature of 20ºC). A message ‘HOT’ will then appear on the display until the internal parts have cooled. When the
‘HOT’ message is on the screen, test current is turned off and all front panel controls are disabled.
Operating at reduced current will considerably extend the operating time.
4.6 Automatic mode
In Automatic mode, only connect the current leads to the sample to be measured. Press the TEST button. The red status
lamp next to the TEST button will flash signifying that DLRO200 is armed and will remain in a state of readiness until the
P circuit is completed. At this time the light will illuminate continuously and the test will be carried out. The progress of
the test is shown by a series of bars progressing across the display.
To make another measurement it is necessary to break P probe contact with the test sample and remake contact.
For example, if measuring joints in a long bus bar, you may leave the current circuit connected at opposite ends of the
bus bar knowing that current will only flow during a measurement i.e. when the P probes are connected. Simply making
contact with voltage probes across the joint(s) you wish to measure will then activate the measurement.
AUTOMATIC mode is abbreviated to AUTO under the TEST heading in the main menu screen. AUTO mode may be
exited by pressing the TEST button while the status light is flashing.

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Operation
4.7 OPTIONS menu
The Options menu has five selections, which control various ancillary functions and which are selected using the
two-axis cursor control and the Enter key. These are Retrieve, Passbands, Set clock, Delete data and Storage.
4.8 Retrieve
Retrieve allows the recall of results which have been stored within the DLRO200’s internal memory. There are two
choices, Display or Download.
4.8.1 Display
Display recalls each test, in sequence, to the instrument display starting with the most recently stored result. Use the
cursor control Up and Down controls to step later or earlier respectively through the stored results.
If you know the number of the test that you wish to display simply type in the number and press Enter.
An asterisk (*) next to the word “MEMO” at the bottom of the screen means that there are notes attached to this
result. Press the right cursor control to view the notes.
4.8.2 Download
Download causes the entire contents of the data store to be output to the RS232 port above the display. A null
modem RS232 lead is supplied with the instrument. Any communications package may be used to download the
data although a copy of Download Manager, which facilitates downloading and formats the data, is also supplied. If
using another package please note the settings should be 9600 baud, 8 data bits, 1 stop bit, and no parity.
Downloading data does not cause the stored data to be erased from memory. To clear data from memory see
“Delete Data” below.
Note: DLRO200 also makes data available via the RS232 Port in real time and is suitable for printing on a self-
powered serial printer. (See later for details.)
The output has the following form:
Test Type
Test Number
Date Format
Date
Time
Selected Current
Resistance
Measured Current
Measured Voltage
Upper Limit *
Lower Limit *
Pass Or Fail *
* The last three lines will only appear if passbands have been set.

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Operation
4.9 Passbands
The passband option allows you to set upper and lower limits between which the test result must lie if it is to be
assigned a Pass. Readings that fall above the upper limit or below the lower limit will be assigned a Fail.
The upper and lower limits are entered via the keyboard complete with decimal points, where applicable, and
including the m or µ symbol as appropriate. It is not necessary to enter the Ω symbol. Entering the m or µ symbol tells
DLRO200 that the entry in that particular field is complete and the cursor will therefore move to the next field. The
upper limit must be less than or equal to 999.9 mΩ and the lower limit must be less than the upper limit.
After completing the upper and lower limits the cursor will move to the ENABLE or DISABLE options. Highlight your
choice using the right and left controls and press Enter. You will return to the Main Menu screen.
Note: Passbands will remain enabled or disabled until you re-enter this screen and change the selection. If all that is
required is to change Passbands from ENABLED to DISABLE or vice versa, enter the PASSBAND screen and press
Enter until the ENABLED / DISABLED choice is shown at which time you may change the selection. Pressing Enter
will skip over the limit values without changing them if none of the numeric keys has been pressed.
If passbands have been set and enabled, at the end of a test the display will show the results and will show the word
PASS or FAIL as appropriate. A PASS will also be signified by a short beep from the instrument, while a FAIL will be
signified by a long beep.
4.10 Set clock
This option sets the date and time as well as setting the date format. When you enter this screen the current date,
time and date format will be displayed. Use the cursor control Up and Down arrows to adjust the highlighted data.
Step to the next item by using the Right cursor control arrow.
The row below DD MM YY HH MM contains respectively the date, the month, the two-digit year (21st century
is assumed), the hour of the day in 24-hour notation and the minute. These must be entered in this sequence
regardless of the date format you wish to use.
The lower DD/MM/YY shows the current date format. Pressing the cursor control Up arrow will cycle through the
available options DD/MM/YY, MM/DD/YY or YY/MM/DD. This is updated when you press Enter to exit the Set
Clock function. However, tests already stored prior to changing the date format will retain the old format.
4.11 Delete data
Select Delete Data if you wish to clear DLRO200’s memory of stored data. In case you have selected this Option by
accident you will be asked to confirm that you wish to delete the data. The default is NO. Change this to YES and
press Enter if you wish to delete all data.
Please note - ALL stored data will be deleted.
4.12 Storage
The Storage option sets the instrument to Store or No Store. At the end of each test you will be offered the
opportunity to change this setting for the test just completed and subsequent tests.
At the end of each test you may enter notes into the MEMO screen, which is accessed by pressing any key on the
alphanumeric keyboard. This will also cause the test to be automatically stored regardless of other settings.
If all memory has been filled, a message MEMORY FULL will appear and no more tests results will be stored
although testing may continue without storing results. The main menu screen will also display “300 MEMORY
FULL” instead of the number of stored tests. Data is stored for up to 10 years in battery backed RAM.

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Operation
4.13 CURRENT menu
There are two options, SET, and LIMIT.
4.13.1 SET
The SET option allows you to set the desired test current. Simply enter the desired value using the numeric keys on
the keyboard and press Enter. If the current selected is greater than the limit that has been set, DLRO200 will beep,
cancel your entry in the Set Current field and wait for you to enter a valid current.
4.13.2 LIMIT
Some samples to be tested may not be able to withstand the passing of heavy currents. In this case set a maximum
level of test current to prevent the accidental entry of an excessive test current. This level defaults to 200A. If a lower
limit is required enter it using the keyboard and press Enter. If the LIMIT current selected is lower than the SET
current, the SET current will be reduced to the same value as the LIMIT.
The Main Menu screen will show the active Current Limit beneath the Set Current.
4.14 Warning messages
The display will, from time to time, display certain warning messages, which may affect measurement accuracy or
operator safety.
4.15 Test circuit continuity
A good measurement requires both the current carrying circuit and the voltage detection circuit to be completed by
the item under test. The DLRO200 checks for this continuity after the TEST button has been pressed.
Initially the Potential circuit is checked. If there is poor continuity in this circuit a message will appear on the display
stating “POTENTIAL FAIL”. Press Enter to clear this message and correct the discontinuity in the P circuit.
Press TEST again. If the P circuit is complete DLRO200 will attempt to pass the test current. If the C circuit continuity
is inadequate, after a little while, DLRO200 will display the message “CURRENT LOOP FAIL”. Press Enter to clear
the message. Correct the fault and start the test again.
4.16 External voltage warning
The item being tested must be voltage free. If, at any time while DLRO200 is connected, the item being tested has a
voltage in excess of 10 volts ac peak or dc with respect to the instrument ground potential, a message “EXTERNAL
VOLTAGE ON TERMINALS” will appear on the display. This is a warning that the item under test is live and might
be dangerous. A test cannot be performed in this condition.
Remove the external voltage. The display will revert to the main menu screen.
If the voltage was detected at the start of a test you may now start the test. If the voltage was detected during or at
the end of a test, the results will be invalid, will not be stored and the test will need to be repeated after removing
the source of voltage.
4.17 Discharge current warning
A message CURRENT FLOW will appear if a current greater than approximately 10 mA is still flowing after a test is
completed. This suggests that an inductive load has been accidentally tested and is still discharging. Do not disconnect
the current loop while the discharge warning is showing.

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Operation
4.18 Entering notes in the memo screen
At the end of each test you may add comments to the test results. Instead of pressing Enter to return to the Main
Menu screen, briefly press any alphanumeric key. You will enter a MEMO screen that allows you to enter up to 160
characters of alphanumeric information concerning the test. When you have entered all information press Enter and the
measurement and memo will be stored in memory.
If you do not wish to add notes press the Test button and a new test will be started, or the Enter button to return to the
Main Screen.
4.19 Test result storage
Each test is numbered sequentially, dated and timed. The test result memory can store a maximum of 300 tests, each
being identified by its test number, date and time. When memory is full the message “MEMORY FULL” will be shown.
Testing may continue but no more results will be stored. See Options Menu – Storage for more information.
4.20 Real time downloading of test data.
DLRO200 will output data to the RS232 port every second. The data is in ASCII format at 9600 baud, 8 bits with 1 stop
bit. Connecting an appropriately configured PC to the RS232 port will enable data to be captured in real time.
The information output is as follows:
If the output is being monitored when the DLRO200 is switched on you will capture the instrument type (DLRO200) and
the version of firmware being run in the instrument.
Thereafter the data will be:
TEST NUMBER 1
START DATE 21/06/02
START TIME 10:23
DATE FORMAT DD/MM/YY
SET CURRENT 50
UPPER LIMIT 0.9990000
LOWER LIMIT 0.0000000
TEST TYPE NORMAL
MEASURED RESISTANCE, CURRENT, VOLTAGE
MEASURED RESISTANCE, CURRENT, VOLTAGE
MEASURED RESISTANCE, CURRENT, VOLTAGE
………….
MEASURED RESISTANCE, CURRENT, VOLTAGE
MEASURED RESISTANCE, CURRENT, VOLTAGE
PASS or FAIL
The Upper and Lower limits are always shown in ohms.

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DLRO®200
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Test techniques and applications
5. Test techniques and applications
When using DLRO200 to measure low resistances at high currents, the heavy current leads should be securely
connected to the item under test using heavy-duty clips or clamps. The use of Duplex handspikes is not
recommended.
Connect the four leads as shown.
CC
PP
It is important that the potential probes are positioned on the test sample inside the current probes.
5.1 Test Sequence
Pressing the TEST button or selecting AUTOMATIC mode starts the test sequence.
Continuity of the P1-P2 loop is checked by passing an ac current (approximately 100 mA @10 KHz) through the test
leads and measuring the ac voltage. Continuity of the C1-C2 loop is not checked until the test is started; the criteria
for continuity is that a current of at least 2 A must be flowing. If this current cannot be established the instrument
will display “CURRENT LOOP FAIL”.
5.2 Lead Resistance
The use of a four terminal measuring technique means that the resistance of the leads is not included in the
measurement.
Furthermore, since the potential leads do not carry any current the type of wire used is not important from
the measurement point of view. However, these leads should be adequately insulated and sufficiently strong
mechanically to support their own weight if long leads are being used.
The size of the current leads will limit the maximum resistance which may be measured at full current or may limit
the maximum current output to a level somewhat less than 200 A. The DLRO200 can generate 200 Amps into a total
current loop resistance of 19 mΩ if the supply voltage is greater than 208 V r.m.s., or 11 mΩ for a supply voltage of
115 V r.m.s.
The 50 mm2 leads supplied as standard with the DLRO200 (DLRO200-115 is supplied with 25 mm2 leads (4 mΩ
each) have a resistance of 2 mΩ each at 20οC, and so the DLRO200 will be able to measure up to 15 mΩ (supply
>207 V r.m.s.), or 7 mΩ (115 V r.m.s.), in the item under test at 200 A with leads at 20οC. As you pass 200 A the
leads will warm up and their ability to pass current will decrease as their resistance increases. Thicker or shorter
current leads increase these limits.
Longer current leads are available if required.
5.3 Interference And Grounding The Sample
Ideally the test specimen should be grounded during the test. If it is not grounded, noise pickup (50/60 Hz etc.) can
affect accuracy and increase measurement errors by up to 1% typically.
Excessive noise will cause the “EXTERNAL VOLTAGE” warning to be shown.

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Download PowerDB
6. Download PowerDB
You can now download direct from the Megger website to ensure that you have the most recent version available.
Visit megger.com/powerdb
The latest edition will be at the top. Click the “download” button beside the file.
This will ask if you want to open or save the file. By clicking “Save” you will begin to download the installation
package.
Then just follow the onscreen instructions to complete installation.

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DLRO®200
18
Specifications
7. Specifications
Specification Detail
Measurement Ranges
Full Scale Resolution Volts (full scale) Max Test Current*
999.9 µΩ 0.1 µΩ 0.2 V 200 A
9.999 mΩ 1 µΩ 2 V 200 A
99.99 mΩ 10 µΩ 4 V 40 A
999.9 mΩ 100 µΩ 4 V 4 A
* Subject to supply voltage conditions (see below).
Accuracy is better than ±1% from 300 µΩ to 100 mΩ and ±2% from
100 µΩ to 300 µΩ, if the maximum possible current is used. If lower currents are used, the following table
applies:
Current Error
2 A* 5.6% + 100 µΩ
5 A* 2.6% + 40 µΩ
10 A 1.6% + 20 µΩ
20 A 1.2% + 10 µΩ
50 A 0.8% + 4 µΩ
100 A 0.7% + 2 µΩ
200 A 0.7% + 1 µΩ
*It is not possible to select a current less than 10 A but since the open circuit terminal voltage is somewhere
between 2 V and 5 V (if input power is 100 V to 250 V), actual test current can be as low as 2 A when loop
resistance is 1 Ω. If actual current is less than 2 A a ‘Current loop fail’ will be reported.
Measurement: Modes Manual, Auto, Continuous
Test Time: < 10 seconds Normal or AUTO
mode, Refreshed every 2.4s in
CONTINUOUS mode
Display: Measurement: Large, high resolution backlit liquid
crystal display
Warnings: Current flowing LED, Inadequate ‘C’ and ‘P’ contact,
External Voltage, Memory Full, Overheating.
Data: Transfer: Real time or batch download via
RS232 using Download Manager
(supplied free of charge).
Storage: 300 sets of results and memo
Capacity: battery backed 10 years.
Memo field: 160 characters max.
Test Current: Range: 10 A to 200 A* unsmoothed DC
Accuracy: ±2% ±2 A
Voltmeter input impedance: > 200 kΩ
Hum rejection: 10 V rms
Power Supply: DLRO200: 100 – 265 V AC rms 50/60Hz
DLRO200-115: 100 – 130 V AC rms 50/60Hz
Input Current: 10 A maximum

www.megger.com DLRO®200 19
Specifications
Specification Detail
Temperature: Operation: -10 ºC to +50 ºC
Storage: -25 ºC to +65 ºC
Calibration: 20 ºC
Co-efficient: < 0.05% per ºC
Humidity (max): 95% RH non-condensing
Altitude (max): 2000 m
Safety: IEC61010-1
EMC: EN61326-1
Operational inaccuracies: Refer to www.megger.com
Dimensions: 410 x 250 x 250 mm
Weight: < 15 kg.
7.1 Cleaning
The DLRO200 may be cleaned using a damp cloth and soap solution.

www.megger.com
DLRO®200
20
Accessories and Equipment
8. Accessories and Equipment
ORDERING INFORMATION – VERSIONS WITH TEST LEADS
Description Part number
DLRO200-EN Low Resistance Ohmmeter DLRO200-EN
200A (English Keyboard),
Industrial Plug 32A IP44 240V 2P+E.
DLRO200-EU Low Resistance Ohmmeter 1001-841
200A (English Keyboard),
Schuko Industrial Plug 32A IP44 240V 2P+E.
DLRO200-FR Low Resistance Ohmmeter DLRO200-FR
200A (French Keyboard),
Industrial Plug 32A IP44 240V 2P+E.
DLRO200-115 US Low Resistance Ohmmeter DLRO200-115
200A (English Keyboard) Filtered Output,
115V Input, US NEMA 5 -15P Plug.
DLRO200-115 FR Low Resistance Ohmmeter 200A 1000-208
(French Keyboard) Filtered Output,
115V Input, US NEMA 5 -15P Plug.
DLRO200-US Low Resistance Ohmmeter 200A 1012-782
(English Keyboard) Unfiltered Output,
100 to 125 V AC Input. US NEMA 5 -15P Plug.
Included accessories (depending on version)
Lead set consists of pair of flexible
high current capacity leads, together
with a separate pair of lightweight
potential leads.
Current leads are fitted with heavy
duty sprung clamps
(60 mm jaw capacity). Potential leads fitted with smaller heavy duty
crocodile clips (22 mm jaw capacity).
DLRO200-EN, DLRO200-EU, DLRO200-FR, DLRO200-US
5 m (16.4 ft.) Lead set set comprising: 6220-755
2 x 50 mm² current leads with clips Reorder code: 1008-028
and 2 potential leads with clips
DLRO200-115, DLRO200-115 FR
5 m (16.4 ft.) Lead set in bag comprising: 6220-787
2 x 25 mm² current leads with clamps Reorder code: 1008-029
and 2 potential leads with clips
INCLUDED ACCESSORIES FOR ALL VERSIONS
Description Part number
Download manager 6111-442
RS232 download cable 25955-025
Description Part number
Quick start guide (English) 6172-782
Quick start guide (French) 6172-783
Warranty card 2000-231
OPTIONAL ACCESSORIES FOR ALL VERSIONS
Lead set consists of pair of
flexible high current capacity
(600 A cont.) leads, together
with a separate pair of
lightweight potential leads.
Current leads are fitted with
heavy duty sprung clamps
(60 mm jaw capacity).
Potential leads fitted with smaller heavy duty crocodile clips
22 mm jaw capacity).
10 m Lead set 2 x 70 mm 6220-756
2 current leads with clamps
and 2 x potential leads with clips
15 m Lead set 2 x 95 mm 6220-757
2 current leads with clamps
and 2 x potential leads with clips
For further information visit the website: www.megger.com
ORDERING INFORMATION – VERSIONS WITHOUT TEST LEADS
Description Part number
DLRO200-EN NLS Low Resistance Ohmmeter DLRO200-EN-NLS
200A (English Keyboard),
Industrial Plug 32A IP44 240V 2P+E.
DLRO200-FR NLS Low Resistance Ohmmeter DLRO200-FR-NLS
200A (French Keyboard),
Industrial Plug 32A IP44 240V 2P+E
Description Part number
DLRO200-115-FR NLS Low Resistance Ohmmeter 6411-164
200A (French Keyboard), Filtered Output,
115V Input, US NEMA 5 -15P Plug
DLRO200-115V NLS Low Resistance Ohmmeter 1000-565
200A (English Keyboard), Filtered Output,
115V Input, US NEMA 5 -15P Plug
DLRO200-US NLS Low Resistance Ohmmeter 1012-783
200A (English Keyboard), Unfiltered Output,
100 to 125 V AC Input. US NEMA 5 -15P Plug