Megger DLRO Operating Manual

M

DLRO®-10 & DLRO®-10X
Digital Low Resistance Ohmmeter

USER GUIDE

GUIDE DE L’UTILISATEUR

BEDIENUNGSANLEITUNG

GUIDA PER L’UTENTE

GUIA DEL USUARIO

GSAFETY WARNINGS

n These safety warnings must be read and understood before the instrument is used.

n Whenever possible, circuits should be de-energised before testing.

If it is impossible to de-energise the circuit, (e.g. high voltage batteries cannot be switched off while their connections are tested) the user must
be aware of the dangers. The instrument terminals will become live when connected to the circuit. Therefore when used on hazardous voltages
custom Megger DH6 test leads must be used.

n Testing inductive circuits can be hazardous:

After testing an inductive load there will be an amount of energy stored in the inductance. This energy is released in the form of a discharge
current. Disconnecting an inductive load while current is still flowing will cause a high voltage arc, which is a danger to both the user and the item
under test.

Although the DLRO 10 and DLRO 10X are not designed as transfromer ohmmeters the DLRO 10 is fitted with a DISCHARGE lamp, marked ‘I’,
which indicates that current is flowing in the C1-C2 loop. This lamp will flash at end of a test on an inductive load while a discharge current is still
flowing and will stop flashing when the current has decayed to less than 1mA. DLRO 10X uses a message on the display to achieve this.

For testing large inductive resistances the current carrying leads should be connected securely to the item under test before starting the test.

It is not recommended that duplex handspikes be used to carry out tests on inductive loads. If inadvertently using the DH4 handspikes on an
inductive load, the L1 lamp on the handspikes will flash amber while discharge current flows, thereby duplicating the function of the ‘I’ lamp on
the instrument. It is important to maintain contact until the L1 light stops flashing amber and turns green indicating the end of the test.

n This product is not intrinsically safe. Do not use in an explosive atmosphere.
n Please note. The neck strap is specifically designed to break if subjected to a strain of approximately 50 kg.

2

CONTENTS

Safety Warnings 2
General Description 4
General Operation - DLRO 10 5

Test Current Indicators 5
Noise Lamp 5
'C' & 'P' Indicators 5
'V' & 'I' Warning Indicators 5

General Operation - DLRO 10X 6

DLRO 10X Top Panel 6
DLRO 10X Main Menu Screen 6
Warning Messages 6

Noise 6
'C' & 'P' Indicators 6

External Voltage Warning 7
Discharge Current Warning 7
The Menuing System 7
Test Menu 7
Options Menu 7

Retrieve 7

Display 7

Download 8
Passbands 8
Set Clock 8
Delete Data 9
Storage 9
Range Menu 9

Entering Notes In The Memo Screen 10
Test Result Storage 10

Keypad Operation 11

Test Modes 12

Normal Mode 12
Automatic Mode 12

Continuous Mode 12
High Power Mode 12
Unidirectional Mode 13

Test Techniques & Applications 14

Testing Using DH4 Duplex Handspikes 14
Testing Using Handspikes Or Individual Leads. 14
Test Sequence 15
Test Lead Resistance 15
Overheating 15

Battery Module And Care 16

The Battery Module 16
Battery Charging 16
The Battery State Indicator 17

Standard Charging. 17
Slow Charging. 17
Standard Charging But At A Slow Rate. 17
There Is A Temperature Problem. 17
Input Voltage Too Low. 17
Battery Nearly Exhausted 17
Error: Reset 17

Overvoltage Problem 18
Specifications 19
Troubleshooting 21
Repair and Warranty 23

Symbols used on the instrument

G Caution: Refer to accompanying notes
t Equipment protected throughout by Double or

reinforced Insulation (Class II)

c Equipment complies with current EU Directives

3

GENERAL DESCRIPTION

The DUCTER DLRO 10 and DUCTER DLRO 10X make up a family of low resistance ohmmeters that measure resistances in the range from 0.1 µΩ to 2 kΩ.
Both instruments provide a maximum test current of 10 Amps d.c. which is automatically selected according to the value of resistance being tested. The
DLRO 10X allows you to override this automatic selection and select your own test current.

The measured value of resistance is output to the instrument display with indication of the units, µΩ, mΩ or Ω. The DLRO 10 uses a large LED display and
indicators to display the value and units respectively, while the DLRO 10X contains all the information on a clear backlit LCD display.

The use of a four terminal measurement technique removes the test lead resistance from the measured value and auto current reversal eliminates the
effect of standing voltages across the test sample. Additionally, before and during a test, test lead contact is monitored to further reduce the chance of
erroneous readings.

A resistance measurement takes approximately 2.5 seconds and comprises a measurement with forward current, reverse current and a display of the
average. On the DLRO 10X all three values are displayed, and optionally, the measurement may be limited to forward current only.

The instrument is powered by a rechargeable Nickel Metal Hydride (NiMH) battery, which permits one thousand 10 Amp tests to be completed on a single
charge. The battery module contains intelligent circuitry, which prevents damage to the battery from overcharging, and a battery state indicator. A
removable lid that is hinged at the back and held closed by magnetic catches covers the top panel. This lid may be removed if required by opening fully
and snapping out of its hinges.

Both instruments are protected against accidental connection to external voltages up to 600 V d.c. applied between any pair of the four terminals for up to
10 seconds. Please note that applying 600 V to the potential terminals will cause some internal heating. Expect errors of up to 30 digits immediately after
the application of such voltage. Full accuracy will be restored within two to three minutes. Both instruments are supplied complete with a pair of DH4
Duplex Handspikes with 1.2 m leads. Other lengths and terminations are available if required.

4

10A
1A
100mA
10mA
1mA
100µA

C P

V I

Ω
mΩ
µΩ

AUTO

TEST

On/Off

Brightness

Mode control

Test current

“Contact fail”

indicators

Voltage on

terminals

Current

flowing

Exces s

noise

GENERAL OPERATION - DLRO 10

Press the On/Off switch to turn DLRO 10 on. All lamps will light, V and I
lamps will flash, the software version will be displayed and the Ω lamp will
light. If the test leads have not been connected to the test sample the 'C'
and 'P' lamps will also light. Press the On/Off button again to turn the
instrument off. If the instrument is not used for 5 minutes it will be turned
off automatically.

Adjust the brightness control to a comfortable level.
Select the Test mode by pressing the Mode button repeatedly. The
indicator lamps will cycle through the various Test modes in turn (see the
section on Test modes). Press the Test button to start a test.

Test Current Indicators

The test current is selected automatically by DLRO 10 and is indicated by
the lamps on the left of the panel. The measured value is displayed in the
main window and the units (µΩ, mΩ or Ω) are shown by the lamps to the
right of the window.

Noise Lamp

Noise in excess of 100 mV 50/60 Hz will light the 'Noise' lamp and
measurement accuracy cannot be relied upon.

'C' & 'P' Indicators

The 'C' lamp illuminates to indicate contact failure in the 'C1-C2' loop. The
'P' lamp illuminates when there is a break in the P1-P2 loop.

'V' & 'I' Warning Indicators

If external voltage is applied to the terminals the 'V' lamp will flash. This is
a warning that the item under test is live and might be dangerous. A test
cannot be performed in this condition.

The 'V' lamp will light if more than 50 V. is applied between either voltage
terminal and a current terminal. If the voltage appears between just the
voltage terminals or just the current terminals the lamp will light at 100 V
peak or 5 V peak respectively.

Please note - The 'V' lamp will only indicate if a voltage appears
between terminals. The lamp will not operate if all terminals are
at the same high voltage. The lamp will not operate if the
instrument is turned off.

The 'I' lamp will light if a current greater than 1 mA is still flowing after a
test is completed. This suggests that an inductive load has been tested and
is still discharging. Do not disconnect the current loop until the 'I' lamp
has gone out.

5

GENERAL OPERATION - DLRO 10X

Enter key

70%

NEXT TEST 1
0 STORED

27/07/00 12.02

DLRO 10X Top Panel

All the controls needed to set up and operate DLRO 10X are located on
the top panel of the instrument.

To the left of the large LCD display are the controls for moving around the
display, controlling the menuing system and adjusting the display contrast
and backlight.

To the right of the display is the large Test button, Power On/Off button
and an alphanumeric keypad for entering notes relating to a test which will
be stored with the test results for later reference.

To turn your DLRO 10X on, press the On/Off button for approximately 1
second. Press again to turn the instrument off. If the instrument is not
used for 5 minutes it will be turned off automatically.

DLRO 10X Main Menu Screen

When first switched on DLRO 10X displays a copyright screen, followed by
the Main Menu screen.

This screen provides you with information such as percentage of battery

6

charge remaining, index number of the next test, number of tests already
stored and the current date and time.

This screen also 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.

Warning Messages

The Main Menu screen will from time to time also contain certain warning
messages

Noise

Noise in excess of 100 mV 50/60 Hz will activate the message 'Noise' at the
bottom of the display. Above this level accuracy cannot be relied upon.

'C' & 'P' Indicators

A good measurement requires both the current carrying circuit and the
voltage detection circuit to be completed by the item under test. DLRO
10X checks for this continuity. If there is poor continuity in either circuit a
message will appear at the bottom of the display. This will read "P OPEN
CIRCUIT" if the voltage contacts are high resistance, "C OPEN CIRCUIT" if
the current circuit is not made or "CP OPEN CIRCUIT" if both circuits are

GENERAL OPERATION - DLRO 10X

TEST NUMBER 2

DD MM YY HH MM
09/10/00 12:24

inadequate. Check the contacts, since a measurement cannot be made if
any of these messages is visible on the display.

External Voltage Warning

If external voltage is applied to the terminals a message "EXT VOLTS" will
flash 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.

The "EXT VOLTS" message will flash if more than 50 V. is applied between
either voltage terminal and a current terminal. If the voltage appears
between just the voltage terminals or just the current terminals the
message will appear at 100 V peak or 5 V peak respectively.

Please note - The message will only appear if a voltage appears BETWEEN
terminals. The message will not appear if all terminals are at the same high
voltage. The message will not operate if the instrument is turned off.

Discharge Current Warning

A message CURRENT FLOW will appear if a current greater than 1 mA is
still flowing after a test is completed. This suggests that an inductive load
has been tested and is still discharging. Do not disconnect the current
loop while the discharge warning is showing.

The Menuing System

Use the Left and Right arrows of the cursor control to highlight the menu
required. Press the Down cursor control to see the options available on
that menu. Select the required option using the cursor control and press
Enter to set that option. Depending on the menu item selected the display
will either present further options or will return to the main menu screen.

Test Menu

This sub-menu selects the test mode. Only one mode can be active at a
time and the active mode is displayed below the heading TEST. (See Test
Modes later in this manual for details of each mode.)

Options Menu

The Options menu has five options that are not related to each other, as
shown below.

Retrieve

allows the recall of stored results to the display or a PC.

Display

recalls each test, in sequence, to the instrument display
starting with the latest stored result.

Use the cursor control Up and Down controls to step
later or earlier respectively through the stored results.
Alternatively, if you know the index number of the test
you wish to display, type the number on the keypad and
press Enter.

An asterisk (*) next to the word "MEMO" means that
there are notes attached to this result. Press the right
cursor control to view the notes.

7

GENERAL OPERATION - DLRO 10X

Download

causes the entire contents of the data store to be output
to the RS232 port to the left of the display. A copy of
AVO Download Manager, which facilitates downloading
and formats the data, is supplied.

Downloading data does not cause the stored data to be
erased from memory. To clear data from memory see
"Delete Data" below.

Please note - DLRO 10X also makes data available via the RS232 Port in
real time and is suitable for printing on a self-powered serial printer.

The output has the following form:

TEST NUMBER

TEST TYPE

DD MM YY HH MM

01/01/00 00:33

FORWARD RESISTANCE

REVERSE RESISTANCE

AVERAGE RESISTANCE

SELECTED CURRENT

UPPER LIMIT

LOWER LIMIT

PASS/FAIL

The last three lines will only appear if passbands have been set

Passbands

This option allows you to set upper and lower limits between which the
test result average must fall if it is to be signalled as a Pass (a long tone
from the buzzer). Readings outside these limits will be signalled as a Fail (a
short tone from the buzzer).

Values are entered via the keypad complete with decimal points, where
applicable, and including µ or m (See section on the Alphanumeric
Keypad). It is not necessary to enter the Ω symbol. The upper limit must
be less than or equal to 2000.0 Ω and the lower limit must be less than the
upper limit.

After completing the upper limit press Enter. DLRO 10X will check that
valid numbers have been entered and will move to the lower limit.
Complete this limit and press Enter. DLRO 10X will check that valid
numbers have been entered and will display the option to ENABLE or
DISABLE the passbands.

Highlight your choice and press Enter. You will return to the Main Menu
screen.

Note: Passbands will remain enabled or disabled until you 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.

Set Clock

This option sets the real time clock date and time settings 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.

8

GENERAL OPERATION - DLRO 10X

The row below DD MM YY HH MM contains respectively the date, the
month, the two-digit year, 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.

TEST OPTIONS RANGE

NORM AUTO

DD MM YY HH MM

09/10/00 15.08

DD MM YY

09/10/00 12.02

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.

The bottom line shows the current setting of date and time. 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.

Delete Data

Select Delete Data if you wish to clear DLRO 10X'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.

Storage

The Storage option sets the default for data storage. It may be set to
always store data or never to store data. Highlight the desired option at

the bottom of the screen and press Enter.

With the exception of tests carried out in Continuous mode, at the end of
each test you have the option to change the default by selecting STORE or
NO STORE at the bottom of the results screen.

At the end of a test, if memory is full this STORE / NO STORE message will
change to MEMORY FULL and no more tests will be stored.

Data is stored indefinitely if a charged battery pack is fitted. If the main
battery becomes exhausted or is removed, data is maintained for a period
of 4 days by an internal backup battery. When a charged battery pack is
refitted, the backup battery will recharge to full capacity within 1 week.

Range Menu

DLRO 10X uses a test current between 100 µA and 10 A to measure the
resistance of the item under test. If set to AUTO, DLRO 10X will select the
current according to the resistance it detects. (see Specifications, Ranges)

However, in some cases it may be desirable set a maximum test current. If
this is so, move the cursor to the desired current and press Enter.

Six test currents are available; 10 A, 1 A, 100 mA, 10 mA, 1 mA and 100 µA.
Selecting the 10 A maximum will have the same effect as selecting AUTO.

The Main Menu screen will show the active current range beneath the
RANGE heading.

ENTERING NOTES IN THE MEMO SCREEN

At the end of each test, (with the exception of a test in Continuous mode),
you can select the STORE or NO STORE option to store the test results or
not. Select the desired option using the cursor control. This overrides the
default setting under Options, Storage for one test only.

9

GENERAL OPERATION DLRO 10X

If you wish to add comments to the test results, instead of pressing Enter,
briefly press one of the twelve keys on the keypad. You will enter a memo
screen that allows you to enter up to 200 characters of alphanumeric
information concerning the test. When you have entered all information
press Enter and the measurement and memo will be stored regardless of
whether STORE or NO STORE was selected.

If you do not wish to add notes and are happy to accept the default
STORE / NO STORE setting you may press the Test button and a new test
will be started.

TEST RESULT STORAGE

Each test is numbered, starting at test 1. This test number is incremented
automatically, as each result is stored. The test result memory can store a
maximum of 700 tests, each being identified by its test number, date and
time.

It is advisable to retrieve all data to a PC and then to delete all data before
the test number reaches this maximum. Deleting the data will reset the
test number to 1. This will save loss of data.

KEYPAD OPERATION

The 12 key keypad is similar to those used on mobile telephones in that
each key is capable of producing one of several characters depending on
the number of times the key is pressed.

The keypad is used to enter data into the Memo field.

Pressing the blue key
marked 9/A changes
the function of the

keyboard between alpha and numeric modes.

In alpha mode a full height flashing vertical bar (|) indicates the cursor.
The keys 2 to 9 will produce the letter shown on the keys depending on
the number of presses. For example if the 2 key is pressed once an 'A' will
appear, twice and a 'B' will appear etc.

The 0 key produces a space.

The 1 key is a destructive backspace.

In numeric mode a half height flashing bar (') indicates the cursor. The
keys marked 1 - 9 and 0 produce that number when pressed. Press the
respective key briefly to enter the desired number. Pausing will cause the
cursor to move on to the next character. If a key is held down it will auto­repeat.

The key at the bottom right hand corner of the keypad marked with a dot
is a special key that produces 20 special symbols. Each press will
sequentially produce the character shown on next page:

10

GENERAL OPERATION DLRO 10X

. Decimal point or full stop

Ω Ohms symbol

m lower case m (abbreviation for milli)

µ Symbol for micro

# Symbol known as hash or pound and commonly used as

shorthand for "number"

% Percent sign

( Left round bracket

) Right round bracket

- Hyphen, dash or minus sign

/ Slash

: Colon

@ "at" symbol;

√ Tick mark

! Exclamation mark

? Question mark

$ "Dollar" symbol

= "Equals" sign

< "Less than" symbol

> "Greater than" symbol

* Asterisk

11

TEST MODES

TEST MODES

DLRO 10 has 4 test modes which are selected by repeated presses of the
Mode button. At the end of each test, DLRO 10 will display the average of
the values obtained with forward and reverse current.

DLRO 10X has 5 modes. On DLRO 10X these modes are selected from the
TEST menu using the cursor control and Enter key. At the end of a test,
DLRO 10X will show three resistance values; that obtained with forward
current, that obtained with reverse current and the average value.

Normal mode

Normal mode makes a single measurement of the resistance of the sample
using forward and reverse current

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. To make another measurement, ensure the test leads
are connected and press the test button.

Automatic mode

If Automatic mode is selected, your instrument will remain in a state of
readiness waiting for both the current AND voltage measuring leads to be
connected to the test piece. When this is done, a forward and reverse
current test will be started automatically.

To make another measurement simply break 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. Simply making
contact with voltage probes across the joint(s) you wish to measure will
then activate the measurement.

Continuous mode

Continuous mode requires the connections to be made before pressing
the Test button. Your instrument will then repeat its forward and reverse
measurements and display the results approximately every 3 seconds until
contact is broken or the Test button is pressed.

Inductive mode

DLRO 10 and DLRO 10X are able to make d.c. resistive measurements on
loads that exhibit an inductive component using the test mode indicated
by the inductor symbol on the DLRO 10, or by using the inductive mode
on the DLRO 10X.

When measuring inductive loads 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.

Having selected inductive mode, connect all four leads to the item being
tested and press the Test button.

DLRO will check that all four leads are in adequate contact with the test
piece and will then apply a test current and try to find the correct range.
The display will show 1 - - followed by 1 - - - -. During this time you may
see the current range increasing or decreasing. On the DLRO 10 the “I”
lamp will flash and the message “Current Flowing” will appear on the
DLRO 10X display.

After a short time resistance readings will appear on the display, reducing
gradually over aperiod of time until eventually a stable reading will be
obtained.

The time required for a stable reading may vary from a few seconds up to

12

Test Modes

several minutes depending on the inductance and resistance of the test
sample. There is no time limit for the inductive mode test, which will
continue until the operator presses the Test button.

When the test is terminated, the “I” lamp will remain illuminated on the
DLRO 10 or the message “Discharging” will appear on the DLRO 10X
display until any stored energy has discharged. When these messages are
extinguished it should be safe to disconnect the “C” leads.

However, the discharge indicator is an active electronic device and should
not be relied upon. You should observe your organisation’s operating
procedures.

At the end of the test both instruments will display the measured
resistance, the DLRO 10 will flash the relevant current lamp while the
DLRO 10X will display the test current used on the display.

Please note:- In inductive mode the 10A test current will not be
used.

Undirectional mode

On the DLRO 10X only, this mode makes the measurement as in automatic
mode but using forward current only.

This mode speeds up measurments on samples that are known to be free
of any standing voltages or thermal emfs. However the accuracy of the
reading may be degraded by any thermal emfs but should not be worse
than 0.2% ± 30 digits.

Since current is only applied in the forward direction, in this mode only a
single resistance value will be displayed.

A test may be repeated by breaking contact and reapplying the test probes
or by pressing the Test button.

13

TEST TECHNIQUES & APPLICATIONS

CPC

P

TESTING USING DH4 DUPLEX HANDSPIKES

Each handspike is marked with the letter P. This indicates the potential
terminals. These should be the 'inside' contacts when making a
measurement (as shown in the next section 'Testing Using Duplex
Handspikes or Individual Leads').

One of the DH4 handspikes is fitted with two lamps marked L1 and L2 and
an extra lead. This lead should be plugged into the 4 mm socket next to
the main terminals on the right hand side of the instrument. These lamps
provide information to the operator, which would otherwise only be
available on the instrument display. The meaning of these lamps is
described below.

For example, using the DH4 Duplex Handspikes with the DLRO 10 in
AUTO test mode:

1. Press the TEST button on the instrument.

2. Lamp L1 will illuminate a continuous red to indicate contact
failure. See the instrument panel for details if required.

3. When all four contacts connect, L1 will extinguish.

4. No lamps will show during the test unless contact fails.

5. Lamp L2 will light a continuous green when current flow has
decayed to less that 1 mA to signal end of test.

6. Removing the probes will extinguish the green L2 (end of test) and
Light the red L1 (no contact).

Since your DLRO always ensures good contact before applying the full test
current, there will be no 'splash' to erode the contact tips. However,
should the tips become worn or blunted, they can be simply replaced by
pulling out the worn tips and inserting new ones.

DLRO 10 and DLRO 10X (no passbands)

Lamp L1 Lamp L2 Meaning

Red Off Inadequate contact at C

and/or P contacts

Flashes Red Off Voltage present between

contacts

Off Green Current less than 1 mA and

test complete.

DLRO 10X ONLY if passbands set

Off Green Measurement Pass
Off Red Measurement Fail

TESTING USING DUPLEX HANDSPIKES OR INDIVIDUAL LEADS.

Connect the four leads as shown.

C

If using Duplex Handspikes ensure that the probe marked P is inside the C
probes.

PP

C

Note: When used on hazardous voltages Megger DH6 test leads must be

.

used

14

TEST TECHNIQUES & APPLICATIONS

TEST SEQUENCE

Pressing the TEST button starts the test sequence.

Contact resistance is checked by passing 100 µA through the C1-C2 loop
and checking that the voltage is less than 4 V. Then passing 80 µA through
the P1-P2 loop and checking that the voltage is less than 250 mV. If either
value is exceeded the respective lamp or warning message will be
displayed.

When all faults have been rectified the test current is increased until the
voltage on P1-P2 is within the 2 mV to 20 mV range. This current is then
applied in a forward and then reverse direction to obtain two
measurements.

Both measurements are displayed by DLRO 10X along with the average,
while the DLRO 10 displays the average only.

If the combined resistance of the current leads and test sample is greater
than 100 mΩ, testing at 10 A will not be possible.
A 1.9 mΩ
(1 A) and the result will be shown as 1.900 mΩ

1.9000 mΩ.

TEST LEAD RESISTANCE

For testing at 10 A, the combined resistance of the current leads must not
exceed 100 mΩ
than 1 volt and will enable 10 A testing under worst case conditions. If you
wish to limit test current to no more than 1 A, on DLRO 10 use current
leads with a resistance of about 1 Ω
maximum test current on the RANGE submenu.

OVERHEATING

When performing rapidly repeated tests at 10 A, using current leads with a
combined resistance of 100 mΩ, 10 W of heat will be dissipated in the

resistor will then be tested at the next lowest current

instead of

. This will ensure that the voltage drop in the leads is less

, or on DLRO 10X select 1A as the

leads and 30 W within your instrument. If the ambient temperature is high
this will cause internal overheating and the message "hot" will appear on
the instrument display and testing will be halted.

After a few minutes to cool down, testing will be allowed to continue.

If this is a persistent problem, use current leads with a higher resistance
(e.g. 200 mΩ to 300 mΩ). This will reduce the generation of internal heat.

15

BATTERY MODULE AND CARE

THE BATTERY MODULE

The battery module contains nickel-metal-hydride cells and has a built-in
battery-management system that controls charging and monitors
discharge. This provides a high capacity, low-weight battery system, which
can be recharged at any time. It is not possible for the user to over-charge
or over discharge the battery. For your own convenience it is best to
charge it regularly to keep it topped up, but leaving it in a discharged state
will do no harm.

On the front of the battery module are two buttons and a
10-segment LED display.
Slow Charge

To find the amount of charge in your battery module, whether connected
to your DLRO or separate, press the Battery Condition Button. The Battery
State indicator will light between
1 and 10 segments signifying between 10% and 100% charge respectively.
After a few seconds this display will automatically go out.

BATTERY CHARGING

Please note - The battery should only be charged within the
temperature range 0°C to 45°C. Fast charging will not be allowed
if the temperature is below 10°C. Fast charging causes the
temperature of the battery to rise. If the temperature exceeds
45°C the charging rate will be reduced automatically.

Battery Condition

Battery State Indicator

To charge the battery, your battery module must be removed from the
instrument. Remove the module by pressing on the raised circular area of
the retaining clips and pull the top of the clip away from the instrument
body. The module now unplugs from the base of the instrument.

Plug in the charger or connect to a 12 volt vehicle-type battery using the
‘cigar lighter’ lead provided. The LED "Battery State" indicator will light
and show movement when the battery is charging. The battery may be
recharged before it has been fully discharged. It will normally be recharged
to 90% of capacity within 21/2 hours. Full charge may take up to 4 hours
before indicating that the battery is full depending on the initial state of
the battery. When charging is complete the battery management circuitry
will switch off so that over-charging is prevented.

Your battery module can be safely used in a partially charged state and will
not suffer if stored in a discharged state. However, you may wish to have a
spare battery that can be interchanged with the one in use to provide
continuous use of your DLRO.

As the battery ages, it may start to loose its capacity. In this case the battery
module has a slow charge facility which is activated by pressing the Slow
Charge button while switching on the charger supply until the indicator
bars start to move. This method of charging can take up to 48 hours and
so is best reserved for a weekend or a period when the instrument is not
required to be used.

A fully charged battery, even if not used, will self discharge over a period of
several weeks (faster at higher temperatures). Always check the "Battery
State" indicator before starting work. A fully charged battery will light all
segments. A fully discharged battery will light no segments.

16

BATTERY MODULE AND CARE

Flashin

Please note that all batteries suffer a reduced life if exposed to
constant high temperatures. A constant temperature of 30°C will
probably cause the battery to fail in less than 5 years. 40°C will
shorten its life to 2 years.

THE BATTERY STATE INDICATOR

The Battery State Indicator provides information on the amount of charge
in the battery, but is also used to signal other conditions as follows:

Fast

Standard Charging.

The battery module is charging at its
standard rate.

Slow Charging.

The battery module is charging at its slow
rate.

Standard charging but at a slow
rate.

The battery has been set to charge at its
standard rate but, because the battery has
become hot, it has switched charge rates to
a lower rate while the battery cools down. Wait for the temperature to
drop and/or move to a cooler location.

Slow

Flashing Slow

Not charging. There is a
temperature problem.

The battery is too hot or too cold and
charging has therefore been interrupted
until the battery returns to a temperature
between 0°C and 45°C (32°F and 113°F)

Input Voltage Too Low.

The charger supply is not supplying
sufficient voltage to the battery module to
charge the batteries.

Battery nearly exhausted

The battery capacity is very low. Recharge
it.

Error: Reset

An error has occurred within the battery
module. The circuitry is resetting. Wait a
few moments and the fault should clear.

Overvoltage problem

The charging supply voltage is too high. Disconnect the charger and
rectify the fault.

Flashing

Rapid

Flashing

Flashing

17

BATTERY MODULE AND CARE

WARNING

Connecting to greater than 15 volts can cause permanent
damage to the battery module.

18

SPECIFICATIONS

Ranges

Full Scale Resolution Accuracy Full Scale Volts Test Current

Resistance ResistanceInduction Induction

1,9999 mΩ
19,999 mΩ
199,99 mΩ

1,9999 Ω
19,999 Ω
199,99 Ω
1999,9 Ω

Display Measurement 41/2digit seven segment LED

Range and Safety LED Indication

Measurement Mode Manual, Auto, Continuous, Inductive Manual, Auto, Continuous,

Control Fully Automatic Fully Automatic with manual

Speed <3s for forward & reverse current and to display average

Test Method Single cycle reversing d.c. ratiometric measurements and average result calculated.

Test Current Accuracy 10%

Output Current Stability <10 ppm per second @ 10 mA

0,1 µΩ

1 µΩ

10 µΩ

100 µΩ

1 mΩ

10 mΩ

100 mΩ

±0,2%±0,2 µΩ 20 mV

±0,2%±2 µΩ

±0,2%±20 µΩ

±0,2%±0,2 mΩ

±0,2%±2 mΩ

±0,2%±20 mΩ

±0.2%±0.2 Ω

DLRO 10 DLRO 10X

<100 ppm per second at higher currents

20 mV
20 mV
20 mV
20 mV
20 mV

200 mV

20 mV
200 mV
200 mV
200 mV
200 mV
200 mV

10 A

1 A

100 mA

10 mA

1 mA
100 µA
100 µA

Large backlit LCD

Inductive, Unidirectional.

override of maximum current

1 A
1 A

100 mA

10 mA

1 mA

100 µA

19

SPECIFICATIONS

DLRO 10 DLRO 10X

Maximum Lead Resistance 100 mΩ total for 10A operation irrespective of battery condition.

Voltmeter Input Impedance > 200 kΩ

Hum Rejection Less than 1% ± 20 digits additional error

with 100 mV peak 50/60 Hz. on the potential leads.
Warning will show if hum or noise exceeds this level.

Data Transfer Real Time or from storage via RS232

Storage 700 tests
Memo Field Up to 200 characters per test via

integral alphanumeric keypad.

Battery Capacity 7 Ah NiMH rechargeable.

Life Typically 1000 x 10 A tests before recharge
Recharge Via External 90V - 260 V 50/60 Hz charger or from 12 to 15 V d.c. supply

Charging Time 2.5 hours to 90% capacity, 4 hrs for full charge

Temperature Operation +5°C to +45°C (41°F to 113°F) at full specification.

-10°C to +50°C (14°F to 122°F) at reduced acuracy
Storage -30°C to +70°C (-22°F to 158°F)
Calibration 20°C (68°F)
Coefficient <0.01% per oC from 5°C to 40°C (<0.006% per °F from 41°F to 104°F)
Standard charging 0°C to +45°C (32°F to 113°F)
Fast charging +10°C to +45°C (50°F to 113°F)

Humidity Max 90% RH @ 40°C (104°F) non-condensing
Altitude Max 2000m (6562 ft.) to full safety specifications
Safety In accordance with IEC61010-1 600 V Category III - only when DH6 leads are used
EMC In accordance with IEC61326-1
Operation inaccuracies Refer to www.megger.com
Dimensions 220 x 100 x 237 mm (8.6 x 4 x 9.5 in)
Weight 2.6 kg (5 3/4 lb.) including battery module

20

TROUBLE SHOOTING

Error Message Fault Action required.

bAtt The main battery module is low. Recharge the main battery or replace with a charged one

_ _ _ _ _ An error has occurred during the measurement. Rectify the error and repeat the measurement.

e.g. contact has been lost at one of the probes.

ERR 114 Checksum Failure in EEPROM. Return for recalibration.

Calibration constants have been lost.
The DLRO will continue to work but the accuracy will now
be typically ± 2%. At switch on the display will show the
software version with dashes each side e.g. - 1.0 -

ERR 115 Checksum Failure in battery backed RAM. Recharge the main battery or replace it with a charged

This can occur if the main battery module and the one. Switch the instrument on.
backup battery become completely exhausted. Calibration constants will be retrieved from EEPROM.

It is possible to reset your DLRO 10X to the original factory settings. This will clear all stored results, set the clock to a default value and format, and will set
all other settings to their default values. This is effected by holding down the '3' button on the alphanumeric keypad while switching on your instrument.

21

ACCESSORIES

Standard Accessories supplied with instrument.

7 Ah NiMH battery module. 6340-101

DH4 Duplex handspikes (2), one with indicator lights.

1.2m / 4 ft 6111-503

Battery charger for operation from 115/230 V.
50/60Hz supply. 6280-333

Cigar lighter adapter for battery charging. 6280-332
User guide. 6172-681
Warranty book. 6170-618

Optional Accessories at extra cost

Carrying case for DLRO10 and all standard accessories. 6380-138
Carrying case for optional lead sets. 18313
Calibration Shunt, 10 Ω, current rating 1 mA. 249000
Calibration Shunt, 1 Ω, current rating 10 mA. 249001
Calibration Shunt, 100 mΩ, current rating 1A. 249002
Calibration Shunt, 10 mΩ, current rating 10 A. 249003
Certificate of Calibration for Shunts, NIST CERT-NIST
Replacement tips for DH4 handspikes. Needle point 25940-012

Waffle end 25940-014

Optional Test Leads at extra cost
Duplex Leads

DH5 straight duplex handspikes (2).
One has indicator lights. 2.5m/8ft 6111-517

DH6 Duplex handspikes (2) suitable for working on
600 V. systems. 2.5m/8ft 6111-518

Duplex Handspikes (2)with spring loaded helical contacts.

2m/7 ft 242011-7

2.5m/8ft 6111-022

5.5m/18ft 242011-18
6m/20ft 6111-023
9m/30 ft 242011-30

Straight Duplex Handspikes (2) Heavy Duty with
fixed contacts. 2m/7 ft 242002-7

5.5m/18ft 242002-18
9m/30 ft 242002-30

Duplex Heavy Duty 5cm (2") C-Clamps. (2) 2m/7 ft 242004-7

5.5m/18ft 242004-18
9m/30 ft 242004-30

Duplex handspikes with replaceable Needle Points 2m/7 ft 242003-7
Duplex 1.27 cm (1⁄2") Kelvin Clips. (2) gold plated 2m/7 ft 241005-7

silver plated 2m/7 ft 242005-7

Duplex 3.8 cm (11⁄2") Kelvin Clips. (2) 2m/7 ft 242006-7

5.5m/18ft 242006-18

9m/30 ft 242006-30
Single Leads
Single handspikes (2) for potential measurement. 2m/7 ft 242021-7

5.5m/18ft 242021-18

9m/30 ft 242021-30

Current clips (2) for current connections. 2m/7 ft 242041-7

5.5m/18ft 242041-18

9m/30 ft 242041-30

22

REPAIR AND WARRANTY

The instrument circuit contains static sensitive devices, and care must be
taken in handling the printed circuit board. If the protection of an
instrument has been impaired it should not be used, and be sent for repair
by suitably trained and qualified personnel. The protection is likely to be
impaired if, for example, the instrument shows visible damage, fails to
perform the intended measurements, has been subjected to prolonged
storage under unfavourable conditions, or has been exposed to severe
transport stresses.

New Instruments are Guaranteed for 1 Year from the Date of

Purchase by the User.

Any unauthorised prior repair or adjustment will automatically

Note:

invalidate the Warranty.

Instrument Repair and Spare Parts

For service requirements for Megger Instruments contact:-

Megger Limited or Megger
Archcliffe Road Valley Forge Corporate Centre
Dover 2621 Van Buren Avenue
Kent, CT17 9EN. Norristown, PA 19403
England. U.S.A.

Tel: [phone] Tel: [phone]

Fax: [phone] Fax: [phone]

Approved Repair Companies

A number of independent instrument repair companies have been
approved for repair work on most Megger instruments, using genuine
Megger spare parts. Consult the Appointed Distributor / Agent regarding
spare parts, repair facilities and advice on the best course of action to take.

Returning an Instrument for Repair

If returning an instrument to the manufacturer for repair, it should be sent
freight pre-paid to the appropriate address. A copy of the Invoice and of
the packing note should be sent simultaneously by airmail to expedite
clearance through Customs. A repair estimate showing freight return and
other charges will be submitted to the sender, if required, before work on
the instrument commences.

NOTE: The batteries are Nickel-metal-hydride and if these are changed the
disposal of old cells should be in accordance with local regulations.

or an approved repair company.

23

24

M

DLRO®-10 & DLRO®-10X
Ohmmêtre digital basse rèsistance

GUIDE DE L’UTILISATEUR

25

OPERATION

Avertissements de sécurité 27

Description générale 28

Fonctionnement général - DLRO 10 29

Indicateurs d’intensité de test 29
Témoin de bruit 29
Indicateurs 'C' et 'P' 29
Indicateurs d’avertissement
'V' et 'I' 29

Fonctionnement général - DLRO 10X 30

Panneau supérieur ­DLRO 10X 30
Ecran du menu principal ­DLRO 10X 30
Messages d’avertissement 30
Bruit 30
Indicateurs 'C' et 'P' 31
Avertissement de tension
externe 31
Avertissement d’intensité de
décharge 31

Le système de menus 31

Menu Test 31
Menu Options 31
Récupérer 31
Afficheur 32
Télécharger 32
Bandes d’acceptation 32
Réglage horloge 33
Effacer les données 33

Stockage 34
Menu Gamme 34

Saisie de notes dans l’écran mémo 34
Stockage des résultats des tests 34
Fonctionnement du clavier 35
Modes de test 36

Mode normal 36
Mode automatique 36
Mode continu 36
Mode Induction 36
Mode unidirectionnel 37

Techniques de test et applications 38

Essais avec les doubles
pointes DH4 39
Essais avec les doubles pointes
ou des cordons Individuels 38
Séquence de test 39
Résistance des cordons d’essai 39
Surchauffe 39

Module batterie et entretien 40

Le module batterie 40
Mise en charge de la batterie 40
L’indicateur d’état de la batterie 41
Chargement standard 41
Chargement lent 41
Chargement standard mais à
cadence lente. 41
Pas de chargement. Il y a un
problème de température. 41
Tension d’entrée trop faible. 41

Batterie presque épuisée 41
Erreur : Réinitialisation 41
Problème de surtension 42

Caractéristiques techniques 43-44

Dépannage 45

Accessories 46

Reparation et garantie 47

Les symboles utilisés sur l’instrument
sont:

G Attention, se reporter au guide de

l’utilisateur.

t Equipement protégé dans son

ensemble par une double isolation
(Classe II).

c Equipement conforme aux

Directives européennes en vigueur.

26

GAVERTISSEMENTS DE SÉCURITÉ

n Il convient de lire et comprendre ces avertissements de sécurité avant d’utiliser l’instrument.

n A chaque fois que possible, les circuits devront être mis hors-tension avant de procéder aux tests.

S’il est impossible de mettre hors tension le circuit (e.g. les batteries haute tension ne peuvent pas être éteintes lorsque l’on teste leurs
connexions), l’utilisateur doit être averti du danger. Les pointes de touche de l’instrument seront sous tension lorsqu’elles seront
connectées au circuit. C’est pourquoi les cordons de test Megger DH6 doivent être utilisés lorsque l’instrument est utilisé sur un circuit
sous tension.

n Tester des circuits inducteurs peut être dangereux :

Après avoir testé une charge inductrice, une certaine quantité d’énergie sera stockée dans l’inductance. Cette énergie se libère sous la
forme d’une intensité de décharge. Débrancher une charge inductrice alors que le courant continue de passer provoquera un arc de
haute tension, ce qui constitue un danger à la fois pour l’utilisateur et pour l’élément testé.

Le DLRO 10 est équipé d’un témoin de
clignotera à la fin d’un essai sur une charge inductrice et cessera de clignoter quand l’intensité aura décliné à moins de 1mA. Le
DLRO 10X utilise un message sur l’afficheur pour ce faire.

Pour tester de grandes résistances inductrices, les fils transportant le courant devront être solidement branchés à l’élément à tester
avant de commencer les mesures.

Il n'est pas recommandé d'utiliser les doubles pointes manuelles DH4 pour effectuer des tests sur des charges inductrices. Si par
inadvertance on utilise les pointes manuelles DH4 sur une charge inductrice, le témoin L1 des pointes manuelles clignotera orange
tandis que le courant de décharge circulera, reproduisant ainsi la fonction du témoin ‘
le contact jusqu'à ce que le témoin L1 arrête de clignoter orange et passe au vert, indiquant la fin du test.

n Ce produit n'est pas intrinsèquement sûr. Ne pas l'utiliser en atmosphère explosive.

n NB : la bandoulière est spécialement conçue pour casser si elle est soumise à une contrainte supérieure à environ 50 kg.

DECHARGE, marqué ‘I’, qui indique qu’un courant circule dans la boucle C1-C2. Ce témoin

I’ sur l'instrument. Il est important de maintenir

27

DESCRIPTION GÉNÉRALE

Le DUCTER DLRO 10 et le DUCTER DLRO 10X constituent une famille
d’ohmmètres basse résistance qui mesurent les résistances dans la gamme
de 0,1 µΩ à 2kΩ. Les deux instruments fournissent une intensité de test
maximale de 10 A c.c. qui est automatiquement sélectionnée selon la
valeur de la résistance testée. Le DLRO10X vous permet de contourner
cette sélection automatique et de choisir votre propre intensité de test.

La valeur de la résistance mesurée est envoyée sur l’afficheur de
l’instrument avec indication des unités, µΩ, mΩ ou Ω. Le DLRO 10 utilise
un grand écran et des indicateurs à diodes électroluminescentes pour
afficher la valeur et les unités respectivement, tandis que le DLRO 10X
contient toutes les informations sur un afficheur à cristaux liquides rétro­éclairé.

L'utilisation d'une technique de test à quatre bornes supprime la résistance
des cordons d’essai de la valeur mesurée, et l'inversion automatique du
courant élimine l’effet des tensions permanentes sur l’échantillon de test.
De plus, avant et pendant un test, le contact des cordons d’essais est suivi
pour réduire encore le risque de lectures erronées.

Un mesurage de résistance prend normalement environ 2,5 secondes et
comprend une mesure avec courant direct, courant inversé et l’affichage
de la moyenne. Sur le DLRO 10X les trois valeurs s’affichent et en option la
mesure peut être limitée au courant direct seul.

L’instrument est alimenté par une batterie rechargeable Nickel Métal
Hydride (NiMH) qui permet de réaliser un millier de tests à 10 A sur une
seule charge. Le module batterie contient un circuit intelligent qui
empêche la batterie de s’endommager par surcharge, ainsi qu’un
indicateur d’état.

Un couvercle amovible articulé sur le dos et maintenu fermé par des prises
magnétiques recouvre le panneau. Ce couvercle peut être entièrement
démonté si nécessaire en le faisant sauter de ses charnières.

Les deux instruments sont protégés contre les branchements accidentels
jusqu’à des tensions de 600 V c.c. appliquées entre n’importe quelle paire
des quatre bornes jusqu’à 10 secondes. Veuillez noter qu’appliquer 600V
aux bornes de potentiel provoquera un certain échauffement interne. On
peut s’attendre à des erreurs allant jusqu’à 30 chiffres immédiatement
après l’application d’un tel voltage. La pleine précision sera rétablie en
deux à trois minutes.

Les deux instruments sont livrés avec une paire de doubles pointes
manuelles DH4 avec cordons de 1,2 m. Autres longueurs et terminaisons
disponibles sur demande.

28

FONCTIONNEMENT GÉNÉRALE - DLRO 10X

10A
1A
100mA
10mA
1mA
100µA

C P

Ω
mΩ
µΩ

TEST

Brightness

Test current

“Contact fail”

indicators

Voltage on

terminals

Current

flowing

Exces s

noise

Intensité de test

Indicateurs de
"Défaut de
Contact"

Tension aux
bornes

intensité
débitée

Bruit
excessif

Marche/Arrêt

Luminosité

Contrôle de Mode

Appuyer sur le bouton Marche/Arrêt pour allumer le DLRO 10. Tous les
témoins s'allument, les témoins V et I clignotent, puis la version du logiciel
va s'afficher et le témoin W va s'allumer. Si les cordons d’essais n'ont pas
été connectés à l’échantillon de test, les témoins ‘C’ et ‘P’ vont aussi être
allumés. Appuyer de nouveau sur le bouton Marche/Arrêt pour éteindre
l’instrument. Si l’instrument n’est pas utilisé pendant 5 minutes, il s’éteint
automatiquement.

Ajuster le contrôle de luminosité à un niveau confortable.

Sélectionner le mode de Test en appuyant à plusieurs reprises sur le
bouton Mode. Les témoins indicateurs vont parcourir successivement les
divers modes de test (voir la section sur les modes de test). Appuyer sur le
bouton Test pour commencerles mesures.

Indicateurs d’intensité de test

L'intensité de test est sélectionnée automatiquement par le DLRO 10
et est indiquée par les témoins sur la gauche du panneau. La valeur
mesurée s'affiche sur la fenêtre principale et les unités (µΩ,
mΩ ou Ω) sont données par les témoins à droite de la fenêtre.

Témoin de bruit

Un bruit dépassant 100 mV 50/60 Hz allumera le témoin 'Bruit' et la
mesure ne sera pas d’une précision fiable.

Indicateurs 'C' et 'P'

Le témoin 'C' s’allume pour indiquer une défaillance de contact dans la
boucle 'C1-C2'. Le témoin 'P' s’allume s’il y a une coupure dans la boucle
P1-P2.

Indicateurs d’avertissement 'V' et 'I'

Si une tension extérieure est appliquée aux bornes, le témoin ‘V’ va
clignoter. C'est un avertissement que le circuit en cours de test est sous
tension et probablement dangereux. On ne peut réaliser de test dans cette
condition.

Le témoin ‘V’ fonctionnera si plus de 50 V sont appliqués à l'une ou l'autre
borne de tension par rapport à une borne d'intensité. Si la tension apparaît
juste entre bornes d'intensité ou juste entre bornes de tension, le témoin
fonctionnera à un pic de 100 V ou de 5 V respectivement.

Veuillez noter que le témoin ‘V’ n'agira que si une tension
apparaît entre les bornes. Le témoin ne fonctionnera pas si toutes
les bornes sont à la même haute tension. Le témoin ne
fonctionnera pas si l'instrument est éteint.

Le témoin 'I' s’allumera si une intensité supérieure à 1 mA continue de
circuler après la fin d’un test. Cela suggère qu’une charge inductrice a été
testée et continue de se décharger. Ne pas débrancher la boucle de
courant avant que le témoin 'I' se soit éteint.

29

FONCTIONNEMENT GÉNÉRALE - DLRO 10X

Touche
Enter

70%

TEST SUIV 1

0 ENREGISTRE

27/07/00 12.02

Panneau supérieur - DLRO 10X

Toutes les commandes nécessaires à la programmation et à l’utilisation du
DLRO 10X se trouvent sur le panneau supérieur de l’instrument.

A gauche du grand écran à cristaux liquides se trouvent les commandes de
déplacement autour de l’affichage, de contrôle du système de menus et
d’ajustement du contraste d’affichage et du rétro-éclairage.

A droite de l’affichage se trouve le grand bouton Test, le bouton
Marche/Arrêt et un clavier alphanumérique pour la saisie de notes
concernant un test et qui seront enregistrées avec les résultats de ce test
pour référence ultérieure.

Pour allumer votre DLRO 10X, appuyer sur le bouton Marche/Arrêt
pendant environ 1 seconde. Appuyer de nouveau pour éteindre
l’instrument. Si l’instrument n’est pas utilisé pendant 5 minutes, il s’éteint
automatiquement.

30

Ecran du menu principal - DLRO 10X

A la première mise sous tension le DLRO 10X affiche un écran de
copyright, suivi de l’écran du menu principal.

Cet écran vous fournit des informations telles que le pourcentage de
charge restante de la batterie, le numéro d’indice du prochain test, le
nombre de tests déjà enregistrés et la date et l’heure actuelles.

Cet écran donne aussi accès au système de menus grâce auquel vous
pouvez configurer instrument et choisir les paramètres de test voulus. La
navigation dans ce système de menus se fait au moyen des commandes du
curseur et de la touche Enter.

Messages d’avertissement

L’écran du menu principal comportera aussi parfois certains messages
d’avertissement.

Bruit

Un bruit dépassant 100 mV 50/60 Hz activera le message 'Noise' (bruit) au
bas de l’affichage. Au-dessus de ce niveau la précision ne sera pas fiable.