Megger BMM2500 User manual

This instrument is manufactured in the United Kingdom.
The company reserves the right to change the specification or design without prior notice.
Megger is a registered trademark
Part No. 6172-491 V06 0207
www.megger.com
Megger Limited
Archcliffe Road, Dover
Kent CT17 9EN England
T+44 (0)1 304 502101
F [phone]
[e-mail]
Megger
4271 Bronze Way, Dallas,
Texas 75237-1019 USA
T+1 800 723 2861 (USA
ONLY)
T+1 214 333 3201
F+1 214 331 7399
[e-mail]
Megger
Z.A. Du Buisson de la
Couldre
23 rue Eugène Henaff
78190 TRAPPES France
T+33 (0)1 30.16.08.90
F+33 (0)1 34.61.23.77
[e-mail]
Megger Pty Limited
Unit 26 9 Hudson Avenue
Castle Hill
Sydney NSW 2125
Australia
T+61 (0)2 9659 2005
F+61 (0)2 9659 2201
[e-mail]
Megger Limited
110 Milner Avenue Unit 1
Scarborough Ontario
M1S 3R2
Canada
T+1 416 298 9688 (Canada
only)
T+1 416 298 6770
F+1 416 298 0848
[e-mail]
M

User Guide
M
BMM2500
Insulation Multimeters

CONTENTS
2
Symbols used on the instrument are:
Risk of Electric Shock
Refer to User Guide.
Equipment protected throughout
by Double Insulation (Class II).
Equipment complies with
current EU Directives.
Equipment must
not be connected to
installations >500V.
>500V
Safety Warnings 3
General Description 4
Continuity Testing 8
Continuity Bleeper 10
Millivolt Tests 11
Capacitance Tests 12
Milliamps Tests 12
Storing Results 13
Datalogging 16
Setup Modes 18
Specification 20
Repair and Warranty 25

3
SAFETY WARNINGS
✱Safety Warnings and Precautions must be read and understood before the instrument is used.
They must be observed during use.
✱The circuit under test must be de-energized and isolated before connections are made except for
voltage measurement.
✱Circuit connections must not be touched during a test.
✱After insulation tests, capacitive circuits must be allowed to discharge before disconnecting the
test leads.
✱The Live Circuit Warning and Automatic Discharge are additional safety features and should not
be regarded as a substitute for normal safe working practice.
✱Replacement fuses must be of the correct type and rating. Failureto fit the correctly rated fuse
will result in damage to the instrument in the event of an overload.
✱Test leads, including crocodile clips, must be in good order,clean and have no broken or
cracked insulation.
✱Ensure that hands remain behind guards of probes/clips when testing.
✱U.K. Safety Authorities recommend the use of fused test leads when measuring voltage on high
energy systems.
NOTE
THE INSTRUMENTS MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS.USERS OF THIS EQUIPMENT
AND/OR THEIR EMPLOYERS ARE REMINDED THATHEALTH AND SAFETY LEGISLATION REQUIRE THEM TO CARRYOUT VALID
RISK ASSESSMENTS OF ALL ELECTRICAL WORK SO AS TO IDENTIFY POTENTIAL SOURCES OF ELECTRICAL DANGER AND RISK
OF ELECTRICAL INJURY SUCH AS FROM INADVERTENT SHORT CIRCUITS.WHERE THE ASSESSMENTS SHOW THAT THE RISK IS
SIGNIFICANT THEN THE USE OF FUSED TEST LEADS CONSTRUCTED IN ACCORDANCE WITH THE HSE GUIDANCE NOTE GS38
‘ELECTRICAL TEST EQUIPMENT FOR USE BY ELECTRICIANS’SHOULD BE USED.

GENERAL DESCRIPTION
4
The Megger®BMM2500 Series instruments are
battery powered Insulation and Continuity testers,
with a measurement capability from 0,01Ω
Continuity to 200GΩInsulation.
Offering multi-voltage facilities, the instruments
take full advantage of microprocessor technology
and feature a large liquid crystal display combining
digital and analogue readings. The analogue
display has the benefit of indicating trends and
fluctuations in readings, while the digital readout
gives direct accurate results. The display is also
backlit giving clear visibility even in low light
conditions.
The BMM2500 Series instruments have the unique
capability of being able to measure voltages down
to a resolution of 0,1mV.This gives the user the
option to fit a wide variety of transducers to further
enhance the capabilities of the BMM Series
instruments, eg temperatureor humidity
measurement.
Acustomised connector on the top of the
instrument enables the optional Megger SP6F
Switched probe to be used for two handed probe
operation.
The 250V, 500V and 1000V ranges can be used to
test electrical installations in compliance with
BS7671 (16th Edition IEEE Wiring Regulations)
IEC364 and HD384, since each range has a 1mA
minimum test current at the minimum pass values
of insulation specified in these documents. The
100V range (BMM2580) is ideal for testing
telecommunications equipment which would be
damaged by higher voltages. The 50V range
(BMM2580) is useful for testing sensitive
equipment, such as electronic components, and
computer peripherals.
The BMM2500 series instruments have a current
facility which enables up to 500mA to be
measured, this together with Ω, V and mV ranges
means that the instrument can realistically be used
in situations wherepreviously a multimeter would
be needed. For higher currents an optional current
clamp is available.

5
The BMM2500 series instruments have an
RS232 interface built in, and will allow the
storage and download of results to a PC. The
instruments come with all the necessary
software to download and tabulate the results.
The download format is also Powersuite
compatible enabling instruments to form part of
an integrated test and certification system. The
BMM2500 series instruments also have the
capability to data-log results over an extended
time period so that long term measurements of
systems can be taken.
Designed to IEC1010-1 the BMM2500 Series are
protected against connection to a 500V
Category III supply. The instruments have a basic
accuracy of ±2% at 20°C. The instruments are
waterproof and dustproof to IP54. This helps
maintain accuracy and ensures maximum
reliability in harsh environments.

OPERATION
6
Refer to Safety Warnings before using
the instrument
Testing is automatically inhibited if:
• An external voltage >25V is present when
switched to any insulation range position.
• An external voltage >10V is present on all
other ranges (excluding OFF/V/mV).
The external voltage is indicated on the display,
on insulation ranges an audible bleeper will
sound if a test is attempted.
Live Circuit Warning
When more than 25V is applied to the terminals
in the insulation ranges, the instrument defaults
to a voltmeter and gives an audible warning if a
test is attempted. On all other switch positions
except OFF/V/mV when more than 10V is
applied the default voltmeter will be activated.
Testing will be inhibited.
Voltage Testing on High Energy Systems
Use extreme care when using or measuring
voltages above 30V, particularly in high energy
systems. Fused test leads are available as
optional accessories for local situations where
increased protection is required.
Auto-shut Off
To conserve battery life, Auto-shut Off (preceded
by a series of bleeps) operates after approx.
10 minutes of instrument inactivity on insulation,
5minutes on all other ranges. If the instrument is
switched on while holding the key, the Auto
shut-Off time is extended to 60 minutes. To
restore operation after Auto-shut Off, select OFF
followed by the required switch position.
Note: It is recommended that the instrument is
switched to the OFF position when not in use.
Backlight
The backlight is activated by pressing the
key. The backlight will remain illuminated
for approx. one minute before automatically
switching off to conserve battery life,
alternatively the key can be re-pressed.
∼

∼
7
Insulation
Tests (MΩ)
(See fig.1)
The insulation tests
apply a known
voltage to the circuit
under test and
measure the resulting
leakage current. The
circuit under test must
be completely de-
energised and
isolated before test
connections are
made.
Insulation tests areonly initiated when the TEST
button is pressed.
1. Set the range switch to the test voltage
required.
2. Connect the test leads, first to the instrument,
and then to the isolated item under test.
3. Press the TEST button to activate the test
voltage. Take the reading.
4. Release the TEST button at the end of the test.
(Press the TEST button if the ltb feature is
enabled). The last reading will hold on the display.
5. Any capacitive circuits charged during a test
will automatically discharge. If significant
voltage remains the voltage warning will occur
and the voltage present displayed.
6. Remove the test leads only when no voltage is
indicated.
Locking Test Button (ltb)
When it is desired to do a long insulation test, the
test can be ‘locked on’ by pressing the key
while the test button is held down. The warning
will appear on the display and both buttons may be
released whilst the test continues. The next press
of the test button will terminate the test.
Note: There is a short delay on the first operation
of ‘1000 V’ range, each time the range is selected.
This is to prevent accidental application of 1kV.
The MΩrange features a leakage current display.
Leakage current is the value of current that flows
during the insulation test. Toview the leakage
current press the key. To view insulation
resistance press the key again.
FIG.1

8
Good procedure whilst Insulation Testing
Care must be taken when taking measurements
greater than a few GΩ.The leads must be clean
dry and in good condition. They must also not be
allowed to tangle. It is also advisable that the
switched probe SP6F is not used as the accuracy
at high value measurements is not guaranteed. The
instrument should also be clean and dry with
particular attention paid to the terminals. Also
attempt to reduce any leakage that may give
erroneous results on the item under test.
Polarisation Index Testing
Polarization Index (PI)is the term applied to the
Dielectric Absorption Ratio when resistance values
are measured after 1 minute and again after 10
minutes. Polarization Index is then the resistance
value after 10 minutes divided by the resistance
value after 1 minute. The test can be run at any
voltage. Moredetailed information on PI Testing and
value assessment can be found in Megger Limited
publications listed in the Accessories page.
Automatic Discharge
When the TEST button is released after an
insulation test (or re-pressed if ltb feature is
enabled), a 200kΩload is automatically switched
across the terminals to discharge the item under
test. Any voltage present will be indicated on the
display so that the discharge can be monitored.
Typical Terminal Voltage Characteristics

Continuity Testing (Ω) (See fig.2)
The continuity tests are activated when the probes
make contact of less than a few kΩ.The test
operates without the need to press the TEST
button. When the test leads are removed the
reading will hold for a few seconds and then reset.
To recall the last result press the key. This
range is not suitable for diode testing since the
automatic contact detector will not be activated
when connected to a diode.
1. Set the selector switch to Ω.
2. Connect the test leads.
3. The test will activate automatically.
4. After the test probes are disconnected, the
reading will be held for a few seconds.
Zeroing of Test Lead Resistance
The resistance of the test leads can be nulled on the
continuity range (up to 9,99Ω). The null information
is retained in non-volatile memory and so will be
remembered when the instrument is switched off.
1. Select the Continuity range.
2. Short the test leads across a known good
conductor using prods.
3. When the reading
has stabilised, press
the TEST button.
The zerooffset
symbol will
appear.
4. To release the zero
offset press the test
button again.
The continuity range
features a range lock
facility. To LOCK the
continuity range press
the key, the LOCK symbol will appear. To
scroll through the available ranges press the
key. Tode-select the LOCK featurehold the
key down.
9
FIG.2