Performing Tests - General - AVO MEGGER BM25 Guide De L'utilisateur

Performing Tests - General

1. Switch the BM25 On by pressing the 'On/Off' switch once. All
LCD segments appear for 5 seconds, then the word 'CAL'
appears for about 5 seconds. When the word 'CAL'
disappears, the instrument is ready for use, and in standby
mode.
Note: When not testing (i.e. in standby mode) the BM25 acts as
a voltmeter. (50 V to 1000 V).
2. Ensure that all test leads are clean and in good condition,
and connect them to the isolated circuit under test.
If an external voltage >50 V is detected the voltage is
displayed together with high voltage symbols.
3. Select the required test mode using the Range keys to move
the right hand cursor.
4. Unless accepting a default test time, use the Selector keys to
move the left hand cursor to the timer position and increment
to the desired test duration using the Range keys. (Maximum
test time is 90 minutes).
5. Use the Selector keys again to set the required test voltage.
The variable voltage position gives the option to select a
non-standard voltage between 25 and 5000 V d.c., or to
continuously vary the voltage in 25 V steps during a test. To
select, move the left hand cursor to the variable voltage
position and adjust the output terminal voltage using the
Range keys. The voltage set is shown at the top of the
display. When set to variable voltage, the test mode cannot
be altered.
Note: Changing the voltage during a test will temporarily alter the
reading. A steady reading will appear when the new voltage
has been stable over a full sample period (typically 5 seconds).
6. Start a test by pressing the red test button for at least 1
second. The flashing red LED and the flashing H.V. symbols
warn that a test is in progress.
7. When testing resistive or moderately capacitive loads (up to
about 1µF) the test voltage will appear within a few seconds.
The test voltage is controlled to within 5% of nominal,
adjusting itself for changes in resistance. The actual output
voltage is displayed during tests. On large capacitive items
the voltage rise will be noticeably slower and on low
resistances (less than 10 MΩ) the voltage may never rise to
its nominal value.
8. Insulation resistance readings are updated once every
second for measurements up to about 100 MΩ. For
measurements between 1 GΩ and infinity the sample
frequency rate will slow to 15 seconds.
9. A test can be manually aborted at any time by pressing the
red test button. A test will automatically terminate if:
- The set test duration is reached.
- The insulation under test suffers a complete breakdown.
- Excessive electrical noise interference (>2 mA at 5 kV).
- The battery becomes exhausted
- Fuse FS2 ruptures.
- An internal fault occurs.
When the test is terminated the item under test will be
automatically discharged.
10. To switch the instrument Off, press the On/Off button once.
Auto switch-off operates after 10 minutes inactivity in 'R' 'I'
and 'Burn' modes, and after 30 minutes inactivity in 'DD',
'PI' and 'SV' modes.
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