Performing Tests - General - Megger BM25 Guia Del Usuario

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
1 µF) the test voltage will appear within a few seconds. The test
voltage is controlled to within 5% of nominal, adjusting
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.
itself for
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