Testing Procedures; Battery - Megger BM11D Manual Del Usuario

Operation

TESTING PROCEDURES

When not testing, i.e. when in standby mode, the instrument acts
as a voltmeter.
1. Select the required test voltage with the selector keys.
2. To start a test, press the red test button for more than one
second. The HV warning LED on the front of the instrument
flashes, together with the display HV warning symbols.
When testing resistive or moderately capacitive loads (up to
about 1 µF) the test voltage will appear within a few seconds.
On large capacitive items the voltage rise will be noticeably
slower and on low resistance (less than 10 MΩ) the voltage may
never rise to its nominal value.
Insulation resistance readings are updated once every second for
readings up to about 100 MΩ. For readings between 1 GΩ and
infinity the sample rate will slow down to once every 20 seconds.
Changing the voltage during a test will upset the reading
temporarily. The correct reading will appear when the new
voltage has been stable over a full sample period.
3. When the test is terminated the item under test will be
automatically discharged. The test can be stopped manually
by pressing the red test button. The test will be stopped
automatically if the test duration is reached, the instrument is
turned off, an internal error occurs, a fuse blows or if
excessive noise is detected (except in Burn mode on the
BM21). When the test has stopped the final reading will be
held on the digital display.
4. (BM21 only) Pressing either of the selector keys will change
the display to show the capacitance of the item under test.
N.B. The capacitance reading is only available if the test has
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run for more than one minute, and provided the reading was
not over-range.
Reading Limitations
The BM11/D can measure currents down to 10 nA. The
highest digital readings obtainable are therefore 50 GΩ at
500 V but rising to 500 GΩ at 5000 V. The analogue display
works at all voltages up to 1 TΩ.
The BM21 is considerably better at the high end of the scale.
The highest digital readings obtainable are 500 GΩ at 500 V
and 5 TΩ at 5000 V. It is possible to read even higher
resistances by switching from 'R' to 'I' mode (using the right
Range keys). The digital display then shows leakage current,
resolving to 0.01 nA. Using this method it is theoretically
possible to measure resistance up to 500 TΩ at 5000 V but it
will be necessary to perform an open circuit calibration test to
establish measurement circuit offset current and test lead
leakage. (This is ±0,2 nA at normal temperatures with new,
clean test leads). Note that if the variable voltage has been
selected, the decision to read 'R' or 'I'' must be made before the
test is started.

BATTERY

The instrument is powered by two rechargeable, sealed, lead-
acid batteries. The state of charge is indicated by the battery
symbol on the display. It is not possible to over charge or over
discharge the batteries. When the last battery segment flashes
there is very little energy left, probably less than 1 hour of
testing. Turning the instrument off completely between tests will
conserve the remaining battery energy. When batteries are
completely exhausted the battery symbol will flash and the
instrument will switch off. For maximum reliability, try to keep
the batteries in a fully charged state and do not charge at
extreme ambient temperatures. The batteries normally last