Battery Condition Indicator; Voltage Indicator; Time Indicator; The Guard Terminal - Megger MEG10-01 Guide De L'utilisateur

circuit. The led will flash until this voltage is removed or discharged.
When the battery is being charged this l.e.d. will shine green.

Battery Condition Indicator.

When the battery is fully charged all segments of the 'Battery
Condition' indicator will be illuminated. As the battery is discharged
the number of segments illuminated will decrease. The battery is
monitored continuously when the instrument is turned on.
If the battery condition becomes excessively low, the 'Battery
Condition' indicator flashes. At this point you should recharge the
battery or switch to an a.c. supply as the power source.

Voltage Indicator

In 'Test Setup' mode the 'Voltage Indicator' shows the requested test
voltage adjusted using the 'Voltage Adjust' buttons. Allowable values
are 500 V, 1000 V, 2500 V, 5000 V and 10000 V. During a test the
indicator shows the actual test voltage as measured at the instrument
terminals. At the end of a test this indicator shows the test voltage
immediately before the test terminated.
If the item under test breaks down during a test, the test voltage will
collapse. It is possible that the breakdown will then clear and the test
voltage will increase until breakdown occurs again.

Time Indicator

In 'Test Setup' mode the 'Time Indicator' shows the requested test
duration after which a test will stop automatically. This is adjusted using
the 'Time Adjust' buttons to set a time between 00 minutes 01 seconds
and 99 minutes 59 seconds. In this case, during a test the indicator will
show the elapsed time.
It is also possible to set the duration to zero (00:00) in which case the
automatic stop feature will be disabled and the test will continue until
the 'Test' button is pressed to end the test. The elapsed test time will
be displayed up to 99:59 after which the time display remains at 99:59.

The Guard Terminal

For basic insulation tests and where there is little possibility of surface
leakage affecting the measurement, it is unnecessary to use the guard
terminal i.e. if the insulator is clean and there are unlikely to be any
adverse current paths. However in cable testing, there may be surface
leakage paths across the insulation between the bare cable and the
external sheathing due to the presence of moisture or dirt. Where it is
required to remove the effect of this leakage, particularly at high testing
voltages, a bare wire may be bound tightly around the insulation and
connected via the third test lead to the guard terminal 'G'.
The guard terminal is at the same potential as the negative terminal.
Since the leakage resistance is effectively in parallel with the resistance
to be measured, the use of the guard causes the current flowing through
surface leakage to be diverted from the measuring circuit. The
instrument therefore reads the leakage of the insulator, ignoring leakage
across its surface.
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