Test Mode Summary - AVO MEGGER BM25 Guide De L'utilisateur

Insulation Resistance Testing (R)
This mode measures insulation resistance at the selected voltage to
provide an instantaneous spot reading. Final test result is given
sequentially with the corresponding leakage current and capacitance
value.
Test Current measurement (I)
This mode measures insulation at the selected voltage to provide
an instantaneous spot reading, but displays leakage current
value on the digital display. (N.B. The analogue scale always
displays resistance). Final test result is given sequentially with the
corresponding resistance and capacitance value.
Polarization Index Testing (PI)
Polarization Index is the term applied to the Dielectric Absorption
ratio, when the insulator is subjected to an insulation resistance
test, and the resistance values are measured after time T1
(Default 1 minute) and again after time T2 (Default 10 minutes).
Polarization Index is calculated automatically from the resistance
value after time T2, divided by the resistance value after time T1.
High dielectric absorption is indicated by high PI ratio (see
'Application of test Techniques'). Final test results are given
sequentially with the corresponding leakage current and
capacitance value. The test will run at any voltage. Custom timed
'PI' values can be set if required (see 'Custom timed PI test' on
page 12).
Dielectric Discharge Testing (DD)
This mode measures the dielectric absorption of an item under
test while ignoring the effects of parallel surface leakage paths.
Default test time is 30 minutes followed by 1 minute discharge.
Final test results are given sequentially with a PI value, the

Test Mode Summary

final resistance value, and capacitance value. Custom timed DD
values can be set if required (see 'Custom timed DD test').
Step Voltage Testing (SV)
This 5 minute test depends on the principle that an ideal insulator
will produce identical resistance readings at all voltages.
Conversely, an insulator which is being over stressed will show
lower values at higher voltages. Operating at either 2,5 kV or 5
kV, the voltage steps up one fifth every minute, and successive
measurements are taken. On completion, each of the 5
separate results are sequentially displayed followed by the
capacitance value.
Fault Conditioning (Burn)
This low current feature is used to carry out continuous testing
under breakdown conditions.
General Notes:
1) A capacitance value reading is only available if the test has run
for more than one minute, and the reading was not over-range.
2) Internal discharge resistors are automatically selected :-
Any voltage remaining on the terminals at the end of a test,will
be displayed until it has decayed to less than 50 V. During a test
output terminal voltage is displayed, together with flashing high
voltage symbols, and the flashing red LED.
- At the end of a test.
- If the instrument is switched off.
- If an internal error is detected.
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