Three-Lead Measurement - Sonel MIC-2501 Operating Manual

Additional information displayed by the meter
NOISE!
READY disappears, LED
lights red, two-tone beep
LIMIT I!
, R
ISO
blinking in red and two-
tone acoustic signal is
generated

4.1.2 Three-lead measurement

In order to eliminate the influence of surface resistance in transformers, cables, etc. the three-
lead measurement is used. For example:

at the measurement of inter-winding resistance of a transformer, G socket of the meter should be
connected to the transformer tank;
Test voltage is present on terminals of the meter.
Interference voltage higher than 25V but lower than 50V, is present
on the tested object. Measurement is possible but may be bur-
dened with additional uncertainty.
Interference voltage higher than 50 V, is present on the tested ob-
ject. The measurement is blocked.
Activation of current limit. The symbol displayed is accompanied by
a continuous beep.
Breakdown of the tested object insulation, the measurement is in-
terrupted. The message appears after displaying LIMIT I! for 20 s
during the measurement, when the voltage previously reached the
nominal value.
LED is During the measurement, AC voltage appeared or the object can-
not be discharged for 30 seconds. Immediately disconnect the test
leads.
OPERATING MANUAL MIC-2501 version 1.04 13