Megger 8 Mk7 AVOMETER Bedienungsanleitung Seite 11

tests of resistance, a check should be made to
ensure that the instrument actually indicates zero
ohms irrespective of the condition of the battery
(within the limits of adjustment described later).
The accuracy should be within ± 5% of the
reading about centre scale, increasing up to about
±10% of the reading around deflections
corresponding to 10% and 90% of full scale.
Resistance tests should never be carried out on
components which are already carrying current.
On the three ranges which utilize the internal
source of voltage, a positive potential appears at
the black common (negative) terminal of the
instrument when set for resistance tests. The
resistance of some components varies according
to the direction of the current through them and
readings therefore depend upon the direction in
which the test voltage is applied quite apart from
its magnitude. Such cases include electrolytic
capacitors and rectifiers.
When measuring the leakage resistance of an
electrolytic capacitor, the black (negative) lead
from the instrument should be connected to the
positive terminal of the capacitor and the ohms
'x 10 k' range employed.
Before making resistance tests the pointer should
be adjusted to the resistance range zero in the
following sequence:
Set the left hand switch at Ω.
1.
2. Connect the test leads to the instrument and
join them together.
3. on the 'Ω x 1' range adjust zero by means of
the knob marked ' Ω x 1'.
4. On the 'Ω x 100' range adjust zero by means
of the knob marked 'Ω x 100'.
5. On the 'Ω x 10 k' range adjust zero by
means of the knob marked 'Ω x 10 k '.
To measure a resistance, set the right-hand switch
at the range required, the leads being connected
across the unknown component.
Resistance is read directly on the 'Ω x 1' range
but readings should be multiplied by 100 and 10
000 on the 'Ω x 100' and 'Ω x 10 k' ranges
respectively.
If on joining the leads together it is impossible to
obtain a zero ohms setting or, if the pointer will
not remain stationary but falls steadily, the
internal battery or cell concerned should be
replaced. It is important that an exhausted battery
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