AVO AVOMETER 8 Instrukcja obsługi - Strona 7
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OPERATION
On
three
ranges which utilise the internal source of voltage,
a positive
potential
appears at the
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
elec-
trolytic capacitors and rectifiers.
When
measuring the
leakage resistance
of an electrolytic
capacitor, the
negative
lead from the meter should
be con-
nected
to the
positive
terminal
of the capacitor and
the ohms
x
1 Ok range
employed.
Before
making resistance
tests the
pointer
should
be
adjusted
to
zero in
the
following
sequence
:
1.
Set
the left
hand
switch at n.
2.
Join the leads
together.
3.
On
the
n x 1
range
adjust zero by means of
the
knob
marked n x
1.
4.
On
the
n x
100 range
adjust zero by means of the knob
marked n x 1 00.
5.
On the n x 1 Ok range adjust zero by means of the knob
marked n
X
1 Ok.
To test 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 n x
1 range
but readings
should
be multiplied by
1
00 and 10,000 on
then
x 100 and
n
x 1
Ok ranges respectively .
If on
joining
the
leads
together
it is impossible to obtain
zero
ohms setting, or if the pointer position
will not re-
main
constant, but falls steadily, the internal
battery or
cell concerned
should be
replaced.
It
is important
that a
discharged
unit should not be left
in
the instrument,
since
it might
cause
damage to the
meter.
If it
is
impossible
to
obtain readings
on
the
n
x
1 and
n x 1
00 ranges,
the 1
A
fuse
located
in
the battery
box
should
be checked.
NOTE: A 15V battery
may age
in
such a
manner
that
al-
though
it indicates a poten tial
of
15V,
its internal resistance
has
increased
so
much
t
hat some loss of
accuracy
can
occur on the
high resistance
range
(!l .x
1 Ok). If
errors
are
suspected on the
high resistancs range, remove
the
battery
and check
its
short circuit
current
on
the 1 OOmA
de
range.
If
the reading
is below
than
25mA it
should
be
discarded.
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