AVO AVOMETER 8 Betriebsanleitung - Seite 10

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OPERATION
If
an overload is
applied
to
the
meter,
either forward or
in
reverse,
the cut-out knob springs
from its
normal
position
in
the panel,
thus
breaking
the main
circuit
and
the red
portion of
the cut-out
knob will show.
This
knob
has only
to be depressed to render the
instrument
again
ready
for
use. It
is
important to note that the
cut-out
should
never
be
reset
when
the instrument
is connected to an external
circuit, whilst
the
fault which has caused
the
overload
should
be rectified before the meter
is
reconnected.
Although
the overload
mechanism
gives
almost complete
protection to the meter,
it
cannot
be guaranteed to
com-
pletely fulfil
its
function
in
the
very
worst
cases of misuse,
such as
the mains being
connected
across the
meter
when
set
to
a current
range.
It
should be
noted that mechanical
shock
to the instrument will sometimes
trip
the cut-out
mechanism.
Additional protection is provided on resistance
ranges
by
a fuse connected in the nx 1 and
i1x1
00
ranges.
WARNING Special
care
must be taken
when using
the
instrument
to service television receivers or
other apparatus
employing capacitors
of large capacitance,
for
the
inclu-
sion of such components in a circuit may mean that very
heavy peak currents may flow when the apparatus is
switched on. Such surges produce
a peaky
wave form and
although these peaks are only of a few milli-seconds
duration, they may,
never-
the-less, damage the Instru-
ment diodes.
8
EHT MEASUREMENT
CAUTION: It is
recommended
that neither
the
meter.
multiplier nor leads
are
handled whilst
high
voltage
tests
are in
progress.
Using the Combined 10kV/30kV Multiplier
A combined
1 OkV
and 30kV de
multiplier
is available for
use with the
instrument
.The Multiplier should be
connected
to the AVO METER set to the 1 OV
de
range. It is recommend-
ed that
the meter is
kept as near
earth potential
as possible
and the Multiplier used at the high
potential
end. e.g.
when measuring
an e.h.t.
voltage
when the negative
line
is
earthy, the Multiplier should be
connected between
the
point
of
positive potential
and
the positive terminal of the
meter. In
addition,
the low potential end of the meter must
be connected to
the
low potential
of
the supply being
measured using the low potential lead provided. A
cap
is
provided which should always be
in
position over the high
voltage
terminal not
in
use.
A resistor connected
permanently across the multiplier
terminals prevents the full
voltage being
present
should
the
meter be disconnected.
General
Note:
When
measuring high ac and de voltages
(say
above
SOOV) unless
th
e common
negative terminal is
either
earthy or connected
to earth,
errors will
be
intro-
duced if the instrument is
touched
during a
reading.