AVO AVOMETER 8 Instrukcja obsługi - Strona 12
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Drukuj stronęDESIGN FEATURES
DESIGN AND CONSTRUCTION
The instrument comprises a moulded
panel
on which
are
mounted the whole of the switching apparatus,
the move-
ment and other components. A carrying strap is fixed
to
moulded lugs on the rear case. The
front panel
is
fitted
into
this
case
with
a dust proof joint.
The
switches are of
generous and robust
design,
the
contacts being arranged
to 'make' before
'break' on adjacent ranges; a feature
which
provides
a
factor
of safety in use.
When the
instrument
is
set for operation on
de the moving
coil is associated with a universal
shunt and series
multi-
pliers, whilst on
ac,
diodes
and a
transformer are also
intro-
duced.
RANGE CONTROLS
The
left-hand knob provides all the de
current
and voltage
ranges (except 3000V)
and
the right-hand
knob
the
ac
ranges (excep't 3000V)
and
also the
resistance ranges.
These
knobs are electrically interlocked so
that readings
can only be
made after ac or de measurement and range
has
been
selected.
Resistance tests
require the
left-hand
switch
to
be set ton and
the
right-hand one to the
desired
range.
The
ranges are marked on
the
panel and arrow heads
in-
dicate
the
actual
range selected. The 3000V
ac and de
ranges
are available at the two 3000V terminals.
10
Wide coverage in
resistance
has been achieved by having
a fundamental range
as marked on
the
scale, together
with ranges of x 100 and x 1 Ok to supplement
it.
In
addition a 200 megohm range marked INS is available,
using
an
external
de
voltage source (See
Page
7).
THE
MOVEMENT
The meter
movement
in the
Model
8
Mark
5
is
a robust
AVO centre pole
movement type ACP1,
fitted with
spring
mounted
jewelled
bearings
and
impregnated coil. The
meter has
a
full
scale deflection of 37.5v.A.
A knife edge
pointer
enables very fine readings to
be
taken, whilst
the
whole movement is
balanced and damped
so that the
pointer
quickly
comes to
rest.
SCALING
The
scale plate
has three main sets of markings. One
is for
resistance measurement and is marked 0 to 2000 ohms,
the
second is for current and voltage (both ac and
de)
and is
marked
0 to 10 whilst
the third
scale calibrated 0
to
3
has
60 divisions and is used
for
current and voltage
measurements.