Marconi TF 933C - Page 12

NOTE : The 'tens'
dial (left-hand BALANCE knob)
should not be
on
the 0
or
positions when
setting
zero. As these
are
the most
sensitive
ranges,
traces of
leakage due to atmospheric humidity
and effect
of
electro—
static
induction may cause the reading to be
a
little
unsteady.
Switch
to any
range other than
0 or I
to
set
zero.
Switch
position
ZERO
is
the
'stand-by' position
during a
series
of measurements.
Read
The
accuracy
of
the
instrument
may
be checked against the internal
standard
resistance
if
required
- see Sect. 4.2.
(1) Having
filled the
cell,
switch to
READ.
(2)
Set the
units dial
(the
right—hand
BALANCE knob) to
approximately
O.
(3)
Rotate
the
tens dial
(the left—hand
BALANCE
knob)
until
the pointer
crosses the
centre line
on
the
meter.
(4)
Adjust
the
units dial
to bring
the
pointer
to the line.
If
the
reading
is
on the
ægative
part
of
the
dial
move
the tens
dial
one
step
counter—clockwise
(unless
it is
already
at 0)
and
rebalance.
The
negative
section
of the
dial should
never be
used
if a
reading
can
be
obtained
on the
positive
section.
The
figures appearing
against
the dial
index
marks
constitute
the dial
reading.
Except for
readings
above
50, little
is
gained
by
recording
the figure
more
closely
than
half
a
unit.
For
readings
between
50 and
60
the
figure
should
be
determined
to
oæ
tenth
of
a unit.
NOTE
:
With
very
low
moisture
content
(i.e.
0 or 1 positions
of
the
'tens'
dial)
the
reading
may
be
a little
unsteady
due to
electrostatic
effects.
Convert
to
moisture
content
Sliding
scales
Transpose
the
readings
obtained
on
the
knob
dials
to the
fixed
black
scale.
Read
the
actual
moisture
content
on
the
sliding
red
scale
opposite
the
point
on
the
fixed
black
scale,
Paper
charts
If
no
scale
is
available
for
the
substance
under
test,
convert
the
dial
reading
to
moisture
content
by
means
of
the
calibration
data
sheet.
NOTE:
Switch
OFF
when
measurements
are
completed
in
order
to
conserve
power.
12
9'3ac
(la)