RECORDING MODE
WRITING
SPEED/
LF
LIMIT
PAPER DRIVE
PEN
DRIVE
POWER
on signal averaging
times,
and consult
the
Level
Recorder
Instruction
Manual
Select
according
to
the
information
given in the
Measuring
Amplifier
or
Level Recorder
Instruction
Manual;
a
brief
sum
-
mary
is given in Table 3.1
See sections
4.2
and 4 .3 on signal averaging
times
and
the
Level Recorder
Instruction
Manual
"Off"
"On"
"On"
5. If AC
or
DC
logarithmic
recordings are
to
be made, calibrate as
follows
:
turn
up the
Level Recorder
SENSITIVITY
to
position
the
pen on
the
chart
paper 4
dB
above a
thick
graduation
line. The pen
movement
is
now
calibrated
to
follow
the
meter
nee-
dle
accurately
,
with
one dB on
the
paper
representing
one dB
on
the
meter
scale.
6.
If
DC
linear
recordings are required,
the
calibration
procedure is
slightly
different
.
Adjust
the
Level Recorder as in 4 above (reversing
polarity
when
the Type
2606
with
negative
output
is used).
Turning
the
DC
LIN POSITION
potentiometer,
position
the
pen on
the
bottom
line
of
the
chart
paper.
Turn
up
the
SENSITIVITY potentiome-
ter
until
the
pen moves up
the
paper
to
the
centre
of
the
chart
(25
dB
/
12,5
dB). The
pen
movement
is
now
calibrated
to
follow
the
meter
needle accurately,
with
chart
graduations
proportional
to
the
voltage scale on
the
meter
.
7 . Release
the
REF
50
mV
RMS.
8. Synchronize
the
paper
transport
with
filter
switching
in
the
following
way
.
9. Set
the
Level Recorder
controls
:
PEN
DRIVE
"Off"
PAPER DRIVE
"On"
10
. On
the
Band Pass Filter push
the
right
-hand FILTER CONTROL MODE
switch
to
"Run",
and
let
the
paper drive
forward
until
it
stops and
the
1/ 3 octave
FILTER
SHIFT
lamp
on
the
Level Recorder
lights
.
The
lit
lamp
means
that
the
Recorder is stopped exactly
at
the
point
where
a
switch-
ing pulse
will
be sent
out,
i.e. a position
equivalent
to
the
changeover
between
two
filters
. This exact
starting
point
is lost
if
the
PAPER DRIVE
button
is
released.
11
. To synchronize
the
paper position
for
1/ 3-octave stepping,
push
the pen up to the
top
of
the
paper
chart
by hand. Using
the
HANDWHEEL, advance the paper
until
the
pen is exactly
half-way
between
the
black square
denoting
the
centre
of
the
third-oc-
tave band
in
which
the
scan is
to
start,
and
the
square
for
the
next
lower
band. The
paper is
now
correctly positioned.
12.
To synchronize
for
1/ 1-octave stepping,
the
paper
should
be adjusted so
that
the
pen is positioned 1/ 3 octave
earlier,
i.e. one and a
half
1/ 3 octaves
(7,5
mm) be-
fore
the
square
denoting
the
centre
of
the
octave band in
which
the
scan is to start.
19
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