Use of extension cables
The
extension
cables
are inserted
directly
into
the
input
stage
socket
of
the 2230, and
secured
by
turning
the threaded retaining ring. The Input
Stage
ZC 0020 is then
attached
to
the cable, and the
Microphone
plus
other
accessories
fastened as
described
previous-
ly. Three Cables are available: AO 0027 (3m),
AO
0028
(10m)
and AO 0029 (30m). The
effect
of
the length is shown Fig.5.6. This
arrangement
allows the
operator
to
be
close
to
the Sound Level Meter,
without
disturbing
the sound field at the
microphone
position.
3.4. CALIBRATION
Due
to
the
quality
of
the instrument,
calibration
should only be
necessary
from
time
to
time
and should
require
very
little
adjustment.
Daily
calibration
checks
may
be
done
with
the internal
reference
signal which
allows
an
electrical
calibration
of
the Sound Level
Meter
but
not
the
Microphone
and the Input
stage. Therefore,
calibration
with
the Sound Level
Calibrator
Type 4230
or
with
the
Pistonphone
Type 4220
must
be
carried
out
from
time
to
time
for
acoustic
calibration
of
the whole Sound Level Meter.
Before
any
calibration
set
REF.-
TEST
-OPERATE
to
"Test"
to
perform
a
display
check.
3.4.1. Calibration with the internal reference oscillator
1.
Set
controls
of
the Sound Level
Meter
as
follows:
POWER:
REF
.-OPERATE:
FSD:
RESET:
FREQ.
WEIGHTING:
EXT. FILTER:
SOUND INCIDENCE:
DISPLAY:
TIME WEIGHTING:
DETECTOR:
"On"
"Ref."
"irrelevant"
"All"
or
"Max./Min."
irrelevant
"Out"
"Frontal"
"SPL"
"Fast"
"RMS"
2.
Read the value
of
the
correction
factor
K
0
given
in the
calibration
chart
supplied
with
the
microphone.
3.
Using a small
screwdriver
adjust
the SENS. ADJ.
potentiometer
to
obtain
a
dis-
played
value
of
94 dB + K
0
4.
Set
REF-OPERATE
to
"Operate",
ready
for
measurements.
3.4.2. Calibration with the Sound Level Calibrator Type 4230
14
The
Type
4230
produces
a
nominal
sound
pressure
level
of
94 dB ± 0,3
dB
(re.
20 x 1
o-
6
Pa). The
calibration
procedure
is as
follows:
1.
Remove
the
Windscreen
if
fitted.
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