Casella CEL CEL-414 - Manual (Page 38)

FL (Linear plus filter) or
FA (A-weighted plus
filter) if a filter is to be
used, and set the filter
to 1kHz,
80-50-20 80 (High range)
(Hi-Med-Lo on
CEL-493/3 to Med).
5. If an external CEL filter set is used,
set its controls as follows:
RANGE High,
WEIGHTING Octave or 1 ⁄ 3 Oct as
required.
6. If not switched on, switch all the
equipment ON, and give it sufficient
time to stabilize at the specified
accuracy.
7. Use the FUNCTION buttons on the
sound level meter to select SPL
measurement mode.
8. Use the push buttons on any external
filter set to select the 1 kHz band.
9. Set the tape recorder to replay mode.
10. Replay the recorded 114 dB cali-
bration signal.
11. Adjust the tape recorder replay level
control so that the sound level
meter display indicates 114 dB.
The system is now calibrated to
replay at accurately determined
levels.
12. Adjust the A-L-FA-FL/A-C-FA-FL
switch on the sound level meter
(and the frequency on the filter set)
to the settings required for the
particular replay task.
13. Replay the recorded material, and
perform any measurements or
analysis required.
14. If the tape recording was made with
the settings given in Section 7.4.1,
steps 11 or 13, the levels indicated
on the sound level meter display will
be correct.
15. If the recording was made with the
settings given in Section 7.4.1, step
14, then 30 dB (or 60 dB) must be
subtracted from the values indicated
by the sound level meter to obtain
the true level.
7.5Graphic Level Recorders
CEL sound level meters can be con-
nected to a graphic level recorder so that
measured sound or vibration levels can
be plotted against time, and if a suitable
filter is connected as described in Section
7.1, the recorder can be used to plot level
against frequency. Some recorders, such
as the CEL-160, are also able to record
the actual signal waveform.
Connection with the level recorder is ac-
complished via the sound level meter aux-
iliary socket. The auxiliary sockets of CEL
filter sets have similar pin identities, so
that the same connecting cables can also
be used with them.
Conventional graphic recorders can be
connected to pin 13, which yields a loga-
rithmic DC signal not exceeding 5 V at ap-
proximately 48 mV/indicated dB.
However some high speed chart re-
corders designed particularly for acoustic
applications require an AC input. They
should be connected to pin 4 to receive a
broadband (unfiltered) AC signal.
Page 34 - General CEL Sound Level Meters Handbook