Casella CEL CEL-160 - Manual (Page 7)

in series with the main attenuator switch
described above. When the instrument is
being used in the AC or RMS modes it should
be set to the CAL position. In the DC mode it
will set the sensitivity in terms of mV/dB and in
this mode of operation the main attenuator
switch (RANGE dB) is not in circuit.
S.L.M. Gain
This control is also in series with the main
attenuator switch and is used to trim the gain
of the AC amplifiers to take account of
differing microphone sensitivities. Full
description is given in the sections dealing
with sound level meter calibration (4.1).
Batt.
The voltage of the internal batteries are
indicated by this meter. As long as it remains
within the scale banded green there is
sufficient power to operate the instrument to
specification.
Contrast
The burn voltage to the writing comb is set by
this control and it can therefor be used to take
out any slight variation in the print contrast
obtained between different batches of
recording paper.
Paper Feed
Feeding of blank paper through the writing
comb is achieved by depressing this button.
10S-10mS
This control sets the averaging time of the
RMS detector and is only operational in the
RMS mode. The fast and slow settings provide
the standardised time constants of 125 mS
and 1 S respectively as defined in the sound
level meter standards.
Lin-Log
The output of the RMS detector is selected as
being either linear in terms of dB (log mode) or
mV (lin mode) and again this control only
operates in the RMS mode.
A.C.-RMS-D.C.
In the AC mode the input signal is fed direct to
the writing head hence allowing the
instrument to operate in the waveform mode.
The RMS setting sends the signal via the RMS
detector to provide operation in the level mode
whilst a similar mode of operation is provided
in the DC setting for DC input signals only. It
must be remembered that in the DC mode the
input must be in terms of mV/dB (i.e. voltage
linear in dB) for correctly scaled results.
Lin-A-Filter (or Flat-A-Filter)
This control routes the AC input signals either
direct to the input amplifier, via the
standardised A weighting filter or diverts the
signal via the filter IN and OUT sockets on the
side panel. In this later mode the instrument
may be used with the CEL-196 Automatic
Third Octave Analyser to provide fully
annotated frequency plots.
Signal +/-
When operating in the DC mode this control
allows for the polarity of an input signal to be
set either -ve or +ve going. 0 V is taken as
0 dB on the 50 dB dynamic range setting.
When the 10 dB or 20 dB dynamic range is
selected in the DC mode it must be noted that
the scale is expanded from full scale deflection
downwards.
Key Pad
This is used for inputting all the main
operational instructions to the instrument.
Each main function is designated one of the
letter codes and this should be preceded by a
number code specifying the exact require-
ment. The main codes are summarised below.
A Sampling rates for transient capture mode
(not operational on Program Level 1 version)
0 = 36 µS, 1 = 108 µS, 2 = 360 µS, 3 = 1080 µS,
4 = 3600 µS.
eg for 108 µS sample rate, key 1A. Start up
state 0A.
A second entry of 5 through to 9A will select
the block length for the data sample. See
section 7.2 and Fig 8.
B Paper Speed
0 = one step up in speed 1 = 30 mm/S
2 = 10 mm/S 3 = 3 mm/S
4 = 1 mm/S 5 = 0.3 mm/S
6 = 0.1 mm/S 7 = 0.03 mm/S
8 = 0.01 mm/S 9 = one step down in speed
eg for 10 mm/s, key 2B. Start up state 3B.
C Clock Setting
The clock automatically comes on at zero time
but may be set to real time by keying in the
actual time required on a 24 hour clock
CEL-160 Graphic Recorder - Page 7