Casella CEL CEL-160 - Manual (Page 6)

provided for cleaning the comb. This
procedure needs to be undertaken with care to
ensure that the pins are not damaged and
should always be brushed towards the ends.
With extended use the writing comb will
eventually wear and will need replacing. These
are available under the part number CEL-3842
and are fitted in the following manner.
First the knobs must be removed from
the 'Gain-Cal' and 'dB-Range' controls. This is
achieved by removing their top covers and
releasing the locking collars with a split
screwdriver. It is then possible to remove the
escutcheon plate and some care is needed
here to ensure that it is not bent. It is held in
place by 'low tack' adhesive and the best
approach is to open the chart compartment
and ease away the area around this with a flat
bladed knife. It is easily freed to the left edge
and it is then possible to free it down and
towards the right.
Having removed the escutcheon plate
take care that dust does not settle on the
adhesive face or it can not be refixed. The
paper tear bar (transparent plastic) may now be
pulled out of its locating slots and the two
screws that secure the comb carrier may now
be released (black plastic). These screws are
visible through the two cutouts in the
instruments top plate, a captive or magnetic
screwdriver is recommended to ensure they
are not lost inside the instrument.
Either end of the comb carrier should
then be held and pulled upwards to release the
comb assembly from its 100-way connector.
The comb (light blue plastic) may then be
unclipped from its carrier and the replacement
fitted by reversing this procedure. New combs
will require to be 'run in' for a short period
before an even burn is obtained, this is best
achieved by running the unit at 10 mm/S in the
AC mode with a full scale deflection input for
about 5 minutes.
3. Shortform Instructions
These instruments are, by definition, complex
devices and it is not, therefore, possible to
give definitive shortform instructions.
However, those who are familair with
advanced acoustic and digital instrumentation
will be able to gain an appreciation of the
operation of the instrument from the
description of the functions of the various
controls and indicators given in the following
section.
3.1 Controls and Indicators
The functions of the various controls are
described below. They are identified by the
legend that appears on the instrument's panel
and may be located by working from left to
right starting with the bottom row.
Power. on-off
This is the main power switch and controls the
instrument on both mains and battery
operation. When in the ON position the
instrument carries out its selected function
whilst in the OFF setting no power is drawn
and no functions are carried out, apart from
battery charging.
Cont. on-off
This switch controls the power supplies to the
paper transport and writing systems. In the
OFF position all the measurement and
processing functions are operational but paper
transport is inhibited, this arrangement allows
for the correct setting up of a measurement
system without wasting chart paper.
Exp. trace. on-off-option
(Not fitted in Program Level 1 versions)
In the expanded trace setting, the instrument
operates in either the expanded trace or
transient capture modes depending on the
setting of the AC-RMS-DC switch. The
OPTION position selects one of the customer
specified options that may be programmed
into the instrument, where an option is
provided its functions are fully detailed in the
section at the end of this manual.
Dynamic Range. 10-20-50
Sets the dynamic range of the print-out in dB.
It is only operational in the RMS mode.
Range (dB)
Sets the full scale deflection value of the trace
when the instrument is operating in the sound
level mode with the CEL-2980 preamplifier. It
also controls the sensitivity of the auxiliary AC
input but over a narrower range, reference
should be made to Section 4.3 of this manual.
Gain-CAL
This is a continuously variable analogue control
that sets the gain of the DC amplifier, and it is
Page 6 - CEL-160 Graphic Recorder