Casella CEL CEL-160 - Manual (Page 10)

is possible, therefore, to place an event within
a few seconds over a period of days and this is
achieved by employing a high stability digital
clock to provide true time prints from one
second to 10 days.
There are three methods of time
marking the paper, namely a time grid, time
markers and full time prints. Time grids are
vertical lines produced across the paper at
intervals of approximately 5 mm whilst the
time markers are short horizontal lines
produced along the top of the paper at
intervals of approximately 5 cm.
Full time prints are produced in
alphanumerical form across the paper with
their position on the Y-axis adjusted by the
software to minimise interference with the
recorded trace. All time annotations are
provided at the exact time with their positions
on the X-axis adjusted to take account of any
discrepancies in the feed rate of the chart roll.
Time annotations should therefore be used in
all measurements of time rather than taking
the total length of chart consumed. The actual
time intervals of the annotations are related to
the chart speed and full details are given in
Figure 3.
Full time prints are annotated with days,
hours, minutes and seconds as per the
following example 9D23H56M37S. Redundant
zeros are not printed. A full time print is also
made whenever the program or paper speed is
changed.
The start up time for the internal clock is
0000 and the instrument will therefore record
elapsed time from switch on. To preset the
clock to real time, key in a four figure
sequence representing the hours and minutes
on a 24 hour clock and this time may be
entered by keying C. Days and seconds will be
set to zero by this procedure. The clock may
be reset to zero simply by keying C.
The time axis annotation is modified
slightly when the instrument is operating in the
RMS expanded trace and transient capture
modes. Full details are contained in the section
of this manual dealing with these functions.
3.3.3 Frequency Axis (X)
When the instrument is in its frequency
analysis mode the X-axis annotation is changed
to frequency scale markings to suit the
associated frequency analyser. For clarity only
the octave centre frequencies are produced
but the position of each third octave is clearly
distinguished by a separation line whilst with
narrow band analysers the frequency is
determined by interpolation between the
marked points.
4. Signal Inputs
4.1 Use with CEL-2980 Preamplifier
When this preamplifier is used in conjunction
with a CEL precision measurement
microphone the CEL-160 becomes a compact
recording Sound Level Meter. Alternatively the
instrument may be used as a Vibration Meter
by adding a suitable vibration transducer to the
preamplifier. This preamplifier has been
specifically developed for use with CEL
precision measuring instruments and includes
remote gain switching arrangements that are
designed to optimise the signal to noise ratio.
The preamplifier should be connected to
the recorder preamplifier socket by means of
the CEL-3686/2 cable and it will accept the
complete range of CEL precision
measurement microphones as well as other
manufacturers' devices if they are produced to
the industry standard dimensions. The start up
state for the recorder annotations suits the
CEL-186/2 series microphones, however, if
higher or lower sensitivities (<25 mV/Pa or
>75 mV/Pa) types are used the annotations
Figure 3: Time annotation at various paper speeds
Paper speed (mm/S) 30 10 3 1 0.3 0.1 0.03 0.01
Time Grid 0.2 S 0.5 S 2 S 5 S 20 S 1 min 5 min 10 min
Time Marker 1 S 1 S 10 S 10 S 1 min 1 min 10 min 10 min
Time Print 10 S 10 S 1 min 1 min 10 min 10 min 1 hr 1 hr
Page 10 - CEL-160 Graphic Recorder