Casella CEL CEL-283 User Manual
Page 4
Casella USA
17 Old Nashua Road #15
Amherst, NH 03031-2839
www.casellausa.com
Page 4 of 6
tel:
(
800) 366-2966
Controls and Indicators
On front panel
OFF/BATT/ON
In the OFF position no functions are performed
and the instrument draws no power. In the
BATTERY position the meter indicates the on
load voltage of the lower of the two batteries
with the end of useful battery life shown as the
lower mark on the scale; hence, when end of life
is indicated both batteries must be changed.
When in the ON position the instrument carries
out its selected functions.
MAX/SPL/LEQ (RESET)
In the SPL position the instrument will display
the current sound pressure level in accordance
with the settings of the other controls. When the
MAX mode is selected the meter display will lack
onto the highest RMS level that occurs during
the measurement sequence. In order to cancel
the maximum hold store a general reset should
be applied and this is achieved by switching the
instrument from the MAX to the SPL position. In
the LEQ mode the meter will display the
accumulated average result from the time of the
last general reset. The meter will be seen,
therefore, to update each time a new answer is
calculated and added to the cumulative result.
Average results are, therefore, available over
any time period from 1 second to 24 hours and
are not limited to fixed time periods. To reset the
LEQ calculation and the overload latch the
instrument should be switched into the
maximum hold mode and returned to the SPL
position. A new LEQ measurement will
commence as the instrument enters the SPL
mode from MAX. The instrument may, therefore,
be switched between SPL and LEQ modes
without resetting the accumulated LEQ. The
LEQ-Tm switches that are located in tire battery
compartment will determine the actual operating
conditions of the average mode. Results on the
fast and slow time constant settings will be LEQ
(Lm) as per the conventional definitions (BSI,
ISO, etc) whilst the average will be impulse
weighted if the impulse time constant is selected
(see following section).
SLOW/FAST/IMP
This switch selects the time constants employed
in the RMS detector and these are as defined in
the International Standards - 125msec for FAST
and 1 second for SLOW, The IMPULSE
response provides a 35msec time constant for
rising edges and 1.5 seconds for falling ones.
FLAT/A
The standardised 'A’ weighting is provided in the
'A’ position of this switch giving results in dB(A).
In the FLAT position the unweighted microphone
signal is passed to the display giving results in
dB(Flat/Lin).
90/60/30
This control selects the measurement range by
setting the meter scale zero to the value
selected; hence, the answer is given by reading
the appropriate scale on the switch plus the
meter. Measurement ranges provided are,
therefore, 30-70, 60-100 and 90-130. It must be
remembered, however, that on the top range the
RMS levels are within specification over a span
90-120 whilst the additional 10dB is provided for
the maximum hold function. This results from the
use of a high sensitivity microphone to enable
measurements to be made at 30dB(A) and it
will, therefore, saturate at 135dB(A).
In Battery compartment
3S-5S LTm
These are located in the battery compartment
and they set the operating conditions of the
integrating mode. When in the LEO position
conventional LEO results are obtained as per
British and International regulations. Selecting
the TM position on the right-hand switch will
amplitude weight the average result in
accordance with DIN and VDI requirements for
LTm measurements. The left hand switch
selects the 3 and 5-second periods required by
these measurements. When in this mode of
operation the results will be seen to up-date at
the end of each 'takt'. The alternative method of
amplitude weighting the results referred to in
West German regulations, LAlm, may be
accommodated by setting the right-hand switch
to LEQ and the time constant switch to impulse.
23 Dec 2005
fax: (603) 672-8053