Casella CEL CEL-181 User Manual
Page 8
Casella USA
17 Old Nashua Road #15
Amherst, NH 03031-2839
www.casellausa.com
Page 8 of 14
tel:
(
800) 366-2966
27 Jan 2006
fax: (603) 672-8053
OVER-RUN
Should the counter exceed its total capacity it
wiII return to zero and commence counting
again. As it over-runs it will trip the over- run
indicator. This indicator will also be reset
whenever the counter is zeroed.
DISPLAY
Five digits display covering thousands through
to decimal. The last three indicators are not
used and are permanently blanked out.
RANGE
Sets the instrument's dynamic range to make
measurements over the ranges noted on the
calibration certificate.
CAL
Adjusts the instrument's calibrations. Should
only be adjusted with the tool provided in
conjunction with a CEL approved Dose Meter
Calibrator. Anti-clockwise rotation will increase
the count rate.
3.2.3 Connection of the Batteries
The permanent magnet should be first placed in
the OFF position as shown in Fig 4 thereby
ensuring that the instrument is off. Using the
alien key provided, the rear cover may now be
removed by releasing the screw and lifting away
the cover from the base and carefully clearing it
from the retaining slot in the top by the dress
clip. The battery compartment located at the top
of the instrument is now accessible and the
connector should be carefully removed taking
care not to strain the connecting wires. It is then
possible to connect the battery taking care to
maintain the correct polarity, i.e. the claw on the
connector to the stud on the battery and
vice-versa.
The battery may now be placed in its
compartment and the rear cover replaced
ensuring that the lip in the top of the cover
located in the keyway is in the case. Placing the
magnet in the ON position as shown in Fig 4 will
switch the unit on and cause the battery level
indicator to flash. This indicator will ensure that
the battery has been correctly fitted and that it
has sufficient capacity for a full eight-hour
measurement. The instrument is now ready for
service; however, it is recommended that the
overall calibration be checked by following the
procedure outlined in the next section of this
manual.
3.2.4 Calibration Checks
All CEL Noise Dose Meters are carefully
checked and calibrated in our laboratory before
dispatch in order to ensure their rigid conformity
with the exacting requirements of the
specification. The measurement procedures laid
down in the various International and National
Standards, however, call for an independent
calibration unit to check the overall performance
of the system before and after measurement
sequences in order that any possible instrument
malfunction can be eliminated from the results
obtained.
These checks may be carried out using the
CEL-182 Dose Meter Calibrator.
To calibrate the Dose Meter first insert the
microphone into the coupler provided with the
dose meter ensuring that it passes over both the
sealing rings and its face fully seats against the
rim in the base of the coupler. Then the coupler
and microphone may be inserted into the
calibration cavity of the calibrator again ensuring
that the coupler passes over the sealing rings in
the cavity and that it is located against the
shoulder in the cavity. Occasional lubrication of
the sealing rings with a little silicone grease will
facilitate the insertion and removal of the
microphone and coupler. Bleed holes are
provided to vent the calibration cavity to
atmosphere to prevent the microphone
diaphragm being damaged by over pressures as
it is inserted into or removed from the calibrator.
It is important, therefore, to ensure that these do
not become obstructed either by ingress of
foreign matter or by covering by the hands.
Having mounted the microphone in the
calibrator the Dose Meter should be set to its
High Range and then it may be switched on by
placing the magnet in the ON position. This will
cause the thousands digit to be illuminated at
first followed a few seconds later by the full
register. Check that the display is 0000.0 and
then depress the ON switch on the calibrator
and as this button is released the calibration
cycle will commence. An LED indicator on the
calibrator will be illuminated to indicate that the
calibration cycle is running and when this is
extinguished the calibrator will have delivered its
standard noise dose and the Dose Meter's
display should be checked. It is important that
the calibrator ON switch is not pressed during