Casella CEL CEL-272 - Manual (Page 2)

DESCRIPTION
The instrument uses a
1
/
4
" electret microphone
capsule installed in an energy absorbing housing
that can be mounted close to the wearer's ear us-
ing the clip supplied. The microphone is connected
to the instrument by means of a slender integral ca-
ble which is long enough for the instrument to be
put in a convenient pocket or clipped to the
wearer's waist-band or belt.
Signals from the microphone are amplified and
passed through an A-weighting circuit that com-
plies with the requirements of IEC 651. The output
from the weighting circuit is squared and inte-
grated over time to produce sound exposure val-
ues in either Pa
2
h or % Dose units. In the
CEL-272, 100% noise dose corresponds to a
sound level of 90 dB lasting for 8 hours - the 2nd
action level.
The readings are shown on a custom-designed
auto-ranging liquid crystal display (see figure). The
4
1
/
2
digit display also carries an indication of which
parameter is being measured and whether the bat-
tery voltage has fallen below 4 V.
In addition, when a signal greater than the 200 Pa
peak action level occurs, colons flash on the dis-
play to indicate the overload. Similarly, if too many
dose counts are recorded the store will overflow
and a reading of 2000 will be flashed on the dis-
play as an indication. These are latching functions
that can be cleared only by resetting the instru-
ment.
A pair of slide switches located beneath a lockable
tamper-proof cover change the display between
Sound Exposure or Noise Dose units. They can
also switch the instrument to calibration mode
which allows it to be calibrated by means of either
a CEL-282 Acoustic Calibrator (IEC 942 Standard
Class 2) or a CEL-284/2 Acoustic Calibrator (IEC
Class 1).
A further switch position permits the display to be
suppressed when required to provide security for
the resulting sound exposure information.
The CEL-272 microphone may be replaced by a
CEL-6100 Dummy Microphone that allows direct
electrical calibration to be performed according
to the requirements of the draft IEC Document.
Please contact Lucas CEL for precise details of the
procedure.
SCHEDULE OF PARTS
A complete "CEL-272 Personal Sound Exposure
Meter" consists of the following items.
CEL-272 Personal Sound Exposure Meter
(including cable, CEL Microphone, and
Battery Holder),
CEL-6048 Microphone Coupler (for calibration),
PP16022 Type AAA Manganese Alkaline
Battery (4 off),
PP38524 1.5mm Allen Key,
PP38054 Trimtool,
PP60111 Instructions.
The following accessories can be ordered sepa-
rately for calibrating the instrument.
CEL-282 Acoustic Calibrator Class 2,
CEL-284/2 Acoustic Calibrator Class 1,
CEL-6100 Dummy Microphone.
PREPARATION FOR USE
The instrument uses four type AAA Manganese
Alkaline batteries that must be inserted in the Bat-
tery Holder (supplied).
Zinc Carbon and rechargeable Nickel Cadmium
batteries are NOT suitable.
To load batteries proceed as follows.
1. Use the 1.5mm Allen Key (PP38524) supplied
to retract the locking screw which frees the
instrument covers.
2. Slide the lower instrument cover out of the
groove to expose the battery compartment
behind the display.
3. Remove the Battery Holder.
4. Install four batteries in the Battery Holder
according to the polarities indicated in the
figure (and in the bottom of the Holder).
5. Insert the Battery Holder into the instrument
according to the arrow mark with the arrow
uppermost as shown.
Correct connection is achieved ONLY when the
Holder is inserted with this orientation.
6. Check the batteries by sliding the Display
switch to ON and the Battery switch to either
Pa
2
h or % Dose.
7. Replace batteries when Lo Bat is indicated.
8. Replace the cover and if required, refasten the
screw.
The instrument is now ready for service.
2 Black
Register
Marks 2 CEL Blue