Casella CEL CEL-272 User Manual

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Reduce the Artwork to 95%

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CEL-272 PERSONAL SOUND EXPOSURE METER

Instructions

September 1990

PP60111

Issue: 2

for

archive Document

Discontinued Instrument

The CEL-272 Personal Sound Exposure Meter is
a totally new instrument designed to fulfill the
measurement requirements of the United Kingdom
"Noise at Work Regulations" 1989, and the re­cently introduced ISO 1999: 1990 "Determination
of Occupational Noise Exposure and Estimation of
Noise Induced Hearing Impairment" which stipu­late standard methods for measuring personal
sound exposure.

The CEL-272 complies with Draft IEC Document
TC 29/WG 4, and substantially meets the require­ments of BS 6402 for Personal Noise Dose Me­ters. Where relevant, the performance of the
instrument also satisfies IEC 804 for integrating av­eraging sound level meters.

Recent European noise exposure legislation men­tions three action levels. At levels below the 1st ac-

tion level (1.0 Pa
hours) "reasonably practicable" noise reductions
should be made. Between the 1st and 2nd action
level (3.2 Pa
sessments must be made, records kept, details
given to employees, and hearing protection issued
to those who ask for it. Above the 2nd and also at
or above the peak action level (200 Pa - 140 dB
for any period), hearing protection measures must
be enforced by the employer.

The Personal Sound Exposure Meter is a mini­ature instrument intended to be worn by an individ­ual so that its microphone is subjected to as nearly
as possible the same sound exposure as the
wearer. It can be switched to give a reading in
either Pa
exposure or % noise
dose (see box).

2

h - equivalent to 85 dB(A) for 8

2

h - 90 dB(A) for 8 hours) noise as-

2

h sound

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DESCRIPTION

The instrument uses a1/4" electret microphone
capsule installed in an energy absorbing housing
that can be mounted close to the wearer's ear us­ing the clip supplied. The microphone is connected
to the instrument by means of a slender integral ca­ble 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 com­plies with the requirements of IEC 651. The output
from the weighting circuit is squared and inte­grated over time to produce sound exposure val­ues in either Pa
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

1

/2digit display also carries an indication of which

4
parameter is being measured and whether the bat­tery voltage has fallen below 4 V.

In addition, when a signal greater than the 200 Pa
peak action level occurs, colons flash on the dis­play 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 dis­play as an indication. These are latching functions
that can be cleared only by resetting the instru­ment.

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.

2

h or % Dose units. In the

CEL-272 Personal Sound Exposure Meter

CEL-6048 Microphone Coupler (for calibration),
PP16022 Type AAA Manganese Alkaline

PP38524 1.5mm Allen Key,
PP38054 Trimtool,
PP60111 Instructions.

The following accessories can be ordered sepa­rately for calibrating the instrument.

CEL-282 Acoustic Calibrator Class 2,
CEL-284/2AcousticCalibratorClass1,
CEL-6100 Dummy Microphone.

(including cable, CEL Microphone, and
Battery Holder),

Battery (4 off),

PREPARATION FOR USE

The instrument uses four type AAA Manganese
Alkaline batteries that must be inserted in the Bat­tery 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

2

h or % Dose.

Pa

7. Replace batteries when Lo Bat is indicated.

SCHEDULE OF PARTS

A complete "CEL-272 Personal Sound Exposure
Meter" consists of the following items.

8. Replace the cover and if required, refasten the
screw.

The instrument is now ready for service.

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Parameter
Indicators

LO BAT

%DOSE

2

Pa h

Overload
Colons

Autoranging
Decimal Point

900044

2

Pa h

Batt Off

+

%

+

Adj

Display

C
A
L

+

+

On

Off