Casella CEL CEL-283 User Manual
Page 5
Casella USA
17 Old Nashua Road #15
Amherst, NH 03031-2839
www.casellausa.com
Page 5 of 6
tel:
(
800) 366-2966
OL
This is the overload indicator and it is illuminated
if the instrument is indicating an incorrect
answer due to overloading of its circuits. When
this occurs the measurement must be repeated
on a higher range. The indicator is illuminated
during an actual overload. When an overload
occurs, an overload latch is set that causes the
overload indicator to be illuminated when the
instrument is in the LEQ mode, and this
indicates to the operator that the instrument has
been overloaded during the current
measurement sequence. The overload latch is
reset by the general reset function (see
MAX/SPL/LEQ (Reset).
OUTPUT SOCKET
This 3.5mm miniature jack socket provides a
feed of the conditioned AC output to ancillary
instrumentation such as tape recorders,
frequency analysers, etc.
Technical Description
The instrument covers the range of sound levels
from 30-120dB(A) in three measurement ranges
and has both fast and slow meter
characteristics. In addition it is provided with the
impulse time constant to facilitate the subjective
assessment of transient sounds as well as a
maximum hold circuit that is operational in
conjunction with all three time constants. For
broad band measurements the standard 'A: and
Flat (Linear) frequency weightings are provided.
The instrument employs a high sensitivity
electret condenser microphone that has a
proven record of calibration stability in respect of
both its amplitude and frequency responses.
Signals are fed through the preamplifier stages
and onto the calibrated range changing
attenuators and the frequency conditioning
circuits. After additional amplification the signals
are processed by a new design of wide dynamic
range RMS detector. This provides a logarithmic
output over a 40dB dynamic range enabling a
clear indication of the sound level on a linear
scaled meter. The wide dynamic range that this
arrangement permits considerably improves the
interpretation of the results as it eliminates the
need for continual range changing that is
necessary when the older style of instrument
having a logarithmic scale is used. When the
maximum hold mode is selected the RMS signal
is fed to an analogue hold that is then connected
to the meter via a buffer amplifier. For the LEQ
result the RMS level is sampled every 10msec
and this result is antilogged and fed to a digital
integrator. This is then sampled every 300msec
with the result being divided by time and the
answer logged to give a result in dB for display
on the meter. The instrument is powered by two
standard 9V batteries and is housed within a
pressed aluminium case that is contoured to
provide the correct acoustic characteristics.
Manufacturer's Servicing And Warranty
Arrangements
Each instrument has been carefully inspected
and calibrated prior to dispatch from our factory
in order to ensure its rigid conformity with the
requirements of our specification. All technical
information relating to individual instruments is
filed under the instrument's serial number. It is
important, therefore, to always quote this
number in any correspondence with the
manufacturers. The serial number is located on
the back of the instrument. The manufacturers
undertake to rectify any defect in the instrument
that is directly attributable to faulty design or
assembly and which becomes apparent during
the first twelve months from the date of the initial
calibration.
Many of the specialized components used in the
instrument are subject to separate warranties by
their actual manufacturers and in all cases
benefit of these undertakings will be passed
onto the end user. However, Computer
Engineering's (CEL’s) liability is limited to items
of their own manufacture and they do not accept
liability for any loss resulting from the operation
or interpretation of the results from this
equipment. In the event of a malfunction
developing the instrument should be carefully
packed and returned to either the
manufacturer's agent in the territory or, in the
case of domestic sales, to our Hitchin factory
along with a detailed description of the fault. The
necessary repairs will be undertaken and the
instrument returned as soon as possible. After
the warranty has expired, except on approved
accounts, service work is undertaken against
quotation and all packing and transit costs are
charged extra. In the case of sales in the UK,
service contracts are available for the
instruments and full details of these are
available on request.
23 Dec 2005
fax: (603) 672-8053