CASELLA USA
CEL-240 DIGITAL SOUND LEVEL METER
FREQUENTLY ASKED QUESTIONS
Casella USA
Page 5 of 6
(800) 366-2966
31 Jan 2008
FAQ’s: INSTRUMENT FUNCTION
What measurement ranges does the CEL-240 cover?
The
CEL-240
is equipped with two measurement ranges each covering a 70 dB dynamic span.
These ranges cover the overall levels from 30 to 100 dB on the low (Lo) range setting, and levels
from 60 to 130 on the high (Hi) range setting.
What results can be measured in a CEL-240?
The
CEL-240
will measure the following parameters during the measurement run:
The
instantaneous sound pressure level
during the run,
The maximum RMS level or
Lmax
,
The last 1 minute or 5 minutes displayed as a trend graph over the full 70 dB
range selected
What rms frequency weightings are available in the CEL-240?
Two broadband frequency weightings are provided in the
CEL-240
for the collection of the rms noise
levels – the ‘A’ and ‘C’ weightings according to the international standards defined in IEC-651 and
ANSI S1.4. Tolerances for these weightings are as specified in the type 2 classifications of these
documents. This allows the
CEL-240
to be used for measuring the NRR rating method for choosing
hearing protectors against excessively high workplace noise exposure.
What time weightings are available in the CEL-240?
The
CEL-240
is equipped with the Slow and Fast and Impulse time weightings to suit all
requirements for general-purpose noise measurements. Use the Slow time response to “dampen” the
readings to make it easier to see what is happening. Use the Fast response to more accurately follow
the changing noise levels as they rise and fall. Use the Impulse response only when the regulations
require it.
What exchange rates or Q values are available in the CEL-240?
There is no specific exchange rate available in the meters since this function is only associated with
instruments that can measure the time average noise levels. Noise levels must be visually averaged
by watching the digital display for the collection of noise dose results to satisfy the US Noise at Work
regulations as specified in the OSHA, MSHA or DoD relevant documents. For most Noise at Work
measurements for OSHA the meter should be set to the A frequency weighting and the Slow time
response on the 60 to 130 dB Hi range.
How do I calibrate the CEL-240?
The
CEL-240
has a unique easy calibration routine that simply involves fitting the acoustic calibrator
over the microphone and switching it on. The
CEL-240
will automatically detect the 1 kHz fixed level
tone and will offer the user the choice to perform the calibration or to leave it as it was and abort the
process. One push of the button on the front panel of the instrument will set the gain circuits in the
meter to match to expected level of the calibrator and the process takes about 5 seconds to
complete. No adjustments with screwdrivers or other keypad controls are required. The auto-
calibration function can be used with 114.0 and 94.0 dB acoustic calibrators that operate at the
industry standard frequency of 1 kHz. This is pre-programmed into the
CEL-240
in the configuration
menu prior to the calibration process being initiated. It remains in the meter’s memory until changed
by the user.
