Casella CEL CEL-193 User Manual
Page 7
Casella USA
17 Old Nashua Rd #15
Amherst, NH 03031 USA
however, a trigger is set when the first overload occurs which will cause the lamp to be permanently on
when the Le
q
or MAX answers are selected. It maybe reset by pressing the RESET button.
(j) PAUSE
Stops the instrument taking samples and from logging time data so that unwanted signals may be
prevented from entering the Leq calculation. It also inhibits the updating of the stored maximum value but
does not affect the operation in the SPL mode.
(k) CALIBRATION ADJUSTMENT
This control is located in the aperture on the back of the nose cone and is used for the trimming of the
amplifier's sensitivity in order to take account of any shift in calibration, due to climatic conditions, etc. It
should only be adjusted in conjunction with the CEL-177 or other suitable Precision Acoustic Calibrator.
(i) +30dB
To enable a clear indication to be obtained, the instrument's display range is split into two 30dB spans.
Normally the lower 30dB is on scale. When this control is depressed, the upper 30dB is available, and
hence, when it is activated, 30 must be added to the displayed result to give the correct answer.
2.3 Calibration Procedure
Each instrument is carefully calibrated and inspected at our factory prior to despatch. However, in line with
accepted instrument practice the instrument should be checked from time to time. For this purpose the CEL-
177 Precision Acoustic Calibrator should be used. The microphone coupler type B2835 provided with the
calibrator should be placed over the microphone ensuring that the microphone is correctly seated against
the shoulders at the base of the cavity and then the calibrator should be placed over the coupler again
ensuring that the coupler is correctly seated in the calibration cavity.
(NB To facilitate removal of the coupler
from the calibration cavity it is not designed to fit flush to the face of the outside rim of the calibrator.) Both
the calibrator and the sound level meter should be switched ON and the latter set to the 90dB range, 'A'
weighted response and FAST time constant with the SPL answer selected. The instrument takes
approximately 30 seconds to reach its nominal operating conditions after which time it should indicate the
113dB level generated by the calibrator. If the instrument calibration has changed due to environmental
conditions, etc. it may be brought back to the correct level by adjusting the sensitivity control with the
screwdriver provided. This control is accessible through the aperture in the back of the nose cone and
should be rotated clockwise to increase the reading and vice versa. The span of the single turn control is
approximately 10dB. Other calibrators such as the PF-003 or NC 72 pistonphones may be used to calibrate
the instrument; however, in such case due consideration must be given to their frequency of operation and
calibration level.
3 Using the CEL-193 as a Sound Level Meter
For general noise surveys the instrument may be handheld. However, for more precise measurements the
microphone and pre-amplifier should be mounted on CT 3 tripods and connected to the instrument via the
CEL-2942/5 Extension Cable. This will prevent errors being introduced by the presence of the instrument
operator near to the measuring point. In order to obtain a readout of sound pressure level the Leq/
SPL/MAX (b) should be set to SPL and the ATTENUATOR control (g) put to the 100 range prior to the unit
being, switched on.
The range should then be reduced until an indication is obtained an the scale. The meter has 2 x 30dB
spans and is clearly marked in 1 dB steps with the measured level being the sum of the meter indication,
Page 7 of 20
Tel: (800) 366-2966
www.casellausa.com
2 Mar 2009
Fax: (603) 672-8053