Casella CEL CEL-193 - Manual (Page 13)

Casella USA
17 Old Nashua Rd #15
Amherst, NH 03031 USA
10 Use with Ancillary Instruments
10.1 Use with tape recorders
Recording procedure
On the socket at the base of the CEL-193 there is a signal from the pre-amplifier that may be connected to
analogue tape recorders. This signal' is always flat (linear) irrespective of the setting of the weighting switch
and is unity gain except when the CEL-193 is on the 20dB to 40dB ranges, where it is amplified by 30dB; on
the 90dB and 100dB ranges it is attenuated by 20dB. This arrangement enables the sound level meter range
to be changed over a wide range without the need for k factors to be added to the recorded signal. If a
Uher 4000 series recorder is used the sound level meter should be connected to the tape recorder via the
cable set type CEL-3026 with the linear cable link in circuit and a 114dB calibrator, i.e. CEL-177, applied to
the microphone.
The sound level meter should first be calibrated in the normal manner and then set to the 60dB range and
then the tape recorder's ‘VU' meter set to -2dB and a short section of calibration tone recorded. This
ensures that both the sound level meter overload and tape saturation occur at the same input level and
gives the following recording ranges:
Sound Level
meter
Uher Range Recording k
Factor
20 - 40 30dB - 85dB -30
50 - 80 60dB – 115dB 0
90 - 100 60dB-135dB +20
If intermediate ranges or A weighted results are required the tape recorder should be connected to the
conditioned output (pin 4) by removing the flat (linear) link from the CEL-3026 cable set.
The signal level provided will then be a constant level for full scale deflection and the system should again
be calibrated as described above to ensure that meter overload and tape saturation occur at the same point.
Each time the attenuator is changed the range of signals recorded will also change so care is needed in
setting the instrument prior to commencing the measurement sequence. A careful note must be made of
the difference between the calibration range and the range used during the actual recording as it will be
necessary to correct the results by this amount in order to establish the correct level on replaying the tapes.
The actual recording ranges provided are as follows:
Attenuator
setting
Signal range
recorded
Recording k
Factor
20 23- 75dB(A) -40
30 26- 85dB(A) -30
40 35- 95dB(A) -20
50 45-105dB(A) -10
60 55-115dB(A) 0
70 65-125dB(A) +10
80 75-135dB(A) +20
90 85-145dB(A) +30
100 95-155dB(A) +40
All the ranges quoted in this section are amended by -10dB if the high sensitivity microphone CEL-190 is
fitted. Because of the high signal level provided by the CEL-193 at full scale deflection it will be found that
the setting of the record level control will be very critical. However, this problem can be overcome by
inserting the attenuating link that is provided with the CEL-3026/1 record cable.
Playback procedure
The tape recorder should be connected to the sound level meter via the CEL-3027/2 cable and JJ2614
adaptor which should be fitted to the preamplifier in place of the microphone. Set the CEL-193 to its 70dB
range, irrespective of the range used for the actual recording and apply the pre-recorded calibration tone.
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