Casella CEL CEL-193 - Manual (Page 6)

Casella USA
17 Old Nashua Rd #15
Amherst, NH 03031 USA
In order to read the maximum value logged during the measurement sequence, the MAX position should be
selected.
(c) PEAK/IMP/FAST/SLOW
This control selects the time constant employed in the RMS detector. The Fast, Slow and Impulse
settings are as required by the relevant National and International Standards. In addition, a 'peak' time
constant is also provided for use in conjunction with the maximum hold mode.
(d) LIN/A/FILTER
The frequency weightings are selected by means of this control. In the LIN (Flat) position the instrument
responds equally to all frequencies within the range 2Hz to 30kHz. The A position introduces the A
frequency characteristic as defined in the precision grade standard thereby giving results in dB(A). When
the EXT position is selected the frequency response is as selected by any suitable network that may be
connected between the filter in and filter out pins on the base of the instrument. The CEL-178 Octave Filter
has been specifically developed for use with the instrument and will provide 10 octave bands plus the
standard A, B, C, D and LIN (Flat) networks. For more detailed analysis the CEL-196 Automatic Third Octave
Analyser is available and full information on both these units is given in separate handbooks.
(e) L
Tm
/L
eq
/L
AX
The integral parameter calculated is selected by means of this switch. When the Leq position is selected the
conventional equivalent continuous level is calculated as per ISO and British Standards by integrating the
RMS level. The LTm position selects a mode which causes the maximum RMS value that occurred in a 5
second period to be taken and integrated for the ensuing 5 second period to provide an impulsive weighting
to the result. Alternatively, a 3 second period may be selected by means of the switch located above the
battery compartment (earlier production units were manufacturer pre-set to either 3 or 5 seconds). The
answers obtained in this mode are therefore in line with DIN 45641. Selection of the LAX setting reverts to
conventional Leq operation but the time counter is fixed at 1 second as required by the LAX formula.
Detailed operational notes are given in the latter sections of this manual.
(f) RESET
When pressed this button will cause the noise dose, elapsed time and maximum level stores to be returned
to zero. It also resets the overload indicator. To prevent accidental resets it only operates when the
Leq/SPL/MAX switch (b) is in either the Leq or MAX positions.
(g) ATTENUATOR
This control is located on the right-hand side of the case and is the rotary range change switch. It selects
the measurement range which is indicated in the window on the left-hand side of the scale pan. The
measured value, therefore, is always this value plus the meter reading (plus an additional 30dB if the range
expander button (I) is depressed). When rotated clockwise it increases the level of sound that the
instrument will measure in 10 dB-steps.
(h) METER
Displays the answer as selected on the controls described above. In order that average values can be
displayed at 0 on the scale the instrument's dynamic range is set at -5dB, +55dB relative to scale zero.
(I) OL Indicator
This illuminates when the instrument's circuits are overloaded and hence a wrong answer is being
indicated. It is triggered from both sides of the frequency correction and hence the instrument's range may
be changed during frequency analysis operation. On SPL the overload indicator is illuminated during the
period of overload only;
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