Casella CEL CEL-228 - Manual (Page 4)

Casella USA
17 Old Nashua Road #15
Amherst, NH 03031-2839
www.casellausa.com Page 4 of 6 tel: ( 800) 366-2966
[email protected] 23 Dec 2005 fax: (603) 672-8053
Controls and Indicators FILTER UP/FILTER DOWN
These push button switches are used to shift the
octave centre frequency with each operation of
the switch moving the filter one step in the
required direction.
OFF/BATT/ON
In the OFF position no functions are performed
and the instrument draws no power. In the
BATTERY position the meter indicates the on
load voltage of the lower of the two batteries
with the end of useful battery life shown as the
lower mark on the scale; hence, when end of life
is indicated both batteries must be changed.
When in the ON position the instrument carries
out its selected functions.
30/60/90
This control selects the measurement range by
setting the meter scale zero to the value
selected; hence, the answer is given by reading
the appropriate scale on the switch plus the
meter. Measurement ranges provided are,
therefore, 30-70, 60-100 and 90-130. It must be
remembered, however, that on the top range the
RMS levels are within specification over a span
90-120 whilst the additional 10dB is provided for
the maximum hold function. This results from the
use of a high sensitivity microphone to enable
measurements to be made at 30dB(A) and it
will, therefore, saturate at 135dB(A).
FAST/SLOW/IMP
This switch selects the time constants employed
in the RMS detector and these are as defined in
the International Standards - 1 25msec for FAST
and 1 second for SLOW, The IMPULSE
response provides a 35msec time constant for
rising edges and 1.5 seconds for failing ones.
OUTPUT SOCKET MAX/NORM
This 3.5mm miniature jack socket provides a
feed of the conditioned AC output to ancillary
instrumentation such as tape recorders,
frequency analysers, etc. In the NORM position the instantaneous RMS
level is displayed on the meter whist in the MAX
setting the meter will hold the maximum level
logged during the measurement sequence. In
order to reset the maximum hold circuit, the
switch should be returned from MAX to NORM.
The maximum hold must be reset if the
measurement range is changed.
OVERLOAD
This indicator is illuminated if the instrument is
indicating an incorrect answer due to
overloading of its amplifiers. When this occurs
the measurement must be repeated on a higher
range.
A/LIN/FILTERS
The standardised 'A’ weighting is provided in the
'A’ position of this switch giving results in dB(A).
In the FLAT position the unweighted microphone
signal is passed to the display giving results in
dB(Flat/Lin). When the filter position is selected
the individual octave bands are connected in
circuit and the particular band is indicated by the
array of indicator lamps above the meter
movement.