Casella CEL CEL-393 - Manual (Page 21)

When the switch is in the Off position, signals are treated as selected on
the weighting switch described above. In the other positions either octave
or third octave analysis functions are selected and these modes are fully
described in Chapter 5.
Detector F - P - I - S
This switch sets the time constant used within the RMS detector. The
settings provide the internationally standardised responses:
F Fast (125 milliseconds),
P Peak (100 microseconds),
I Impulse (35 milliseconds risetime, 1.5 seconds
decay,
S Slow (1 second).
The setting to be used in any given measurement situation is usually
specified in the measurement protocol being followed. In the absence of
any specific statements, use the F setting.
All time constants may be used in conjunction with any of the instrument's
functions, and their effect is overiding.
It should be noted that the 100 microsecond time constant for the peak
setting is faster than the display refresh rate and sample speed. There-
fore, the peak setting is best used in conjunction with the maximum
capture arrangement. Again, as with the weighting switch, a reset is
applied when the control is operated, to avoid confusion with the settings
used on answers stored in the memory.
Keypad.
Other controls are exercised via the keypad, which comprise both
numerical and control keys.
Until experience has been gained in using the instrument it is advised
that selections should be made from the SPL mode ie, after switch on,
wait until the battery check has been completed and the instrument will
393 Handbook /17.