Casella CEL CEL-281 - Manual (Page 40)

it into logarithmic form and transmits it into the digital section of the in-
strument where all subsequent manipulations are performed.
3.2.2 Digital Section
Logarithmic signals entering the digital section from the analog section
of the instrument are immediately converted into digital information and
transferred to the microprocessor.
All instrument control functions and commands made by the operator
are exercised via the microprocessor. This performs the calculation rou-
tines necessary to yield the information available for display, including
the calculation of Fast or Slow time constants.
The display (shown in Figure 7) can indicate any of the calculated pa-
rameters continuosly. However when necessary, the parameter value
can be suppressed leaving just the ON legend, and when relevant the
OVERLOAD, LOW BAT, and RUN legends (i.e. just the top line).
The display legends have the following interpretations.
ON Instrument has been switched on by push-ON/
push-OFF switch (located beside the 15-line
connector in the bottom of the instrument)
and is currently powered.
MAX Display is showing maximum levels, or a time
(or date) related to a maximum level.
LAVG Display is showing time averaged levels
(including L
eq which is L AVG with Q = 3).
TIME Either: Display is showing time information
in hh:mm:ss format (hh = hours, mm =
minutes, and ss = seconds),
Or: Display is showing measurement start and
stop times in nn:hh:mm format, where nn is
How It Works
Page 32 - CEL-281 Operator's Handbook