Casella CEL CEL-368 - Manual (Page 32)

• Whether 200 Pa level was exceeded during the event
(70 - 140 dB range only),
• Whether overload occurred during the event,
• Whether the battery volts fell below 3.6 V during the event.
A schematic representation of the relationship between the operating
modes is given in Figure 1. More storage space becomes available
when event mode or one or more of the profile store functions are
switched OFF.
A user selected data set can be downloaded directly to a Centronics
compatible printer to create a hard copy report. Note however, that not
all of the stored data is accessible from the instrument display and key-
pad.
4.3 Instrument Description
The CEL-268 and CEL-368 consist of microphone and preamplifer input
stage, analog sound level meter section where the gain and frequency
weighting are applied to the input signal, analog to digital converter feed-
ing a microprocessor that samples the signal more than three hundred
times per second and makes calculations based on the measured lev-
els, and a non-volatile memory in which results are stored.
A- or C-weighting, or Linear response may be used for the measure-
ments, but once the analog input has been converted into a digital sig-
nal and entered the microprocessor (Figure 2), all subsequent
manipulations and calculations are performed by the software, including
calculation of Fast and Slow time weightings.
Similarly, once the instrument is switched ON, all subsequent com-
mands and operations are also controlled via the microcomputer by
means of a combination of keys and menus.
4.4 Acoustic Input
Note* If the sound level is above the threshold level when a cumulative run starts or
stops, the results for the current event will be incomplete, therefore no data is
saved for this event and the results lost.
Similarly, if the pause key is used to interrupt measurement during an event,
again as the results for the event will be incomplete, no data will be saved.
Page 28 - CEL-268/368 Operator's Handbook