Casella CEL CEL-450 - Manual (Page 69)

6.2.2 CEL-490 Versions
In addition to the features listed for the CEL-450, the CEL-490 has the
following.
Measured Parameters:
See Table 2.
Period Timer:
Single period timer from 10 millisecond to 1 hour.
Should be divisible by the profile timer.
The period timer provides a set of period measurements after
each specified period.
Delayed Start/Stop Timers:
7 user specified sets of start and stop times, identified by date to
the nearest minute.
L N Measurement:
5 L N percentile statistics.
CEL-450/490 Operators Handbook - Page 69
Specification