Casella CEL Nomad portable weather station - Manual (Page 50)

needed and it is this approach that is used by the Online Pro application to
provide automated configuration. The menu system is activated by default but it
can switch between the two as and when required.
While the Sensus Logger is running it is at all times performing a series
of tasks in the background.
Sensor scanning: This task is performed at regular intervals
determined by the period set in the profile.
Each time it runs fresh data is collected from
the attached sensors, this data is in turn
processed to provide the values logged by the
system and used in alarm comparisons.
Logging: Again, this task is performed at an interval
defined in the profile. While running, all data
values marked to be logged are moved to a
buffer store then written either to the internal
memory or to external CompactFlash™ card.
Alarms: At fixed intervals current data values are
compared against active alarm channels and
alarm states and actions are updated at this
time.
A comprehensive description of Sensus Operations will be found in the
“Sensus Digital Data Logger - User Manual”.
7.2 Commands
A detailed description of all the commands available on the Sensus Logger is
beyond the scope of this manual. When this information is essential to your
particular application, please contact Casella CEL and request a copy of the
document: “Sensus - A Programmers Guide”.
7.3 Logging
By default, the Sensus logs data to its internal record store at an interval
specified by the user. If the logger detects the presence of a compatible
CompactFlash™ card, it automatically uses this instead. When the card is
removed, the logger reverts to using its internal store.
For information on the use of CompactFlash™ cards please refer to
Section 7.6.
The logger operates with two logging rates, one normal rate and one
fast rate. Switching between these two rates is handled automatically by the
alarm system. For further information about alarms, please refer to the Sensus
User Manual. Both logging rates can be set to any value between 5 seconds and
24 hours.
Any data channel that has its “log active” flag set will be included when
the next log event occurs. Logging globally can be disabled/enabled by changing
the “log active” flag held in the logging configuration. This allows logging to be
suspended temporarily without changing all the channel flags.
7.3.1 Internal Capacity
The Sensus Logger has 512 kBytes of internal Flash storage available to hold
logged information. This store is updated in a first-in-first-out manner so that
the earliest records are always being replaced with the newest ones. While this
means the logger will never stop recording data, only a set period of time will
remain available for collection at any time.
The number of records held and the period of time covered by the
internal store depend on both the number of channels being logged and the
logging interval.
Sensus Data Logger
Page 50 of 68
NOMAD Portable Weather Station
Users Handbook