Rockwell Automation T7832 ICS Regent+Plus Historian Packages for Winterpret - Manual (Page 16)

Historian Package for W INTERPRET (T7832)
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Industrial Control Services
recorded each Sample Time. Ladder logic turns off the
Start contact after a time delay less than or equal to the
Period of the process historian.
This method is used to routinely capture vital process
information during equipment start-up or shutdown
periods. This information can be retrieved and analyzed
be plant personnel for monitoring efficiencies and
operating characteristics of plant equipment. This
information can be useful for scheduling preventive
maintenance of major process equipment.
Clear Contact
The Clear contact is a discrete variable name that an
application program may turn on to clear the recorded
variable entries currently in the process historian buffer. The
Clear contact should normally be off. The Clear contact may
be turned on then off after the historian buffer has been
retrieved and saved using the monitor and collect functions of
W
INTERPRET .
While the Clear contact is on the process historian function
block is idle and does not record values, regardless of the
status of the Start contact.
Sample Time
The Sample Time determines the recording interval of the
process historian function block. Sample Time can be
expressed as an integer number of scans or in time units.
When expressed in time units, the actual recording interval
will be equal to or slightly larger than the Sample Time
defined. For example, if sample time is 200 milliseconds
(Sample Time = 2, Units = 0.1 seconds) and the Regent scan
time is 31 milliseconds, the actual recording interval will be
211 milliseconds (7 scans at 31 ms each = 211 ms). If the
Regent scan time varies during execution of the application
program, the effective Sample Time of the process historian
will range from:
Sample Time <= Actual Sample Time <= Sample Time + one scan cycle
If the Start contact is on, each Sample Time a time stamp and
values for the selected variables are recorded in the historical
buffer. One Sample Time recording is called a frame.