Rockwell Automation T3832 ICS Regent Historian Package for Winterpret - Manual (Page 17)

Historian Package for W INTERPRET (T3832)
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Units
The Units is the time base units that apply to both the sample
time and period for the process historian control parameters.
You can select scans, .01 seconds, .1 seconds, seconds, minutes
or hours in the drop-down select box for Units.
Period
The Period is an integer constant that defines the length of
the historical buffer. Period is represented in the same units
as Sample Time. For example, if Sample Time is entered as
200 milliseconds (Sample Time = 2, Units = 0.1 sec) and
Period is entered as 1000, the historical buffer length is 100.0
seconds.
Planning the Size for the Process Historian Buffer
Period is used indirectly to size the historical buffer by
determining the amount of memory required to store the
number of frames that Period represents. For example, with
the control parameters for Units set to 0.1 seconds, Sample
Time set to 15 and Period set to 3000, the process historian
buffer would be sized to store 200 frames or recording
intervals.
The maximum size of a historical buffer in the Regent is
65534 bytes. Two things affect the size of the historical buffer:
1. The number of variable entries.
2. The number of frames (Period / Sample Time).
The size, in bytes, of the historical buffer can be calculated
using the equation below:
Buffer Size = (# frames) * [6 + 2*(QtyIO + QtySVR) + 4* (QtySVFP)]