Specifications

8 – Configuring Points
168 R400
• 1-hour averages of the 1-minute snapshots
• 8-hour averages of the 1-minute snapshots
• 24-hour averages of the 1-minute snapshots
The averages are calculated using the 1-minute base interval. That is, for 6-minute
averages are calculated on six 1-minute values. If you change the 1-minute base
interval the averages are still calculated from the base interval. For example, if
you change the base interval to 30 seconds, 6-minute averages are calculated on
twelve 30-second values.
Extended History
When you configure Extended History collection for a point, the following
process history snapshots are stored:
• 1-hour snapshots
• 8-hour snapshots
• 24-hour snapshots
Fast History
You use Fast History to take snapshots of data of selected point parameters every
1 to 30 seconds, depending on the rate you selected during installation.
To configure one or more points for Fast History collection:
1 Use Quick Builder to select Fast History for the appropriate parameters for
each point.
2 Follow the instructions in “Configuring Trend Set Displays” on page 230 for
configuring a Trend Set display for a point that has been configured for the
collection of Fast History.
The retention period and the number of samples for each history interval are
shown in the table below.
History Types Intervals Default Retention Period
Duration Number of Samples
Standard History 1-minute snapshot 24 hours 1442
6-minute average 7 days 1682
1-hour average 7 days 170
8-hour average 3 months 281
24-hour average 1 year 368
Table 8.3 Default Retention Periods
plscpcg.book Page 168 Monday, May 28, 2001 10:11 AM