Rockwell Automation 2711E-ND1 PanelBuilder 1400E Reference Manual - Manual (Page 156)

154 Trends
Publication 2711E-820 – January 1998
Panel
Maximum
Median
Minimum
Pens
Time & Date labels
for Minimum Time & Date labels
for Median Time & Date labels
for Maximum
All pens in a Trend can be configured to plot values either in the
foreground or in the background, or the individual pens in a trend
can be configured (independently of the trend as a whole) for
foreground or background plotting.
If one or more pens are configured to use background plotting, the
Trend begins to plot values for those pens when the application
enters Run mode, and continues to plot values whether or not it is
displayed. The Trend does not retain data when you switch modes or
select a new application. It also does not retain data across power
cycles of the PanelView terminal. For pens not configured to use
background screen plotting, the Trend object begins to plot values
when it is displayed on the PanelView terminal. These values are not
saved when you switch to a different screen.
You can configure up to 85 pens in your application for background
plotting, but the total number of data points cannot exceed 3000 for
all pens using background plotting. You can see the total number of
data points in use for background plotting in your application in the
Configure Trend Object dialog box, when you enable the background
screen for one or more pens.
The Trend plots from the right side, scrolling to the left to make
room for a new data point each time a new point is plotted. The time
labels on the horizontal axis, if used, are updated every time a data
point is collected.
The Trend object includes Trend Minimum Value and Trend
Maximum Value controls to specify the range of values to display at
a given point in time. The Minimum and Maximum values allow the
Trend to zoom in and out by adjusting the range of values displayed
on the vertical axis. If you change the value for the minimum or
maximum value displayed, the Trend is re-plotted at the new range
of values.