ST-72 User's Manual
Document: UM-1007
Revision Level A
7
Bar Graphs Screen
1.3.4
COMBINATION SCREEN
The ST-72 Combination screen shown in Figure 1-5 offers a view of a single channel but
displays the data as a 30 minute trend, bar graph and large engineering units. The bar
graph and the background color changes and flashes indicating alarm condition. Once
the alarm is acknowledged they stop flashing. Colored lines across the bar graph and 30
minute trend indicate alarm levels. The alarm level lines have triangles on the right end
that indicate high and low trip for each alarm level. A triangle that points up represents
a high trip alarm and one that points down represents a low trip alarm. The
Combination Screen is also useful for testing inputs for stability since MAX, MIN &
AVERAGE values reset each time this screen is selected. For example, to test stability
over a one hour period for an input, begin timing as soon as the channel is selected.
One hour later record the MAX, MIN & AVERAGE values. The visible trend is only 30
minutes, but the difference between MAX & MIN indicates peak to peak excursions over
the one hour period and AVERAGE is the average for the hour. Longer or shorter tests
may also be run. A blue vertical line is drawn on the screen when the screen is selected
and moves to the left indicating how long this screen has been active. The example
below (Figure 1-5) has been active for 26 minutes.
Ch07
PCTLEL
2400 Counts
Measurement Name
50
Min:
0
Avg:
32
Max:
90
Zero:
0
Span:
100
27
24
21
18
15
12
9
6
3m
100
80
60
40
20
0
Figure 1-5
Combination Screen
Summary of Contents for ST-72
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Page 129: ...ST 72 User s Manual Document UM 1007 Revision Level A 123 8 5 4 PROGRAMMABLE RELAYS Figure 8 8...
