Rockwell Automation 9301 Series RSView32 Users Guide - Manual (Page 128)

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RSView32 User’s Guide
use the AlarmEvent command to respond to your own alarm
detection algorithms for annunciation, logging, printing, and for
display in alarm summaries
Key concepts
An alarm occurs when something goes wrong. It can signal that a
device or process has ceased operating within acceptable, predefined
limits or it can indicate breakdown, wear, or a process malfunction.
Set up a system of alarms in the Tag Database editor by linking alarms
to tags you want monitored. When the tag values are updated in the
value table, they are compared to the limits you assigned when you
configured the alarm. If a tag value exceeds the configured limits, an
alarm of a preset severity is triggered.
Alarms for analog tags
An analog tag can trigger a number of alarms when it crosses various
predefined threshold levels (unlike a digital tag, which is either on or
off).
Thresholds
When defining an analog tag, you can assign up to eight alarm
thresholds with different levels of alarm severity to indicate the alarm’s
importance. The lowest threshold is one and the highest is eight. You
do not have to use all eight thresholds for a tag, but the ones you use
must be configured in ascending order. For example, you can assign
thresholds one, two, and eight as long as you assign them in that order.
Thresholds can be increasing—monitoring for a rising value that
crosses the threshold, or decreasing—monitoring for a falling value
that crosses the threshold. The following illustration shows a tag with
both increasing and decreasing thresholds. In this example, the
deadband setting is zero.