Rockwell Automation 9301 Series RSView32 Users Guide - Manual (Page 132)

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RSView32 User’s Guide
The following illustration shows an increasing threshold of 4,000 rpm
with a deadband value of 500 rpm. In this example, the rpm would
have to fall to 3,500, and then rise above 4,000 rpm before it would
retrigger the alarm.
A deadband range may be absolute, as illustrated, or it may be a
percentage of the minimum/maximum range for a tag. If the
deadband in the illustration was two percent, its range would be two
percent of 5,000 rpm, or 100 rpm.
If a buffer is not required, the deadband must be configured to zero.
With a deadband of zero, alarms will be triggered as soon as the tag
value crosses any of its thresholds.
5,000
4,000
3,500
3,000
2,000
1,000
0
In alarm
Out of alarm
In alarm
again
rpm
Threshold
Time
Deadband
n
Use the deadband carefully in safety–critical applications. In the
above example, the variable would have to fluctuate by more than
500 rpm before retriggering an alarm.
IMPORTANT