Protocol 3
TM
User Guide E105, 313327, REV A
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countries. No part of the contents of this manual may be reproduced, copied or transmitted in any form
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Three types of process alarms are implemented in the Protocol 3: High, Low,
Band. If the process variable passes the boundary, the alarm activates as
depicted in Figure 27.
The control subtracts the process value from the setpoint. If the resulting
value exceeds the alarm value setting the alarm will activate.
Signal Change
Per Min Alarm
An alarm based on the rate of change in the measured process variable. If the
PV changes at a rate greater than the alarm level per minute, the alarm will
activate. The rate of change must be above the alarm threshold for longer
than the Minimum Duration Of Change time, before the alarm will change
state. Caution: If the duration is less than this time, the alarm will not activate
no matter how fast the rate of rise.
Figure 27. How High, Low and Band process alarms are implemented.
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