West Control Solutions 8700+ - Manual (Page 139)

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Page 134
Glossary 59305, Issue 7 – March 2014
Alarm Hysteresis Type: General Parameter
An adjustable band on the “safe” side of an alarm point, through which the process variable
must pass before the alarm will change state, as shown in the diagram below. E.g. a high
alarm’s hysteresis band is below the high alarm value, and a low alarm’s hysteresis is above
the low alarm value.
Also refer to Alarm Operation.
Figure 41. Alarm Hysteresis Operation
PROCESS
HIGH ALARM
PROCESS
LOW ALARM
BAND ALARM
DEVIATION
HIGH ALARM
DEVIATION
LOW ALARM
Inactive Inactive
Inactive
Inactive
Inactive Inactive
Alarm Inactive Alarm Inactive
Alarm Active
Active
Inactive Inactive
Active Active Inactive
Active
Active
Alarm Value
Alarm Value
Alarm Value
(from Setpoint)
Setpoint
Process Variable
Process Variable
Process Variable
Process Variable
Process Variable
Alarm Hysteresis Value
Alarm Hysteresis Value
Alarm Hysteresis Value
Alarm Hysteresis Value
Alarm Hysteresis Value
Alarm Hysteresis Value
Setpoint
Setpoint
Alarm Value
(from Setpoint)
Alarm Value
(from Setpoint)
Alarm Value
(from Setpoint)