Process Alarm; Process Alarm Examples - ABB AWT420 Operating Instruction

AW T4 2 0 | U N I V E R S A L 4 - W I R E , D U A L- I N P U T T R A N S M I T T E R | O I/A W T4 2 0 - E N R E V. B

Process Alarm

Menu
Processs Alarm
Exit Select
Menu
Comment
Alarm 1 (to 8)
Source Select the sensor signal for the process alarm source.
Type Select the alarm type:
• High Process/Low Process/High Latch/Low Latch
Tag
Enter an alphanumeric alarm identification tag (16 characters maximum).
The tag is displayed as a diagnostic message and appears in the Diagnostic Status Bar and on the
Diagnostic View page at Operator level – see page 27.
Trip
Set a trip value in engineering units.
Hysteresis Set a hysteresis trip value in engineering units. The alarm is activated at the alarm trip level but
deactivated only when the process variable has moved into the safe region by an amount equal
to the hysteresis value – see Process alarm examples (Figure 32 and Figure 33) below.
Time Hysteresis Set a time hysteresis trip value between 0.0000 and 9999.0 seconds.
If the alarm trip value is exceeded, the alarm is not activated until the Time Hysteresis value has expired.
If the signal goes out of the alarm condition before the Time Hysteresis has expired, the hysteresis timer
is reset.

Process alarm examples

Trip point
PV
On
Alarm
state
Off
Figure 32 High and low process alarm action
Trip point
PV
On
Alarm
state
Off
On
Alarm
state
Off
Figure 33 High and low latch alarm action
Used to configure up to 8 independent process alarms.
Hysteresis
High process alarm
Hysteresis
Acknowledged
after condition
cleared
Active Latched
Acknowledged
before condition
cleared
Active Acknowledged
High latch alarm
Hysteresis
Trip point
On
Alarm
state
Off
Low process alarm
Hysteresis
Trip point
On
Alarm
state
Off
Acknowledged
before condition
On
Alarm
state
Off
Active
Low latch alarm
Acknowledged
after condition
cleared
Active Latched
cleared
Acknowledged
43
Default