Honeywell Fusion4 MSC-L Installation & Operation Manual page 518

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Alarm Handling - Operations on alarms
6.5 Operations on alarms
A number of operations can be performed on alarms. Not all operations
are directly accessible. However, they are explained in the following
sections to give a clear understanding of the way alarms work.
6.5.1 Raising
For each alarm, a specific raise conditions is periodically checked. If the
raise condition is met, then a RaiseAlarm operation is performed. A
RaiseAlarm operation activates the alarm if the alarm is not active yet.
6.5.2 Clearing
Clearing is performed through user interaction. On the alarm screen (or
through external interfaces), an individual alarm is selected and a
ClearAlarm operation may be requested for that alarm. The ClearAlarm
operation causes the alarm to be deactivated. However, if the raise
conditions for that alarm are still met, the effect of the ClearAlarm
operation is immediately overwritten by the RaiseAlarm operation.
Some alarms, such as the Tank Low Level alarm, perform automatic
clearing. For such alarms, there is a raise condition and a clear
condition that is periodically checked. When the clear condition is met a
ClearAlarm operation is performed and the alarm is deactivated. In case
of the Tank Low Level alarm, the clear condition is the complement of
the raise condition, but this is not so in general.
6.5.3 Resetting
Resetting an alarm is a user operation. An individual alarm is selected
and a ResetAlarm operation is requested to reset the alarm. For most of
the alarms the ResetAlarm directly translates to performing a
ClearAlarm operation. But this is not true in general.
An alarm may have some state associated with it. When the raise
condition is based on this state, then only clearing the alarm causes the
alarm to be raised immediately again, even if the situation is such that
you do not expect that alarm to come back again. For example, the
'Pulse hardware error' alarm maintains a counter that counts the
number of erroneous pulses. If the ResetAlarm operation does not clear
that counter but only clears the alarm, then the value of the counter
causes a new RaiseAlarm operation, even if there are no new pulse
errors detected.
6.5.4 Acknowledging
Acknowledging an alarm is a user operation. An individual alarm is
selected and an AcknowledgeAlarm operation is requested to
acknowledge an alarm. This operation has no effect on clearing/raising
Fusion4 MSC-L
Installation & Operation Manual
Part No.: 4418309_Rev09
Honeywell