User Manual

Alarm management
Alarm response of the function blocks
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associated alarm state transition. This is equivalent to the standard BACnet
property Event_Time_Stamps.
Notification function selector [NotifSel]
This variable specifies if the alarm function is executed as per default pattern
(Simple-/Basic-/Extended alarm) or as per a customized alarm function.
9.4 Alarm response of the function blocks
Alarm Collection
The default value of [EnEvt] for the Alarm Collection object is FALSE, that is,
[EvtSta] transitions are not notified.
An OFFNORMAL alarm is generated when:
● The following applies to one or more alarm collection members:
[EvtSta] <> NORMAL and applies simultaneously for all these members:
[StaFlg].Fault = false.
A FAULT alarm is generated when:
● The following applies to one or more alarm collection members:
[StaFlg].Fault = true and therefore is set [Rlb] = UNRELIABLE_MEMBERS.
Analog Input, Analog Value, Analog Output
The Analog Input, Analog Value and Analog Output function blocks all have an
identical alarm handling procedure.
The analog output function block also has a feedback value [FbVal]; however,
this is not used for alarm monitoring. High and low alarm limits (variables
[HiLm] and [LoLm]) are set for the OFFNORMAL alarms of analog objects. An
OFFNORMAL alarm occurs either when the high alarm limit is exceeded, or
when the current value falls below the low alarm limit. OFFNORMAL alarms are
thus subdivided into two subcategories: HIGH_LIMIT and LOW_LIMIT. In
addition, the variable [Nz] can be used to define a switching hysteresis for
[HiLm] and [LoLm] to prevent over-frequent switching of alarms around the
alarm limit.
An OFFNORMAL alarm is generated:
● [PrVal] has either remained above the high alarm limit specified by the
[HiLm] variable for a period of time longer than the period specified in
[TiMonDvn]
● or [PrVal] has remained below the low alarm limit specified by the [LoLm]
for a period of time longer than the period specified in [TiMonDvn]
An existing OFFNORMAL (HIGH_LIMIT) alarm will disappear when [PrVal] has
remained below the value ([HiLm] + [Nz]) for longer than the time specified in
the variable [TiMonDvn].
An existing OFFNORMAL (LOW_LIMIT) alarm will disappear when [PrVal] has
remained below the value ([HiLm] + [Nz]) for longer than the time specified in
the variable [TiMonDvn].
● A FAULT alarm is generated as soon as the [Rlb] property of the function
block assumes any value other than NO_FAULT_DETECTED. In particular,
this is the case when [Rlb] changes from a value not equal to
NO_FAULT_DETECTED to another value not equal to
NO_FAULT_DETECTED.
● A FAULT alarm will disappear as soon as the [Rlb] property of the function
block changes from a value not equal to NO_FAULT_DETECTED back to the
value NO_FAULT_DETECTED.
Alarm response