User Manual

Alarm management
Effects of BACnet properties on alarm response
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Present value [PrVal]
OFFNORMAL alarms are monitored exclusively on the basis of the current
value of [PrVal] the present value variable. The source of this present value
(whether a process value, operator value, replacement value or commanded
value) is irrelevant. This is equivalent to the standard BACnet property
Present_Value.
Reliability [Rlb]
The value under [PrVal] is only plausible if [Rlb] = NO_FAULT_DETECTED.
When [Rlb] <> NO_FAULT_DETECTED, this is precisely the condition for a
FAULT alarm.
The BACnet Device Info Object is an exception. The value of [Rlb] for the
BACnet device object is NO_FAULT_DETECTED, except in the case of the fault
FLASH_FULL (FAULT condition). This is equivalent to the standard BACnet
property Reliability.
Reference value [RefVal]
[RefVal] is a set point, used to set the value which [PrVal] (the measured
value) must assume in order to initiate an alarm after the time defined by
[TiMonDvn] has expired. [RefVal] is equivalent to the standard BACnet
property Alarm_Value.
Reference values [RefVals]
The variable [RefVals] comprises a list of multistate elements. The value range
(number of states) of the items in the list is the same as for [PrVal]. All states
to be treated as OFFNORMAL are entered under [RefVals]. [RefVals] is
equivalent to the standard BACnet property Alarm_Values.
Example of [RefVals] : STEP 1, STEP 2, STEP 4
Name Value
State 1 STEP 1
State 2 STEP 2
State 3 STEP 4
In this example, an incoming OFFNORMAL alarm will be detected if [PrVal] =
STEP 1, STEP 2 or STEP 4 after expiry of the period defined by [TiMonDvn].
State flag [StaFlg]
The variable [StaFlg] includes the two bits 'In_Alarm' and 'Fault'.
By definition, In_Alarm is TRUE whenever [EvtSta] is not equal to NORMAL.
By definition, FAULT is TRUE whenever [EvtSta = FAULT].
The value of these two [StaFlg] variables is thus derived from another variable.
For each change of the variable [StaFlg] a Change of Value (COV) notification
is sent to all COV subscribers of the alarm-generating object. In this way, the
COV subscribers can be kept informed of an alarm state in their COV server.
This is equivalent to the standard BACnet property Status_Flags.
Suppress event detection [SupEvtDet]
[SupEvtDet] (Boolean type) lets you turn the OFFNORMAL and FAULT alarm
detection on/off. OFFNORMAL and FAULT alarms are only detected when
[SupEvtDet] = FALSE. This is equivalent to the standard BACnet property
Event_Algorithm_Inhibit.
Event time stamp [TiStmEvt]
This variable (ARRAY [3], type TimeStamp), contains time stamps for the last
changes of state of the alarm-generating object TO_OFFNORMAL, TO_FAULT
and TO_NORMAL. The value of the variables is updated immediately after the