The DiscrepancyAlarmType is commonly used to report an action that did not occur within an expected time range.
The DiscrepancyAlarmType is based on the AlarmConditionType. It is formally defined in Table 110.
Table 110 – DiscrepancyAlarmType definition
|Subtype of the AlarmConditionType defined in 5.8.2.|
|A & C Discrepancy|
The TargetValueNode Property provides the NodeId of the Variable that is used for the target value.
The ExpectedTime Property provides the Duration within which the value pointed to by the InputNode shall equal the value specified by the TargetValueNode (or be within the Tolerance range, if specified).
The Tolerance Property is a value that can be added to or subtracted from the TargetValueNode’s value, providing a range that the value can be in without generating the Alarm.
A DiscrepancyAlarmType can be used to indicate a motor has not responded to a start request within a given time, or that a process value has not reached a given value after a setpoint change within a given time interval.
The DiscrepancyAlarmType shall return to normal when the value has reached the target value.