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 112.

Table 112 – DiscrepancyAlarmType definition

Attribute	Value
BrowseName	DiscrepancyAlarmType
IsAbstract	False
References	Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the AlarmConditionType defined in 5.8.2.
HasProperty	Variable	TargetValueNode	NodeId	PropertyType	Mandatory
HasProperty	Variable	ExpectedTime	Duration	PropertyType	Mandatory
HasProperty	Variable	Tolerance	Double	PropertyType	Optional
ConformanceUnits
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.