ANSI C Based OPC UA Client/Server/PubSub SDK
Reference NodeClass BrowseName DataType ValueRank TypeDefinition ModellingRule
HasSupertype ObjectType AcknowledgeableConditionType  
HasComponent Variable ActiveState LocalizedText Scalar TwoStateVariableType Mandatory
HasComponent Variable EnabledState LocalizedText Scalar TwoStateVariableType Mandatory
HasProperty Variable InputNode NodeId Scalar PropertyType Mandatory
HasProperty Variable MaxTimeShelved Duration Scalar PropertyType Optional
HasComponent Object ShelvingState ShelvedStateMachineType Optional
HasProperty Variable SuppressedOrShelved Boolean Scalar PropertyType Mandatory
HasComponent Variable SuppressedState LocalizedText Scalar TwoStateVariableType Optional

An abstract type that extends the AcknowledgeableConditionType by introducing an ActiveState, SuppressedState and ShelvingState.

The AlarmConditionType inherits all Properties of the AcknowledgeableConditionType. The following states are substates of the TRUE EnabledState.

Variable ActiveState

ActiveState when set to TRUE indicates that the situation the Condition is representing currently exists.

When a Condition instance is in the inactive state (ActiveState when set to FALSE), it is representing a situation that has returned to a normal state. The transitions of Conditions to the inactive and Active states are triggered by Server specific actions. Subtypes of the AlarmConditionType will have substate models that further define the Active state. Recommended state names for LocaleIds are listed in the following table.

LocaleId FALSE State Name TRUE State Name
en Inactive Active
de Inaktiv Aktiv
fr Inactive Active

Variable SuppressedState

Used internally by a Server to automatically suppress Alarms due to system specific reasons.

For example, a system may be configured to suppress Alarms that are associated with machinery that is shut down, such as a low level Alarm for a tank that is currently not in use. Recommended state names for LocaleIds are listed in the following table.

LocaleId FALSE State Name TRUE State Name
en Unsuppressed Suppressed
de Nicht unterdrückt Unterdrückt
fr Présent Supprimé

Object ShelvingState

Suggests whether an Alarm shall (temporarily) be prevented from being displayed to the user.

It is quite often used to block nuisance Alarms.

See also

Variable SuppressedOrShelved

The SuppressedState and the ShelvingState together result in the SuppressedOrShelved status of the Condition.

When an Alarm is in one of the states, the SuppressedOrShelved property will be set TRUE and this Alarm is then typically not displayed by the Client. State transitions associated with the Alarm do occur, but they are not typically displayed by the Clients as long as the Alarm remains in either the Suppressed or Shelved state.

See also

Variable MaxTimeShelved

Optional Property used to set the maximum time that an Alarm Condition may be shelved.

The value is expressed as duration. Systems can use this Property to prevent permanent Shelving of an Alarm. If this Property is present it will be an upper limit on the duration passed into a TimedShelve method call. If a value that exceeds the value of this property is passed to the TimedShelve method, then a Bad_ShelvingTimeOutOfRange error code is returned on the call. If this Property is present it will also be enforced for the OneShotShelved state, in that a Alarm Condition will transition to the Unshelved state from the OneShotShelved state if the duration specified in this Property expires following a OneShotShelve operation without a change of any of the other items associated with the Condition.

See also

Variable InputNode

Provides the NodeId of the Variable the Value of which is used as primary input in the calculation of the Alarm state.

If this Variable is not in the AddressSpace, a Null NodeId shall be provided. In some systems, an Alarm may be calculated based on multiple Variables Values, it is up to the system to determine which Variable’s NodeId is used.