OPC Events and external events, as described in External events, provide means to store events collected from any third-party system that supports the OPC A&E server interface. Contrary to this, internal events are events that are generated based on numerical data collected to RTDB. Event generation is controlled by creating event triggers ("EventTrigger" Vtrin class, or "Event definition" in user interfaces). The following sections give detailed information on how to use and understand available events, as well as how to create new event triggers to spawn new internal events.

Event triggers are configured for database variables. The system uses event triggers to generate events with different severities (critical alarms, warnings, notices, and non-alarms) when the conditions that have been specified for the triggers are fulfilled. Typical triggers for analog variables are high limits and low limits. Typical triggers for binary variables are state changes.

For example, a high limit trigger would let the system generate an event of a certain severity when the value of the variable exceeds the high limit. Another event might be configured to be generated when the value returns below the high limit.

The following figure illustrates the logical relationships between related classes.

Event triggers are created using the "Event Configuration" list available from Vtrin in Maintenance\System\Events and Alarms. The "Event Configuration" list is a master-detail list where variables, which have event triggers associated, are presented in the upper part. The event trigger associated with a particular variable is shown in the lower part when the variable is selected in the upper part. After installation, there are no event triggers available, and the display is empty.

For example, a row could define that a warning event is triggered when the value of the variable specified on the row becomes higher than the limit specified on the row.

To be able to configure events, write access is needed to the database.

The easiest way to create event triggers is by using Vtrin. The "Event Configuration" list is found from the main tree in Maintenance\System\Events and Alarms. In the following example, a new variable, "EventTriggerTestVariable" is created. It is used to generate events whenever the current value of the variable becomes greater than 10.

A new variable is created from the upper part of the "Event Configuration" display. If a variable is created from this display, the value of the "Events" property is automatically set to "true". If an existing variable is used, this should be set to true manually (this has to be done from the list view or from the generic properties, as the property is not available in the custom variable dialog).
A new event trigger is created from the lower panel (from "Edit mode", click the "New" button). The property "InUse" should be set to "true". The limiting trigger value 10 is configured to the property "Limit" (by default, the "TriggerType" is already "High limit"). Finally, the value of the "Log" property is set to "true". This enables logging into the "Alarm log". In case the value of the "Log" property would be "false", the warning would only be visible from the variable instance's blinking current value with an appropriate warning icon. Changes are committed using the "Commit" button, and after that returning from "Edit mode" to "Normal mode" (Revert).
Testing the configuration can be done by double-clicking the variable and feeding a value bigger than 10 for the current value.

The following figure illustrates the situation after the three steps above are executed.

EventEngineering Attributes (RTDB Core)

Attribute	Type	Description
Variable (IDN)	uint32	Reference to the variable instance where the event trigger is applied.
PathId	GUID	Hierarchical path to the variable.
PropertyId	GUID	Identifier of the property definition on the variable instance to which the event trigger is attached.
ReferenceInstance	GUID	Identifier of the specific object instance that the trigger’s reference points to
ReferenceProperty	GUID	Identifier of the property definition on the referenced instance whose value is used by the event trigger.
EER	binary	Combines in binary format all the other attributes except IDN.
Description	string[64]	Description of the variable where the event trigger is applied.
InUse	bool	True if the trigger will be evaluated, false if not.
EventTriggerId	GUID	ID of the event trigger
Trigger	uint32	Read the next chapter for more detailed value descriptions.
TriggerCause	uint32	Why the trigger actually fired
Limit	object	Defines the limit that causes the state transition in event triggering. The type is derived from the variable instance"s type, and can be either 64bit integer or double. NOTE: if low level access (e.g. RTDB Core ODBC) is used for writing the value, the data type must be Int64 or Double. When written via VtrinLib, the data type will automatically be corrected if given differently.
Format	uint32	Output format for trigger
ReturnFormat	uint32	Output format for return
Period	double	Time period in seconds, if the event or limit value represents some time-dependent value.
Area	uint64	Defines which alarm area the event trigger belongs to. The numeric value should not exceed 65535 because the value in AlarmLog is only 16 bits. If the setting is zero, the ProcessArea from the alarming Variable or Equipment property is used instead. (Version info: before 5.1/2017-04-25, the setting was ignored and worked as it was given as zero).
DeadBand	object (float/int)	After some state change has been triggered, the return back to normal state happens once the limit has been exceeded with the specified dead band (absolute deadband used). NOTE: if low level access (e.g. RTDB Core ODBC) is used for writing the value, the data type must be Int64 or Double. When written via VtrinLib, the data type will automatically be corrected if given differently.
External	uint32	External event observation identification. If EventEngineering.External is greater than 0, the event observation, or limit handling, for the event is performed by the source of the value (e.g. an external data acquisition system). The event identification is provided in the latest value attribute CLEX (=EventEngineering.External), if the event is triggered (limit violated) and it has higher priority than the other external events.
Reference	uint32	In addition to using a static limit, there is the possibility to use another variable's value as a dynamic limit. "Reference" is set to contain a reference to the variable that contains the current value to be used as the dynamic limit.
TriggerMethod(TriggerM)	uint32	In case the "Trigger" is 13 ("Event trigger method"), the "TriggerMethod" defines the method that is used to evaluate the trigger condition. If the method returns true, the event state is valid.
SuppressionMethod(SuppressionM)	uint32	Alarm suppression method. If the conditions for the event are fulfilled, but the method execution specified by EventEngineering.SuppressionM returns a nonzero value, the specified alarm (EventEngineering.Priority) is suppressed. An indication for the suppressed alarm is set (CSAS). The event observation is continued. The special suppression method is AlarmSuppressed (11), which means that the alarm is suppressed without executing any other method.
ActionMethod(ActionM)	uint32	Action method to be executed when entering the event state. If EventEngineering.ActionMethod is zero, no method is executed. EventEngineering.ActionM is a user-written method.
ReturnMethod(ReturnM)	uint32	Action method to be executed when leaving the event state. If ReturnMethod is zero, no method is executed. ReturnMethod is a user-written method.
Diary	bool	If true, event is stored into diary log if available.
Log	bool	If true, event is stored into alarm log.
OpcEvent	bool	If true, event is stored into Opc Event log. (From Version: 5.3/2022-12)
DiaryReturn	bool	If true, event from returning back to normal state is stored into diary log.
LogReturn	bool	If true, event from returning back to normal state is stored into alarm log.
OpcEventReturn	bool	If true, event from returning back to normal state is stored into Opc Event log. (From Version: 5.3/2022-12)
SetQuality (Set Validity)	uint2	Status that the system sets for the variable when the triggering condition becomes true ("No change", "Set questionable", "Set bad").
Evaluation	uint8	If the variable has several event triggers, the "Evaluation" defines the priority that the triggers are evaluated by.
Priority	uint8	Alarm priority used when condition is triggered.
ReturnPriority	uint8	Alarm priority used when returning back to normal state.
Modified	DateTime	Row modification time shows the last time when the event trigger instance has been modified.
RowModificationTime	DateTime	Last modification timestamp (local time)
RowModificationTime_UTC	DateTime	Last modification timestamp (UTC)
Speak	bool	If a sound-support package has been installed, the events generated are spoken.
EvaluateAlways	bool	The system checks this trigger always even if an earlier trigger is active, so that multiple triggers can be active for the same variable. Notice that when multiple alarms are active, the "Alarm Priority" information of the current value only describes the priority of the first active alarm in the evaluation order. The other active alarms can be found from the ActiveAlarm class (ActiveAlarms database table), from entries where the "IsActive" property is true (version info: 5.3_25.06)
EvaluateAlsoForInvalid	bool	Evaluate this trigger also if the current value was invalid. Without this, most triggers evaluate only for valid current values. (version info: 5.3_25.06)
EvaluationConditionVariable	uint32	If non-null, the value of this variable must be in the set of Condition Flags of property EvaluationConditionValue to enable evaluation of this trigger. This property together with the EvaluationConditionValue property can be used to implement "Plant Mode" specific triggers. The plant modes are integer values between 0 and 9. (Values up to 30 can be used but only the first 10 has been declared in UIStrings as Flags to be used in EvaluationConfitionValue). For example, if the EvaluationConditionValue is 48, it means that this trigger is evaluated if the plant mode is currently 4 or 5 (i.e. 2^4 + 2^5 = 16 + 32 = 48). The user interface presents the EvaluationConditionValue as a "flags" style enumeration, so that the user does not need to perform the above calculations, but can just define the settings as "M4 \| M5" (I.e. for plant mode 4 and 5). Notice that in many cases a site has only one plant mode variable, but the configuration supports multiple of them because the setting is trigger definition specific. (version info: 5.3_25.06)
EvaluationConditionValue	int32	Set of Condition flags. Multiple settings can be entered separated with pipe character (\|). See description of "EvaluationConditionVariable". (version info: 5.3_25.06)

Type Enumeration of Event Trigger

Value	Description
High limit	Triggers when the value of the associated variable exceeds the value in the "Limit" property.
Low limit	Triggers when the value of the associated variable goes below the value in the "Limit" property.
Change speed limit	The maximum change per time period (the time period defined in "Period"), and the limit value is "Reference" or "Limit". Valid only for double type variables.
Difference limit	The maximum difference to the reference variable ("Reference"). Valid only for double type variables.
Total match	To detect binary value states. Triggers when all bits match. Valid only for int64 and binary type variables.
Any bit match (bitwise AND not zero)	To detect binary value states. Triggers when any bit matches. Valid only for int64 and binary type variables.
Oscillation surveillance	If the value of the binary point changes more than once within the specified time period ("Period"), the event is generated. Valid only for int64 and binary type variables.
In-transit state surveillance	If the state change of a two or four signals digital input value has taken more than the specified time period ("Period"), the event is generated. Valid only for binary type variables.
Binary indicated limit violation	Indicated by a separate binary variable specified in the "Reference" property. When the binary goes to 1, the event is triggered. "Reference" defines the limit indicator binary for the analog variable, and the corresponding analog variable for the binary indicator.
Expiration surveillance	If the time since the last update (CLT) of the variable is longer than defined in the period ("Period"), an event is generated.
Disabled processing surveillance	If the current value processing of the variable is disabled (EGE=false), an event is generated.
Bad measurement group surveillance	If the latest value has "bad measurement group" status (CLSBG), an event is generated.
Bad value surveillance	If the status of the latest value is "bad" (CLSB), an event is generated.
Trigger condition method	User-written trigger method ("TriggerMethod") is used as a trigger condition. Note: the actual implementation is not documented yet in detail.
Pulse input power surveillance	Time derivation aggregate is decreased, if a new pulse value has not been produced in the time interval defined in "Period".
Reset reference variable	Set the value of the "Reference" variable to zero, when the state changes to binary value on (1). This trigger is only valid for binary variables. The event does not stay valid and it does not cause the event actions, event logging, or alarm priority changes.
-22.	Reserved for RTDB_GradeServer use.
Change limit, absolute	Triggers when the value changes more than the given absolute limit. Deadband is taken into account.
Change limit, signed	Triggers when the value changes more than the given signed limit (grows if positive or decreases if negative). Deadband is taken into account
Value range violation	Triggers when the value is outside of the measurement range
Limit clamping to measurement range	Triggers when the value is outside the measurement range and substitutes the value with the min or max value respectively.

EventTrigger Attributes for Variables (VtrinLib)

Column	Type	Description
Id	GUID	Unique event trigger identifier
Variable	uint32	Variable ID this trigger applies to
Description	string	Variable description
InUse	bool	Trigger enabled
Period	double	Time period in seconds
Area	uint64	Alarm area identifier
External	uint32	External event handler ID
Reference	uint32	Reference variable (dynamic limit)
ReferenceInstance	GUID	Referenced instance
ReferenceProperty	GUID	Referenced property
Trigger	uint32	Trigger type (limit, state, method, etc.)
TriggerCause	uint32	Cause code of trigger activation
Limit	double	Trigger limit value
DeadBand	double	Deadband for return to normal
TriggerMethod	uint32	Trigger evaluation method
SuppressionMethod	uint32	Alarm suppression method
ActionMethod	uint32	Method executed on trigger
ReturnMethod	uint32	Method executed on return
Priority	uint32	Alarm priority
ReturnPriority	uint32	Priority on return
Speak	bool	Text-to-speech enabled
Diary	bool	Log event to diary
Log	bool	Log event to alarm log
OpcEvent	bool	Generate OPC event
DiaryReturn	bool	Log return event to diary
LogReturn	bool	Log return to alarm log
OpcEventReturn	bool	OPC event on return
SetQuality	uint32	Quality state to set
Evaluation	uint32	Evaluation mode
EvaluateAlways	bool	Always evaluate trigger
EvaluateAlsoForInvalid	bool	Evaluate even if value invalid
EvaluationConditionVariable	uint32	Conditional variable ID
EvaluationConditionValue	int64	Conditional comparison value
Modified_UTC	datetime	Last modification timestamp
TriggerDescription	string	Human-readable trigger text

Equipment Model Event Triggers

It is possible to trigger events when a specific property on an equipment instance changes. This is done using the EventTriggerEquipmentProperty class (the class name is "Event definition for Equipment Property" in user interfaces).

1662 — A conceptual model that shows how event triggers are related to the equipment model.

There are three ways of how property events can be set to trigger:

When the property of a specific instance changes
When the property of any instance of a specific equipment type changes
When the property of any instance of a specific equipment type under a hierarchy subtree changes

From a configuration perspective, 1. and 2. are just special cases of 3. In 1., the subtree contains just the one instance and in 2., the subtree equals the whole hierarchy.

EventTriggerEquipmentProperty Attributes (VtrinLib)

Column	Type	Description
Id	GUID	Unique identifier of the event trigger.
Instance	GUID	Equipment instance to which the trigger is applied.
Property	GUID	Property definition on the equipment instance being monitored.
Trigger	uint32	Trigger type enum that defines how the event condition is evaluated.
InUse	bool	Enables or disables the trigger.
Limit	int64	Limit value used by limit-based triggers. Data type must match the monitored property type.
DeadBand	int64	Deadband used for return-to-normal evaluation.
Period	double	Time period in seconds for time-dependent triggers.
Priority	uint32	Alarm priority when entering the event state.
ReturnPriority	uint32	Alarm priority when returning to normal state.
Area	uint64	Alarm area identifier.
External	uint32	External event observation identifier. Zero means internal handling.
Reference	uint32	Reference variable or identifier used for dynamic limits or comparisons.
ReferenceInstance	GUID	Target instance providing the referenced value for dynamic or reference-based triggering.
ReferenceProperty	GUID	Property on the referenced instance whose value is used by the trigger.
TriggerMethod	uint32	Method used to evaluate the trigger when method-based triggering is configured.
SuppressionMethod	uint32	Method used to suppress alarms when conditions are met.
ActionMethod	uint32	Method executed when entering the event state.
ReturnMethod	uint32	Method executed when leaving the event state.
Diary	bool	If true, the event is written to the diary log.
Log	bool	If true, the event is written to the alarm log.
OpcEvent	bool	If true, an OPC event is generated on trigger activation.
DiaryReturn	bool	If true, a diary entry is written on return to normal.
LogReturn	bool	If true, an alarm log entry is written on return.
OpcEventReturn	bool	If true, an OPC event is generated on return to normal.
SetQuality	uint32	Quality value to set when the trigger activates.
Evaluation	uint32	Evaluation mode controlling how trigger conditions are processed.
EvaluateAlways	bool	If true, the trigger is evaluated continuously.
EvaluateAlsoForInvalid	bool	If true, the trigger is evaluated even when the property value is invalid.
EvaluationConditionVariable	uint32	Variable or identifier used as an additional evaluation condition.
EvaluationConditionValue	int64	Comparison value for the evaluation condition.
Speak	bool	Enables speech output when the event is triggered.
TriggerDescription	string	Human-readable description of the trigger, mainly for UI and diagnostics.