Events & Alarms

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Events & Alarms

Events

Path: Objects > TestServer > Events

Custom Event Types

The server defines 3 custom event types in namespace ns=1:

SimpleEventType

Inherits from: BaseEventType

Property DataType Description
EventPayload String Custom payload string

Plus all inherited fields: EventId, EventType, SourceNode, SourceName, Time, ReceiveTime, Message, Severity.

ComplexEventType

Inherits from: BaseEventType

Property DataType Description
Source String Source identifier
Category String Event category
NumericValue Double Associated numeric value

SystemStatusEventType

Inherits from: BaseEventType

Property DataType Description
SystemState String One of: "Running", "Idle", "Busy", "Maintenance"
CpuUsage Double Simulated CPU usage (0-100)
MemoryUsage Double Simulated memory usage (40-90)

Event Emitter

BrowsePath Type EventNotifier
Events/EventEmitter Object 1 (SubscribeToEvents)

The EventEmitter object is linked to the Server object as an event source. To receive events, subscribe to events on either the EventEmitter node or the Server node.

Automatic Events

The server generates events automatically at fixed intervals:

Event Type Interval Severity Message Pattern
SimpleEventType Every 2 seconds 200 "Periodic event #N" (N increments)
ComplexEventType Every 5 seconds 300 "Complex event #N"
SystemStatusEventType Every 10 seconds 100 (600 for Maintenance) "System status: <state>"

On-Demand Events

Call the Methods/GenerateEvent method to raise a BaseEventType event with custom message and severity. See Methods.

Testing Events

Basic event subscription

  1. Create a subscription on the Server node (or EventEmitter)
  2. Add an event monitored item with a SimpleAttributeOperand select clause:
    • EventId (ByteString)
    • EventType (NodeId)
    • SourceName (String)
    • Time (DateTime)
    • Message (LocalizedText)
    • Severity (UInt16)
  3. Wait 2 seconds -- you should receive a SimpleEventType event

Filtering events by type

Use a ContentFilter with OfType operator:

  • Filter for SimpleEventType -> receive events every 2s
  • Filter for SystemStatusEventType -> receive events every 10s

Filtering by severity

Use a ContentFilter where Severity >= 500:

  • Only SystemStatusEventType events during Maintenance state (severity 600) should pass

Reading custom properties

For SimpleEventType, include EventPayload in the select clause:

SelectClause: [Message, Severity, EventPayload]

The EventPayload field contains "payload-N" where N matches the event counter.

Alarms

Path: Objects > TestServer > Alarms

Alarm Source Variables

Two variables drive the alarms:

BrowsePath DataType Access Behavior
Alarms/AlarmSourceValue Double RW Oscillates as 50 + 60 * sin(t) every 1 second. Range: approximately -10 to 110.
Alarms/OffNormalSource Boolean RW Toggles every 20 seconds

You can write to these variables to manually trigger alarm states.

Alarm Instances

HighTemperatureAlarm (ExclusiveLimitAlarm)

Property Value
Type ExclusiveLimitAlarmType
Source AlarmSourceValue
LowLow Limit 5
Low Limit 20
High Limit 70
HighHigh Limit 90

States based on AlarmSourceValue:

Value Range Active State
value > 90 HighHigh (critical)
70 < value <= 90 High
20 <= value <= 70 Normal (inactive)
5 <= value < 20 Low
value < 5 LowLow (critical)

Only one state is active at a time (exclusive).

LevelAlarm (NonExclusiveLimitAlarm)

Property Value
Type NonExclusiveLimitAlarmType
Source AlarmSourceValue
LowLow Limit 0
Low Limit 15
High Limit 75
HighHigh Limit 95

Multiple states can be active simultaneously (non-exclusive). For example, if the value is 96, both High and HighHigh states are active.

OffNormalAlarm

Property Value
Type OffNormalAlarmType
Source OffNormalSource
Normal State matches OffNormalSource

Active when OffNormalSource deviates from its normal state.

Alarm Operations

All three alarms support:

Operation Description
Acknowledge Client acknowledges the alarm condition
Confirm Client confirms the alarm (after acknowledge)
AddComment Client adds a comment to the alarm

Testing Alarms

Monitoring alarm state changes

  1. Subscribe to events on the Alarms folder or Server node
  2. Wait for AlarmSourceValue to oscillate through the limit thresholds
  3. Verify you receive ConditionType events with changing states

Manually triggering alarms

  1. Write 100.0 to Alarms/AlarmSourceValue -> triggers HighHigh on both alarms
  2. Write 50.0 -> returns to normal
  3. Write -5.0 -> triggers LowLow on HighTemperatureAlarm, Low + LowLow on LevelAlarm

Acknowledging an alarm

  1. Wait for an alarm to become active
  2. Read the alarm's EventId
  3. Call the Acknowledge method with the EventId and a comment
  4. Verify the AckedState changes to true

Testing OffNormalAlarm

  1. Write true to Alarms/OffNormalSource
  2. The alarm should activate
  3. Write false -> alarm deactivates