Alarms and Conditions
- Last UpdatedJun 26, 2025
- 2 minute read
- PI System
- Adapter for OPC UA 1.6
- Adapters
Alarms and Conditions alert users to system conditions that could potentially cause an issue so action can be taken. An alarm can be configured to show as active when a value exceeds a defined limit. For example, you can set an alarm for a pump that warns when no fluid pressure is detected.
Users can configure the OPC UA adapter to perform a discovery of data items or event types that persist in the data source (the OPC UA server). With Alarms and Conditions, users can perform a discovery of only event types and use the results as the data selection configuration to collect alarms and conditions data.
The DiscoveryType enumeration type can be used within a Discovery query to find Event Types available on the adapter's server. DiscoveryType has three allowed values:
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Data - Only data items are retrieved in the discovery results.
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Event - Only event types are retrieved in the discovery results.
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DataAndEvents - Both event types and data items are retrieved in the discovery results.
Subscriptions to event types are maintained within the Data selection configuration.
Event notifications from alarms and conditions are processed by the OPC UA adapter. When an alarm is triggered, you are notified through an event notification. Event fields from the incoming event notification are extracted and concatenated into a string with a delimiter as specified in "EventStringDelimeter" attribute of Client Settings configuration.
The event notification displays the fields specified when the alarm was configured. For example:
Low fluid pressure | 1 | Pump 3A
The adapter is capable of resynchronizing the latest condition states that are of interest within the server through the Condition Refresh functionality in the OPC UA specification. This typically occurs during start-up but it is also done whenever event types are modified in the data selection or in cases such as failover.
For more information on configuring event types, subscribing to alarms and conditions, and the impact to client-side and server-side failover, see the Alarms, Conditions, and Events.