Alarm Definition

In the alarm management in CODESYS, the definition of an alarm consists of the following components:

General description (ID, monitoring type, message text, etc.)
Description of the cause of the alarm (expression to be monitored, limits, min. pending time, etc.)
Description of the alarm effects (notification actions, acknowledgment method, display options, etc.).

Parts of the alarm definition are grouped in the form of alarm classes. A single alarm is typified in its definition within an alarm group with one of the classes. Parts of the definition are located in the alarm group and apply to all alarms of this group.

Below you see an overview of which parameters and properties of an alarm are defined in which object of the alarm configuration:

Alarm Class	Priority Archiving yes/no Acknowledgment method Single acknowledgement yes/no Notification actions on alarm status transition Representation in the visualization
Alarm Group	Text list for message texts Archiving object Deactivation variable
Single alarm within the alarm group	ID Monitoring type and expression to be monitored Individual deactivation variable Alarm Class Message text Pending time Latch variables (for example to display additional variable values in the message text or to be able to filter the alarms in online mode) Higher priority alarm (whose triggering acknowledges the alarm defined here)

Acknowledgment method, single acknowledgement: To make sure that the user has been alerted to an alarm, define an acknowledgement method and one or more notification actions for each alarm class. The acknowledgement method specifies which statuses and status transitions are processed for acknowledgement when an alarm occurs. You use the notification actions to define which actions should be executed for a status transition. As soon as the user has acknowledged an occurring alarm, it is removed from the current alarm list. The different acknowledgment methods are described in diagrams which are available as a tooltip of the Acknowledgment method in the dialog of the alarm class configuration.

Alarm condition: In the definition of an alarm, the alarm condition, for whose fulfillment the alarm occurs, is defined in the monitoring type. Depending on the monitoring type (Digital,Upper limit, Lower limit, Outside range, Inside range, Change, Event), a suitable alarm condition should be specified in the Details column (for example for monitoring type Digital: PLC_PRG.xAlarm1 = TRUE).

Different input fields are available for this, each depending on the monitoring type.

Alarm event: An alarm event is linked to an alarm condition. While an alarm condition can exist over a lengthy period, the alarm event describes the momentary occurrence of a change, for example the change from the normal state to the alarm state. In the CODESYS alarm configuration, the same names (Active, ACK, Inactive) are used for the three types of events and the associated alarm status.