This section describes how to configure, log, and respond to alarms and events with the LabVIEW Datalogging and Supervisory Control (DSC) Module applications.

An event is an instantaneous occurrence that happens to an individual element of an application or to the DSC Module environment. Examples of events include changes in shared variable alarm states, changes in a front panel control, user log ins, and changes in historical logging. Events can be divided into two groups: shared variable events that occur to individual shared variables and system events that occur in the overall DSC Module application. An example of a shared variable event is a change of alarm state for a shared variable. Examples of system events include a user logging on to the system or a user enabling historical logging for the system.

An alarm represents a specific, abnormal condition associated with shared variable or with a user-defined state. You can set and configure alarms for shared variables. Examples of alarms include bad status or high/low values for a shared variable. Alarms have two types of status: TRUE or FALSE, and acknowledged or unacknowledged. Any time an alarm transitions from FALSE to TRUE is an alarm instance. Besides these two status values, every alarm instance contains data such as timestamps, user names, setpoint, shared variable value, priority, alarm area, description, and acknowledgement comments.

An alarm is a specific kind of event associated with a shared variable or with a user-defined state. An event can be virtually any instantaneous activity such as a mouse click. An alarm typically has the following characteristics:

• Denotes an abnormal condition
• Occurs under certain, specific conditions
• Must be acknowledged by the user or configured for automatic acknowledgment

Refer to the DSC Alarms Demo.lvproj in the labview\examples\lvdsc\Data and Alarm Historical Logging\DSC Alarms Demo directory for an example of using alarms.