At run-time, alarms produce visual cues in your pictures. These cues appear as colored or flashing text in the Alarm Summary object and in Data links, or as animated objects triggered by alarms. You can configure alarm-based visual cues to remain on the screen until your operators acknowledge the alarms that cause them and the block's value returns to normal.
iFIX maintains latched and current alarms. The current alarm is a block's current alarm state, and the latched alarm is a block's most severe unacknowledged alarm. If a block generates a High High alarm, the latched and current alarm are the same: High High. If the block then generates a High alarm, the current alarm changes to High, but the latched alarm remains High High.
Data links, animated objects, and Alarm Summary objects each handle alarm acknowledgements differently. For example, a Data link shows the current alarm until either a new alarm occurs, or the block's value returns to normal. Similarly, a Data link displays the latched alarm until an operator acknowledges the alarm. Then, the link shows the next most severe unacknowledged alarm. For a list of alarms and their severity, refer to the Block Alarm Severity table.
Alarms in the Alarm Summary object, on the other hand, respond identically to the latched alarm. The most severe unacknowledged alarm appears in the object's spreadsheet. When an operator acknowledges the alarm, the next most severe alarm appears, text stops flashing, and colored text returns to its original color. Then, the Alarm Summary Service waits for the block's value to return to normal. Once this happens, the service automatically deletes the alarm.
Alarms used to animate objects handle alarm acknowledgments similar to Data links. For example, suppose you animate the visibility of an object using the current alarm. When the alarm state is OK, the object is invisible. However, when an alarm occurs, you display the object to show that there is a value in alarm. In this setup, the object may remain visible even after an operator acknowledges the alarm, because the current alarm is always the current alarm state of the data source. Consequently, only when the object's data source returns to normal does the object disappear.
NOTE: If you want the object to disappear when an operator acknowledges an alarm, use the field A_NALM in the data source. For more sophisticated alarm-handling, you could create a complex data source with an expression such as:
(FIX32.FERMENT1.OVEN1.A_CUALM<>"OK")AND_
(FIX32.FERMENT1.OVEN1.A_NALM="YES")
Animating an object with a latched alarm works in a similar way to the current alarm. For example, assume you color an object based on the latched alarm. When a latched alarm occurs, the object's color changes to match it. As operators acknowledge alarms, the latched alarm changes and the object's color changes with it. As a result, the object is always the color of the most severe unacknowledged alarm.
