A Low Alarm will generate an alarm condition when the value of the tag is below the Low Alarm Limit. The tag will remain in Low alarm until it is acknowledged and the tag’s value rises above the alarm limit plus deadband.
If a Low-Low Alarm is also configured, and the tag’s value decreases below the Low-Low Limit, the Low-Low Alarm will be reported and the point will go out of Low Alarm.
The Alarm Limit is set during configuration of the tag, but can be changed in run-time VIEW while on-line from the point detail display if the user has access to the Security Level 127 configured for Tag Fields. The alarm Limit can also be changed by appending the .ALMLO to the tagname in the Point Info Dialog Box (point Browser).
The relevant fields to consider when configuring a Low Alarm are the Low Alarm Priority, Low Alarm Limit, the Deadband, and the Span High and Span Low of the Tag.
To configure a Low Alarm see 7.4Alarm Configuration.
1. Enter a non-zero Alarm Priority by clicking on the field in the field labeled Lo Priority. This is an abbreviation for Low Alarm Priority.
If you are using a Low-Low Alarm also, then the Low Alarm Priority must be less than or equal to the Low-Low Alarm priority.
2. Enter a numeric value for the LO Alarm Limit. The alarm limit is in engineering Units.
If you are using the Low-Low Alarm also, then the Low Alarm Limit must be greater than the Low-Low Alarm Limit.