National Instruments BridgeVIEW - Manual (Page 138)

© National Instruments Corporation 5-1 BridgeVIEW User Manual
5
Alarms and Events
This chapter introduces the basic concepts of alarms and events, and
explains how to view, acknowledge, and configure them within the
BridgeVIEW system. This chapter also provides activities that explain
how to build an alarm summary display and acknowledge alarms from
your HMI.
What are Alarms and Events?
An alarm is an abnormal process condition pertaining to a tag.
In BridgeVIEW, alarms are generated based on changes in a tag value
or status.
An event is something that happens within the BridgeVIEW system.
Events can be divided into two groups: those that pertain to individual tags
and those that pertain to the overall BridgeVIEW system. An example of a
tag event is a change of alarm state for a tag. Examples of system events
include a user logging on, the Engine starting up, or historical logging
being turned on. For more information about system events, see Chapter 2,
BridgeVIEW Environment .
Alarm States
For analog tags, an alarm state can be of type HI_HI, HI, LO, or LO_LO.
For all data types (analog, discrete, bit array, and string), if the server
returns a bad status, and you have enabled alarming on bad status, the tag
goes into Bad Status alarm. All data types except string also support alarms
based on tag value. If an analog tag exceeds a preconfigured alarm limit,
one of these alarms can occur. Discrete and bit array tags are either not in
alarm or in alarm.
Alarm Limit
An alarm limit is the numeric value an analog tag must exceed to go into
an alarm state.