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Chapter 5
Alarms and Events
5-6
© National Instruments Corporation
How Do You Display Event History Information?
To read all the alarms and events in the BridgeVIEW system that have 
occurred since the Engine was started (unless limited by buffer size) drop 
the Event History Display from the Alarms and Events palette on your 
front panel. Then, you can invoke the HMI G Wizard to create the diagram 
code for an event history. You also can build your own diagram and use the 
Read Event History VI in your block diagram. If you want to change the 
default fields (time, date, tag name, alarm limit) that are visible in the Event 
History Display, you can use the Event History Format control from the 
Controls»Alarms and Events palette and change the checkbox selections. 
You also can change the default colors of alarms, events, normal and 
acknowledged alarms with the Color Codes for Event History control, 
which also is available in the Alarms and Events palette.
You also can report the status of alarms currently in the system using the 
output of either Read Alarm Summary VI or Read Event History VI, or by 
using the Get Alarm Summary Status VI. This gives information on the 
number of active alarms and unacknowledged alarms in the system. You 
can use the Alarm Summary Status control available in the Alarms and 
Events Controls
 palette to display this information on your HMI. 
How Do You Acknowledge Alarms? 
You can view the acknowledgment status of alarms in the Alarm Summary 
or Event History Display. To acknowledge alarms currently in the system, 
use the ACK button from the Controls»Boolean palette on the front panel 
and the Acknowledge Alarms VI in the Functions»Alarms and Events 
palette in the block diagram. Activity 5-2, Acknowledge Alarms in the 
Alarm Summary Display
, takes you through this process.
When you acknowledge these alarms, the acknowledgment status in the 
Alarm Summary Display changes from 
UNACK
 to 
ACK
, and the color of the 
text changes from red to yellow. These are the default colors, and you can 
change them.
There are two modes for handling tags that were previously in alarm but 
have returned to normal: Auto Acknowledge and User Must Acknowledge
These modes are configured in the Tag Configuration Editor for each tag. 
If a tag is configured for Auto Acknowledge, when the tag returns to 
normal, the acknowledgment status automatically changes from 
UNACK
 to 
ACK
. However, if it is configured for User Must Acknowledge, the status