Rockwell Automation FactoryTalk View Machine Edition Users Guide - Manual (Page 131)

9 • Set up alarms
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The log file is saved every 30 seconds, if there are new alarms. The log file is also saved
when the application is shut down.
The alarm log file is also referred to as the alarm history. For example, the operator
presses the clear alarm history button to remove all alarms from the log file.
The alarm log file is retained when you restart an application after a shutdown or power
loss. You can delete the log file from the run-time computer at application startup.
For information about deleting the log file, see page 15-16.
If you download a newer version of an application to the run-time computer, the alarm log
file for the older version is deleted automatically.
Alarm trigger data types
When you create alarm triggers, you must specify the type of data the trigger’s tag or
expression uses. The type of data affects how alarms are triggered.
The Value trigger type
To trigger alarms based on integer or floating-point values, use the Value trigger type.
When the value of the trigger connection equals the trigger value of a message, an alarm is
generated.
If you use an analog tag (either an HMI tag or a data server tag) or an expression, you can
use any non-zero integer or floating-point value to trigger an alarm. Floating-point values
are rounded to the nearest integer. For information about how values are rounded, see
page 7-2.
Trigger values cannot be 0. Digital tags have two possible values, 0 and 1. Therefore, if
you use a digital tag (either an HMI tag or a data server tag) you can only use the value 1
to trigger a message. If you want to use a digital tag to trigger two different messages,
create an expression that adds 1 to the digital tag’s value. That way, you can use the trigger
values 1 and 2.
Example: Integer trigger values
This example shows how to set up alarms using integer trigger values to monitor the level
of acid in a 100-gallon tank. Alarms are generated when the tank is 75percent full and 90
percent full.
1. Create an alarm trigger for the tag Acid_tank_level. This tag points to an address in a
programmable controller that is linked to a sensor in the tank. The tag’s minimum
value is 0 and its maximum value is 100.
Use this expression for the alarm trigger: