Alarm Latching

Alarm latching lets you latch a module alarm in the set position once the alarm is triggered. The alarm remains set even if the condition that triggered the alarm disappears, until the alarm is unlatched.
Alarm latching is available on a per channel basis. You can latch the following alarms:
I/O Type
Available Alarms
Input modules
  • Process Alarms
  • Rate Alarm
Output modules
  • Clamp Alarms
  • Output Ramping Alarm

Enable Latching

You can enable alarm latching in Module Properties:
  • For input modules, go to Chxx - Alarms view to enable latching for Process Alarms and Rate Alarm.
  • For output modules, go to Chxx - Limits view to enable latching for Clamp Alarms and Rate Alarm.

Unlatch Alarms

IMPORTANT: Before you unlatch an alarm, make sure that the condition that triggered the alarm is no longer exists.
Once an alarm is latched, you must manually unlatch it. You can use the module tags to unlatch an alarm. The alarm type determines which module tag you must change.
For example, to unlatch a Low Low alarm on the analog input module, set the
Chxx.LLAlarmUnlatch
 output tag to 1.
IMPORTANT:
After an alarm is unlatched, change the module tag back from 1 to 0.
You must change the module tag from 0 to 1 to unlatch the alarm each time an alarm is triggered.
If you do not change the module tag back to 0 and the alarm is latched again in future, the alarm remains latched despite the
Unlatch
 tag value being 1.
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