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Alarms and Chronological Event List

Audit Trail

alarms and chronological event list

Identifying errors and their causes quickly and consistently is a precondition for ensuring high productivity and saving resources. With its alarm capabilities and the documentation of events in the Chronological Event List, zenon provides all the necessary tools. Pre-configured functions, simple setting of parameters and full compatibility with standards such as FDA CFR 21 Part 11 keep implementation costs low.

Alarms and Chronological Event...

Fact Sheet

Alarms and Chronological Event List

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Administration and display

zenon offers three options for displaying alarms and events:

1. Alarm status line: Shows a current alarm in a status line that is overlaid on all other screens.

2. Alarm message list (AML): Displays alarms with all relevant information.
3. Chronological Event List (CEL/Audit Trail): Lists process relevant events and zenon system messages in chronological sequence.
These lists can be individually adapted. The functionalities are fully pre-configured in zenon and can be used without extra programming.

Fast Facts

  • Compatibility with FDA CFR 21 Part 11
  • Administration of alarms, Audit Trail and chronological events
  • Definition via limit values or central reaction matrices
  • Grouping and prioritization
  • Comprehensive filtering capabilities
  • High performance
  • Immediately redundancy-compatible
  • Graphical display with a clear overview

Limit values and reaction matrices

If limit values of variables are breached, an alarm or a fault report is triggered. In the engineering phase it is defined which limit violations trigger an alarm and cause an entry in the Chronological Event List. For automatic, event-controlled reactions, you can link these breaches with actions. The linked function can also be executed manually, at the press of a button in an alarm screen. Alarms can also be defined via reaction matrices. If flittering values often exceed limit values, alarms and messages are suppressed in a defined hysteresis range or by a threshold value.


Alarms can be configured and presented in many ways in zenon. The allocation takes place, for example, according to alarm groups, alarm classes and alarm areas. If alarms require acknowledgment or deletion it is ensured that the alarm has been noted in a traceable manner. All actions are logged in detail. The acknowledgement of an alarm in zenon can be combined with acknowledgement from the PLC by setting an acknowledgement bit. A status line displays current alarms where they can also be acknowledged.

Alarm message list

The Alarm Message List (AML) displays current and historical alarms. Diverse criteria for filtering alarms are pre-defined in the Editor. In addition, filters can also be created in Runtime and saved there for any given user.

Chronological event list

The Chronological Event List (CEL/ audit trail) shows process- related events, fault messages that cannot be acknowledged and zenon system messages in chronological order. Just as with the alarms there are also a variety of filter criteria in the CEL. The alarms and chronological event list (CEL/ audit trail) benefit from full redundancy compatibility, simple administration, excellent performance and fulfill FDA 21 CFR Part 11 requirements.