About Historian Alarms and Events

Historian includes Alarm and Event (A&E) archiving, to provide the ability to retrieve and store Alarm and Event Data from any OPC-compliant A&E server through the OPC Alarm and Event collector. Additions have also been made to the Excel Add-In and OLE DB Provider to support alarm and event data.

Alarms are generally defined as tags going into an abnormal condition. For example, an alarm could be set on a boiler when it reaches a specified temperature. Alarms usually have a well-defined life cycle, which is defined by the individual data sources the alarms are collected from (iFIX, for example). They enter an alarm state, are generally acknowledged, then return to normal.

Historian handles alarm data in two ways. You can view the entire Alarm as a single record that contains all information about the alarm, or you can view the Alarm History, which shows the transitions of the alarm as individual records.

Events are generally defined as activities in a system that occur once only. For example, a user logging on to a device is an event. When viewing this data in Historian, each event is returned as a record.

Historian's OPC Alarm and Event Collector offers the ability to link alarm data with associated process data. This allows you to quickly perform queries, through either the Excel Add-In or OLE DB Provider, that join process data with alarm and event data, giving you a full picture of what may have caused an alarm to occur.