Learn about event frame generation analyses

An event frame generation analysis specifies the conditions to start and end event frames automatically.

This type of analysis includes either one or two expressions. When a single condition triggers both the start and the end of an event frame, only a start trigger expression is needed, depicted by the StartTrigger1 field. For example, a temperature value rising above a threshold might start an event frame and end it when the value returns below the threshold. When the start and end conditions are different, an EndTrigger expression is also needed. Because they test start and end conditions, expressions in event frame generation analyses must evaluate to true or false. See Learn about start and end trigger conditions.

You can write up expressions to be used as start or end triggers. If your expression gets very complex, you can break it into a group of smaller expressions and assign them to variables. See Expression simplification with refactoring.

Beginning with the 2018 release, a new way of event frame generation is possible where you do not have to set an explicit trigger. See Understand implicit modes of event frame generation.

When configuring event frame generation analyses, you can add expressions to Outputs at Close group to write outputs back to event frame attributes. Depending on whether you want to save the history of the output, you can select either attributes configured with a PI point data reference or static event frame attributes. When saving output history to event frame attributes configured as a PI Point data reference, the attribute must be mapped to a corresponding PI Point data reference attribute of the referenced element.

• Outputs from root cause event frames are only written to static attributes.

• Parent event frames with multiple child event frames will also write only to static attributes. See Learn about child event frame generation with multiple start triggers.

In your expressions, you can use inputs that come from assets to write outputs to event frame attributes at the close of an event frame. You can also use the EventFrame function to access the start time, end time and duration of the event frame. See expression function EventFrame.

An event frame naming pattern typically includes substitution parameters. See Naming patterns.

• Parameters %Endtime% and %Duration% in an event frame naming pattern will be evaluated at the end of an event frame when the event frame closes.

• An attribute value may update at any given time. To avoid confusion, substitution parameter %@Attribute% (which resolves to a value of an attribute) in an event frame naming pattern will always be (re-)evaluated in the context of a start of an event frame.

• Default naming pattern (%ANALYSIS% %STARTTIME:yyyy-MM-dd HH:mm:ss.fff%) will be used in the absence of a name or if the event frame name evaluates to a null value.

• In a rare case when the duration of an event frame with %@Attribute% in its naming pattern matches the configured True for, the event frame name will revert to the default naming pattern.

You can create multiple start triggers for your analysis and specify different Boolean conditions to trigger each event frame. See Learn about child event frame generation with multiple start triggers.

Note: If you change the name of a start trigger from the default name, you must change all the start triggers and use unique names for each trigger.

A spike in input data can trigger the start of an unwanted event frame. To counter the effects of data spikes, you can require that the start trigger remain true for a set time interval before creating an event frame. Enter a value in the True for field to specify the time interval.

You can also specify a Severity level for the trigger. The choices for severity are: None, Information, Warning, Minor, Major, and Critical.

An event frame generation analysis is based on an event frame template, which specifies the attributes for the generated event frames. Before you create an event frame generation analysis, be sure an appropriate event frame template is available.

Event frames usually include a referenced element collection. The element associated with an event frame generation analysis becomes the primary reference element for its generated event frames. See Primary referenced element. Other elements can be referenced using relative paths based on the primary referenced element, as described in Understand data attribute references to other elements.

For some events, such as a forced shutdown, you may want to evaluate the conditions leading up to the event. To do that, you can have PI Analysis Service generate root cause event frames. When configured, every generated event frame includes a child root cause event frame that captures attributes for a specified time interval just before the start of the generated event frame. For more information on generating a root cause event frame, see step 11 on Create an event frame generation analysis template.

Video

For information on how to set up event frame generation analyses, watch this video: