Up until now, you have used Flow to retrieve, calculate and report on time period summary information. As described in the "Extracting Value from Time-Based Data" section, Flow also understands event periods, allowing the association of additional contextual information overlaid onto the summary information.
Locate the “FL001.State” (Filler 1 State) tag in your Historian. Double-click on it to open the Data Source Preview …
Zoom out to show about 15 hours of detailed data. Notice the Filler 1 cycles through a pattern of states. The states are:
0 = Idle
10 = Setup
20 = Running
30 = CIP
Flow can be used to automatically detect the start and end of event periods. Let’s define an event that starts when the Filler state changes to 10 (“Setup”) and ends when the Filler state changes to 30 (“CIP”).
Drag the Event icon from the Flow Zone onto the “Filler 1” folder …
By default the new metric will take on the name of its parent folder. Rename this event to “Filler 1 Run”. You should see the red disk appear on the event because it is not completely configured yet.
Double-click on the new event to open its Editor …
The top section of the Event Editor displays a few general properties for the Event:
- Description – Event description.
- Refresh Offset – this is the number of seconds before “now” that Flow will start querying the Historian data. Flow defaults this property to 0 seconds.
- Backfill – the date and time used by the Engine to go back in history and retrieve the event period information from the Historian.
The event triggers define how Flow determines the start of an event and the end of an event. Locate the “FL001.State” tag in the Historian and drag it into the “Triggers” section …
Flow creates a “Start Trigger”. Notice Flow has created a link to the “FL001.State” tag and setup the default “Trigger” condition properties. Let’s discuss these trigger properties:
- Tag – this is the tag Flow will monitor in the data sources and evaluate against the “Trigger” condition properties.
- Trigger – this defines the type of condition Flow will use to detect the trigger event.
- Condition – this tells Flow how to evaluate the tag’s value against the “Condition Value”.
- Condition Value – this is the value Flow evaluates the tag’s value against to determine whether an event is triggered.
For the “Start Trigger”, set the trigger “Condition Value” to 10. Flow will use this to start a new event period when it detects the tag’s value is equal to 10 (“Setup” state).
Now drag the “FL001.State” tag onto the “Triggers” section again …
Flow creates an “End Trigger”. Set this trigger’s “Condition Value” to 30 (“CIP” state).
Deploy the Event and open the “Triggers” diagnostic chart window. Refresh the diagnostic chart and confirm that event periods have been detected and created by Flow.