Source, Destination and Trigger Tags
The Calculation Collector utilizes three types of Historian tags:
- Source tags
- One or more tags used in a calculation formula.
- A Destination tag
- A single Historian tag that stores the result of the calculation and which must be different from the Source tag(s) of the calculation. A Destination tag can be the source of another calculation.
- Trigger tags
- Tag that causes an event-based calculation to fire. You can have a Trigger tag that is not a Source tag.
Understanding Trigger Tags
With the Calculation and Server-to-Server Collectors, there are polled and event-based calculation triggers. When you use event-based triggers, you also have trigger tags. A trigger tag controls the firing of an event-based calculation.
The following figure shows how you can use the Calculation Collector to perform a more complex calculation with several tags and multiple calculations resulting in one output tag. It also shows how the output of one calculation can be used as input to another.
