Configure tags for PIWEBAPI

You can calculate and import/export data from the PI points and PI performance equation points by configuring tags.

• For configuring PI points, refer to steps below described in topic Import/Export Tag Configuration.

• For PI performance equation points, the data exchange can be defined in two ways. This supports only average data:

  • Performance equations defined in PI Server: Import/export data by using PI tags (performance equations) as defined in the PI server.

  • Performance equations defined in AVEVA Production Accounting: Define equations in AVEVA Production Accounting by using PI archive tags. (Note that this is supported for importing data only).

What are performance equations?

PI WEB API has a Calculation Controller, which provides a mechanism to execute performance equation expressions over objects in Asset and Data Servers.

Performance equations support summary values and archive values.

• It executes real time calculations.

• Can use many different tags in the equation.

• Can be used as PI Tag to store the results, so that anyone can access the same calculation.

  Examples of performance equations defined in the PI Server:

  • 'TagA' *2 – This expression evaluates the expression by multiplying TagA value with 2.

  • 'TagA'/ 'TagB' – This expression evaluates the expression by dividing TagA value with TagB.

  • IF expr0 THEN expr1 ELSE expr2

    Example: IF 'Tag1' < 50 THEN "under limit" ELSE "good"

    Example: IF 'Tag1' > 0 THEN 'Tag2' ELSE 0

    Note: Performance equation doesn’t support the IF logical operator in the Equation Editor.

For more information about performance equations and summary calculations in the PI Server, refer to the PI Server documentation.

Import/Export tag configuration

Configure tags to import/export the measured value from the PI server using the PI WEB API interface.

To configure import or export tags, see the procedure for import/exports tags described in the topic Tag Configuration as the steps are the same.

AF tags configuration

• For data exchange with the PI AF database, you must define the entire hierarchy of the attribute (of the tag) in the Edit Tag Info screen. For example, the syntax is \\RootElement\ChildElement1...\Child element2..|Attributename

• For example:

  To define Reactive Power as highlighted in the image, the syntax would be \\Flynn River Hydro\Flynn I\GU1\GU1 Generator|Reactive Power.

  

  The rest of the steps are the same as in topic Tag Configuration.