Calculating Cross-Element Attributes in PI AF: A Comprehensive Guide

Calculating Cross-Element Attributes in PI AF: A Comprehensive Guide

In the complex world of industrial data management, the ability to effectively calculate, manipulate, and store data is paramount. One common scenario for PI System users is the need to perform calculations on attributes sourced from different elements. In this guide, I’ll walk you through how to set up such calculations, particularly when your data is queried from external sources like Oracle databases, using PI AF (Asset Framework).

Scenario Breakdown

Imagine you have two elements in PI AF:

• Element A with an attribute Event A
• Element B with an attribute Event B

Both attributes are populated through templates that query external data sources, specifically Oracle databases. The task is to calculate a new attribute, Event Total, which is the sum of Event A and Event B.

How to Set Up the Calculation

To sum attributes from different elements, you’ll need to set up an Analysis in PI AF. Here’s how you can do it effectively:

Step 1: Understand Your Hierarchy

Before setting up the calculation, make sure you clearly understand your data hierarchy. The user case outlined involves two separate elements, with their attributes sourced from external databases.

Step 2: Use PI System Explorer

Open PI System Explorer to configure your Analysis. This is your workspace where you will reference attributes from different elements.

Step 3: Referencing Complete Attribute Paths

When setting up the Analysis, ensure that you reference the complete path to each attribute. This is crucial because PI AF needs the full path to correctly locate and retrieve data from different elements. Extra pathways can be easily obtained by right-clicking any attribute in PI System Explorer and selecting "Copy path." This functionality eradicates the need to manually enter the full path, reducing the chances of errors.

Step 4: Configure the Analysis

In PI System Explorer:

• Navigate to the Analyses tab of your designated element.
• Create a new Analysis.
• Use the expression syntax to sum the attributes: Event Total = '\\ElementA\Event A' + '\\ElementB\Event B'.

Step 5: Execution and Scheduling

After configuring the analysis, set the scheduling service to execute as needed. This could be triggered by events or set at regular intervals, depending on your operational needs.

Considerations

Data Storage

While setting up server-side calculations offers operational flexibility, it’s vital to consider the implications of storing these calculations, notably if you're contemplating storing all raw and calculated values in the PI Server.

• Licensing: Evaluate the cost implications of storing additional data points within the PI Server. Licensing models may impose limitations on the number of tags or data streams stored.
• Consult the User: Before opting for PI Server storage of calculations, ensure necessary discussions are held with your stakeholders or users regarding cost and resource usage.

Conclusion

Performing calculations on attributes drawn from various elements is a functional necessity for comprehensive data analysis in PI AF. By correctly setting up Analyses and referencing attributes through their full paths, you can ensure seamless operation and integration of cross-element calculations. As always, balance operational needs with considerations on licensing and data storage to optimize your PI AF environment effectively.

For more insights and technical guides, continue to explore our blog where we delve into the nuances of PI System engineering and data solutions.