Performance equations (PE) syntax and functions reference

The performance equation (PE) subsystem provides an equation syntax and library of built-in functions that allow you to perform a wide variety of calculations on PI data.

PI performance equations can work with frequently updating snapshot and archive values, where tools like spreadsheets only have archive data and limited access to snapshot update values. Typical calculations include heat and material balances, unit performance, real-time cost accounting, and so on.

How to use steam functions

You typically use the PE subsystem in one of two ways:

• To create calculated points that have the PE subsystem as their source. The PE subsystem determines the value of these points by performing a PE calculation that the user specifies when creating the calculated point. You can use PI SMT to create calculated points (Points > Performance Equations).

• To add calculations programmatically, through PI SDK or PI DataLink client applications. For more information on these products, refer to the documentation included with each.

Steam functions

The PI System includes two contexts where steam functions are applied:

• Performance Equations (PE): Tag-based calculations.

• Asset Analytics: Asset-based calculations.

To compare and cross-reference for both contexts, see Learn about steam functions in asset and tag-based analytics.

Where to find more details

For an alphabetical list of PE functions, see Alphabetical reference for PE functions. For usage guidance, see the Knowledge Base article: PI Performance Equation (PE) Tips and Tricks.

Note: Client applications may not support all existing PI performance equations offered by the PE Subsystem.