Pablo Benvenuto

PI 101, Module 2: What are Assets and Tags?

Discussion created by Pablo Benvenuto Champion on Sep 25, 2012

Welcome to Module 2, here we are going to discuss the technical aspects of the PI System in more detail.

PI Asset Framework or PI AF

The PI Asset Framework (AF) Server is a part of the PI System. It contains asset or “metadata” that is usually organized according to the assets (i.e. the equipment in your facility) containing the tags being monitored. Assets can be helpful to users of the PI System who do not know or are not familiar with tags or even with the equipment. Using assets they can find the data they need without understanding the technical details of each piece of equipment or its location. Assets are also helpful in finding all of the tags associated with a specific piece of equipment.

Elements: An element normally represents a piece of equipment. An example might be a turbine, a reactor tank, a railcar, a well, or something else that is tangible. It can also represent an intangible concept, like a production line or area.

elements.jpg

Attributes: Attributes are components of elements. An attribute is normally Something that has measurable value. This may be some sort of constant like a serial number, last maintenance date, model or dimension of the element. An attribute can also be an alias for a process tag, like a temperature, pressure, or other measurement scanned at regular intervals.

attributes.jpg

There are four types of attribute: Static (None), PI Point, Formula, and Table Lookup.

What is a PI Tag?

A PI Tag is a unique storage point for data in the PI Data Archive. It is simply a single point of measurement. It has been the traditional unit in the PI Server.

So What Types of Data Can PI Store? (Point Types) The answer is pretty much everything. Below are the data types:

Digital: Discrete value (On/Off, Red/Black/Green)
Int16: Integer value, 16 bits (0 to 32767, acc: 1/32767)
Int32: Integer value, 32 bits (-2147450880 to 2147483647)
Float16: Scaled Floating Point number, 16 bits (1/32767 times range)
Float32: Floating Point number, 32 bits (single precision)
Float64: Floating Point number, 64 bits (double precision)
String: Text value up to 976 characters
Blob: Binary large object up to 976 bytes
Timestamp: Any Time/Date in the range 1-Jan-1970 to 1-Jan-2038

Some Basic Point Attributes and Why They are Important to You

Each PI tag has a set of attributes that define it. There are some common tag attributes that are often used in client tools. Most of these attributes are used for display or informational purposes.

Tag Name: Unique name of the PI point used to search for tags. Most tags are built using a local naming convention. Sometimes knowing the naming convention can be helpful in searching for tags. For example, try to determine what the following tag may refer to: M03_E1P2_MOTDRV1202_RUNSTAT (answer: Machine 3, Enclosure 1, Panel 1, Motor Drive 1202, run status)

Descriptor: This is the human-readable description of the PI Tag. It is often used as a search criterion in place of the tag name when the tag name is not intuitive. Very often the tag name is some sort of abbreviation convention and the descriptor is used to capture the “full name.”

PointSource: All tags are related to their interfaces that collect the data by an attribute called PointSource. This means that in many cases you can find all of the tags associated with a particular device by searching for all tags of a certain PointSource. This assumes that the user knows the point sources in use and that will not be true in most situations.

Review Questions

Activity

This activity is designed to help you become familiar with your systems and how they can be represented in the PI System. Take a few minutes to think about processes or equipment that you work with in your company. Think about their relationship in terms of location or function and sketch an appropriate PI AF structure for them. Determine the type of data that they produce and make a list (i.e. temperature sensor = floating point value). The list could represent the attributes of the elements in the structure. Feel free to post your comments in this thread about your ideas and the best ways to represent your processes and equipment in PI AF.

You can now go to Module 3 where we will discuss how to connect to a PI System or you can go back to the Workshop Outline.

MORE LEARNING OPTIONS

Alternatively, you can watch the playlist below to learn about Elements, Attributes and Tags.

http://www.youtube.com/playlist?list=PLFSuDbq3pKVGFDjnA-IEpiCCseiF2JsPl

Outcomes