Opto 22

43044 Business Park Drive, Temecula, CA 92590 USA
Local & outside the USA:(951) 695-3000
Toll-Free within the USA:(800) 321-6786
Fax: (951) 695-3095
Email: sales@opto22.com

Hot Tips from PSG: Using Persistent Variables

New Trending Video Shows How to Use PAC Display SuperTrends

Updated Specification Guide for SNAP PAC System

July Training Class Added, Seats Available

Hot Tips from PSG: Using Persistent Variables

PAC Control

When you develop your PAC Control program (called a strategy), you use variables to hold pieces of information. As the strategy runs, the variable name stays the same, although its value may change.

Most variables are set to an initial value (which you specify when you configure the variable) whenever the strategy is run or downloaded to the controller. But sometimes you'll want to make a variable persistent.

Persistent variables are initialized only when the strategy is first downloaded, and they're saved in battery-backed RAM. Persistent variables are handy when you want to be sure to keep the variable value even if you run, stop, start, or re-download the strategy, or if you cycle power to the controller.

Think about using a persistent variable for a PID loop's P, I, and D values. You've probably spent a lot of time tuning these values while running your process. You wouldn't want to lose them if you have to re-download the strategy after a program change.

Another example is keeping track of accumulated times or counts. Again, a persistent variable holds those values through power cycles and strategy re-downloads.

Note that persistent variable values are NOT saved when:

  • A strategy with a different name is downloaded
  • The controller's RAM is cleared
  • Firmware is downloaded
  • The persistent variable object itself is changed (for example, a persistent table's length is changed)

Watch for more persistent variable tips in the next OptoNews.

Questions? Contact Opto 22 Product Support.

New Trending Video Shows How to Use PAC Display SuperTrends

PAC Display Trends video

The latest trend is right here: a step-by-step video showing you how to use SuperTrends in PAC Display.

PAC Display is our automation software for creating operator interfaces (HMIs). In addition to security and alarming, PAC Display includes both realtime and historical trending—a must for automation applications.

In this video, Opto 22 Director of Training Alexi Beck Gray walks you through configuring and viewing a SuperTrend, which plots up to 16 realtime or historic trend lines.

Watch the video now.

Updated Specification Guide for SNAP PAC System

SNAP PAC System Specification Guide

We've just updated the workhorse SNAP PAC System Specification Guide.

Whether you're just starting to learn about the SNAP PAC System, specifying new system parts, or ready to wire field devices to I/O, this guide will help.

The guide:

  • Describes the system's four components (software, controllers, brains, and I/O)
  • Shows you how to build a basic system and how to expand it
  • Includes dimensional drawings and specifications for all parts
  • Provides installation instructions and wiring diagrams

Download the Specification Guide now.

July Training Class Added, Seats Available

So many people wanted to come to free training in Temecula this summer that we've added another SNAP PAC System training class in July. As of this writing, there are still seven seats left for the new July 27-30 class, and you can register online using your my.opto account. (If you don't have one, it's easy to get.)

Your next chance for training in Temecula is in mid-September.

For more information, see the Class Details page on our website or contact the Opto 22 Training Department:
Phone: 1-951-695-3080
Toll-Free (in the U.S.): 1-800-835-6786
Email: training@opto22.com

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