Tuesday, February 24, 2015

Part Two: Simplifying Remote SCADA with the Scheduler Plug-In

Posted by Sam Elsner

Last week, I described several challenges that SCADA engineers face while determining a remote data acquisition schedule. I also shared the top seven features that our market research identified as helping to resolve those issues. Today, I'm happy to introduce Kepware’s new Scheduler Plug-In for KEPServerEX, which allows our industry-leading communications platform to take on the role of a dedicated polling engine. We’ve designed the Scheduler’s UI with the same clean, minimalist look and feel that users expect from Kepware products. This means we paid attention to reducing mouse clicks and creating intuitive and tidy organizational structures, wizard-driven configuration for more complex features, and a workflow design that is consistent with all of the other tools that you’re used to using within KEPServerEX.

With the Scheduler Plug-In, users now have the Scheduler ability to control what and when KEPServerEX reads from devices—all within KEPServerEX itself. The plug-in allows users to create an unlimited number of schedules for an unlimited number of data points within KEPServerEX. It includes standard features that customers expect from a polling engine, such as the ability to define multiple polling periods per schedule with interval polling in addition to specific days and times. It also includes the ability to define exception periods where a schedule should not operate at all. And each schedule in the Scheduler Plug-In is, at its heart, a simple list of individual data points that should be read at the same time. The devices from which data is read are treated with secondary importance to the grouping of logically-related data (for example, all of your alarm points, all of your current flow pressures, and so forth) that may exist across multiple devices but that should be collected at the same time.

In addition to the standard functionality expected from polling engines, the Scheduler includes sophisticated features like the option to quickly reprioritize schedules, to adjust schedules in real-time to use different pre-programmed polling intervals, and to quickly map and automatically resolve multi-protocol collections of device data point addresses with any devices defined in the KEPServerEX project. Further, many of the Scheduler Plug-In’s features are exposed as data points (also known as tags) across our server interfaces, allowing SCADA client applications to adjust many aspects of an individual schedule’s behavior—or even the behavior of an individual device that belongs to the schedule —in real-time.

Much of the Magic You Can’t See

The notable features I described last week are features that users can see for themselves while using the Scheduler Plug-In. Behind the scenes, the entire KEPServerEX communications platform itself has been enhanced to support the concept of prioritized reads in a manner that precisely meets two key customer requirements:

  1. Don’t build something that forces users to manage a driver read request queue.
  2. If a high priority schedule starts while a low priority schedule is running, the higher priority schedule should be serviced immediately.

Drivers in KEPServerEX now understand read request priority granularly. If a high priority schedule begins to initiate while a low priority schedule is being processed, the drivers that are reading from devices that have data belonging to both schedules will pause their reads for the lower priority schedule (remembering the data that’s left to read) and immediately service the reads resulting from the higher priority schedule. Once the higher priority schedule completes, the driver will continue on with the device to service the lower priority schedule, picking up just where it left off.

Continuing with this example, for devices whose data belongs only to the lower priority schedule, if the telemetry system and project design permits it, the drivers will continue reading from these devices to service the lower priority schedule while the other devices in the project are being read to service the higher priority schedule. This intelligence greatly reduces users’ need to manage a read request queue, and it helps to prevent stale data on SCADA windows.

Polling Engines Are Required, But Here’s a Better Mouse Trap

Until the day that connectivity is so cheap that even the least expensive industrial device can have its own high bandwidth connection directly to headquarters, SCADA engineers who work with remote devices will need to be concerned with scheduling data acquisition. The Scheduler Plug-In for KEPServerEX seeks to provide and improve on the features offered by today’s polling engines, reducing the time and complexity of a task that is already time consuming and highly complex.

Next Steps

The Scheduler Plug-In is included in the new KEPServerEX version 5.17. Download it today to see how it can resolve data acquisition issues in your control system. Then, leave us a comment below. We’d love to hear what you think.

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