Alarming Differentiation in Modern Control Architecture
Alarming in modern control architecture is the process of setting automated notifications when certain changes in operation occur. Over time, different methods of alarming have been developed. The right one for your project will depend on your application and the specific types of products and alarms you use. In general, however, the time it takes for machine operators and workers to receive these notifications is a key determining factor, as this affects the speed with which potential issues are resolved.
The traditional method of alarming for most manufacturers, including Rockwell Automation’s legacy controllers (non-Logix5000), is server-side HMI alarming. Server-side alarming involves configuring alarms within the HMI server, seperate from the controller program. The HMI server then polls the various process controllers for alarms. Rockwell Automation® continues to offer this functionality in FactoryTalk View Studio.
Modern server-side alarms are more advanced than RSView32 or legacy HMI alarms, but they come with considerable downsides:
- They must be configured within both the HMI programming software and the process controller programming software, so any changes to the alarms require coordinated edits to both programs.
- They constantly poll the controller, creating a large amount of network traffic. If there are other devices on the Local Area Network (LAN) and many alarms are continually scanning, the bandwidth capacity can very quickly be exceeded.
- They are time-stamped at the HMI, not the process controller, affecting the accuracy of the event time.
Logix-based alarming is an alternative method to server-side alarms that has decreased load on the network due to the following:
- They are configured only in the process controller; there is no alarm configuration in the HMI server software.
- Logix 5000 controller-based alarms are easily added and modified while online with the controller through Studio 5000 Logix Designer.
- The alarm condition is detected by the process controller and produced onto the network.
- FactoryTalk View SE HMI clients subscribe to the produced alarm.
- They come with an alarm broadcast functionality that notifies every HMI client attached to the processor when a Logix-based alarm is triggered.
Additionally, time stamping for Logix-based alarms is more accurate than in server-side alarming, as time stamps for events are generated from the processor within milliseconds. They are then sent to the HMI clients to be logged into the alarm history.
Both Logix 5000 controller-based alarms and Logix tag-based alarms are centrally managed from Studio 5000 Logix Designer, a platform designed for ease of use and speed when configuring or editing alarms. These alarming methods can handle applications with a high number of configured alarms as they have a small memory footprint, need only to be evaluated periodically and enable XML imports and exports. When triggered, whether it is analog or digital, an alarm automatically registers in FactoryTalk Alarms and Events.
The products that you use to employ your chosen alarming method will be those that fit with your application’s needs and limitations. As with any tool, however, Logix 5000 controller-based and Logix tag-based alarming methods work best when integrated with the products designed to support them. The following Logix 5000 controllers support Logix 5000 controller-based alarms and Logix tag-based alarms:
- CompactLogix 5380
- CompactLogix 5480
- GuardLogix 5580
- Compact GuardLogix 5380
- ControlLogix 5580
- FactoryTalk Logix Echo (V2 and up)
For the HMI, either FactoryTalk View or FactoryTalk Optix can be used for these alarm types.
FactoryTalk View and FactoryTalk Optix do have some differing capabilities when it comes to alarming. With FactoryTalk Optix, you can specify Optix-based (internal) alarms that do not originate from the controller. These alarms require no HMI design and support precise time stamps, customization of alarm messages and evaluation at scan rate. There are also differences in the shape that pre-built alarm objects take in FactoryTalk View vs. FactoryTalk Optix. FactoryTalk View SE offers an alarm banner and alarm summary, while FactoryTalk Optix enables users to access an alarm banner (which displays active alarms at runtime), alarm grid and an alarm history grid within the template libraries.
Whichever alarming method you choose, make sure it supports your the processes and products that make up your facility's process control system and gives you the speed you need for notifications.
Additional Resources
- Introducing FactoryTalk Optix: The Latest Visualization Platform by Rockwell Automation (Article)
- Using Logix Tag-based Alarming with FactoryTalk View SE (Video)
- FactoryTalk Optix Getting Started - Alarms (Video)
- Introduction to FactoryTalk Alarming with FactoryTalk View SE (Video)
- Rockwell Automation Alarm Types
Looking for more information?
The Reynolds Company, as an authorized Rockwell Automation distributor, can supply you with any of these products. Our automation specialists will work with you to understand the specifications of your application and suggest the alarming method, controllers and HMI to fit your needs. We host training events and online learning sessions throughout the year to ensure our partners are well-equipped with the skills and knowledge to get the most out of these products. If you have any questions about the best ways to optimize your control architecture, reach out to your account manager at The Reynolds Company or your nearest branch.