Emerson’s Jonas Berge is an active member in the ISA SP104 committee, responsible for advancing the Electronic Device Description Language (EDDL) standard (also known as IEC 61804-3.) You may recall Jonas from earlier EDDL posts. This standard creates interoperability between digital field devices from simple sensors to complex devices (drives, analyzers, etc.) with control and asset management systems. Interoperable communications include device diagnostics, asset management and user interface displays.
Jonas has written a short piece, OPC Made Easy, in the April issue of Control Engineering Asia magazine. In this article, he describes how EDDL can save many hours of OPC server configuration, which can help speed up a project’s completion. For background, he begins by reminding readers how this important standard makes sharing data between OPC servers and OPC clients easy:
…external software in HMI clients and other users can easily access the wealth of detailed diagnostics and information in hundreds or thousands of intelligent devices around the plant.
Configuring OPC clients is easy: just point and click on data in the OPC server.
The challenge is in the configuration of the OPC server:
Configuring the OPC server includes entering device addresses and communication settings as well as creating the “namespace” which entails entering tag or descriptor for each and every piece of information along with the memory register address for the parameter as well as its data type, and range where applicable. This parameter “mapping” is the most time consuming and error prone part of OPC integration, but once done the rest is easy.
Jonas explains how EDDL can automate the creation of the OPC server configuration for devices digitally communicating via HART, Foundation fieldbus and Profibus. He writes:
Automatic OPC server configuration is made possible because EDDL is a descriptive technology similar to XML or HTML, declaring the properties of the data in the device for use by the auto-configuration mechanism. EDDL is the only device integration solution that is declarative.
Although not in the article, Jonas relayed an example to me where an AMS OPC Server was used to pass a slug flow alert from a Micro Motion HART device to an older distributed control system (DCS) that did not support HART communications pass-through. Before the solution was implemented to send this alert to the DCS via OPC, slug flow would cause over-charging of materials added to a batch. Now, the operators are alerted to slug flow conditions and can pay special attention to the surrounding process equipment.
The EDDL.org website remains the best source for information about this standard. You can also join the EDDL email list hosted by ISA to keep up and participate in the conversation around this standard.