What is OPC ? OPC stands for Openness, Productivity, and Connectivity. OPC is a specification that has been developed over the last 8 years by a team of 150 companies and represents a shining example of how industry specification organizations can be effective. The OPC Foundation is an independent organization that is supported by the fees paid on a equitable basis by the members of the foundation. Software Toolbox was a Charter Member of the OPC Foundation.
The goal of the OPC specification is to provide an open, flexible, plug-and-play software standard for modular software interoperability in the automation industry. The specification is based upon the Microsoft Component Object Model (COM) and addresses the specific needs of the automation industry such as data access (i.e. drivers), alarming, historical data access and trending, batch, and more. You may ask “what about ActiveX - I thought it was the standard?” Well, OPC takes the concepts of properties, methods, and events that you learned about for ActiveX controls (see related articles in Object Technology Center) but goes a step further to address automation specific issues and actually provide specific names for many of the interfaces based on the application type. For some products, ActiveX will be all you need, for others you may choose to use an OPC compliant product.
The long-term benefits for the user of OPC come from the ability to pick best-of-breed application modules such as trending, alarming, graphics, etc. from various sources and bring them together with common interfaces. For example, your graphics environment could function as an OPC client, getting it’s data from an OPC data server connected to your PLCs. The trending package you choose could function as an OPC client to the graphics package to get it’s data, which also happens to be an OPC server! Or it could go direct to the OPC data server. Although this concept may sound like the old DDE server model that has been around since the late eighties, but it is not. When DDE was invented, COM and the whole 32 bit world did not exist. The OPC specification is built upon COM and uses Windows technologies to provide superior performance and robustness that will never be found when using DDE. Simply put, 15 years of technological advancements since DDE was first used (circa 1988 in Windows 2.0) make a huge difference!
So as you begin looking at manufacturing software packages, whether they are HMI or others, find out if they are OPC compliant. If they are, you’ll be able to shop Software Toolbox and find all the OPC products that you need in one place. To learn more, visit our website as we’ll be adding more technical articles there as OPC becomes more and more popular.