【正文】 g with automation within a pany, from the enterprise management level through the process supervision level right down to the control equipment on the plant floor, will have a direct and positive influence on the pany operations.The software used in pany administration and that used in process automation are moving closer and closer to each other. This development is largely due to the widespread and growing use of Windows NT as the single operating system in many organizations. Windows applications are so widely used today, especially in the administrative environment, that it would be hard to imagine running a business without them. The next level we are aiming at is the standardization of munication between the different levels in a pany. With the fast developments in both PC hardware and software technology, powerful and integrated systems (such as Microsoft with Windows NT and lntellution with FIX and Visual Batch) are available that, earlier, were only possible with high investments. Earlier systems also had the disadvantage of frequently offering only island solutions. The greatest amount of effort and therefore costs involved with implementing automation systems has been related to solving the problem of interfaces between different types of equipment hardware and software.The historical problem has always been that the data of different systems all have different formats and munication protocols. This is very important when, for example, drives are connected to a PCbased SCADA system. Software vendors, such as Intellution, with their process monitoring, control, and data management system, the FIX, were required to develop an individual I/O driver for each protocol. This I/O driver would then allow for the connection of the SCADA software to each of the different field I/O devices (PLC39。s, I/O systems, controllers). Clearly the development by software vendors of unique drivers for each different type of plant floor control equipment is not only time consuming and inefficient but also inherently adds additional risks to the successful and timely pletion of a project. It is for these reasons that five panies with Microsoft, decided to work together to remove these munication barriers.2. What is OPC (OLE for Process Control)In cooperation with Microsoft, an OPC Task force consisting of 5 panies, Intellution, Opto22, FisherRosemount, Rockwell Software and lntuitive Software was founded in May 1995. The mittee39。s aim was to fully define interfaces that are based on the OLE/COM standard (OLE=Object Linking amp。 Embedding, COM=Common Object Model) with Microsoft. The first draft of the specification was pleted by the end of to the collaboration of 90 panies worldwide, which checked this daft specification, the first release of the specification was pleted in August 1996. The goal of the OPC mittee is to provide a standard application programming interface for data exchange that can simplify I/O driver development and improve operator interface system performance.Any people still remember installing how difficult and time consuming it could be to install a printer on a DOS based system. Today Plug and Play with Windows 95 and Windows NT makes the entire process almost effortless. Plug and Play means that all cards inside the PC or devices connected to the PC are automatically recognized by the operating system. The user very often simply has to confirm the puter choices or select an option from a picklist. The aim with OPC is to achieve the same kind of easeofuse with the connection of process control equipment to a PCbased process monitoring or control system. In the example of image , Without OPC it is clear that in this scenario, the applications X , Y and Z must municate with four different types of process control equipment. That calls for using 12 different I/O drivers. With OPC, every participant can municate using a standard interface.Many manufacturers of hardware and software have already announced their intention to release products that follow this standard. The following ments are to explain why and how OPC simplifies the interfaceproblem and decreases the costs and time of automation projects.OLE/COM stands for Microsoft39。s object technology that aims at integrating applications with a great deal of patibility between the various applications. For example, a CAB drawing can be integrated into a Word document or an Excel table. Even applications that are programmed in different languages can be integrated. OLE is based on the binary standard and munication between different OLE ponents is possible. The importance of the OLE/COM integration for automation solutions was realized by the software providers. OPC is a munication standard that is based on OLE, and it will allow for more efficient and easier munication between the different automation levels. Using the OLE technology described above, OPC defines methods and objects to achieve munication between the different software applications, no matter if these exist on a PC in the process management environment, or on the process control equipment.The expansion of OLE functionality39。s makes software systems seem more and more like modules or ponents. This makes the information accessible to all connected OLE clients (see image ).3. Standard InterfaceMany manufacturers of DCS systems, PLC39。s and controllers have already tested the OPC specifications and will shortly begin to ship OPC interfaces with their hardware. This development allows the user to decide freely which hardware ponent is best suited to a particular application. There is no longer and need for long discussions or I/O driver development. Hardware manufacturers of DCS’s , PLC’s and controllers will benefit from the reduced development expenses. Each hardware or software manufacturer only has to support one interface. There will no longer be a driver required for each hardware system released by various manufacturers. A produc