In current control systems, it is important to get information from field devices just when the information is needed for applications such as maintenance, asset management or diagnosis. However, getting information for those applications is not always easy. Many control systems do not provide enough information for those purposes, because they are designed for its own purpose: to control the plant. Since the devices themselves possess the necessary information, it is desirable for such applications to have direct access via open and standard interfaces. It is shown that an OPC XML-DA (XML Data Access) server embedded in the device is a possible candidate for this objective. We have developed a prototype server on a small embedded controller. In this paper, we evaluate the experimental system consisting of the embedded OPC XML-DA server and data acquisition application, and discuss where performance bottlenecks are and how the performance can be improved of the. server. Finally, we discuss the performance evaluations on the improved server and the architecture which makes effective use of the server.
