Ari Koponen, Manu Huttunen, Riku Pöllänen, Olli Pyrhönen

Applicability of OPC to real-time data collection: simulation study

The OPC OLE for Process Control provides an easy way to connect simulation systems to control systems, but there has been little research on the reliability and timing accuracy of OPC servers.

Actual sampling time of data can be determined using a fast counter as a variable. Variations in the sampling time can be examined using consecutive sampled values of the timer to construct jitter values. Difference in sampling time between variables can be observed by reading the same counter value from different server channels.

In this study timing accuracy of one OPC server was considered and reliability of variable values assessed. Accuracy of the time stamp provided by the OPC server was evaluated and network and CPU load monitored. Tests were conducted using different settings at both server and client side.

According to the results the timing accuracy and variable reliability varies depending on the server and client settings. By using correct settings the timing accuracy of the server is good and it provides correct values. Settings also affect the accuracy of the time stamp as well as the CPU and network load.