Evaluation of Delays Induced by Profibus PA Networks

The delays associated with the use of Profibus process automation (PA) networks within control loops are investigated in this paper. A SMAR IF303 device, a SMAR FI303 device, a DeltaV distributed control system, and a Siemens DP/PA link are used to implement a Profibus-PAnetwork-based test loop. Both analysis and experiments are performed on the test loop. Loop-back delay models are developed and then validated against experimental results. Suggestions to potentially reduce Profibus-PA-network-induced delays are provided. A comparison between the estimated and the measured loop-back time demonstrates the accuracy of the delay models. Furthermore, the Profibus-PA-network-induced delays are compared against the delays induced by an equivalent Foundation Fieldbus H1 network with either hybrid or control-in-the-field architecture.