Investigation of Industrial Environmental Influences on Clock Sources and their Effect on the Synchronization Accuracy of IEEE 1588

Networked Industrial Devices must fulfill requirements regarding temperature ranges, noise immunities, and mechanical loads (e.g. DIN EN 60068-2-6). The effects of these environmental conditions on the stability of the frequency of clock sources are well studied [1, 2]. However the influence on the synchronization characteristics of IEEE 1588 can be derived only partly from these investigations. The dependency between the frequency drift (df/dt) and the transmission period of the synchronization frames T is very important for the achievable accuracy of IEEE 1588-based networks. In order to examine these effects, a novel measuring method is proposed in this paper. The results of exemplary measurements at a crystal oscillator with different temperature and mechanical loads will be discussed. These results are compared with the existing requirements for industrial communication systems, especially for the Industrial Ethernet system PROFINET. The objective is to derive coherences and rules for the implementation of functional components of the synchronization procedure.