#7 - PROFIBUS installation and design tips

Despite  being a relatively old protocol (almost 30 years old),  PROFIBUS is still widely used and has more than 60 million nodes in operation,  according to PI . 

There are sophisticated equipments to do network analysis, however before using them an advice is to review some key points from the design and installation point of view that we will show in this post.

In practice, many simple mistakes are made that can be avoided such as:

• Failure to observe the minimum distance between the PROFIBUS network cables and the power cables (motors). Try to have at least 10cm between these cables and, if possible, install an aluminum or steel separator inside the tray for better segmentation of the power network. When these cables have to cross, only in 90 degrees.
• It is not allowed to have a loop on PROFIBUS cables or short radii (minimum 20 times the cable diameter). In addition, it is important to have a minimum length of PROFIBUS cables of 1 meter.
• Lack of grounding of the trays with the network cables. A grounding point is recommended every 20-30 meters.
• Exaggerated number of devices per network segment. In practice, it is better to avoid having more than 30 devices per segment (including repeaters) on the PROFIBUS network.
• Maximum network distance exceeded by the  network bandwidth. For example, for a 1.5Mbps network, do not exceed 200m of network length.
• Failure to ground the PROFIBUS network cables. PROFIBUS cables must be grounded at the entrance to the main panel at the bottom. It is important to have only this single grounding point in the PROFIBUS network to avoid having a ground loop. 

For more details on the subject a great document is this " Installation Guidelines for Cabling and Assembly ".