This configuration of S7-400H PLC is better or not without repeater.

(in previous  the network communication between RIO7 & RIO8 by FO but due to OLM/FO cable  issue it replaced by profibus DP)

Hello Prasa;

You show a good representation of your network, but we still need a bit more information to help you out. Or you may find enough in this post to help you calculate your needs yourself.

The reqiurement for a repeater on a Profbus-DP network relies on the definition of a Profibus segment: every time your network exceeds a segment, you need a repeater.

That being said, the definition of a segment depends on 2 factors, and as soon as you exceed one, the need for a repeater is immediate.

So: first, the length of a segment depends on the baud rate of your network. See the screenshot below, taken from the Procentec site:

https://procentec.com/content/profibus-cable-length/

If you maintain a network baud rate of 12 MB, you first segment must end after 100m; if you bring the speed down to 500 kB, you can run up to 400m before you need to use a repeater. Note that these lengths are actual cable runs, not estimated distances between  2 nodes on your engineering plans.

On the other hand, RS-485 networks (Profibus is based on RS-485 standards) cannot handle more than 32 stations on a segment (a repeater counts as a node, even though you do not attribute it a Profibus address), so a real total of 31 nodes is your second limit.

So as soon as you overextend your segment length, or as soon as you try to place node a 32nd node on your network, a repeater is mandatory.

One more consideration: you show cabinets containing more than one node. An important design guideline, to prevent reflections during transmission, is that the minimum distance between 2 nodes must be more than one meter, even inside a single cabinet.

Please make sure this is looked after, and take into account the extra lengths of cable if it matters.

Hope this helps,

Daniel Chartier

Thank you dchartier for my clarification about communication performance

regards,

prasa