Diagnostic repeater

[Plc_User]

I am intending to use a diagnostic repeater for a new project.
There are over 32 nodes, so I have to use a repeater whatever. But because it is a revamping of an old installation with reuse of some old profibus cables and profibus modules, I prefer to have the diagnostic options. Has anyone experience with this diagnostic repeater of Siemens? What are the possibilities to visualise the diagnostic info of the repeater on the touch panel?
I read that for correct topology of the fault, the minimum cable length between the nodes has to be one meter. I also read in general profibus information that Siemens proposes a minimum cable length of one meter (it should be better reflections or somthing like that). My experience is that especially between drives the cables are less then one meter. What are your experiences with cable lengths? And towards using a repeater, if there are less then 32 nodes, above what cable length do you prefer using a repeater? Will this repeater also result in bus with less disturbations?
Thanks

 

[Bratt]

Siemens have a standard fc and fb for this (FC/FB125) the fc is a simple version and the FB have more diagnostics. You can download this blocks free togheter with pictures for diffrent HMI's from Siemens website. You can also use system diagnostics in the HW config that will create DB125 for you. If you have a diagnostic repeater the pictures will display more info but the package can be used without a repeater. Remember that the repeater will only display error from nodes that are connected after the repeater. If you are running at low speed 1,5mb and the bus is properly installed the cable can be pretty long more than 100m before you run into trouble