Profibus DP "tee"s

Guys, we are installing a profibus DP system and have some analysers to connect to. We are concerned about daisy chaining the devices since the connection blocks have no internal connections between the incoming and outgoing cores. This means that a fault, or disconnection of one analyser will bring down the whole leg. "Tees" have been suggested but I have heard that teeing profibus DP cables is not a good idea. Can anyone shed any light on this please.
Regards
Steve D

Steve_D said:

We are concerned about daisy chaining the devices since the connection blocks have no internal connections between the incoming and outgoing cores.

Click to expand...

What are you saying there ? It makes no sense at all.
Anyway, daisychaining is the standard cabling structure with Profibus.

Hello Steve_D;

In the plants we are commissioning the client has the same requirements for our process valves and flowmeters. These do not have sub-D 9-pin interface for Profibus-DP, only screw terminals, and the client felt we had to provide a way for him to service the equipment without affecting the network.

We are using Weidmuller T-connectors for Profibus-DP, models 8714260000 and 8714240000 (this last with integrated terminator, externally powered, 24 V. To make sure we have as little effect as possible on network stability, we specify max. length of the spurlines to be 20 cm each (some Profibus documentations specify a maximum total length of all spurlines at 1,5 MB to not exceed 6 m; we try to remain as far from that limit as possible). The esiest way to ensure that is to install the T-connector on the pipe wue use to bring power to the equipment, very near the gland entrance for the network connection.

At 1,5 MB, we have yet to have a major problem with this setup, and we are finishing our 22nd plant over 3 years as we speak.

Hope this helps,

Daniel Chartier

Daniel,
Thank you, thats exactly the info I was after. Glad to see that you have been doing this for a while so the bugs would have had time to surface. We too will be making our spurs a short as possible.
Thanks again