Profibus DP to a flowmeter


Thread Starter

John Barnet

How do you connect a Profibus DP flowmeter to the network? The problem we are having is that Profibus DP must be Daisy Chained instead of Spur line/trunkline like Profibus PA. We have one 1" conduit hole to go through. We need to have a line coming in and a line going out. How can you seal around a conduit fitting with two Profibus DP lines? The sheilds on the Siemens DP cable do not have a drain wire so how can you ensure that the shields are continuous? My idea was to use a spade lug for the A&B lines then connect them to the proper terminals within the housing but no idea of how to do the shield. The main problem is that we are not putting this device on the end of the line so we must continue to the next device and still be able to remove this meter for service.

Daniel Chartier


Profibus-DP prefers daisy-chained connections, but tolerates spur-lines as long as the spurs are very short. We connect our ABB flowmeters using Weidmuller (there are other manufacturers of such equipment, check on Google) T-Connectors for Profibus-DP, and keep the spur at less than 20 cm. We install the T-connector on the conduits for the flowmeter power line, so we are within that tolerance. These connectors come in 2 types: pass-through (regular inline connections) and terminated (end-of-line connectors) with a 24 V DC power connection for the termination circuit.

As far as the shield connection, we strip a 3- inch length of Profibus cable, twist the shield on itself and insert it in in a heat-shrink or isolating wire sheath. That way we ensure mechanical strength and electrical connectivity for the shield connection.

We have used this setup for more than 2 years now, in seven plants, without any problems. We use it on flowmeters and valves on our process line.

Hope this helps,
Daniel Chartier