RS-485 cable recommended reference


Thread Starter


hi members,

I want to know the reference (type) of the recommended cable for Modbus communication (RS485) between DCS (Yokogawa) and MVI94-MCM (Prosoft) to know that the environment in which I want to establish this communication is characterized by:
1-the distance between the two system is more than 500 m.
2-vibration because of (crusher, compressor motors of medium and high power).

I also want the cable, not influenced because electromagnetic interference.

and it is possible that members are already qui'ont this experience into practice gives me the steps and details as small, and thank you in advance.

And if it were possible members who have had this experience in the field they give me the details and the list of supplies is due and the type of cable

best regards.

Lynn August Linse

I agree with Curt - anything over 100m needs a good cable sold as 'suitable for RS-485'. All cable makers should sell such cables.

Vibration shouldn't hurt the cable, but you may want to carefully anchor the ends entering the terminal block - perhaps even use a non-corrosive chalk/sealant to immobilize the ends, because you will find if the stiffer main cable vibrates, it will be slowly flexing the finer wires crimped into the terminals with each move.

Be careful of your surge & grounding, and I'd suggest 1 end or the other MUST be isolated. Many people sell rs-485-to-485 isolators. This also prevents the 'blame game' with the DCS folks (who are never wrong, by the way). So if 'their' side of the isolator burned out ... then they must of mis-wired something. If 'your' side burned out, you need to pay to fix.
I have to apologize, Belden doesn't make a bonded pair RS-485 cable, the cat cables would probably work but 485 really should have individually shielded pairs. But they do have industrial strength cables for RS485, Profibus, Devicenet, etc. Those should do nicely.

For long runs a quality cable is important and 100% shielding is best on the factory floor. The bonded pairs are for vibration and so flexing doesn't change the characteristic impedance. I would expect a BP 485 cable to come along.