Instrument cables between Control room and field instrumentation

Hi all,
I want to know what kind of instrument cable (4-20mA signals) between Control room and field instruments in temperatures up to 50oC? Cables.

when I should use Instrument single-pair cable of 2.5mm2 core area OR Multi-pair cable with 1.5mm2 core area.

I have differen type of instrumentation flow instrument, Temperature Transmitter, Pressure Transmitter, Level switch, Level indicator.. etc.

plz guid me to choose the cable that can be used, the maximum length between feild instrument and control room is 200m.

Any help will be highly appreciated.

Omar

I use 0.75 sq mm screened twisted pair for all these and most of my comms as well. Ground the screen in the PLC cabinet only, not at both ends.
If you are using voltage signals - 1-5 V, 0-10 V, you may need to use larger cable due to voltage drop problems.
The other problem with voltage inputs are that noise can be induced into them very easily.
Best to stick with 4-20 ma wherever possible.

If more than 4 or 5 cables of that distance seems like distributed I/O over ethernet or some other protocol would be your best option.

Less wiring = Lower cost. Plus no degradation of signals

Thanx guys I appreciat ur help so much.

I have also MCC "Motor Control Center" should be controled from the same control room, so I have many signals should be connected from the MCC to CR, such as Motor fast,Motor slow, Alarm ,Start,Stop ..etc

Omar