Instrument Signals and Interference with Telecommunications

Ideally your RF and control lines should be routed separately -- especially if RF leakage into the terminal equipment via your signal lines could cause a potentially dangerous situation or equipment malfunction. But whether your current loops are routed with the RF cables or not, I would strongly advise using shielded cables for your 4-20 mA signals. Offshore oil platforms are electrically-noisy environments, to be sure, and co-located RF cables won't be your only potential source of spurious signals. Err on the side of safety. Always.

thanks

Can you route your signals in a separate-but-parallel metal tray? Preferably a ferrous one? Point out to your manager that running high-power RF cables alongside control signals is setting the stage for Bad News. Cite safety concerns due to potential equipment malfunction should RF leak into the terminal equipment. I'm a real bastard when it comes to safety issues, so have him/her write me here if he wants an earful. Offshore oil platforms are no place to cut corners.

If RFI is a problem -- given that you're >required< to co-locate your signal lines with RF cables (are there no alternatives?) -- you can use ferrite beads on your signal lines where they come into the equipment. Here are some links for your review (below). You may also wish to google various shielding techniques where RF and control signals must be co-located.

Amidon (mfr of ferrite products, including beads and cores)

RFI supression

RFI supression

RFI supression

RFI supression

Dear

I'd like to explain the case to you in more details, it seems you are an expert on this. on the platform , there is only one small control room, this control room has all the EDS/F&G/HIPPS and DCS system cabients, it has also the telecom cabients which feed the microwave anttennas, so the control system field cables will run out the control room to be connected to the field instruments (4-20 mA, Digital, serial coms,..etc) , the intermidiate Frequency (IF/RF 0-350MHZ) goes through the antenna cables to the microwave anttenas. my point now is to know the regulation concerning the RFI and the minimmum separation distances and the proper desgin for this separation to separete between the RF carriying cablles and the control system cables. Also the separation between the telecom equipment generating the RF and the control system equipment.

How long is this control cable? what signal type do you use in the cable?

What meaning is antenna cable IF(140,35MHz) 140Mhz, 35M or 35Mhz(IF) 140M?

the RF cable is arround 60 meters, from the control room to the microwave anttena. the frequency range from 0-350 MHZ

haha, IF=\=RF, field different, engineering is also differnet.

how many ports do you want? how long are these cables?

IF(intermediate frequency, which is a range from the radio frequency RF), cables are 60 meters

I wonder why this is a problem? A coaxial cable for rf and a shieding twist wire for 4-20ma. you can even bind them together.

What signal could ocupy so wide band? are you confirming it from 0-350Mhz?

I try to listen to expert's answer.