I am working in a project with fieldbus instrumens, however, we have bought conventional 2-Wire 4~20mA instrument cable. Can I use this cable with the fieldbus devices or I have to use a specific fieldbus cable?

Regards,

Thiago Fonseca
[email protected]

 

You do NOT have to use Fieldbus cable though you do need to be sure it is shielded twisted pair to get respectable results. The specification supports 4 cable types. By not using Fieldbus cable the 'penalty' is distance you can run your cable. Tools are available to test the ability of your cable to reliably run Fieldbus signals.

To learn more about the use and types of different cables you can download the Physical Layer guidelines at the Foundation Fieldbus web site http://www.fieldbus.org or the Wiring guide from Relcom at http://www.relcominc.com

Good luck with your project!

Ian Verhappen

 

Thiago,

If you use PlantTriage instead of fieldbus, you can use any cable you want and you get lots more analysis.

See: http://www.expertune.com/r2.asp?f=NerdsInControl&d=Jun04&l=fieldbus.html

for a comparison to fieldbus.

Regards,

John Gerry

 

you can use the same cable for 4-20ma and fieldbus, the grounding concepts are also the same.

Hope this helps.

 

Usually for new installations specific cables to be used however ordinary instrument cables could be used in fieldbus systems causing some distance limitations in cabling for intrinsic safety loops.

 

Depending on the spec of your cable you may be limited to only a few hundred meters. If the wire pairs are not twisted you will not get good communication.

Fieldbus was designed to work using regular instrument wires, but that is primarily intended to make migration from conventional to Fieldbus easier. For any new installation make sure to buy proper cable.

I suggest you purchase Fieldbus cable

Jonas Berge
SMAR
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www.smar.com
Learn fieldbus at your own pace: www.isa.org/fieldbuses