RS485 Comm Cable for Outside Use

Question

RS485 Comm Cable for Outside Use

ariccardo (Electrical)

(OP)

1 Jul 11 14:10

Can anyone please tell me what communication cable anyone one reccomends or uses for RS 485 communication outside in conduit? I use to use Belden 9742 but that is not reccomended for outside use the jacket is made out of PVC. Any help would be appreciated.

Thanks

MacGyverS2000 (Electrical) · Answer 1 · 2011-07-02 12:44:42

Are you saying it's in conduit, and the conduit is outside? If so, why do you care if the cable is rated for outside use?

Dan - Owner
http://www.Hi-TecDesigns.com

ariccardo (Electrical) · Answer 2 · 2011-07-05 06:27:23

Because any conduit in the ground fills with water which is what I am trying to avoid is moisture.

robertjo24 (Industrial) · Answer 3 · 2011-07-05 12:18:58

I often use an OSP rated Cat-5 cable that has a heavy PE jacket with a water blocking yarn. Genesis has one, P/N-50901008. Belden also makes them.
The Belden 9742 cable you mention isn't really meant for communications. I know it works, but it technically should not be used for that purpose. The problem is that the cable size and construction isn't meant to support RS-232 or RS-485 communications.
For proper operation, RS-485 communications should be carried across a small gauge (22 – 24) that has an appropriate twist and 120 ohms impedance. The OSP Cat-5 works great for that purpose.

If you go to Belden's web site and search RS-485 in their e-catalog, you will see some examples of industrial comms cable.

ariccardo (Electrical) · Answer 4 · 2011-07-21 19:22:37

So should this also be sheilded it looks like it should be from documentation. Does anyone know where or a link to where I can find a really good resource with recommendations on what to use for RS485 cable? what guidlines for the communication what is the communication?

Thanks

danw2 (Industrial) · Answer 5 · 2011-08-01 17:29:03

http://www.belden.com/pdfs/prodfaq/faqpr485.htm

Manufacturing of RS-485 Cables
Belden manufactures RS-485 cables. See part numbers 8132-8155 and 9841-9844.

Plenum RS-485 Cables
Belden manufactures RS-485 cables. See part number 1269, 8995-8996, 82729, 82841-82842, 88102-88107, 88109, 88112, 88118, 88125, 89182, 89207, 89705, 89728-89732, 89734, 89757-89758, and 89841-89842.

Run Length of RS-485 Cables
The maximum permissible length is a function of several variables including data rate and noise. The appendix of the RS-485 standard contains application guidelines including information related to cable length.

danw2 (Industrial) · Answer 6 · 2011-08-01 17:35:31

URL for Belden's catalog for Automation and control cabling. See page 28 for RS-485

http://www.belden.com/pdfs/03Belden_Master_Catalog/18Industrial_Cables/18Industrial_Cables.pdf

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RS485 Comm Cable for Outside Use