Minimum length of profibus cable

Plc_User

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Dec 2005

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Belgium

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• Mar 13, 2008

• #1

I read somewhere that the profibus cable between two nodes has to have a minimum length of 1 meter. Although I see a lot of panels with very short profibus segments. What could be the reason for this minimum, and what is your experience and opinion?

Thanks

 

erolgke

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Dec 2006

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DÜZCE

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• Mar 13, 2008

• #2

Minimum cable length is not a problem in profibus comminucation,

 

Olaf

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Mar 2008

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Netherlands

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• Mar 13, 2008

• #3

True, in most cases it doesn't matter. But sometimes (don't ask me why) lengths < 1m cause strange problems!

 

krk

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• Mar 13, 2008

• #4

I take it you're referring to this note in the Siemens PROFIBUS network manual?

I specify 1m minimum length between nodes even though it can be a bit of a nuisance to lose the excess cable and keep the installation neat.

 

Olaf

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Mar 2008

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• Mar 13, 2008

• #5

Well you can take the risk and use lengths < 1m. Our machines are fairly standard (electric wirering) and we tested it once and apply it ever since.
But keep in mind, when you're having an unstable bus be sure to check the cable lengths first. Even when diagnotics points in the oposit direction!