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rajant_2001
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Join Date: Jan 2007
Posts: 35
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Type of Digital Input Cable for PLC/DCS

08/04/2011 5:06 AM

We are Boiler manufacturer. The boilers supplied to Steel and other process industries. The control is through SCADA based PLC or DCS. We are having some kind of dispute on the type cable to be used for digital inputs (i.e) Screened pair cable or multicore control cable. The introgation voltage is 24V DC. Forum can give their views with pro and cons.

R.Thiyagarajan.
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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#1

Re: Type of Digital input cable for PLC/DCS

08/04/2011 5:23 AM

Multicores are widely in use for digitals, using one core as the 0V common return.

Multipairs are a better bet for analog circuits.

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bravo88
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#2

Re: Type of Digital Input Cable for PLC/DCS

08/04/2011 12:02 PM

Use shielded twisted pair.

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Mikerho
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Hobbies - Musician - Engineering Fields - Chemical Engineering - New Member Engineering Fields - Control Engineering - New Member Engineering Fields - Instrumentation Engineering - New Member

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#3

Re: Type of Digital Input Cable for PLC/DCS

08/04/2011 2:13 PM

And the twisted pair vs multicore digital cable dispute spreads like a virus to CR4.

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msamad
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#4

Re: Type of Digital Input Cable for PLC/DCS

08/05/2011 2:57 PM

I would suggest to use instrument cable (screened pair) rather than the multi-core control cable. Screened pair cables are capable of keeping the original signals of the cables separated from outside noise, such as, electromagnetic, electrostatic and radio frequency interference. For the case of SCADA and PLC sensitive signals, instrument cables are used to avoid the inference with the surrounding noise.

See this comment:

http://cr4.globalspec.com/comment/537874/Re-when-can-I-called-a-cable-to-be-a-power-cable

- MS

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