Author Topic: Replace unshileded cable with shielded cable, is it a good idea?  (Read 686 times)

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Offline OmegaHyperion

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Replace unshileded cable with shielded cable, is it a good idea?
« on: September 05, 2017, 09:23:37 pm »
Well, the title basically asks the question,

What im up to this time, is repairing a piece of equipment, where i need to create a custom cable of sorts. Basically i need to put 2 75 ohm 2.8mm OD 2KV (at least) rated coax cables, together with 4 normal conductors into a single cable.

The coax isn't the problem, as i already know what will work. The question is, i would like to replace the 4 conductor ribbon cable that got destroyed, with 2 separate cables. The most convenient one for bundling the cable, is a 2.8mm OD shielded 110ohm cable.

The 4 conductors are for the fallowing:
+-15V power for an opamp.
Opamp Offset control cables (going to a pot that is more convenient to access, then where the amp is)

The question is, will the heightened capacitance of the shielded cable pose a problem with the amp offset correction, and if not, should i ground the shields, or leave them floating? (the connector happens to have a ground connector).

If this poses a problem, ill go for unshielded cables.
 

Offline Armadillo

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Re: Replace unshileded cable with shielded cable, is it a good idea?
« Reply #1 on: September 05, 2017, 09:38:01 pm »
I think the shielding forms a capacitance and helps reduces RF and background noises since the application is merely DC power supply.
But for practical purpose, this benefit can be simply replaced by a ceramic capacitor so in reality is a expensive way to run the cable like so.
Furthermore the braids could come in contact with the core cable creating a short circuit.
I would just follow the original for flex and aesthetic even though it will work with slight benefit.
 

Offline OmegaHyperion

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Re: Replace unshileded cable with shielded cable, is it a good idea?
« Reply #2 on: September 05, 2017, 10:14:48 pm »
 

Offline Armadillo

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Re: Replace unshileded cable with shielded cable, is it a good idea?
« Reply #3 on: September 05, 2017, 10:19:10 pm »
Be sure that the core size [mm2] is thick enough for the power supply current and the voltage drop is the same or better than the original.

Edit: 0.4mm2 Forget it! Just Drop the idea.


« Last Edit: September 05, 2017, 10:21:15 pm by Armadillo »
 

Offline OmegaHyperion

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Re: Replace unshileded cable with shielded cable, is it a good idea?
« Reply #4 on: September 05, 2017, 10:25:52 pm »
Good call, i had asumed the ribbon cable was a typical one, with 0.25mm^2 conductors, turns out its a 0.785 mm^2 conductor. Should have checked instead of assume i know.
 


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