Turns on ferrite for front-panel wiring

  • Thread starter Thread starter Peter Rossiter
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Peter Rossiter

What is the purpose of the ferrite ring I see in a lot of PCs?

On my PC, the wires going to the front panel are given one turn
around it.

On a technical note, does it make any difference if the loop of
wires through the ferrite ring is tight (all wires close against
the ring) or loose (part of the loop an inch or two away from the
ring)?
 
"Peter Rossiter" said:
What is the purpose of the ferrite ring I see in a lot of PCs?

On my PC, the wires going to the front panel are given one turn
around it.

On a technical note, does it make any difference if the loop of
wires through the ferrite ring is tight (all wires close against
the ring) or loose (part of the loop an inch or two away from the
ring)?
Click to expand...
EMI supression. I think it's enough that it passes through the ring,
and the loop is just to hold it in place, but I could be wrong.
 
mutual inductance, an increase the flux level = a decrease in rf operating
freq.
the more turns, the tighter, the better.
however, for stray RF from a PC a single loose turn is often enough
microhenrys to squash it

mike
 
Peter said:
What is the purpose of the ferrite ring I see in a lot of PCs?

On my PC, the wires going to the front panel are given one turn
around it.
Click to expand...

Keeping RF noise out of the wires. Not really essential.
On a technical note, does it make any difference if the loop of
wires through the ferrite ring is tight (all wires close against
the ring) or loose (part of the loop an inch or two away from the
ring)?
Click to expand...

For this purpose, not really.
 
mike said:
mutual inductance, an increase the flux level = a decrease in rf operating
freq.
the more turns, the tighter, the better.
however, for stray RF from a PC a single loose turn is often enough
microhenrys to squash it

mike
Click to expand...

The RF choke is probably there simply because some fool of a competitor
fitted one, and customers now expect to see one fitted.

If it has one turn, it's probably that is the absolute minimum necessary
to meet the current EMC radiation specs. Although more turns would
probably be more effective, this would increase the cost.

Ian.
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