Re: Serial Connection -- shielding
* Stan Hoeppner <firstname.lastname@example.org> [110328 06:24]:
> Moczik Gabor put forth on 3/28/2011 12:01 AM:
> > Stan Hoeppner wrote:
> >> We bought DB25 plugs in bags of 100, and used spooled CAT5 as the noise
> >> rejection is many times that of CAT3, allowing greater distances across
> >> sprawling warehouses.
> > RS-232 uses single-ended signaling and requires shielded cable, twisted
> > pair doesn't help either.
Shielding provides immunity (not always perfect) against
radio-frequency interference. But shielding (aside from an enclosure
or conduit of iron or steel) provides no immunity against magnetic
If an RS-232 cable does not run near electric motors or switchgear, or
make a long run parallel to power cables, and if radio-frequency
interference is not a problem, then CAT5, CAT3, or even multiple
strands of lamp cord may be satisfactory, without a shield. In fact,
lamp cord -- typically 18 AWG stranded copper -- should allow longer
runs, because of its much lower resistance (and thus, lower signal
attenuation). And, at some point, capacitance of the circuit can
become a problem, because it limits the usable data rate.
Who is this that darkeneth counsel by words without knowledge? - Job 38:2