Specifications

20
Schneider Electric
Choice of the Physical
Communication Medium
Various Types of Physical Media
Two types of shielding:
Note: Shielded cable with a simple braid can increase protection by a factor of up to
a 100 from a few MHz up if the shielding is properly connected.
Shielded cable should be chosen when it is necessary to:
b Limit outside interference that could affect a "sensitive" cable.
b Keep a "polluting" conductor from interfering with nearby cables or equipment.
Only metal pairs are described below, since they are the most frequently used for
data transmission today.
Advantages of metal pairs:
b Lowest price of all media (approximately 0.30 euros/meter).
b Easy to implement.
b Simple and inexpensive connections.
Major disadvantages:
b High signal attenuation: signal regeneration circuits are required after
approximately 2000 m.
b Signal distortion unacceptable for high transmission speeds (greater than a few
Mbits/s).
b Small bandwidth.
b Problem of crosstalk between pairs in the same cable. Use of shielded cable can
limit crosstalk.
Summary table of media:
Note: You can also use electromagnetic waves that do not require a physical
medium.
Three types of conductors can be used:
E52286
b Metal pairs.
E52287
b Coaxial cable.
E52288
b Optical fiber.
Twisted pairs with braided shielding are
recommended for all RS485
communication cables for Schneider
Electric products.
Definition: (according to IEC 439-1)
Screening (or shielding) is used to protect
conductors or equipment against
interference caused in particular by
electromagnetic radiation from other
conductors or equipment.
Type Advantages Disadvantages
E52289
Foil shield Easy to install. Fragile.
High-frequency protection
provided by the metal foil is
diminished by cable handling
(tension, torsion, etc.)
E52290
Single braid Excellent protection from
electromagnetic interference,
particularly at high frequencies.
Fairly easy to implement.
Sturdy.
Compatible with Sub-D and
mini-DIN connections.
The effectiveness of a shielded
cable depends on the choice of
shielding, and above all how it
is used.
Foil tape
Drain wire
Braid/shield
Medium Speed Distance Notes Approx. cost
Shielded twisted
pair
Avg: 100 kbits/s
Max.: 500 kbits/s
1 Km Easy installation
Easy connection
Low immunity
0.30-0.45 euros/m
Coaxial baseband Avg.: 1 Mbits/s
Max.: 50 Mbits/s
2,5 Km Easy connection
Good immunity
High performance
0.60 to 1.20 euros /m
Coaxial wideband Average: 300
Mbits/s
10 to 50 Km Idem 0.60 to 1.20 euros /m
Optical fiber 1 Gbit/s > 10 Km Perfect immunity
Low attenuation
Large bandwidth
Price still high
4.50 to 6.00 euros/m
Cabling Guidelines