Download Directed Electronics MERLIN 2000 Specifications

Choice of the Physical
Communication Medium
Cabling Guidelines
Various Types of Physical Media
Two types of shielding:
Three types of conductors can be used:
b Metal pairs.
E52286
Type
E52289
Foil shield
Advantages
Disadvantages
Easy to install.
Fragile.
High-frequency protection
provided by the metal foil is
diminished by cable handling
(tension, torsion, etc.)
Foil tape
E52287
b Coaxial cable.
Drain wire
E52288
E52290
Single braid
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.
Excellent protection from
electromagnetic interference,
particularly at high frequencies.
Braid/shield
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.
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:
Medium
Shielded twisted
pair
Speed
Distance
Avg: 100 kbits/s 1 Km
Max.: 500 kbits/s
Coaxial baseband Avg.: 1 Mbits/s
Max.: 50 Mbits/s
2,5 Km
Coaxial wideband Average: 300
Mbits/s
Optical fiber
1 Gbit/s
10 to 50 Km
> 10 Km
Notes
Approx. cost
Easy installation 0.30-0.45 euros/m
Easy connection
Low immunity
Easy connection 0.60 to 1.20 euros /m
Good immunity
High performance
Idem
0.60 to 1.20 euros /m
Perfect immunity 4.50 to 6.00 euros/m
Low attenuation
Large bandwidth
Price still high
Note: You can also use electromagnetic waves that do not require a physical
medium.
20
Schneider Electric