Rockwell Automation 57C570 AutoMax PC3000 User Manual - Manual (Page 43)

3Ć5
3.2 Choosing the DCSĆNET Network Media
A DCSĆNET network can be built using coaxial cable or fiberĆoptic
cable. FiberĆoptic cable is recommended when the following factors
are required by the application:
D High noise immunity Ć FiberĆoptic cable is not affected by
electromagnetic interference and can be installed with other signal
or power wiring.
D Isolation Ć Ground loops and spurious signals are prevented since
there is no electrical connection between the two ends of the
fiberĆoptic transmission system.
D Safety Ć FiberĆoptic cable can be used in chemical plants, as well
as in oil and gas refineries, since glass is unaffected by most
chemicals or solvents. Breaking a fiber will not create a spark
leading to a potential explosion. In addition, since there is no
electrical current flowing, exposure to water will not cause a short
circuit in the fiberĆoptic cable.
D Distance Ć Fiber normally has much lower attenuation than copper.
Therefore, longer links can be constructed with fiberĆoptic cable
than with copper (coaxial) cable.
Unlike the DCSĆNET coaxial cable network, which allows multiple
drops to be connected to a main trunkline, a fiberĆoptic link provides
pointĆtoĆpoint communication only. Therefore, a different network
configuration and different hardware components are required to
enable communication between drops. A star topology" network
configuration is used for the DCSĆNET fiberĆoptic network, as shown
in figure 3.3; whereas, the DCSĆNET coaxial network uses a
trunkline/dropline configuration, as shown in figure 3.4.