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Choice of PROFIBUS data transfer cable type
GFK-2746
1 Introduction
1-31
Chapter
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Depending on the application, the user can choose between electrical and optical fiber
data transfer cables. The following types of electrical data cables can be used:
Standard bus cable
Standard bus cable with halogen-free sheath (type FRNC)
Cable with PE Sheath for use in the food and manufacturing industries. (It differs
from the standard bus cable solely in the cable sheath).
Direct buried cable with additional protective sheath for lying in the ground.
Trailing cable: This is a special cable type which is used where parts of the
machine move occasionally or continuously.
Festooned cable: Compared to a trailing cable, a festooned cable has an
additional strain relief element.
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The bus cable is specified in EN 50170 part 8-2 as "Cable Type A", and should
comply with the parameters in the following table. Cable Type B, which is also
described in EN 50170, is outdated and should no longer be used.
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Parameters for standard type A bus cables:
Table 22: Parameters for Standard Type A Bus Cables
Parameter
Characteristic impedance in Ω
Operating capacity(pF/m)
Loop resistance (Ω/km )
Core diameter (mm)
Cora cross-section (mm)
* The cable cross-sections used should be compatible with the mechanical
specifications of the bus interface connector.
The cable parameters specified for standard Type A bus cables result in the maximum
length of each bus segment for the respective data transfer rate as shown in the below
table.
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Maximum Cable Lengths per Segments
Table 23: Maximum Cable Lengths per Segments
Baudrate
9.6
19.2
Maximum
segment
1200
1200
Length in
'm'(m)
Note:
In a PROFIBUS-DP/FMS installation, you must choose a data transfer rate which
is supported by all devices connected to the bus. The chosen data transfer rate
then determines the maximum segment lengths as shown above.
Chapter Chapter
Chapter
Cable Type A
135..165 at a frequency of (3..20MHz)
< 30
<=110
>0.64*
>0.34*
45.45 93.75
187.5 500
1200
1200
1000
400
1500
3000
6000 12000
200
100
100
100
1
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