EDS84DMOTPBUS EN 3.0 - 11/2011 L 25
Communication manual 8400 motec PROFIBUS
Installation
Electrical installation
5.2.3 Bus cable specification
Bus cable length
The bus cable length depends on the baud rate used:
Tip!
For high baud rates, we recommend taking the use of optical fibres into
consideration.
Advantages of optical fibres:
• External electromagnetic interferences have no effect on the transmission
path.
• Bus lengths of several kilometres are also possible with higher baud rates.
The bus length is ...
– independent of the baud rate;
– dependent on the optical fibre used.
Note!
Only use cables that correspond to the given specifications of the PROFIBUS user
organisation.
Area Values
Cable resistance 135 ... 165 Ω/km, (f = 3 ... 20 MHz)
Capacitance per unit length ≤ 30 nF/km
Loop resistance < 110 Ω/km
Core diameter > 0.64 mm
Core cross-section > 0.34 mm
2
Cores Twisted in pairs, insulated and shielded
Baud rate Length
9.6 ... 93.75 kbps 1200 m
187.5 kbps 1000 m
500 kbps 400 m
1500 kbps 200 m
3000 ... 12000 kbps 100 m
Note!
The baud rate depending of the data volume, cycle time and number of stations
should only be selected as high as required for the application.
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