7.9.2 PROFIBUS cables and connectors
Cable specication
The PROFIBUS cable is 2-wire, twisted, and shielded with dened technical data.
Table 7-20 Cable specications for X126 and X136
Characteristics Version
Connector type 9-pin SUB D connector
Cable type PROFIBUS cable
Max. cable length 100 m at 12 Mbit/s
Table 7-21 Technical data for PROFIBUS cables
Characteristics Values
Wave impedance Approximately 135 to 160 Ω (f = 3 to 20 MHz)
Loop resistance ≤ 115 Ω/km
Eective capacitance 30 nF/km
Damping 0.9 dB/100 m (f = 200 kHz)
Permissible conductor cross section 0.3 mm
2
to 0.5 mm
2
Permissible cable diameter 8 mm + 0.5 mm
Cable lengths and data rate
The data rate determines the cable length of a subnet segment.
Table 7-22 Permitted cable length of a subnet segment for specic data rates
Data rate Max. cable length of a segment (in m)
19.6 to 187.5 kbit/s 1000
1)
500 kbit/s 400
1.5 Mbit/s 200
3 to 12 Mbit/s 100
1)
With isolated interface
Longer cable lengths:
If you must realize greater cable lengths than permitted in one segment, you must use RS 485
repeaters. The maximum possible cable lengths between two RS 485 repeaters correspond to
the cable length of a segment. You can connect up to 9 RS 485 repeaters in series.
Note that an RS 485 repeater must be counted as a subnet node when determining the total
number of nodes to be connected. This is true even if the RS 485 repeater is not assigned its own
PROFIBUS address.
Connecting
7.9 PROFIBUS DP
NCU 7x0.3B PN
68 Equipment Manual, 10/2020, 6FC5397-1EP40-6BA1
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