Connection Components In Profibus - Siemens SINUMERIK ONE NCU 1750 Equipment Manual

Table 8-15
Characteristics
Wave impedance
Loop resistance
Effective capacitance
Damping
Permissible conductor cross-section
Permissible cable diameter
Cable lengths and data rate
The data rate determines the cable length of a subnet segment.
Table 8-16
Data rate
19.6 to 187.5 kbit/s
500 kbit/s
1.5 Mbit/s
3 to 12 Mbit/s
1) With isolated interface
Longer cable lengths:
If you must realize longer 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.
Connector features
The bus connector connects the PROFIBUS cables to the PROFIBUS DP interface X126, thus
establishing a connection to additional nodes.
Only bus connectors with a 35° cable outlet should be used in order to ensure that the front cover
can be closed.
8.9.3

Connection components in PROFIBUS

Connection components
Individual nodes are connected by means of bus connectors and PROFIBUS cables. Remember
to provide a bus connector with a programming port at either end of the subnet. This will give
you the option of expanding the subnet if required, for example, for a programming device.
NCU 1750
Equipment Manual, 01/2022, A5E45627807B AE
Technical data for PROFIBUS cables
Permitted cable length of a subnet segment for specific data rates
Values
Approximately 135 to 160 Ω (f = 3 to 20 MHz)
≤ 115 Ω/km
30 nF/km
0.9 dB/100 m (f = 200 kHz)
0.3 mm to 0.5 mm
2 2
8 mm + 0.5 mm
Max. cable length of a segment (in m)
1000
1)
400
200
100
Connecting
8.9 PROFIBUS DP
77