Connecting
7.8 PROFIBUS DP
NCU 7x0.3 PN
Manual, 09/2011, 6FC5397-1EP40-0BA0
65
Terminating resistor
A cable must be terminated with its own surge impedance to prevent line disturbances
caused by reflections. Activate the terminating resistor at the first and last node on a subnet
or segment. The control unit must be either the first or the last node on the subnet.
Make sure that the stations to which the terminating resistor is connected are always
supplied with voltage during power-up and operation.
7.8.4 Rules for the laying of PROFIBUS cables
Laying of bus cables
During laying of the PROFIBUS cable, you must avoid:
● twisting
● stretching and
● squeezing
Supplementary conditions
During laying of the indoor bus cable, you must also consider the following supplementary
conditions (d
O
= outer diameter of the cable):
Table 7- 23 Supplementary conditions for the laying of PROFIBUS cables
Features Supplementary conditions
Bending radius for a single bend 80 mm (10xd
O
)
Bending radius (multiple times) 160 mm (20xd
O
)
Permissible temperature range for cable routing -5 °C to +50°C
Temperature range for storage and stationary operation -30°C to +65°C
Additional references
For length codes of prefabricated cables and additional information on PROFIBUS cables,
refer to "Electrical networks" in the PROFIBUS section of the IK PI catalog titled "Industrial
Communication and Field Devices".
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