Terminating Resistors Terminating resistors must be used if the C-BOX is
installed at the beginning or end of the PROFIBUS cable
segment. In this case, it is recommended to use
PROFIBUS connectors which contain an integrated
terminating resistor. It is recommended to use connectors
from ERNI and Siemens. If the bus is incorrectly
terminated, this can lead to errors in data transfer or to
damage to other stations on the bus.
Bus Connectors It is recommended to use only commercially available
PROFIBUS connectors for connecting the bus. It is
recommended to use connectors from ERNI and Siemens.
Cable Shield Shielded cables are less sensitive to interference due to
electromagnetic fields. With shielded cables, the
interference currents are led to ground through the
shielding rail, which is electrically connected to the case.
To ensure that the interference currents which flow
through the shielding do not themselves interfere with
other devices, it is important to provide a low impedance
connection to the protective ground. Observe the following
rules for the shields of the PROFIBUS cable and the serial
interface cable:
– The braiding of the shielding should have a
degree of coverage of more than 80%.
– The shielding should include a braided shield and
should not consist solely of foil shielding, since
the latter can be easily damaged by cable tension
and pressure.
– To ensure good immu nity to interference at high
frequencies as well, the shielding of the cable
should be attached to the shielding rail at both
ends of the cable.
When connecting up the C-BOX 3X0, it is recommended to observe the guidelines in
the VDE 0100 regulations for handling electrical equipment.
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