Installation
PROFIBUS manual
Version FELD-V2002.02
Page 9
Commercially available connectors allow the incoming data cable to be
connected directly to the outgoing data cable in the connector. This avoids
stubs, and the bus connector can be connected to the bus or disconnected
from the bus at any time without interrupting data traffic. These connectors
include a bus termination that can be switched in or out. To avoid line
reflections, connectors containing integral series inductors should be used to
compensate for the capacitive load of the station. This is essential for transfer
rates > 1.5 Mbaud.
9-pin
SUB-D
connector
Additional
fieldbus stations
9-pin SUB-D
connector
Wiring of bus lines with bus termination
Note
Take care not to swap over the data lines when connecting the stations.
Always install the bus termination at the
start and end of the bus line
. The
bus termination uses the supply voltage VP from the device, so ensure that
the voltage supply to the slave device on which the bus termination is
installed is always on.
Since the connectors contain built-in series inductors, avoid fitting connectors
that are not connected to field devices, because the non-existent device
capacitance may cause transmission errors.
It is essential to use a shielded PROFIBUS cable in order to achieve high
system immunity to radiated electromagnetic interference. As far as possible,
the shield should be connected at both ends to the protective ground via large-
area shielding clamps providing good conducting contact. In addition, ensure
that the cable is positioned as far as possible from all power cables. At data
rates >1.5 Mbit/s, stubs must be avoided at all costs.
An equipotential bonding conductor must be installed to reduce potential
differences introduced by different network input points from different parts
of the system.