Keeping the World Flowing
19
4.5 Cable Types
The network must be connected using a suitable cable for
Profibus DP applications. Two conductors plus a shield are
required and there is a Profibus specification for the cable.
Amongst the cable manufacturers Belden have PVC
jacketed single pair 2 core cable, which meets the minimum
requirement. Information on Belden cable may be found on
the Belden website (www.belden.com).
PVC sheath, usually
coloured purple
Tinned
copper
screen
Signal wires
Red is positive, ‘B
Green is negative, ‘A’
Typical Profibus DP Cable Specification
Impedance 135 up to 165 ohm at a frequency
of 3 to 20 MHz
Cable capacitance <30 pF per metre
Core diameter >0.34 mm
2
(corresponds to AWG 22)
Cable type Twisted pair cable, 1x2 or 2x2 or
1x4 lines
Resistance <110 ohm per km
Signal attenuation Max 9 dB over total length of
line section
Shielding Copper shielding braid or shielding
braid and shielding foil
Fig. 11: Typical Profibus DP cable specifications
The terminals to which the wires connect in each actuator
type will be different and the actuator wiring diagrams must
be consulted to establish the connections.
4.6 Termination Network
In order to operate correctly all Profibus segments must be
terminated at each end in an active network termination
circuit.
The Profibus DP card includes the necessary components to
allow an active termination to be connected. The termination
can be set using the HMI or Accent software. It is advised
that internal termination is only used during the testing/
commissioning phase, because upon removal of power to the
unit or removal of the unit itself, the termination will be lost,
affecting communications of the entire network.
It is therefore advised that external termination is used during
full operation.
Active termination resistors are included on the Profibus card.
These can be switch on or off using the menu. Please see the
CK manual for details.
Profibus
cable
screening
+5V (VP)
390Ω
390Ω
220Ω
(RxD/TxD-P)
(RxD/TxD-N)
(DGND)
green A conductor
red B conductor
Single and Dual Data Highway Configurations
A4 US
US
A4
US
A4
A4 US
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