12
RS485
Terminal resistors
All devices are connected in a bus structure
(line). Up to 32 stations can be connected
together in one segment. The cable is termi-
nated with resistors at the start and end of a
segment.
If there are more than 32 stations, repeaters
must be used in order to connect the indi-
vidual segments.
Shielding
A twisted-conductor and shielded cable must
be provided for connections through the
RS485 interface. In order to achieve sufficient
screening effectiveness, the screening must
be connected to large areas of the housing or
cabinet parts at both ends of the cable.
Cable type
Recommended cable types:
Unitronic Li2YCY(TP) 2x2x0.22 (Lapp cable)
Unitronic BUS L2/FIP 1x2x0.64 (Lapp cable)
Cable length
1200m for a baud rate of 38.4k.
Installation
Correct
Wrong
Terminal strip in the control cabinet.
Device with RS485 interface.
(Without terminating resistor)
Device with RS485 interface.
(With terminating resistor at the device)
RS232
The achievable distance between two RS232
devices depends on the cable used and the
baud rate. As a rule of thumb, for a transfer
rate of 9600 baud the distance should not
exceed 15m to 30m.
The permissible ohmic load must be greater
than 3kOhm and the capacitive load caused
by the transmission cable must be smaller
than 2500pF.
The 2m connection cable included in the
RS232 interface scope of supply can be used
to transfer data with the maximum settable
baud rate of 38.4kBit/s.
Interfaces
Diagr. Connection diagram RS232 cable
