Circutor STM-H10, Instruction Manual

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21
Instruction Manual
STM-S12, STM-S24, STM-H6, STM-H10, STM-H20
5.- RS-485 COMMUNICATIONS (STM-S12-RS485 AND STM-S24-RS485 MODELS)
The
SMT-S12-RS485
and
SMT-S24-RS485
have an RS-485 communications port, with communica-
tions protocols: MODBUS RTU ®.
5�1�- CONNECTIONS
The RS-485 cable must be wired using twisted pair cable with mesh shield (minimum 3 wires), with
a maximum distance of
1200 meters
between the
SMT-Sxx-485
and the master unit.
A maximum of 32 SMT-Sxx-485 can be connected on this bus.
For communication with the master unit, we must use a smart RS-232 to RS-485 network protocol
converter.
B(-) A(+)
S
RS-232 / USB / Ethernet / Profibus ...
PC
RS-485
RS-485
RS-232
USB
Ethernet
Profibus
...
Alimentación Auxiliar
Power Supply
+ -
Figure 11: RS-485 connection diagram�