5. Installation and Wiring
5-7
RS-485 Communication Port
5.5.2.
■
RS-485 Communications Port Wiring
This product has four RS-485 communications ports for RS-485-connected measurement
devices. Up to 31 devices can be connected to one port.
Maximum transmission distance is 500 m for RS-485 communications.
For an RS-485 communications port cable, a shielded twisted-pair cable of AWG24 to14 (0.205
to 2.081 mm
2
) or higher must be used. To prevent malfunction, a shielded wire for the RS-485
communications cable must be connected to the ground or FG terminal.
This product has a built-in terminal resistor on each RS-485 communications port terminal. The
RS-485 cables must be wired so that this product should be on one end of the terminal. For a
device that is connected to the terminal end opposite to this product, a terminal resister of 120
Ω
(1/2 W) must be attached.
Precautions for
Correct Use
- The RS-485 cables must be wired through measurement devices in one loop. Branching
and/or star wiring is not available.
Maximum Transmission Distance of 500m
Up to 31 devices