Selecting Cables And Terminal Resistors (Modbus Rs-485); Twisted Pair Cable - Mitsubishi FX3U Series User Manual

FX Series Programmable Controllers
3U
User's Manual - MODBUS Serial Communication Edition
4.3

Selecting Cables and Terminal Resistors (MODBUS RS-485)

Select cables using the procedure described below.
4.3.1

Twisted pair cable

Use shielded twisted pair cables for connecting communication equipment operating in accordance with
MODBUS RS-485.
1. Cable structural drawing (reference)
Example of two-pair cable
structural drawing
2. RS-485 cable specifications
Cable type
Number of pairs
Conductor resistance (20°C)
Insulation resistance
Dielectric withstand voltage
Electrostatic capacitance (1 kHz)
Characteristic impedance (100 kHz)
22
Pair
Shield
Item
60nF/km or less by an average
4.3 Selecting Cables and Terminal Resistors (MODBUS RS-
Example of three-pair
cable structural drawing
Description
Shielded cable
2p, 3p
88.0 Ω/km or less
10000 MΩ-km or more
500VDC, 1minute
110±10 Ω
4 Wiring