User`s manual
23
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
4 Wiring
4.3 Selecting Cables and Terminal Resistors (MODBUS RS-
1
Outline
2
Specifications
3
System
Configuration
4
Wiring
5
Communication
Setup
6
Related
Devices and
Comm. Status
7
MODBUS
Standard
Commands
8
Master
Specification
9
Slave
Specification
10
Creating
Programs
4.3.2 Connecting cables
1. European type terminal block
Use shielded twisted pair cables for connecting communication equipment operating in accordance with
MODBUS RS-485.
The table below shows applicable cables and tightening torques.
The cable ends, either stranded or solid, should be left as it is, or used with a bar terminal with insulating
sleeve.
• When leaving the cable end as it is
- Twist the end of stranded cables so that the individual wires do not poke out
- Do not plate the cable end
• When using a bar terminal with insulating sleeve
Because it is difficult to insert a cable into the insulating sleeve
depending on the cable sheath thickness, select the proper cable
according to the outline drawing.
•Tool
- When tightening a terminal on the European terminal block, use a
small straight-shaped commercial screwdriver, as shown in the figure
on the right.
4.3.3 Connecting terminal resistors
Make sure to provide a terminal resistor at each end of the line.
1. When using the FX3U-485ADP-MB
The FX3U-485ADP-MB has a built-in terminal resistor.
Set the terminal resistor selector switch accordingly.
Cable size when
one cable is
connected
Cable size when
two cables are
connected
Cable size for bar
terminal with
insulating sleeve
Tightening
torque
Tool size
A B
FX
3U-485ADP-MB
AWG22 to
AWG20
AWG22 AWG22 to AWG20
0.22 to 0.25
N·m
0.4 (0.01") 2.5 (0.09")
Manufacturer Model name Caulking tool
Phoenix Contact AI 0.5-8WH CRIMPFOX UD6
Manufacturer Model name
Phoenix Contact SZS 0.4 × 2.5
Approx. 9 mm
(0.35")
8 mm (0.31")
Contact area
14 mm
(0.55")
2.6 mm
(0.1")
Insulating sleeve
A B
Select a
screwdriver
with a
straight tip.
For sizes A and B, refer to the
table on the left.
Terminal
resistor selector
switch
330
Ω
OPEN
110
Ω