37
2.
Installation and wiring
2.6 RS-485 wiring (continued)
The following diagram shows wiring for RS-485 communication.
The configuration of the connection should be either 1:1 or 1:N. If the 1:N connection is Modbus, up to 99 of this
product can be connected. If CompoWay/F, up to 31 can be connected. Enable the terminating resistor that shorts
terminal numbers 4 and 5 in the end unit.
Setting the communication address
When wiring is finished, turn the rotary switch to set the communication address.
The value on the left is circuit A communication address tens place and the value on the right is the ones.
[Reference]
• If the upstream device does not support RS-485 communications, refer to the table below to select a converter for your purpose.
Important
• The terminal panel is the push-in type. Also read "Cautions when connecting the Push-In Plus terminal
(RS-485 communication terminal and pulse output terminal) (
34)" when wiring.
• Only the communication address for circuit A can be set with the rotary switch. Refer to "Settings for circuits B to D
(when measuring 2 circuits or more)" (
56) to set the communications addresses for circuits B to D.
• The addresses for circuits B to D are automatically set, where 1 is added for each circuit in order to the address set
for circuit A. Refer to "Settings for circuits B to D (when measuring 2 circuits or more) (
56)" for details.
• If the communications address exceeds 99 when multi-circuit metering, the value is invalid.
• If the host device you are using does not have its own built in terminating resistor, connect a terminating
resistor to the host device. The terminating resistance is 120
Ω
(1/2W).
• Do not wire in a terminating resistor terminal on any of these products that are along the transmission
path. This can cause communication failures.
• There is no FG terminal on this product. Connect only the
i
wire and
j
wire of RS-485.
• Use twisted pair cables.
• For wiring to the RS-485 terminals, use 24 to 14 AWG (cross section surface area of 0.2 to 2.0mm
2
) electrical wire.
• Single wires, stranded wires, and ferrule terminals can be used. The recommended stripped wire length when using
single wires or stranded wire is 8 to 10mm (however, 10mm must be used when using AWG14).
• To avoid the influence of noise, use separate wiring for the RS-485 communications and for the power.
• Irrespective of the transmission distance and number of units connected, perform communications
checks with the actual units.
• During use, make sure the terminal panel cover is closed.
Protocol
KM-N Setting Tool
USB/RS-485 converter operability confirmed
Modbus
Yes
SI-35USB (LINEEYE Co., Ltd.)
No
CompoWay/F
Yes
No
K3SC-10 (Omron), SI-35USB (LINEEYE Co.,Ltd.)
＋
−
Communications
master
(host device)
Maximum transmission distance 1200m
Terminating resistor
terminal and short
Rotary switch (units of 10)
Rotary switch (units of 1)
