Omron NT31 Operation Manuals page 119

Connecting to the Host's RS-232C Port
Connection between NT31/NT31C Units (RS-485)
1
13
108
The relay terminal board is not included in the figure below. Insert a relay terminal
board so as to achieve the wiring configuration indicated below.
NT31/NT31C
RS-485
:
NT31/NT31C side
14
Abbreviation
FG
−
RS-232C/
SD
422A/485
RD
connector
RS
CS
−
SG
−
TRM
RDB (+)
SDB (+)
−
−
−
SDA (−)
25
RDA (−)
−
−
RSB (+)
RSA (−)
−
(25-pin type)
* Make the connection pin numbers 9 and 10 at the terminal NT31/NT31C (marked "
in the figure above).
In order to avoid an FG ground loop, make the connection between the connector
hood and the shielding at the one side only.
Pin number Pin number
Shielding wire
Connector Connector
hood hood
1
2
3
4
5
6
7
:
8
9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
−
23 23
24 24
25 25
Section 5-1
Host
1
NT31/NT31C side
Abbreviation
FG
−
1
RS-232C/
2 SD
422A/485
3 RD
connector
RS
4
CS
5
−
6
SG
7
−
8
9 TRM
RDB (+)
SDB (+)
−
−
−
SDA (−)
13
RDA (−)
−
−
−
RSB (+)
RSA (−)
−
(25-pin type)
14
25
"
: