Omega RD100B User Manual page 33

3.2 Terminal Arrangement and Signal Names and the Connection Procedure of the RS-422A/485 Communication Interface
Host
computer
Terminator (external) 120 Ω 1/2W or greater
RS-232
TD( - )
TD( + )
RD( - )
RD( + )
SHIELD
Converter
Host
computer
Terminator (externally attached) 120 Ω, 1/2 W or more
SDA( – )
SDB( + )
RDA( – )
RDB( + )
SG
3-4
(The following figure illustrates the case when the host computer's interface is RS-232.)
RS-422A/485
terminal on the
recorder
SD A
(SDA)
SD B
(SDB)
RD A
(RD A)
RD B
(RD B)
SG
(SG)
FG
#1
• Two-Wire System
Connect the transmission and reception signals with the same polarity on the RS-
422A/485 terminal block. The two-wire system can be used only when using the
Modbus protocol.
RS-422A/485
terminal on the
recorder
SD A
(A)
SD B
(B)
RD A
RD B
SG
(SG)
FG
#1
SD A
(SDA)
SD B
(SDB)
RD A
(RD A)
RD B
(RD B)
SG
(SG)
FG
#2
Do not connect terminators to #1 through #n-1.
Terminator (externally attached)
SD A
(A)
SD B
(B)
RD A
RD B
SG
(SG)
FG
#2
Do not connect terminator to #1 to #n–1
Terminator (external)
SD A
(SDA)
SD B
(SDB)
RD A
(RD A)
RD B
(RD B)
SG
(SG)
FG
#n
(#n ≤ 32)
SD A
(A)
SD B
(B)
RD A
RD B
SG
(SG)
FG
#n
(#n ≤ 31)