ATI Technologies d12 series - Modbus RS485 Multi-Drop; Figure 18. Modbus RS485 Multi-Drop Connections

ATI Series D12 Toxic Gas Transmitter with H10 Smart Sensor
Revision N (7/15) 23
Modbus RS485 Multi-drop
RS485 operation requires the transmitter to be wired in 3- or 4- wire mode. Modbus permits up to 247
devices to communicate digitally on the same bus; however, RS485 limits this to 32. Request the D12
Transmitter Modbus Interface Manual for complete details on the Modbus interface.
Figure 18. Modbus RS485 multi-drop connections
Common
B(+)
A(
-)
DCS, SCADA, or
Computer System
(Modbus master)
Primary Supply
12 to 30 VDC
Class 2 Power
Source
+
-
24
TB1
N
3-Wire Transmitters
TB1
3-Wire Transmitter
(furthest from master)
1
Common
B(+)
A(
-)
Common
B(+)
A(
-)
RS485
Unterminated
Install RS485 Unterminated jumper
block on all CPU boards except on
transmitter furthest from master.
Install RS485 jumper block
on transmitter furthest from
master.
RS232
-
to
-
RS485 Adapter
RS485
-
Primary Supply Voltage
(12v Minimum)
+
0