Installation Instructions

Micropilot FMR20 Modbus RS485
12 Endress+Hauser
2
3
DO / A(+)
+
D1 / B(-)
-
1
+
-
+
-
A0037751
 6 Block circuit diagram for Modbus RS485 connection
1 Device with Modbus communication
2 Modbus master/RTU
3 Power supply
Up to 32 users can be connected on the RS485 bus.
DO / A(+)
+
D1 / B(-)
-
1
+
-
3
2
4
DO / A(+)
D1 / B(-)
A0038149
 7 Block circuit diagram for Modbus RS485 connection, multiple users
1 Power supply
2 Device with Modbus communication
3 Bus termination
4 Modbus master/RTU
The bus cable should be a type-A fieldbus cable with a maximum length of 1 200 m (3 937 ft).
If the device is installed in a hazardous environment, the cable length may not exceed
1 000 m (3 281 ft).
A terminating resistor must be connected at both ends of the RS485 bus.
Modbus RS485 bus terminating resistor
The bus terminating resistor should be installed as per the RS485-IS specification.
200 Ω
510 Ω
510 Ω
-
+
DO / A(+)
D1 / B(-)
A0038150
 8 Representation of the bus terminating resistor as per the RS485-IS specification