FB3000 RTU Instruction Manual
D301851X012
November 2023
Installation 35
2.10.3 Connecting to COM3 (3CPU16/3CPUSG)
You can configure the COM3 port on the CPU personality module for RS-485 (2-wire)
communications. When connecting COM3 to an RS-485 port on another device (such as a
Rosemount 4088B transmitter), use a cable with configurations as shown in Figure 2-26:
Figure 2-26. Wiring COM3 on the CPU Module for RS-485 (2-wire) and Connecting to a
4088B Transmitter
Enable AC termination using switches
RS-485 bus; twisted pair required
Connect cable shields to suitable Instrument Earth connection point