Biasing The Modbus Rs-485 Network; Figure 9: Modbus Rs-485 Biasing Switch On The Protonode N34 (Left) And Protonode N35 (Right) - FieldServer Protocessor ProtoNode FPC-N34 Startup Manual

Triangle Tube's ProtoNode Startup Guide
3.2.1

Biasing the Modbus RS-485 Network

An RS-485 network with more than one device needs to have biasing to ensure proper communication.
•
The biasing needs to be done on one device.
• The ProtoNode has 530 Ohm resistors that can be used to set the biasing. The ProtoNode's default
positions from the factory for the Biasing jumpers are OFF.
• The OFF position is when the 2 RED biasing jumpers straddle the 4 pins closest to the outside of the
board of the ProtoNode. See
• Only turn biasing ON:
o IF the BMS cannot see more than one device connected to the ProtoNode
o AND you have checked all the settings (Modbus COM settings, wiring, and DIP switches).
• To turn biasing ON, move the 2 RED biasing jumpers to straddle the 4 pins closest to the inside of the
board of the ProtoNode.
Figure 9: Modbus RS-485 Biasing Jumpers on the ProtoNode N34 (left) and ProtoNode N35 (right)
ProtoCessor 1991 Tarob Court Milpitas, California 95035 USA Web: www.protocessor.com
Figure 9.
RS-485 Bias Jumpers
Email: support@protocessor.com
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