RAM 9000 Series Hardware Guide 2-35
Hardware Installation Revised 2015-07-16
Serial RS485 Wiring
RS485+ connect a resistor of the desired value between the VBIAS terminal and the RS485+ terminal. To bias the
RS485- connect a resistor of the desired value between the IGND terminal and the RS485- terminal. As mentioned
above, 1K ohms is a typical value for a biasing resistor but other RS485 devices may recommend other values.
Note: The RAM 9000 RS485 port is designed in such a way as to never need biasing, but it includes the VBIAS
screw as a convenience for use with 3rd party devices that require network biasing but lack the VBIAS connection.
If the RS485 network is made up exclusively of RAM 9000 devices, then these bias resistors are not necessary.
Note:
• Terminals are sized to hold 28 to 12 gauge wire, 12 AWG wire area is 3.31mm2.
• Torque spec for terminals is 0.5 Nm.
• Use copper wire rated to 90°C or above.
PIN NAME DESCRIPTION
RS485 (Top of unit)
IGND Isolated Ground RS485 signal ground optically isolated from other ground.
VBIAS Voltage Bias Connect to add RS485 Network Biasing.
TERM Termination Connect to add RS485 Network Termination.
485- RS485- Two wire RS485 negative terminal.
485+ RS485+ Two wire RS485 positive terminal.
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