In-Situ RDO PRO Process Optical Dissolved Oxygen Sensor Manual - Manual (Page 14)

5.4 Modbus Master with Built-in RS485
Signal Color
Ground/Return Black
External Power (12-36 VDC) Red
RS485 (-) Green
RS485 (+) Blue
 Cable length must not exceed 1219 m (4000 ft.)
Page 14 Controller Requirements and Connections