Knowledge Base

RS485 circuits contain 2 wires, A and B. The adaptor has screw terminals for A and B, plus one labelled 0V. The latter is connected to ground (0V) of the controller. If you are using screened cable (2 cores + shield), connect the shield to 0V.

With an RS485 hookup all A terminals on all devices should be connected together and all B wires should be connected together. If you should swap A and B somewhere the system will not work. For long runs it pays to use shielded twisted pair cable. In that case the shield should connect to the 0V or Gnd terminal of each RS485 device.