Connecting Modbus sensors using "RS485 to USB adapter" (legacy)

Owned by Vladimir Tayzhev
Last updated: Mar 19, 2024
2 min read

Physical description

"USB485 / Modbus RS485 to USB adapter" is used for connecting Modbus RTU devices/meters/sensors to Vutlan VT325, VT335, VT805, VT825, VT960 series monitoring units.

Connection

Please read the article Connecting Modbus devices first.

Example 1: Using "RS485 to USB adapter" with internal termination.

  • Sensors are connected in a daisy chain connection.

  • 120Ω resistor is used at the end of the chain.

  • A twisted pair cable is used for A(+) and B(-).

  • "RS-485 to USB adapter" has an internal termination and it is switched ON.

  • The data is transferred to the Vutlan monitoring unit using the USB port.

  • Up to 31 devices can be used.

  • Overall cable length no more than 1000 meters.

Example 2: Using "RS485 to USB adapter" without internal termination.

  • The same as the first example with the exception that the "RS-485 to USB adapter" does not have a built-in termination.

  • Termination (120Ω resistor) is added at the start of the chain.