Physical description
"RS-485 to USB adapter" is used for connecting Modbus RTU devices/meters/sensors to Vutlan VT900 and VT960 monitoring units.
Connection
Please read 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.
- 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 Vutlan monitoring unit using USB port.
- Up to 31 devices can be used.
- Overall cable length no more than 1000 meters.
Example 2: Using "RS485 to USB adapter" withiout 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.
- T ermination (120Ω resistor) is added at the start of the chain.
Activating Modbus interface:
After "VT85 / Modbus extension board" and all of the Modbus devices have been connected to it, you need to activate it and configure: Creating virtual Modbus RTU element
Developer notes: