Salicru CV30 User Manual page 100

It is recommended to use shielded cables and make the shield layer as the grounding wires during RS485
remote communication.
In the cases with less devices and shorter distance, it is recommended to use 120Ω terminal resistor as the
performance will be weakened if the distance increase even though the network can perform well without
load resistor.
7.2.1.1 Single application
Figure 1 is the site Modbus connection figure of single inverter and PC. Generally, the computer does not
have RS485 interface, the RS232 or USB interface of the computer should be converted into RS485 by
converter. Connect the A terminal of RS485 to the 485+ terminal of the inverter and B to the 485- terminal. It
is recommended to use the shielded twisted pairs. When applying RS232-RS485 converter, if the RS232
interface of the computer is connected to the RS232 interface of the converter, the wire length should be as
short as possible within the length of 15m. It is recommended to connect the RS232-RS485 converter to the
computer directly. If using USB-RS485 converter, the wire should be as short as possible, too.
Select a right interface to the upper monitor of the computer (select the interface of RS232-RS485 converter,
such as COM1) after the wiring and set the basic parameters such as communication baud rate and digital
check bit to the same as the inverter.
Figure 1 RS485 physical connection in single application
7.2.1.2 Multi-applications
In real multi-applications, the chrysanthemum connection and star connection are commonly used.
Chrysanthemum chain connection is required in the RS485 industrial fieldbus standards. The two ends are
connected to terminal resistors of 120Ω which is shown as figure 2.
100 - 140 Communication protocol