Unitronics UMI-B1 UL Series Operation Manual page 112

UMI-B1 UL Series Inverter
differential transmission which is called balance transmission, too. It uses twisted pairs,
one of which is defined as A (+) and the other is defined as B (-). Generally, if the
positive electrical level between sending drive A and B is among +2–+6V, it is logic "1", if
the electrical level is among -2V–-6V; it is logic"0".
485+ on the terminal board corresponds to A and 485- to B.
Communication baud rate means the binary bit number in one second. The unit is bit/s
(bps). The higher the baud rate is, the quicker the transmission speed is and the weaker
the anti-interference is. If the twisted pairs of 0.56mm (24AWG) is applied as the
communication cables, the Max. Transmission distance is as below:
Baud Max.transmiss
rate ion distance
2400
5906ft (1800m)
BPS
It is recommended to use shield 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 7-1 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
shield 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.
Baud Max.transmiss
rate ion distance
4800
3937ft (1200m)
BPS
Baud Max.transmis
rate sion distance
9600
2625ft (800m)
BPS
110
Communication protocol
Max.transmi
Baud
ssion
rate
distance
1920
1969ft
0
(600m)
BPS