
4
6. RS-485 Communication
6.1 Parameters
Protocol: Modbus RTU mode
Address: 1~255
Baud rate: 2400, 4800(default), 9600
Parity: None
Data bits: 8 bits
Stop bit: 1 bit
Distance: 1500 M (max)
Terminate resistor: 120~300Ω/0.25W(typical: 150Ω
6.2 Address setting
The address can be set through the communication and dip switches. It is able to
choose only one way to proceed each time.
When 4 dip switches are switched to "OFF", it means the address can be set by
the communication only; while the dip switches are switched to "ON", it means the
address can be set by the dip switches only. The address setting range: 1~15, 1:
ON; 0: OFF.
Modbus Address 1 2 3 4
Use communication to
set the address 0000
1 0001
2 0010
...... ...... ...... ...... ......
15 1 1 1 1
6.3 Parameters table
Function Code:03h
Address Description Size Data format Range Unit Default R/W Notes
0x0000 Current wind
speed value 1 INT16U 0~300 0.1m/s R
0x0001 Current air volume
value 1 INT16U 0~65535 0.1
m3/h R
0x0002 Current air volume
value 2 FLOAT32 0~6553.5 m3/h R
Function Code:03h, 06h
Address Description Size Data format Range Unit Default R/W Notes
0x004E Drift register
coefcient A 2 FLOAT32 R/W
Drift register y=Ax+B,
coefcient A
(x=current wind speed)
0x0050 Wind speed
correction value 1 INT16 0.1m/s R/W Drift register y=Ax+B,
coefcient B
0x0200 Current duct cross
sectional area 1 INT16U 0~65535 cm2R/W
0x07D0 Address setting 1 INT16U 1~255 1 R/W
0x07D1 Baud rate setting 1 INT16U
0: 2400
1: 4800
2: 9600
1 R/W