F-901B Reference Manual
Page
8
of
15
Absolute Maximum Rating
Voltage range at A or B ……………………………………………….
-8V to 12V
Voltage range at pin 3,6,7
,8 ………………………………………..
-0.3V to 4V
Electrostatic discharge at A and B ……………………………….
±8kV
RS485 Modbus Parameters
Parameter
Value
Default address
50
Baud Rate
19200
Data bits
8
Parity
Even
Stop bits
1
F-901B MODBUS Specifications
•
Operates as a slave, half-duplex mode
•
Modbus functions supported:
o
0x01 - Read Coils
o
0x03 - Read Holding Registers
o
0x04 - Read Input Registers
o
0x05 - Write Single Coil
o
0x06 - Write Single Register
o
0x0F - Write Multiple Coils
o
0x10 - Write Multiple Registers
•
Exception messages supported
•
Default address:
o
RTU: 50
o
TCP/IP: 192.168.1.50
Input Registers
Mode: Read-only, size: 16 bits
Name
Address
Description
C2H4
0
C2H4 measurement x 10, ppm
CO2
1
CO2 measurement x 100, %
O2
2
O2 measurement x 10, %
TEMPERATURE
3
Temperature measurement x 10, C
RELATIVE HUMIDITY
4
Relative Humidity measurement x 10, %
BAROMETER
5
Barometric pressure measurement x 10, mbar
VAPOR PRESSURE
6
Vapor pressure measurement x 10, mbar
ERROR STATUS
9
0 = OK.
1 = C2H4 offset error, Sensor over-exposed or KMnO4 filter
needs to be replaced.
C2H4_RAW
10
C2H4 raw measurement, count
O2_RAW
11
O2 raw measurement, count
