Vaisala Optimus OPT100 - Modbus Communication Examples

A.6 Modbus communication examples
Reading acetylene value
Device address used in the following examples is 240 (F0
hex
).
The values returned by the device dier depending on the measurement
conditions. Your device may not return the same values.
Request
Bytes on the line (hexadecimal) Description
(silence for > 3.5 bytes) Start of Modbus RTU frame
F0
hex
OPT100 address
03
hex
Function (Read Holding Registers)
00
hex
Register address (Acetylene)
16
hex
00
hex
Number of 16-bit registers to read (2)
02
hex
30
hex
Modbus RTU checksum
EE
hex
(silence for > 3.5 bytes) End of Modbus RTU frame
Response
Bytes on the line (hexadecimal) Description
(silence for > 3.5 bytes) Start of Modbus RTU frame
F0
hex
OPT100 address
03
hex
Function (Read Holding Registers)
04
hex
Number of data bytes
40
hex
Value of first register (least significant word)
40
hex
00
hex
Value of second register (most significant word)
00
hex
OPT100 User Guide M211858EN-U
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