Modbus to send a command to the flowmeter "EKHO-R"?

Question

C++ / C#

Dear workers of process control system, there is a flow meter "EKHO-R-02" connected to the com-port.
How can I understand this

5. Received commands:
03 – request for transmission of archived data, or current values ​​of speed or
flow rate, or instrument settings (according to the specified addresses - see item 6);
08 00 – request to execute diagnostic function Return Query Data.

Answer 1

As far as I can tell, 3 is a read request.
> function code 3 (read holding registers)
Send command 03 accordingly <number of the first register> <number of registers>
As far as I can judge, two 16-bit registers are allocated for each value.
for example, reading the current value of the level counter will be something like this:
03 0000 0002 (you just need to pack it correctly according to the protocol rules)
Then catch the answer and unpack it.
Command 08 is a diagnostic. I can't say more about her.