SLW Liquid turbine flow meter is a kind of cheap digital flow meter, it can have digital display to show instant flow and total flow , it can measure vegetable oil, ethanol, diesel, palm oil flow range.SLW series liquid turbine flow meter can have 4-20mA ,pulse output, scaled pulse output, Hart Protocol, Modbus Communication. This article is mainly talking about the configuration of RS485 Modbus Communications for SLW turbine flow meter.
This type of gas turbine flow meter is MODBUS RTU.
The data format is n,8,1 ( 1 start bit,8 data bits, no check,1 stop bit.)
Baud rate options: 1200, 2400,4800 , 9600,19200
The instrument address is “01-99”, “0”is for broadcasting.
Our protocol does not support broadcasting, others address is reserved.
The flow measuring instruments applied MODBUS 0 x03 commands
|
Read single or multiple registers |
THE data in the protocol is single floating-point number ,format is IEEE754, the data is from high to low.
Command 3 formats (read the register command)
Modbus Query
|
Address |
1 BYTE |
01-F7 |
|
Function |
1 BYTE |
03 |
|
Starting Address |
2 BYTE |
0-FFFF |
|
Read Numbers |
2 BYTE |
N(1-7D) |
|
CRC Low |
1 BYTE |
|
|
CRC High |
1 BYTE |
|
MODBUS Response
|
1 BYTE |
01-99 |
|
|
Function |
1 BYTE |
03（06、10） |
|
Byte Count |
1 BYTE |
N*2 |
|
Input state |
N*2 BYTE |
|
|
CRC Low |
1 BYTE |
|
|
CRC High |
1 BYTE |
|
Error Response
|
Address |
1 BYTE |
01-F7 |
|
Function |
1 BYTE |
83 |
|
Error code |
1 BYTE |
01、02、03 (see note) |
|
CRC Low |
1 BYTE |
|
|
CRC High |
1 BYTE |
|
Note: 01-Register address wrong, 02- Register length wrong, 03- CRC wrong
Date Definition
|
Property |
Address (hex) |
Register length(word) |
Data type |
Illustration |
|
R |
0001 |
2 |
Float |
Instant flow |
|
R |
0003 |
2 |
Float |
Totalized flow |
|
R |
0005 |
2 |
Float |
CPU voltage, unit V |
Example (turbine flow instrument address 01)
|
Query |
01 03 0001 0004 15C9 |
CRC low in the front, and at the same time read instant flow and totalized flow. |
|
Response |
01 03 08 00 00 00 00 (instant flow =0) 42 84 00 00 (Totalized flow=66) C1 86 |
Float high in the front, CRC low in the front |
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