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Gas Turbine Flow Meter Rs485 Modbus Rtu Configuration

Silver Automation Instruments supply gas turbine flow meters, the gas turbine flow meter with varies functions according to customers' demands. Our turbine flow meters can have unscaled pulse output or scaled pulse output, 4-20mA or 0-20mA output, HART Protocol, RS 485 ,Mobus RTU communication.  This article is talking about how to configure our SGW Gas turbine flow meter MODBUS RTU parameters.

Gas turbine flow meter

SGW Series 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.)

Gas meter Baud rate options: 1200, 2400,4800 , 9600,19200,default is 9600

The gas flow instrument address is “01-255”, “0”is for broadcasting.

Our protocol does not support broadcasting, others address is reserved.

The flow instruments applied MODBUS 0 x03 commands

Command 03(HEX)

Read single or multiple registers


The data in the protocol types:

Single floating-point number, format is IEEE754, the data is from high to low.

Double float-point r, format is IEEE754, the data is from high to low.

Unsigned int is 0-65535

Command 3 formats (read the register command)

Modbus Query

Address

1 BYTE

01-FF

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

Address

1  BYTE

01-FF

Function

1  BYTE

03

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-FF

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


Gas turbine flow transmitterDate Definition

Property

Address (hex)

Register length(word)

Datatype

Illustration

R

0001

2

Float

Instant flow

R

0003

2

Float

Totalized flow

R

0005

2

Float

CPU voltage, unit V

 

RS485,Modbus RTU Example (Flow meterinstrument 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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