Modbus register read test (ARF8240)

Modified on Fri, 21 Jun 2024 at 02:49 PM


  • Slave Modbus output must be Modbus RTU Protocol (RS485- RS232)
  • Know the Modbus serial link settings (slave address, baud rate, parity, Bit Stop, etc.)
  • Know which registers you want to test/set (address, number of words, type)
  •  The sensor must be connected to a power supply of between 6-36V DC.
  •  The sensor must be connected to the slave you wish to interrogate.
  •  The Modbus transmitter must be the only serial link master.
  •  Access to IoT configurator maintenance mode (PC or Android phone + connection cables)

Reading test: 

For this tutorial I am using a SOCOMEC Diris B-10 counter with the following serial parameters:


            - Baud Rate: 19200     

- Parity: None (N)           

- Bytes stop: 1  


The technical documentation for the meter supplied by the manufacturer gives its Modbus table.

I want to read the Total Active Energy (Ea+), the Modbus table gives the following parameters:


- Slave address: 1

- Register address: 19843 or 0x4D83     

- Number of words: 2             

- type: holding (0)


Once the prerequisites have been met, simply connect the product to the IoT configurator, then in maintenance mode click on "Test Modbus reading" and enter the parameters defined previously and "OK".  


Une image contenant texte, capture d’écran, logiciel, Icône d’ordinateur

Description générée automatiquement

The command sent must return the value of the register to be read.

The value returned is in hexadecimal and must be converted from format type to decimal format.

The register value returned is 0000 0537 in U32, this value converted to decimal gives 1 335 kWh.

Simply compare this value with the counter's graphic display to confirm that the correct register has been read.

Once the read test has been validated, you can configure your Modbus with the elements which have just been tested














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