Modbus TCP communication with Horiba VA 5000 flue gas analyzer

[Yixiao-uncle]

Hi everyone. Have any of you had experience communicating with a Horiba VA5000 smoke analyzer via Modbus TCP? I can't communicate. I can create a Modbus instance without errors; if instead I disconnect the etherner cable and try to create the Modbus instance again, after the timeout I obviously get an error. I can create and close a Modbus instance, without doing any other read or write operations without errors But as soon as I try, for example to read a Holding register, I get error 56. Do you have any suggestions or additional checks I can do?

Thank you

Antonio

[ZYOng · Accepted solution]

Test with another Modbus master like QModMaster to ensure you have configured the correct parameter to communication with the instrument.

[Yixiao-uncle]

Hi, ZYOng:

youir suggestion has been very usefull; we tested with QModMaster and we understood that we forgot to add the Unit ID (strange, with other Modbus devices it was not necessary, for exmple Siemens S7).

Noe we can communicate properly with VA5000 using LabVIEW.

Thanks again.

A

[ZYOng]

Unit ID is usually only used in Modbus RTU and ignored in TCP, but it is possible that the vendor still implements it anyway.