Hi Cas_Sun,
I found another forum post dealing with what seems like the same issue with the Bertan 225 Series.
If you open up LabVIEW and go to your Example Finder application under Help >> Find Examples, you should be able to find a VI called Simple Serial. Try using copying the code from this example and trying to connect to your device through this. If we can make a connection through this example, we'll be on good footing to move forward with debugging.
Tyler O
Tyler O.
Applications Engineer
National Instruments