Hi Pedro,
The error code 0xBFFF000E is defined as:
VISA: (Hex 0xBFFF000E) The given session or object reference is invalid.
This most likely means that either you have not opened a connection to the instrument, or you have closed the handle prematurely. Check your code and use NI-Spy to debug what is actually happening.
Best Regards,
Aaron K.
Application Engineer
National Instruments