User`s guide

24 Agilent VISA User’s Guide
2 Building a VISA Application in Windows
viOpen This function establishes a communication channel
with the device specified. A session identifier (vi) that
can be used with other VISA functions is returned.
This call must be made for each device you will be
using.
viVPrintf and
viVScanf
These are the VISA formatted I/O functions. The
viVPrintf call sends the IEEE 488.2 *RST command
to the instrument (plus a linefeed character) and puts
it in a known state. The viVPrintf call is used again
to query for the device identification (*IDN?). The
viVScanf call is then used to read the results (strRes)
that are displayed in a Message Box.
viClose This function must be used to close each session.
When you close a device session, all data structures
that had been allocated for the session will be
deallocated. When you close the default manager
session, all sessions opened using that default
manager session will be closed.
Table 3 Summary of VISA Function Calls in Visual Basic Sample