Opens a session to the specified resource
[status, vi] = viOpen(sesn, rsrcName, accessMode, openTimeout)
contains the return code of the operation.
will be the computer's identifier for other functions.
resource Manager session-should always be a session returned from viOpenDefaultRM().
unique symbolic name of a resource (please see the ViOpen() official help page for details)
specifies the mode by which the resource is accessed, here the session uses VISA-supplied default values (please see the ViOpen() official help page for valid values).
specifies the maximum time period (in milliseconds) the operation waits before returning an error (this does not set the I/O timeout-to do that you must call viSetAttribute() with the attribute VI_ATTR_TMO_VALUE).
The viOpen() operation opens a session to the specified resource.