Disconnecting and Cleaning Up
Disconnecting an Instrument Object
When you no longer need to communicate with the instrument, you should disconnect
                the object. Interface objects are disconnected with the fclose function; device objects
                are disconnected with the disconnect function.
You can examine the Status property to verify that the object
                is disconnected from the instrument.
obj.Status
ans =
    closedCleaning Up the MATLAB Workspace
When you no longer need the instrument object, you should remove it from memory
                with the delete function.
delete(obj)
A deleted instrument object is invalid, which means that you
                cannot connect it to the instrument. In this case, you should remove the object from
                the MATLAB® workspace. To remove instrument objects and other variables from the
                    MATLAB workspace, use the clear command.
clear objIf you use clear on an object that is connected to an
                instrument, the object is removed from the workspace but remains connected to the
                instrument. You can restore cleared instrument objects to the MATLAB workspace with the instrfind function.