A method and a system for using an internet protocol address of a user data processing system to obtain from a software vendor an authorization code for activating a software application. The accuracy of contact and via capacitance measurements are improved by eliminating not-to-be-measured capacitance from the measurement results. The cleaning agent is applied to the surface as a gel, in particular as a gel that has a purely physical cleaning effect. The operating personnel, possibly in conjunction with a control functionality of the examination device are thus provided with a visualization of an X-ray image to be anticipated.