establishing at least a data connection between a control unit and a handset of the ultrasonic device;

sending a signal to the handset;

receiving from the handset a response to the sent signal; and

checking an operating condition of the ultrasonic device based on said response,

wherein the sending step comprises sending to the handset the signal in the form of a signal having a frequency variable within a frequency range, and wherein the checking step comprises calculating at least one parameter indicative of a frequency response of the ultrasonic device,

wherein the calculated parameter is the variation in impedance as a function of the frequency of said signal, providing an impedance curve representing the frequency response of the ultrasonic device, and

wherein the checking step comprises performing an analysis of the whole measured impedance curve, said analysis being based on reference models.