A device includes a charge variation sensor having at one or more electrodes. The charge variation sensor, in operation, generates a charge variation signal indicative of changes in an electric or electrostatic charge induced on the one or more electrodes by an alternating current power source. Processing circuitry, coupled to the charge variation sensor, generates a frequency spectrum signal based on the charge variation signal and identifies a frequency of operation associated with the alternating current power source based on the generated frequency spectrum signal. A control signal is generated based on the identified frequency of operation. An image acquisition device sets an image acquisition frequency based on the control signal.