The invention concerns an ultra-sensitive and accurate electrical impedance spectroscopy technique for the detection and characterization of bubbles in liquids that is required in numerous industrial processes as well as in the humans blood circulation during Decompression Sickness. The method is based on measuring non-invasively the electrical impedance variation of two-phase mixtures: liquid as conductive phase, resp. gas as non-conductive phase, applying an AC excitation signal of the proper frequency value identified by preliminary frequency scanning. The system takes advantage of innovative signal acquisition (hardware) device, and digital signal processing (software) methods and manages to detect accurately for the first time even the presence of a few bubbles corresponding to extremely low volumetric gas fraction values, up to < 0,1%. Also, the high measurement sensitivity of 0,001% in conjunction with advanced signal processing provides valuable qualitative and quantitative information on bubble size characteristics and allows for correlating bubble size to the spectral content of acquired signals.
