System for determining the characteristics of a pressurized gas contained in the system comprising: - at least one continuous wave laser which emits at least one incident beam of coherent and monochromatic light, said laser being of a type with short wavelength, blue, violet or UV, to have a scattered light with a greater signal and whose power is on the order of 100 mW; - at least one optical lens; - scattered light detecting means of scattered light, said detecting means comprising at least one photo-detector, said photo-detector being composed of an array of photo-detecting devices, CCD or CMOS type, for converting light into an electric signal and allowing to detect the shape of the geometric locus of a beam of scattered light, through the one or more optical lenses adapted to collect the scattered light from molecules on which said beam of coherent and monochromatic light is incident and to focus it within a solid angle onto the said photo-detector array; - at least one measuring chamber containing said pressurized gas, said at least one beam, said detecting means and said at least one lens being located within said at least one measuring chamber, said measuring chamber being elongate in the direction of the laser beam and also in the direction of detection by the photodetector, said measuring chamber comprising therein light absorbing means arranged at an opposite end with respect to said laser; - screening means which are arranged along the path of said incident beam to prevent light scattered in random directions in said measuring chamber from reaching said detecting means, said absorbing means being coloured black; and - control means operatively connected to said photo-detector for recording an amount of scattered light according to the Rayleigh scattering principle depending on the physical characteristics and on the pressure or density of the molecules of said gas, and on a wavelength of said coherent and monochromatic light, said control means measuring the light intensity and regulating the exposure time of said photodetector so that said photo-detector always operates within its own measuring range, said control means computing the gas pressure value depending on a Calibration Coefficient, CC, and on the composition of inserted gases; wherein said system further comprises additional means for absorbing the laser radiation, said additional means for absorbing being placed inside said measuring chamber and facing said photo-detector on an opposite side of the incident laser beam to said photodetector and arranged at an opposite end of the measuring chamber with respect to the photodetector. - at least one continuous wave laser which emits at least one incident beam of coherent and monochromatic light, said laser being of a type with short wavelength, blue, violet or UV, to have a scattered light with a greater signal and whose power is on the order of 100 mW; - at least one optical lens; - scattered light detecting means of scattered light, said detecting means comprising at least one photo-detector, said photo-detector being composed of an array of photo-detecting devices, CCD or CMOS type, for converting light into an electric signal and allowing to detect the shape of the geometric locus of a beam of scattered light, through the one or more optical lenses adapted to collect the scattered light from molecules on which said beam of coherent and monochromatic light is incident and to focus it within a solid angle onto the said photo-detector array; - at least one measuring chamber containing said pressurized gas, said at least one beam, said detecting means and said at least one lens being located within said at least one measuring chamber, - screening means which are arranged along the path of said incident beam to prevent light scattered in random directions in said measuring chamber from reaching said detecting means, said absorbing means being coloured black; and - control means operatively connected to said photo-detector for recording an amount of scattered light according to the Rayleigh scattering principle depending on the physical characteristics and on the pressure or density of the molecules of said gas, and on a wavelength of said coherent and monochromatic light, said control means measuring the light intensity and regulating the exposure time of said photodetector so that said photo-detector always operates within its own measuring range, said control means computing the gas pressure value depending on a Calibration Coefficient, CC, and on the composition of inserted gases;