A spectrometric sensor for measuring a spectra value of a flowing fluid. The spectrometric sensor comprises a light source for emitting a first light flux toward a sample of the flowing fluid, a light detector for measuring a first intensity of a reflection of the first light flux from the flowing fluid and a second intensity of a second light flux received via the flowing fluid, and a control unit configured for generating at least one spectra value according to at least one of the first and second intensities.