A method of standardizing an output of an electrical property sensor includes calculating a reference magnitude (Condr) of an electrical property of an electrically conductive liquid, based on obtaining, by a spectrometer, spectral data resulting from an interaction of light with the electrically conductive liquid, and applying, in a data processor, a mathematical model to the spectral data to calculate the reference magnitude (Condr) of the electrical property, wherein the mathematical model links the spectral data to magnitudes of the electrical property; comparing, in the data processor, a measured magnitude (Condm) of the electrical property of the electrically conductive liquid with a reference magnitude (Condr) of the electrical property, wherein the measured magnitude (Condm) of the electrical property is obtained with the electrical property sensor; determining, in the data processor, a standardization factor (F) dependent on a ratio of the reference magnitude (Condr) and the measured magnitude (Condm).