A method of standardizing an output of an electrical property sensor for determining an electrical property of an electrically conductive sample liquid comprising the steps of: providing an electrically conductive liquid having a known relationship between the electrical property and spectral data resulting from an interaction of light comprising wavelength bands which contain at least a portion of one or more ultraviolet, visible and infrared regions with the electrically conductive liquid and operating the electrical property sensor to generate the measured magnitude (Cond m) of the electrical property for receipt by the data processor; calculating a reference magnitude (Cond r) of the electrical property comprising obtaining by a spectrometer spectral data resulting from an interaction of light comprising wavelength bands which contain at least a portion of one or more ultraviolet, visible and infrared regions with the so provided electrically conductive liquid and applying in the data processor a mathematical model to the obtained spectral data to calculate the reference magnitude (Cond r) of the electrical property, which mathematical model links spectral data to magnitude of the electrical property; comparing in the data processor the measured magnitude (Cond m) of the electrical property of the electrically conductive liquid obtained with the electrical property sensor with the reference magnitude (Cond r) of the electrical property; determining in the data processor a standardization factor dependent on a ratio of the reference magnitude (Cond r) of the electrical property and the measured magnitude (Cond m) of the electrical property; and applying in the data processor the standardization factor to subsequent measured magnitudes (Cond ms) of the electrical property of the electrically conductive sample liquid obtained with the electrical property sensor to generate a standardized electrical property measurement (Cond std). providing an electrically conductive liquid having a known relationship between the electrical property and spectral data resulting from an interaction of light comprising wavelength bands which contain at least a portion of one or more ultraviolet, visible and infrared regions with the electrically conductive liquid and operating the electrical property sensor to generate the measured magnitude (Cond m) of the electrical property for receipt by the data processor; calculating a reference magnitude (Cond r) of the electrical property comprising obtaining by a spectrometer spectral data resulting from an interaction of light comprising wavelength bands which contain at least a portion of one or more ultraviolet, visible and infrared regions with the so provided electrically conductive liquid and applying in the data processor a mathematical model to the obtained spectral data to calculate the reference magnitude (Cond r) of the electrical property, which mathematical model links spectral data to magnitude of the electrical property; comparing in the data processor the measured magnitude (Cond m) of the electrical property of the electrically conductive liquid obtained with the electrical property sensor with the reference magnitude (Cond r) of the electrical property; determining in the data processor a standardization factor dependent on a ratio of the reference magnitude (Cond r) of the electrical property and the measured magnitude (Cond m) of the electrical property; and applying in the data processor the standardization factor to subsequent measured magnitudes (Cond ms) of the electrical property of the electrically conductive sample liquid obtained with the electrical property sensor to generate a standardized electrical property measurement (Cond std). comparing in the data processor the measured magnitude (Cond m) of the electrical property of the electrically conductive liquid obtained with the electrical property sensor with the reference magnitude (Cond r) of the electrical property; determining in the data processor a standardization factor dependent on a ratio of the reference magnitude (Cond r) of the electrical property and the measured magnitude (Cond m) of the electrical property; and applying in the data processor the standardization factor to subsequent measured magnitudes (Cond ms) of the electrical property of the electrically conductive sample liquid obtained with the electrical property sensor to generate a standardized electrical property measurement (Cond std).