Multi-wavelength absorption water sensor with high ultraviolet wavelength resolution and extended visible and near infrared measurement range

A method operable by a controller of a submersible apparatus for measuring light absorption of a liquid sample surrounding the submersible apparatus, wherein:

• the submersible apparatus comprises:
• a broadband light source configured to output broadband light in an ultraviolet light spectrum and light in one or more of a visible light spectrum and a near infrared light spectrum;
• a measurement region including the liquid sample, which propagates the broadband light emitted from the broadband light source;
• a light beam splitter configured to split the broadband light, after passing through the measurement region, into a first light beam and a second light beam;
• a light sensor configured to detect an intensity of visible or near infrared light from the first light beam;
• an optical slit configured to produce an approximate point source of light from the second light beam;
• a diffraction grating configured to resolve the second light beam propagating from the optical slit into a plurality of resolved and substantially adjacent narrow ultraviolet bandwidth regions;
• and
• a line sensor array configured to detect a plurality of individual light intensities corresponding to the ultraviolet bandwidth regions produced by the diffraction grating, and
• the method comprises:
• recording and outputting the intensity measurements of visible or near infrared light detected by the light sensor;
• recording and outputting the intensity of the plurality of individual light intensities corresponding to the ultraviolet bandwidth regions detected by the line sensor array;
• and
• calculating an absorbance of light by the liquid sample using the recorded intensity measurements of ultraviolet and visible or near infrared light.