Patent ID: 7924424

Claim:
A method comprising: directing light into a fluid delivery medium in which presence or absence of a product is to be determined; detecting light in each of a plurality of wavelength ranges transmitted through the fluid delivery medium and producing therefrom a plurality of detector outputs; calculating at least one color ratio based on at least two of the detector outputs; normalizing each of the plurality of detector outputs based on baseline detector outputs obtained when product is present in the fluid delivery medium, thereby producing a plurality of normalized detector outputs; associating at least one out-of-product threshold with each of the plurality of normalized detector outputs; associating at least one color ratio out-of-product threshold with the at least one color ratio; performing an initial comparison, wherein each of the normalized detector outputs are compared with the associated at least one out-of-product threshold; based on the initial comparison, i) determining the presence of product within the fluid delivery medium, or ii) triggering a second comparison, wherein each of the at least one color ratios are compared with the associated at least one color ratio out-of-product threshold, the second comparison indicating whether product is present or absent within the fluid delivery medium.