Abstract: The automated selection of the best calibration for measuring selected physical, chemical or atomic properties of continuous moving sheets, or of a coating on the sheets, is provided by the use of an on-line qualitative multi-band infrared measurement of the material. The multi-band qualitative measurement produces a spectral pattern of the material, which is matched to a library of potential materials. Once the best spectral pattern match is selected, then the known calibration constant values are used to make quantitative measurements on selected properties of the sheet of material, or of a coating on the material. Typically, a property of interest is the weight per unit area (i.e., grams per square meter) of a plastic coating on a paper substrate. The automated selection may be done on a periodic basis to adapt to variations in the substrate material that would otherwise cause the quantitative measurements of the coating to become erroneous due to calibration errors.