A method of spectrometer calibration, comprising: performing, with a spectrometer , a diagnostic measurement on a secondary reference sample standard for evaluation of an aspect of calibration in near-infrared spectroscopy; analyzing a result of the diagnostic measurement to determine a deviation from an expected result of the diagnostic measurement ; applying a correction algorithm to the aspect of calibration based at least in part on the deviation from the expected result; performing, with the spectrometer , a secondary diagnostic measurement ; wherein after applying the correction algorithm, determining whether a deviation still exists from the expected result of the diagnostic measurement and comparing the deviation to benchmark performance criteria characterized in that it further comprises the following steps: based on a determination that the diagnostic measurement matches the benchmark performance criteria for the secondary diagnostic measurement, performing, with the spectrometer , a product model diagnostic measurement on the secondary reference sample standard using a product calibration model stored in a product model criteria for evaluation of the aspect of calibration in the spectrometer for a particular product being analyzed for measurement; analyzing a result of the product model diagnostic measurement to determine a product model deviation from an expected result of the product model diagnostic measurement; applying a product model correction algorithm to the aspect of calibration based at least in part on the product model deviation from the expected result of the product model diagnostic measurement; and verifying the aspect of calibration by performing a verification measurement on a product sample. performing, with a spectrometer , a diagnostic measurement on a secondary reference sample standard for evaluation of an aspect of calibration in near-infrared spectroscopy; analyzing a result of the diagnostic measurement to determine a deviation from an expected result of the diagnostic measurement ; applying a correction algorithm to the aspect of calibration based at least in part on the deviation from the expected result; performing, with the spectrometer , a secondary diagnostic measurement ; wherein after applying the correction algorithm, determining whether a deviation still exists from the expected result of the diagnostic measurement and comparing the deviation to benchmark performance criteria characterized in that it further comprises the following steps: based on a determination that the diagnostic measurement matches the benchmark performance criteria for the secondary diagnostic measurement, performing, with the spectrometer , a product model diagnostic measurement on the secondary reference sample standard using a product calibration model stored in a product model criteria for evaluation of the aspect of calibration in the spectrometer for a particular product being analyzed for measurement; analyzing a result of the product model diagnostic measurement to determine a product model deviation from an expected result of the product model diagnostic measurement; applying a product model correction algorithm to the aspect of calibration based at least in part on the product model deviation from the expected result of the product model diagnostic measurement; and verifying the aspect of calibration by performing a verification measurement on a product sample. <EOS>