JJG (Light Industry) 48-2000 "Reflectance Photometer verification regulations" specify the method of verification of reflectance photometers, which is applicable to the instruments required by GB/T7973, GB/T7974, GB/T7975 and other standards. The regulations cover newly manufactured, in-use instruments and repaired equipment, involving the verification of whiteness meters and color difference meters. The instruments are required to meet the standards of Appearance, Lighting and Observation Conditions, and have good Repeatability, Stability and Precision. The verification items include Appearance, Repeatability, Stability, Precision and Mirror reflection errors of the instrument, calibrated and verified using standard swatches and whiteness paper samples. The verification period is one year to ensure the long-term stability of the instrument performance.