The JJG (Light Industry) 48-2000 "Reflectance Photometer" standard specifies the verification procedure for reflectance photometers, which is applicable to the reflection measurement of pulp, paper and Cardboard, including newly manufactured, in-use and repaired instruments. The standard details the measurement performance requirements of reflectance photometers, including Repeatability, Stability, Precision and mirror reflection error. The standard cites a number of relevant literature and uses specific standard swatches and paper samples for verification. The instrument must meet the requirements of Appearance, Lighting and Observation Conditions, and the instrument with qualified verification results will be issued a verification certificate. The standard also stipulates that the verification period is generally one year.