JJF 1947-2021 Platinum-Cobalt Colorimeter calibrating specification applies to the calibration of platinum-cobalt Colorimeters in the (0~ 500) Measurement range. The standard is based on the principle of Spectrophotometric method, spectra-trophotometry, and specifies the procedure and method for calibrating platinum-cobalt Colorimeters. The platinum-cobalt chroma unit Pt-Co Unit (PCU), as a standard unit for measuring solution Color, is specifically defined and applied in this specification. The Colorimeter consists of a Light source, Optical inspection system, Colorimetric dish, measurement chamber, photoelectric detection element and display unit to calculate and display the platinum-cobalt chromatic value of the sample by measuring the transmitted Light spectrum. The implementation of this specification is to ensure that the measurement results of Colorimeter are accurate and reliable, meeting the requirements of liquid Color measurement in industry and laboratories.