High Accuracy Spectrophotometric Colorimetry at the National Office of Metrology.

An automatic spectrophotometer for colorimetry purposes was developed suitable to determine the color characteristics of standard color sets used in calibrating colorimeters. The measuring system has a single light path, a geometry of 45 degree /0 degree , and measurement data are processed by a computer. As a working standard, the Sovietic opal glass plate MC-20 is used, which in turn is calibrated with respect to a surface pressed of barium sulfate powder. The repeatability, long-time stability of the equipment has been determined. Accuracy of measurements is checked by comparisons with measurements performed at the NPL.