ANSI C78.376:2001 pdf free download – Specifications for the Chromaticity of Fluorescent Lamps
1. Scope
This standard covers the objectives and tolerances for the chromaticity of T8, T10 and T12 fluorescent lamps with a nominal loading of from 5 to 10 watts per foot at their normal 100 hour rating point. This standard also covers some compact lamps. where noted. The colors included are 2700K, 3000K/warm white, 3500K/white, 4000K/4 100K/cool white, 5000K, and 6500K/daylight. The lamp under test shall be operated under reference conditions as specified in ANSI C78.375 Guide for Operation of Fluorescent Lamps and in the relevant C78 lamp standard.
2. Color specification basis
The x and y coordinates used in this specification are based on the 1931 CIE* Chromaticity Diagram. Lamps shall be rated in terms of the measurements standards established by the National Institute of Standards and Technology.  Tolerances are based on the ellipses defined by David L. MacAdam in his paper “Specification of Small Chromaticity Differences” printed in Journal of the Optical Society of America, vol 33, no.1, Jan 1943, pp 18-26.  International Committee on llumination.
3. Nominal color temperature
Values of correlated color temperature (CCT) wilt vary within a chromaticity tolerance ellipse since they are a function of color coordinates. For colors. which are designated by nominal color temperature, the value shall be based on the CCT of the objective chromaticity. For new colors, the nominal value of the color temperature shall differ from the CCT of the objective chromaticity by less than 100K. For a color with a nominal color temperature generally established prior to this standard, the value may be retained when it differs from the CCT of the objective chromaticity by a slightly greater amount.
5. Chromaticity tolerances
For the lamps covered by this standard the chromaticity tolerance is defined by a 4 step MacAdam ellipse. The ellipses are shown in figures 1 through 6. In the construction of these elipses the data shown in Table 2 are used. The values of 911, 2912, and 922 are taken from MacAdam’s paper referred to above. They are the basis for calculating e, a, and b. e is the angle between the major axis of the ellipse and the X axis. a and b are major and minor semi-axis of a one step elipse, respectively.
6.Color Rendering Index (Ru)
6.1 Definition
Color rendering index or CRI is the measurementof degree of color shft obiects undergo when iluminated by a reference source of comparable color temperature. It is abbreviated Rg
6.2 Measurement
The value for CRI for a given lamp shall be determined in accordance with the method specified in CIE Publication 13.3_ The required spectroradiometric measurement and characterization shall be conducted in accordance with methods given in IESNA LM-58 and IESNA LM-16. For compliance with federal requlations see 10CFR 430.24.
6.3 Specification
The initial reading of the Color Rendering Index. R。. of a _test lot shall not be less than the rated value decreased by three.