Spectroradiometer specbos 1211

Measurement of Energy Saving Lamps and Fluorescent Tubes

The following measuring set ups can be used to characterize energy saving lamps and conventional fluorescent tubes:


4pi meas trans 450



energy saving lamp 450

fluorescent tube 450
Measuring geometries
Left - Luminous flux for both types, center - Luminous intensity for energy saving lamps, right - Luminance for conventional fluorescent tubes
1211 kugel 450 1211 1 450  1211 2 450
Characterization of a fluorescent lamp by its luminous flux (left), luminous intensity (center) and luminance (right)


The common measuring set ups to characterize the photometric and colorimetric properties of fluorescent lamps are Goniophotometers and Integrating sphere systems. The latter are especially used in production because of their much higher measuring speed (left figures). The diameter of the sphere needs to fit to the tube dimensions, therefore spheres with 1 ... 3 m diameter are necessary for long fluorescent tubes.



Point like sources as compact energy saving lamps can also be characterized by their Luminous intensity (figures in centre). The measurement is based on a illuminance measurement and afterwards converted into the luminous intensity value (see: Radiant Intensity Calculation Using Irradiance Measurement). Here the the measuring distance has to be large enough.


Fluorescence tubes can be characterized in Luminance mode (see right figures). It allows to get the result from a selected part of the tube surface. Repeated measurements on different locations allow to obtain a distribution along the tube. The measuring diameter can be adapted by changing the measuring distance of specbos 1211 to the tube. The target circle of specbos 1201 and 1211 can easily be used to adjust the measuring position on the tube.



Classification according to McAdam ellipses

Each luminescence material has its characteristic spectrum. Different materials will be mixed according to special receptures to achieve desired chromaticities and color temperatures of fluorescent lamps. It is necessary for quality control to monitor these data and the prefered method is to measure the spectra by a spectroradiometer and calculate the values.
 spec of fluorescence lamp 450 lival
Spectrum of a fluorescent lamp, measured with specbos


McAdam ellipses are used to specify the chromaticity tolerances. These ellipses were defined by McAdam in 1943 and are still used in lamp industry [1]. They show the areas in the xy or uv diagram wherein the human eye cannot distiguish between different colors. They are different in size and orientation across the color gamut.
 mcadams 7step small
McAdam ellipses for different color temperatures in the region of the Planckian radiator in the xy diagram


Some ellipses covering the black body locus are used to specify fluorescent lamps. They are defined for several color temperatures from 2700 to 6500 K for industrial use (see the standards for US [2] and for EU [3]). It is defined the central location of xy and the accepted tolerance ellipses. The used equiation for the ellipses is as follows:


SDCM g delta



g11, g12 and g22 are the individual coefficients for each ellipse, Δx and Δy are the deviations from the rated values x and y and SDCM means standard deviation of color matching (tolerance factor or McAdam Color steps). So the ellipses are defined in position, orientation and size.
SDCM is a scaling factor and can be varied between 1 and 10 to vary the ellipses for different tolerance requirements. The value of 1 for SDCM characterizes the original ellipse of non distinuishable chromaticities. Higher values are used to extend the tolerance ranges with regard to the costs and yield of the production. The software JETI LiVal contains these definitions of ellipses, therefore it can be easily used for the characterization of fluorescence lamps in production process.
defin ellipse 450


Definition of the McAdam ellipse for 4000K and SDCM = 5 (from JETI software LiVal)


diagr dif ellipse 450

Detail of xy diagram with a defined ellipse



Color type Color Temperature Name x y  g11 g12 g22
F 6500 6 400 K Daylight 0.313 0.337 86 x 104 - 40 x 104 45 x 104
F 4000 4 040 K Cool white 0.380 0.380 39.5 x 104 - 21.5 x 104 26 x 104
F 3500 3 450 K White 0.409 (EU), 0.411 (US) 0.394 (EU), 0.393 (US) 38 x 104 - 20 x 104 27.5 x 104
F 3000 2 940 K Warm white 0.440 0.403 39 x 104 - 19.5 x 104 86 x 104
Selected data from standards [2] and [3]


Measurement of the exciter

The excitation of fluorescent lamps is done by UV emitting tubes. If such tubes have to be characterized a spectroradiometer with an extended wavelength range into the UV is necessary, e.g. specbos 1211 UV. The following figure shows a UV tube (Philips TUV 16W) and the spectrum obtained with a specbos 1211 UV.


spec of uv excitatio lamp 450

UV exciting tube and its spectrum
Specification of Small Chromaticity Differences. MacAdam, D.L.: JOSA 33(1943) 1, p. 18-25
ANSI C78.376-2001
EN 60081:1998, appendix D