presents a LED-Tube Light that gives a cold white light, is 60 cm long and contain 174 small leds. Many parameters are also found in the Eulumdat file.

See this overview for a comparison with other light bulbs.

Summary measurement data

parameter	meas. result	remark
Color temperature	2875 K	Cold white
Luminous intensity Iv	365 Cd
Beam angle	91 deg
Power P	9.9 W
Power Factor	0.80	For every 1 kWh net power consumed, there has been 0.8 kVAhr for reactive power..
Luminous flux	782 lm
Luminous efficacy	79 lm/W
CRI_Ra	78	Color Rendering Index.
Coordinates chromaticity diagram	x=0.3109 and y=0.3213
Fitting	FL-tube	Direct connection to the mains voltage.
D x L external dimensions	30 x 600 mm	External dimensions of the light bulb.
W x L luminous area	24 x 550 mm	Dimensions of the luminous area (used in Eulumdat file). This is equal to the surface of the area on which the leds are mounted.
General remarks		The ambient temperature during the whole set of measurements was 25 deg C. Warm up effect: during the warm up time the illuminance and power decreased with 8 %. Voltage dependency: the power consumption nor illuminance are not dependent on variation of the input voltage. See the end of the article for one more photo.
Measurement report (PDF)
Eulumdat file		Right click on icon and save the file.

Eulumdat light diagram

An interesting graph is the light diagram, indicating the intensity in the C0-C180 and the C90-C270 plane. This light diagram below comes from the program Qlumedit, that extracts these diagrams from an Eulumdat file.

The light diagram giving the radiation pattern.

It indicates the luminous intensity around the light bulb. The C0_c180 plane is the plane defined by the length direction of the tube and the height direction. The C90-C270 plane has two directions: the height and the direction perpendicular to the tube’s length. Both planes give the same diagram; the leds used have the same light pattern all around.

The unit is Cd/1000lm, meaning the intensity in Cd assuming there would be 1000 lumen in the measured light bulb. This enables comparing different types of light bulbs.

Illuminance Ev at 1 m distance, or luminous intensity Iv

Herewith the plot of the averaged luminous intensity Iv as a function of the inclination angle with the light bulb.

The radiation pattern of the light bulb.

This radiation pattern is the average of the light output of the light diagram given earlier. Also, in this graph the luminous intensity is given in Cd.

These averaged values are used (later) to compute the lumen output.

Intensity data of every measured turn angle at each inclination angle.

This plot shows per inclination angle the intensity measurement results for each turn angle at that inclination angle. There are differences in illuminance values for different turn angles. However for further calculations the averaged values will be used.

When using the average values per inclination angle, the beam angle can be computed, being 91 degrees. This is the average value for all C-planes on average. There is little difference between the C-planes so this beam angle is accurate for most C-planes.

Luminous flux

With the averaged illuminance data at 1 m distance, taken from the graph showing the averaged radiation pattern, it is possible to compute the luminous flux.

The result of this computation for this light spot is a luminous flux of 782 lm.

Luminous efficacy

The luminous flux being 782, and the power of the lightbulb being 9.9 W, yields a luminous efficacy of 79 lm/W.

A power factor of 0.80 means that for every 1 kWh net power consumed, a reactive component of 0.8 kVAr was needed.

Light bulb voltage (used on power supply!)	230 VAC
Light bulb current	54 mA
Power P	9.9 W
Apparent power S	12.4 VA
Power factor	0.80

Of this light bulb the voltage across ad the resulting current through it+its power supply are measured and graphed.

Voltage across and current through the light bulb

There are peaks in current near the tops of the voltage. This results in a waveform for the current that is different from the sine form of the voltage, resulting an a power factor less than 1. The peaks are also not symmetrical, resulting in a further decrease of the power factor.

Also the power spectrum of the current is determined.

Current power spectrum in % of the first harmonic (50 Hz).

The current peaks result in a current power spectrum with a considerable amount of higher harmonics.

Color temperature and Spectral power distribution

The spectral power distribution of this light bulb.

The measured color temperature is about 6650 K which is cold white.

This color temperature is measured straight underneath the light bulb. Below a graph showing the color temperature for different inclination angles.

Color temperature as a function of inclination angle.

The color temperature is given for inclination angles up to 75 degrees, since at higher angles there is almost no light output anymore.

The value remains constant within 15 % of the value at 0 degrees inclination angle.

Chromaticity diagram

The chromaticity space and the position of the lamp’s color coordinates in it.

The light coming from this lamp is situation on the path of the Planckian Locus (the black path in the graph).

Its coordinates are x=0.3109 and y=0.3213.

Color Rendering Index (CRI) or also Ra

Herewith the image showing the CRI as well as how well different colors are represented (rendered). The higher the number, the better the resemblance with the color when a black body radiator would have been used (the sun, or an incandescent lamp).

Each color has an index Rx, and the first 8 indexes (R1 .. R8) are averaged to compute the Ra which is equivalent to the CRI.

CRI of the light of this light bulb.

The value of 78 is lower than 80 which is considered a minimum value for indoor usage.

Note: the chromaticity difference is 0.0031 indicates the distance to the Planckian Locus. Its value is lower than 0.0054, which means that the calculated CRI result is meaningful.

Voltage dependency

The dependency of a number of lamp parameters on the lamp voltage is determined. For this, the lamp voltage has been varied and its effect on the following light bulb parameters measured: illuminance E_v [lx], the lamppower P [W], the (Correlated) Color Temperature [K] and the luminous efficacy [lm/W].

Lamp voltage dependencies of certain light bulb parameters, where the value at 230 V is taken as 100 %.

The consumed power nor illuminance vary significantly when the voltage is varied between 200-250 V. Except for values lower than 210 V, where a further decrease in voltage leads to a quick decrease in power and illumination levels.

When the voltage at 230 V varies with + and – 5 V, then the illuminance varies within 0.1 %, so when abrupt voltage changes occur this effect is not visible in the illuminance output.

Warm up effects

After switch on of a cold lamp, the effect of heating up of the lamp is measured on illuminance E_v [lx], color temperature CT or correlated color temperature CCT [K], the lamppower P [W] and the luminous efficacy [lm/W].

Effect of warming up on different light bulb parameters. At top the 100 % level is put at begin, and at bottom at the end.

The warm-up time is about 25 minutes, during which the illumination drops with 8 % as well as the consumed power.

Photo of the light bulb

A close up photo of the used leds.