Renewable Energy

Lioris Tubo T24120CWFrosted

Posted by Marcel van der Steen in Led lights, Light measurements Add comments

lioris_tubo_120_frosted presents a 120 cm long led-TubeLight. It has 364 leds hidden behind a frosted cover. There is intelligence in this lamp; it can be dimmed, by switching the lamp within a certain timeperiod ofter switching off. The designed notes that the lam pis install-safe. When the installer holds one end and puts the other side in a power carrying lamp holder, then ther is no risk of getting a shock at the pins at the other side of the tube.

This article shows the measurement results. 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 6901 K Cold white.
Luminous intensity Iv 539 Cd Measured straight underneath the light bulb.
Beam angle 129 deg Valid for the C90-C270 plane, perpendicular to the length side of the tube. For the C0-C180 (along the tube’s length) the beam angle is 107 deg.
Power P 24.3 W
Power Factor 0.99 For every 1 kWh net power consumed, there has been 0.1 kVAhr for reactive power.
Luminous flux 1843 lm
Luminous efficacy 76 lm/W What actually is meant here is luminaire efficacy, this accounts for all driver, thermal and luminair optical losses.
CRI_Ra 79 Color Rendering Index.
Coordinates chromaticity diagram x=0.3083 and y=0.3138
Fitting FL-tube This tube is connected directly to mains voltage.
PAR-value 5.3 μMol/s/m2 The number of photons seen by an average plant when it is lit by the light of this light bulb. Value valid at 1 m distance from light bulb.
S/P ratio 2.2 This factor of higher efficacy when used in very low light circumstances.
D x L external dimensions 30 x 1197 mm External dimensions of the light bulb (D = diameter endcaps). L = Length without pins at end.
L x W luminous area 1150 x 30 mm Dimensions of the luminous area (used in Eulumdat file). This is equal to the protected surface of the frosted cover (to a flat plane) of the tube.
General remarks The ambient temperature during the whole set of measurements was 23-23.5 deg C.

Warm up effect: during the warm up time the illumination and the consumed power decreased about 6 %.

Voltage dependency: the power consumption and light output depend linearly on the voltage applied.

Also the dim-ability is tested in the positions 100, 75, 50 and 25 %.

Measurement report (PDF) olino-pdf
Eulumdat file olino_eulumdat Right click on icon and save the file.

Overview table


The illuminance values are measured in the far field (i.e. at least 5 times the distance of the largest illumination dimension) such that the light bulb can be seen as a point source. From this distance the values are calculated to values at the given distances.

If the light is not anymore a point source at any given distance, then the real measured values (with an actual lux meter) will be lower than indicated in this table.

In general, the light source is not anymore a point source starting from distances lesss than 5x the length of the luminous area. For this tube, this is starting from a distance of less than 5 x 1150 mm.

Having the Eulumdat file, then with a light calculation program it is possible to compute the illuminance values in the near field.

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 tube. The C0-C180 plane (along length direction of the tube) has a smaller beam angle than the C90-C270 plane (perpendicular to the length direction). This latter also directs some light backwards (not useful).

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 normally 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 107 degrees for the C0-C180 plane (length direction) and 129 degrees for the C90-C270 plane.

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 1843 lm.

Luminous efficacy

The luminous flux being 1843 lm, and the power of the light bulb being 24.3 W, yields a luminous efficacy of 76 lm/W.

A power factor of 0.99 means that for every 1 kWh net power consumed, a reactive component of 0.1 kVAr was needed.

Light bulb voltage 230 VAC
Light bulb current 106 mA
Power P 24.3 W
Apparent power S 24.4 VA
Power factor 0.99

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


Voltage across and current through the lightbulb

The current is in phase with the voltage. It has a sinusiodal form. Just perfect.

Also the power spectrum of the current is determined.


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

Due to the nice sinusiodal form of the current there are virtually no higher harmonics.

Color temperature and Spectral power distribution


The spectral power distribution of this light bulb, energies on y-axis valid at 1 m distance.

The measured color temperature is about 6900 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.

At an inclination angle of 75 deg the illuminance was so low (less than 5 lux) that is stopped measuring color temperature.

The (maximum) beam angle is 129 degrees, meaning at an inclination angle of 64.5 degrees there is 50 % left of the initial illuminance value at 0 degrees. Most of the light energy is within this area. In this area the variation in light color is about 3 % of its value at 0 degrees inclination angle.

PAR value and PAR spectrum

To make a statement how well the light of this light bulb is for growing plants, the PAR-area needs to be determined. PAR stands for Photosynthetic Active Radiation which is that radiation that participates actively to photosynthesis and is expressed in μMol/s/m2.

Photosynthesis is the essence for growth and flowering of plants, where the blue part of the light spectrum is responsible for growth and the red part is responsible for flowering and budding (for gemmation). For photosynthesis it is more important to count the number of photons rather than the power in the light. The power spectrum (power per wave length) of the light of the light bulb is converted into the number of photons (number of photons per wave length) and then these number of photons is weighted against the relative sensitivity of an average plant (which varies in value dependent on the wave length). The relative sensitivity curve in DIN-norm 5031-10:2000 is used for this. The next image shows the result.


The photon spectrum, then the sensitivity curve and as result the final PAR spectrum of the light of this light bulb

The black curve gives the power spectrum of the light of this light bulb, in number of photons per wave length. In red the relative sensitivity curve of an average plant (according to DIN norm 5031-10:2000). Multiplying these two results in a curve showing the number of photos per wave length of the light of this light bulb, the PAR spectrum. Summing all the photons, gives a PAR number that for this light results in 5.3 μMol/s/m2. This value is valid at 1 m distance from the light bulb and in the area within the beam angle.

Dividing the PAR number by the total number of photons of the light of this light bulb gives a sort of PAR efficiency, which is 67 % (valid for the PAR wave length range of 400 – 700 nm). So maximally 67 % of the total of photons in the light is effectively used by the average plant (since the plant might not take 100 % of the photons at the frequency where its relative sensitivity is 100 %).

Note: when mentioning this percentage of efficiency, it is important to verify if all wavelengths are present in a sufficient manner. Not that only blue light is available, when the plant is going to be used for flowering where specifically red light is needed.

S/P ratio

The human eye uses rods and cones. The rods work at scotopic light levels (twilight, night) and the rods at high(er) light levels (daytime, but also close to twilight).

Each type of receptor has its own sensitivity for light. The rods are 2.7 times more sensitive than cones, and most for light at a blueish-greenish color whereas compared to the cones’ sensitivity for green light (555 nm).

The S/P ratio gives the maximum difference in sensitivity of the rods at their most sensitive wavelength compared to the cones at their’s. The more blueish (cold white) the light, the more the S/P ratio can be.

The light of this light bulb has a certain spectrum leading to an S/P ratio of 2.2. The light of this lightbulb at scotopic light levels is perceived this factor higher than it would be a photopic light levels.


The power spectrum, sensitivity curves and resulting scotopic and photopic spectra (spectra energy content defined at 1 m distance).

It concerns a light bulb with neutral white light, and therefore contains a lot more of blue relative to red/green. Therefore the S/P ratio is high, being 2.2.

More explanation of the S/P ratio will come in a separate article.

Chromaticity diagram


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

The light coming from this lamp is close to the Planckian Locus (the black path in the graph). Its coordinates are x=0.3083 and y=0.3138.

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 lightbulb.

The value of 79 is the a bit lower than 80 which is considered a minimum value for indoor usage.

Note: the chromaticity difference is 0.0057 indicates the distance to the Planckian Locus. Its value is higher than 0.0054, which means that the calculated CRI result is not 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 and illumination do vary linearly when the voltage varies between 200-250 V.

When the voltage at 230 V varies with + and – 5 V, then the illuminance varies within 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.

During the warm up time of about 20-25 minutes, the consumed power and illuminance decrease 6 % (the jump in power consumption at the very start not considered).

Dim ability

The dim-ability was tested. By switching off and after a few seconds but before 5 seconds are again switching on, then this light tube will flicker a few times and the run from 100 % to 75, 50 and 25 % every 3 seconds. After this it will come back at 100 %.

Switching off in the mean time will establish the then actual dimming position and will be saved in lamp’s memory. Switching on after minimally 5 seconds will then bring this light tube into the dimming situation that was stored.

It is an easy way of dimming when a whole area is equipped with these lights; a separate dimmer is not needed, only a switch.


Lamp parameters as a function of the mechanical knob position of the dimmer.

The light tube is well dim-able. The presets 100 %, 75, 50 and 25 correspond well to the amount of light emitting the tube.

The power consumption decreases somewhat quicker than the illumination decreases, which is understood since at lower currents the leds operate at lower junction temperature and therefore more efficient.

The color temperature decreases a bit during the dimming action, which makes believe that the dimming is done by reducing the amplitude of the current (rather than PWM).

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