Page 129 - Catalog auto parts lighting technology BOSCH for cars and trucks

Auto Parts / Automotive bulbs | A127

“Weibull distribution”

Proportion of failed bulbs (%)

Bulb service life (h)

Luminous efficiency Color temperature Service life
Lumionous efficiency is a measure of the The color temperature specifies the shade The Weibull distribution has become
efficiency of the process of converting of a light source (see Fig. DIN 5033 standard established as the standard for analyzing the
electrical energy into light energy. The color table). The reference object used is a service life of technical products. This shows
luminous efficiency of a halogen bulb is ap- black solid, which glows in different light the failure rate in % over the entire service
prox. 22–30 lm/W (efficiency below 10 %), colors as heating increases. The emitted life of the bulb.
while that of a gas-discharge bulb is light changes from red to yellow and white
approx. 90 lm/W. through to blue. For example, a bulb with B 3 value: Represents the early-failure rate
Unit: Lumens per watt [lm/W]. warm white light has a color temperature of bulbs. 3 % of all bulbs tested had failed at
of approx. 2,700 Kelvin, a gas-discharge this burning time.
bulb with light similar to daylight approx.
4,000 Kelvin. T c value: Represents the characteristic
Unit: Kelvin [K]. failure rate of 63.2 % of bulbs.

B 50 value: Reflects the mean service life of
the bulbs. The failure rate is 50 %.

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