APPROACHES TO DEFINITION OF USEFUL AVERAGE DURATION OF GLOW OF LIGHT SOURCES

Abstract

Experimentally there has been established that in traditional light sources  (thermal, high and low intensity discharge lamp) nominal average duration of glow (ADG) equivalent the average duration of glow. This is so because traditional light sources breaking down earlier than their luminous flux will decrease to 70 %. Thermal light sources (TLS) commonly losing 10-15 % of luminous flux during ADG (1000 hours) by decreasing the diameter of luminous body and contamination the inner surface of the bulb by tungsten evaporations.  High quality fluorescent lamps  –  5,  10 % after 20,000 burning hours by photochemical degradation of the luminophor. Compact fluorescent lamps (CFL)  – no more than 20% after 10,000 burning hours. For the semiconductor light sources, these concepts are clearly delineate. This is because light emitting diode (LED) are rarely completely breaking down. There has been suggested approach and analytical expression to determine the constants of time of the transition process light sources’ luminous flux decrease during operation. The law of luminous flux decrease accepted exponential. To determine the constants of time of the transition process of semiconductor light sources’ luminous flux decrease there has been investigated dynamic of exponential luminous flux decrease for specific values of useful ADG light sources.Exponential dependences were builted by method of gradual approximations. Selection the constants of time values for different average duration of glow performed in such a way that the sought curves crossed horizontal direct 70 % luminous flux decrease in a certain specific points of the argument that define useful ADG. Measurement accuracy influence on determination uncertainty of useful ADG of SLS by extrapolation of experimental data obtained during 10,000 burning hours (standard  LM80) carried out graphical way.  There have been established that the measurement error of 1 %, leads to significant uncertainties in determining of useful ADG LS, namely: a)for mines 1 % error mines 25 %; b)  for plus 1 % error plus 46 %; c)for plus-mines 1 % error mines 24,2 %. Taking into account the fact that the measurement error of luminous flux in photometric balls in the range of 5 %, it certainly can be say that to predict the useful value of ADG according to data measurements during 10,000 hours is impossible. Needed another approaches.