GENERATION, CONTROL, AND MEASUREMENT 



181 



For equal power input all sources will add the same thermal load to 

 a constant-temperature room, but the fluorescent lamp tends to heat 

 directly the air surrounding it, whereas the incandescent lamp produces 

 most of its heating effect upon the objects incident to the flux. For this 

 reason the radiation from a fluorescent lamp "feels cooler" than that of 



Table 3-13. Comparative Spectral Characteristics of Sources 



Source 



Sun, air mass = 2. . . 

 Incandescent lamp 



General service ... 



General service. . . . 



Photoflood 



Mercury arc 



AH-4 



EH-1 



AH-6 (all quartz) . 



UA-2 (all quartz) . . 



Germicidal 



Fluorescent lamp 



Standard cnol white 



Blue 



Green 



Pink ,. . . . 



Gold 



Red 



Sodium lamp 



NA9 



Power. 



40 



500 



1000 



100 



400 



1000 



250 



30 



40 

 40 

 40 

 40 

 40 

 40 



180 



Percentage of input lamp watts radiated in each 

 wave band 



0-280 





 

 





 



3.1 



4.6 



23.0 





 

 

 

 

 



280-320 

 m/i 



0.4 





 

 0.02 



0.7 



0.02 



7.5 



4.3 



0.5 



0.2 



0.05 



0.04 



0.08 















320-380 

 vniji 



2.6 



03 

 0.09 

 0.3 



4.3 

 2.5 

 9,0 

 3.4 

 0.4 



0.6 



1.2 



0.4 



0.2 











0.82 



380-500 

 m^ 



13.6 



G 

 1.2 

 2.6 



4.6 

 6.0 

 15.0 

 2.8 

 1.4 



6 



16 



3 



2 

 

 



500-600 

 niM 



19.3 



1.6 

 2.7 

 4 9 



5.6 

 8.5 

 10.5 

 3.8 

 0.7 



8.7 

 5.5 

 16.0 

 3.3 

 6.6 

 1 



11,4 



600-760 

 m^ 



24.8 



5.0 



8.0 



11.0 



0.2 

 1. 1 

 3.7 

 0.4 

 0.04 



760- = 

 mM 



39.3 



76 

 79 

 77 



Percentage 

 of total 

 radiated 



83 

 91 

 96 



a bare incandescent lamp and produces less heating of irradiated objects 

 for the same visible irradiance. 



The electrical efficiency of the large white fluorescent lamps in lumens 

 per electrical watt is the highest of any source for general irradiation, 

 varying between 50 and 65 lumens w~^ for the various white lamps alone 

 and 40 to 50 lumens w~' for the lamp in combination with the ballast. 

 Because of the variation in efficiency of the different types of ballasts, 

 manufacturers rate gaseous discharge lamps on the basis of the efficiency 

 of the bare lamp, not including the ballast losses, which amount to 15 to 

 30 per cent of the total power consumed by the combination. 



TEMPERATURE 



Unlike that of the incandescent lamp, the intensity of the fluorescent 

 lamp is markedly influenced by air temperature and the rate of air circu- 

 lation about the tube. The tube temperature for maximum efficiency is 

 about 48°C. At 30° and 60°C the intensity is between 70 and 80 per cent 



