On the Flux Pulsations of Fluorescent Lamps

• Published in: Journal of the Illuminating Engineering Institute of Japan Vol. 39; no. 10; pp. 387 - 398
• Main Authors: Nonaka, Mamoru, Shikakura, Toshiro
• Format: Journal Article
• Language: English; Japanese
• Published: The Illuminating Engineering Institute of Japan 1955
• ISSN: 0019-2341; 2185-1506; 1349-838X
• DOI: 10.2150/jieij1917.39.10_387

When the fluorescent lamp is connected to the a. c. power supply, its luminous flux pulsates at frequencies twice as high as those of source. This phenomenon has been understood as the flicker or the stroboscopic effect by many people, but it has been failed to notice that the wave-form of the flicker is not the same at any part of a lamp and so the brightness distribution along the tube axis does not change similarly during a cycle. In the present experiments the periodical alternation of the brightness distribution of the fluorescent lamp operated on a 50 c/s supply has been obtained by the arrangement shown in Fig. 1. There is a special sector with narrow slits driven by a synchronous motor in front of the entrance slit of the photometer. The flux from a measured part of the fluorescent lamp passes through the slit at an instant during a cycle of source and enters the multiplier phototube. By adjusting the phase difference between sources of the fluerescent lamp and the synchronous motor with a phaseshifter, and moving the lamp along the lamp axis, the brightness distributions are measured at various phases during a cycle. In addition, the wave-forms of flickers from parts of a lamp have been observed by using a cathode ray oscillograph and electronic switch. Based on the above experiments, we obtained the following results. When a fluorescent lamp is supplied by an a. c source, the high and low brightness positions, that correspond to the negative glow and Faraday dark space, are presented at phases of a cycle, and these conditions vary as the kinds of phosphors used. Besides, the high frequency oscillations superpose on the norn al flicker near the electrodes. Therefore, at both ends of a lamp, the flicker of the flux considerably includes 50 c/s component and so we are apt to perceive the flicker. Then, the mean value of the brightness distribution during a cycle does not show a smooth curve as already reported, and the brightness distribution of the end of a lamp depends on the position of the cathode spot on the filament.