The Relation of the High-Intensity A-C. Arc to the Light on the Projection Screen

The effect on the amount and uniformity of light on the projection screen of changing the position of the arc with respect to the reflector, varying the arc length, decreasing the current, and irregular feeding of the carbons is measured and discussed. The importance of proper draft conditions in the lamp house is emphasized. The comparatively low temperature at the film aperture for a given amount of light on the projection screen from this type of arc is demonstrated. — The unique wave-form of the screen light from this high-intensity alternating-current arc is compared with the wave-form of the screen light from the low-intensity alternating-current neutral cored carbon arc and the rectified neutral cored carbon arc. A logical explanation is furnished by a consideration of these wave-forms for the comparative freedom from light beat or fluctuation with this type of alternating-current arc. It is pointed out that this arc gives no greater light fluctuation on the screen than the arc from rectified current. Other causes of fluctuation of the screen light are cited and suggestions are given for minimizing their effects.

Print ISSN

0097-5834

Published

1934-07

Content type

Original Research

DOI

10.5594/J07440