PHOTOMETRY AND COLORIMETRY OF RAILROAD FUSEES

Abstract

In connection with the preparation of a standard specification, it became necessary to investigate the luminous intensity and color of a large number of railroad fusees. The rapid and wide fluctuations in intensity made it necessary to use special methods of colorimetry. The intensity was recorded by a highspeed electronic potentiometer and a barrier-layer photocell with correcting filter. To the pen carriage of the potentiometer was attached a special diaphragm which, with a lens and slit, acted as a 'light valve' to keep the flux into the colorimeter at a constant level over a range of about four to one. The very rapid flickering was, of course, not entirely eliminated. Visual colorimetry was used, the comparison field being produced in the lower half of a divided integrating sphere, the upper half of which received light from the fusee under test. The field, 2° in diameter, could be observed with both eyes. The accuracy of the colorimetry was made adequate by a careful choice of filters, advantage being taken of a fortunate circumstance regarding the color of the fusees. The results of testing more than 200 fusees are summarized.