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of ILLUMINATING ENGINEERING r—----.....
Some Engineering Aspects of Lighting from y Cold-Cathode Fluorescent ^urce*s:
By H. J. CHAN'ON and A. C. BARR4^ .-rff^f r;., _
' * V.y
The potentialities of cold-cathode tubing in commercial and other fields of lighting have been treated in numerous articles and papers. There is^hss familiarity with the technical aspects, the specific characteristics, of high-voltage fluorescent tubing as a source of illumination. Quantitative information needed for design of systems has not been generally available. The authors point out the differences from the better-known multiple hot-cathode lighting. They present the effects of the major variables that determine the performance of cold-cathode tubing, thus supplying the illuminating engineer with data needed for definite evaluation and specification.
ELECTRICALLY, the cold-cathode, high-voltage lighting tubing of today is in basic principle similar to that originallv developed bv D. McFarlan Moore. In one of his earlv installations, in 1904, he used a single tube about 180 feet in length and if inches in diameter operated from a transformer with a secondary voltage of approximated 11,00c. Cooper-Hewitt had developed a tube with a discharge of direct current through mercury vapor between a cathode and a metal or graphite anode. Moore, on the other hand, utilized 60-cyele alternating current and the discharge took place between cold electrodes through carbon dioxide or nitrogen. The gas was gradually consumed by the discharge and so provision was made for replenishing through an automatic valve. The efficiency of light production was materially lower than in the Cooper-Hewitt lamp.
After the inert gases, neon, argon, helium, krvpton and xenon became available. Georso Claude, in ;y o, ^pphcJ some ot these in eicctnc-disch.irc,; tubes. The vScan-up of the #a" bv the discharge proceeded at such a verv • / slow rate rh.it replenishment w.is no longer necessary over periods up to »omc , t\' thousands or hoars. Within a decade, the neon sign industry was born and \* a range ot colors gradually evolved through the addition of mcrcurv and of colored and fluorescent glares to the rare-gas pallctte. The efficiency of light prod i\ nor. remained too L"\\ to be signiticanr for. general illumination application
The third major development in this field was that of coating the tubes with phosphors which serve as converters of invisible radiation from the
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