454 skogland: vacuum tungsten lamps 



This process though smiple, requires considerable time before a 

 solution is obtained. The direct reading device here described 

 and presented ready for use solves directly and without prelimi- 

 nary reduction all problems introducing as variables the volt- 

 age, candlepower, and wpc of vacuum tungsten lamps. Its con- 

 struction depends directly upon the characteristic equations 

 mentioned above. 



This device consists of volt, watts per candle, and per cent 

 candlepower scales. The wpc and per cent Cp scales are fixed in 

 their relation to each other. The volt scale is arranged to be 

 detached from the plate, so that it may be applied to the fixed 

 scales at the point corresponding to observed values of wpc and 

 voltage. From a single setting of the volt scale to observed 

 values within the range of from 0.70 to 2.05 wpc can be read 

 values of any one of the variables at any other point within this 

 range. The volt scale has a range of from 94 to 166 volts. The 

 chosen limits of wpc and voltage are considered sufficient to 

 include settings and solutions for 105-130 volt lamps in standard- 

 izing and life test-work. 



A test of the device, illustrated in part by examples, indicates 

 that, on an average, values of per cent Cp and of wpc read 

 therefrom deviate from those obtained by use of Tables 20 and 

 22 of the paper just referred to by amounts not exceeding 0.10 

 per cent and 0.05 per cent respectively; also that values read 

 from the scales agree with observed values nearly as closely as 

 those computed by use of the tables. All of the points (referred 

 to horizontal and vertical scales of equal parts) through which 

 lines of the scales of this device were' drawn have been tabu- 

 lated, so that similar scales of the same or different range can be 

 constructed directly from these values. Sufficient discussion of 

 the derivation of these values and of the relative position of the 

 scales has been given to direct the construction of scales not .in- 

 cluded within the wpc range here employed. By the general 

 method of this paper any related functions of exponential form 

 and of the same degree as the characteristic equations can be 

 represented and used as scales of a similar device. 



