PAPERS ON CHEMISTRY AND PHYSICS 



269 



justed to a certain value. The variable signal standard 

 for comparisons is furnished by means of tube S. T., audi- 

 bility meter N being used to attenuate this signal in a 

 given ratio to match that from D. Choke coils A and A^ 

 are used to maintain constant potential between plate 

 and filament when the audibility meters are changed. 

 Space cannot be given to a comi^lete discussion of this 

 apparatus. It should be mentioned here that in all sig- 

 nal intensity measurements, a weak sigTial, having a di- 

 rectly measured audibility of 5.5 times on a standard 

 tube, was furnished to the receiving circuit connected to 

 the tube under test. The cuiwes of Fig. 1 are typical for 

 several tubes tested, the gas content being air or nitro- 

 gen or neon, etc. The figure also shows the operating 

 voltage curve for a tube with different gases which were 

 introduced successively. In order to determine the ef- 

 fect of various kinds of gases upon the sensitiveness of 

 a detector tube, different gases were introduced succes- 

 sively into the same tube and signal intensity compari- 

 sons measured for each gas. The tests were repeated 

 several times for the same tube, and for different tubes, 

 so that the results were conclusive. Hydrogen, nitrogen, 



*=*»T 



Lm 





S, ^/T 



^•o//s 



Diagram B 

 Standard Circuit for Audibility and Intensity Comparison Tests. 



