Humidity Recorders 



By E. B. WHEELER 



DIKING recent years, the study of atmospheric conditions and 

 their bearing on various industrial problems from the stand- 

 point both of their efifects on human efificiencN' and on manufacturing 

 processes, is a matter that has received much attention, and the use 

 of air conditioning systems, which have been developed in the last 

 few years, has resulted in greatly improved working conditions, as 

 well as in increased outputs of manufactured products of better 

 quality than obtainable when air conditioning was not employed. 



It is not so well appreciated, perhaps, that atmospheric conditions 

 have a material efifect upon the operation of intricate electrical and 

 mechanical apparatus, such as those found in telephone systems. 



Water vapor, and both gaseous and solid impurities in the air, 

 hasten oxidation and corrosion of metals and also reduce the value of 

 the insulation afforded by insulating materials. These effects usually 

 are greatly accelerated if the temperature is high and if the materials 

 are subjected to differences of electrical potential. Telephone ap- 

 paratus and equipment consist of combinations of materials which 

 are subject to both of these effects and, in general, the parts are small 

 and the materials used in making them must be carefully chosen 

 with regard to the necessary physical and electrical properties required 

 for proper functioning of the apparatus. Therefore, the severe 

 atmospheric conditions, which may be encountered in service, either 

 must be eliminated by the use of air conditioning systems or the 

 apparatus must be designed to withstand those conditions. 



Accordingly, in order that the problem may be handled intelligently, 

 accurate information must be available showing the character of the 

 atmospheric conditions which exist in typical localities where tele- 

 phone equipment is installed, so that the effects of these conditions 

 on proposed designs may be studied under carefully controlled similar 

 conditions in laboratory "humidity rooms." An outline of some of 

 the work which has been done in an effort to obtain such information 

 may therefore be of interest. 



The first recourse would seem to be the data recoaletl b\ the \ arious 

 stations of the United States Weather Bureau. However, since 

 these data usually represent periodic observations of outdoor con- 

 ditions which are olitaincd primarily for meteorological purposes, 

 it was found that while they indicate the general climatic conditions 

 of different localities, they can not be taken to represent typical 

 conditions in central office buildings, and therefore it has been 



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