106 



METEOROLOGICAL EQUIPMENT FOR SHORT WAVE 



amplifier has been constructed, wherein the top tube 

 is the phite load for the lower tube of the two-story 

 amplifier. The output of this amplifier is approximate- 

 ly equal to one-half the amplification factor of the tube. 

 As shown in Figure 5, this amplifier is fed by a 

 cathode follower which has impressed upon it from the 

 series limiter only the positive peaks of the a-c voltage 

 drop across the hygrometer or temperature element. 

 The voltage across the elements can be as low as Vk 

 to V2 V, depending upon the sensitivity adjustment of 

 the amplifier. It will operate with voltages as high 

 as 30 to 60 V across the elements. 



Keducing Amplifier Output to Geound 



The amplifier output is at one-half the positive volt- 

 age of the plate supply above ground. However, this 

 output can be reduced to ground by the introduction 

 of a cathode follower or more simply by three series 

 sections of a resistor and glow tube connected in series. 

 The output of the two-story amplifier is fed into the 



junction between the first and second sections while 

 the output is taken from the junction of the second 

 and third sections, where the first section is connected 

 to the positive plate supply and the third section con- 

 nects to a negative potential equal to one-half the posi- 

 tive voltage. It is not necessary to make this addition 

 to the present equipment. 



Kecoeder Accuracy 



It is possible to measure temperatures to less than 

 Vi of a degree Fahrenheit and humidities to less than 

 1/2 of 1 per cent. However, this accuracy is not neces- 

 sarily required for low-level atmospheric soundings 

 and construction of M curves. 



Conclusion 



Direct automatic recording of low-level temperature 

 and hygrometer readings is suggested. The method is 

 especially adaptable for fixed or shipboard station 

 operation. 



