570 



AUSTIN: RADIO MEASUREMENTS 



capacity, D is a contact detector, G a high resistance galvanometer, 

 K a paper condenser of one microfarad capacity, and R a resistance 

 which may have any value from 0.1 to 100 ohms. The greater 

 part of the radio-frequency current passes through R, while a 

 small portion is shunted through the condenser X and the detector. 

 The direct current from the detector after passing through the 

 galvanometer returns through R. On account of the high re- 



c. 



# 



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R=0.1-IO0-n. 

 K = 1 Mf . 



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R 

 Fig. 1. Shunted contact detector 



sistance of the detector, the total resistance of the detecting sys- 

 tem is practically identical with R, as has been experimentally 

 tested between 0.1 and 100 ohms. 



The sensibility of this arrangement is much greater than that 

 of the best vacuum thermoelements of equivalent resistance. 



In the case of most of the well-known detectors the proportion- 

 ality between deflection and current-square is excellent. Galena, 

 while the most sensitive of any of the detectors tried, shows a 

 slight deviation from the square law. For absolute current 

 ' measurements the system must of course be calibrated by com- 

 parison with a known thermoelement at the time of experiment. 



