104 



M. L. Schwendler on a Practical Method 



vast extent, has created the necessity of having a reliable method 

 by which such insulators can be detected, and other perfect ones 

 substituted with the least possible expense. 



It is clear that such a method, to be practicable, must be very 

 simple, and the instruments used portable and handy*. 



After some searching in this direction, the following method 

 was found to answer the purpose most satisfactorily. 



The principle of the method is to produce magneto-electric 

 currents through the resistance of the insulator under test, and 

 to measure these currents by the effect they have on the body of 

 the tester. 



The subjoined diagram shows the connexions readily. 





\ (£& 



; 



\ / 

 fSt\ 1/ 



^ 



LjJP 







J is a magneto- electric machine, the two terminals t and t' of 

 which are insulated from each other and from the ground. 



t is in permanent contact with a perfectly insulated leading 

 wire I, long enough to reach the insulator, to the iron hood of 

 which it is to be hooked. 



* To use a deflection method is out of the question, because the still 

 comparatively high resistance of the insulators which have to be detected 

 would necessitate a high electromotive force and a very delicate galvano- 

 meter, which arrangements could not be made easily portable, as is required 

 when the tester proceeds along a line. 



