AUTOMATIC MACHINE GAGING 



717 



value of the resistance of the coil under test to that of standards 

 contained in the bridge. If this resistance is too high in one case or 

 too low in the other, the shutter is closed, preventing the light beam 

 from reaching the photo-electric cell. This in turn through the action 



Fig. 9 



of the vacuum tube amplifier and relays R actuates the trip on the 

 machine which discharges the coil at the proper point. 



While designing this machine much attention was given to producing 

 a type that could be adapted readily to the testing of other parts 

 requiring several operations. 



Fig. 9 illustrates the fundamental parts of the machine. It is 



