Shunts and inductors for surge-current measurements

in one of t he appendices. The advantages of using a mu t ual inductor for obtaining oscillograms of the rate of change of curren t durin g a surge are ou tl i ned, and ~eve ral t ypes of mu t ual ind uctors de \'eloped especially for t his purpose are described. Theoretical derivations, given in t he appendi ces, indicat e that t he concent ric-t ube m ut ual inducLors described in this paper can be used to measnre t h e h igh -frequency compo nents of a current surge up to 70 megacycles with less