Magnetic Measurements at Low Flux Densities Using the Alternating Current Bridge
01 January 1936
HE modern alternating current bridge, with its high precision and sensitive balance, has almost completely superseded the ballistic galvanometer for determining the magnetic properties of core materials at the low flux densities employed in telephone and radio apparatus. The suitability of the alternating current bridge for this purpose has been recognized for some time, 1 but the continued improvements in magnetic materials, and the more exacting requirements of modern communication apparatus, have necessitated refinements in apparatus, in technique, and in interpretation of measurements. This paper considers the modified technique required to take account of eddy current shielding and hysteresis in the magnetic core, distributed capacitance and leakance in the coil winding, and the necessary details of the bridge and associated apparatus to realize the desired accuracy of measurements.