Use of bismuth-bridge magnetic fluxmeter for A-C fields

THE methods most often used for the measurement of d-c, a-c, and transient magnetic fields depend upon one fundamental law: that a voltage is generated in a conductor cutting lines of magnetic flux. However, for each of these fields the apparatus and procedure are entirely different. Perhaps the greatest difficulty arises in the study of a magnetic field under transient conditions, since the resulting voltage oscillogram is a composite of several components having more or less intricate phase relations. Thus the actual magnetic-field values or changes are rather difficult to obtain. A single instrument, adapted for use in any of the three fields, would be very desirable. With this object in view, the following report describes the work done in attempting to use, for the measurement of a-c and transient magnetic fields, an instrument previously proposed for use only in the d-c field.