Some developments and simplifications in permeameters

The effect of mechanical strains introduced in preparing test pieces for magnetic tests in steady fields is discussed, together with the means adopted to minimize them. The need for testing under uniform and strain-free conditions of magnetization is dealt with, and details are given of permeameters which not only produce these conditions but also enable normal testing procedure to be rationalized in order to accelerate the process. A new magnetometer for measuring field strength, which effects a marked simplification in testing without sacrificing accuracy, is described, and the use of a drift-free fluxmeter is mentioned. A new permeameter deriving its excitation from a variable, permanent-magnet source is described. This requires no external electric supply and eliminates problems of overheating.