Abstract: An apparatus for measuring the magnetic content of non-metallic samples includes operating and reference sine wave oscillators of identical frequency, a mutual synchronization loop for said oscillators, and a phase meter connected to the oscillator outputs for measuring the phase shift between their oscillations, when a test sample is placed inside the inductance coil of the operating oscillator. The mutual synchronization loop includes a switchable resistive attenuator for varying the resistance of the mutual synchronization loop according to the magnetic content of the test sample, such that the phase shift between the oscillations of the oscillators, with any value of content within the specified measuring range, is not in excess of 30 deg.

Abstract: A method of nondestructive quality control of carbon articles includes the steps of determining the rate of propagation of excited acoustic vibrations in each carbon article (3) of a group of carbon articles and in a specimen cut out from at least one carbon article (3). Then there are selected the carbon articles (3) with the lowest and highest determined rates of propagation of the acoustic vibrations, and "n" specimens are cut out from them longitudinally of the specimens, and "m" specimens are cut out from them across their longitudinal axes.