Very low frequency magnetic hysteresis measurements with well-defined time dependence of the flux density

For the investigation of magnetic properties at frequencies between 5 mHz and 400 Hz we present an electronic device for measurements at well defined time dependence of the magnetic field strength or the flux density. Any function which is monotonous between two peak values can be produced. The measuring device may be used in connection with all conventional magnetizing systems according to the transformer principle, especially with the Epstein frame. The set-up comprises an arbitrary waveform generator, a power amplifier delivering the magnetizing current, and two ADC channels to sample and digitize the magnetic field strength and the induced voltage. The flux control is accomplished by software feedback using a personal computer which also handles the control of the experiment and the documentation. To demonstrate the capabilities of the apparatus we present a hysteresis family measured at .1 Hz with sinusoidal flux density, and the frequency dependence of the complex spectral components of the magnetic field strength measured at peak inductions of 1.0 T and 1.5 T, resp., in the range from 5 mHz to 70 Hz.