Three–Parameter Feedback Control of Amorphous Ribbon Magnetization

Abstract

This work describes a specially developed software for controllable magnetic hysteresis measurements of amorphous and nanocrystalline ribbons. The sophisticated algorithm enables to simplify a hardware design and to suppress an influence of experimental conditions on the measurement results. The main software feature is a three-stage feedback algorithm, which accurately adjusts the magnetization conditions: magnetization amplitude, geomagnetic bias and magnetization waveform. Air flux compensation of the induction signal is also performed by the software using an effective value of the coil cross section obtained from a calibration measurement without the ribbon. Applicability of the designed setup is illustrated for a series of nanocrystalline Hitperm ribbons measured at the power-line conditions: 50 Hz frequency and sinusoidal magnetization waveform.

A system for controllable magnetic measurements of hysteresis and Barkhausen noise

“…The technical details of the measurement system were comprehensively described in [3], [12]; only the necessary experimental parameters and the presented improvements are specified below. Flat samples are usually magnetized by an attached V-shape Fe-Si yoke carrying the magnetizing wind ing.…”

“…1) [12]. The first parameter is the magnetic waveform amplitude Bmax or Hmax, which is adjusted by changing the amplitude of the magnetizing voltage Vmax.…”

“…2(a» [3], [6], [7], [12]. The second method adjusts the amplitude of the magnetizing signal using the relative differ ence between the required and the actual magnetic waveform…”

“…2 The constant 0 � kph � 1 is responsible for the adjustment accuracy and is chosen manually for a certain experimental condition. Coincidence between the measured magnetic and the required standard waveforms is estimated by the mathemat ically accurate way using a Pearson's correlation coefficient kcor, which equals to 1 at the perfect coincidence [3], [12]. If this coefficient exceeds the chosen critical value kcor c::= 0.99999 and the two other controlled parameters, Bmax (or Hmax) and bHmax/2, are within the prescribed accuracy limits, the feedback loop stops and the final magnetic data are measured with the Vmag(t) of the last iteration step.…”

“…The oscillations can be suppressed by decreasing the proportional coefficient, kBmax or kHmax, however, this also increases the convergence time. The serious drawback of the phase correction method (kph = 1) is an exclusively monotonous Vph(t) profile [4], [12]. The combination of Vph and Vamp moderates the mentioned disadvantages of each method: the Vph transformation smooths the Vamp oscilla tions, whereas, the Vamp correction makes a non-monotonous contribution to the final V mag (t).…”