Being able to control the anisotropy of a magnetic core plays an important role in the development of a fluxgate sensor. Our aim is to induce anisotropy orthogonal to the direction of excitation because it generates a stable, low-noise fluxgate, as cited in the literature. In this paper, we present an original method for electroplating a ring core for a fluxgate with built-in radial anisotropy by performing the electroplating in a radial field produced by a novel yoke. The results show that the resulting anisotropy is homogeneously radial and makes the magnetization rotate, avoiding domain wall movement for low excitation fields.

Large DC and AC electric currents are often measured by open-loop sensors without a magnetic yoke. A widely-used configuration uses a differential magnetic sensor inserted into a hole in a flat busbar. The use of a differential sensor offers the advantage of partial suppression of fields coming from external currents. Hall sensors and AMR sensors are currently used in this application. In this paper, we present a current sensor of this type that uses novel integrated fluxgate sensors which offer a greater range than magnetoresistors and better stability than Hall sensors. The frequency response of this type of current sensor is limited due to the eddy currents in the solid busbar. We present a novel amphitheater geometry of the hole in the busbar of the sensor which reduces the frequency dependence from 15% error at 1 kHz to 9%.

Offset and its long-term stability is a weak point of fluxgate sensors. Even the ultrastable sensors kept at no vibrations and stable temperature at magnetic observatories show offset drift. Such drift of fluxgate tri-axial sensor can be only partly corrected by scalar resonance magnetometer. Periodical calibration of absolute reading should be made using non-magnetic theodolite. In this paper we study the origin of fluxgate offset. We distinguish the real magnetic sensor offset from the offset contributions originating in false 2 nd harmonics signal which leaks to the sensor output from the distortion in the excitation signal, or which is borne as harmonic distortion when the signal processing electronics is subjected to large 1 st harmonic signal leaking from the excitation. We analyze the offset dependence on the angular position of the sensor core and its response to large field shocks. The experiments give an indication that only a part of the magnetic offset stems from a remanence of magnetically hard core regions. The residual part may be caused by magnetostrictive signal, belonging to false signal contributions, but not considered in previous studies.

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Fluxgate sensors have typically only 100 µT range, which sometimes limits their applications. Main obstacle for increasing the measurement range power dissipated in their feedback coil. Until now the feedback was always continuous. We suggest to use pulse excitation only for the active part of the period, in which output signal is present. In this paper we show for the first time that if the sensor is excited by short pulses, the feedback need not be continuous, but it can be formed by pulses slightly wider than the excitation pulses. We have shown that in our case the feedback current duty cycle can be only 17.25 %. This means that for the same power we can increase maximum feedback current and thus the range by the factor of three. We show that this can be done without compromising the sensor performance.