Bp 463 en
Excitation unit for orthogonal fluxgate with dc bias flipping
Author: Coroli Iurie
The goal of this bachelor thesis is to develop a system for suppression of the offset and its temperature drift in an orthogonal fluxgate in fundamental mode. The offset is gen-erally high, unstable and has a large thermal drift, which results in a large low-frequency noise. We propose a system that periodically flips the polarity of both DC and AC excitation currents to overcome this issue. The polarity flipping however introduces transients and additional noise at larger frequency; we overcome this issue by digital signal processing, excluding the first periods after polarity flipping from integration. We managed to achieve thermal offset variation of about 0.015 nT/°C with tolerable increase of the noise floor at high frequency. The achieved offset stability and low noise floor are comparable to top class available fluxgates. Such combination of characteris-tics has never been achieved on a cheap fluxgate sensor so far. Moreover, we have low power consumption because we use low excitation current below 100 mA and there is no need for expensive electronics.
- Iurie Coroli, mailto:coroliur@fel.cvut.cz
