Low-Noise Orthogonal Fluxgate Using Flipped Current Joule Annealing

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68407700%3A21230%2F19%3A00338489" target="_blank" >RIV/68407700:21230/19:00338489 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1109/TMAG.2019.2894302" target="_blank" >https://doi.org/10.1109/TMAG.2019.2894302</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1109/TMAG.2019.2894302" target="_blank" >10.1109/TMAG.2019.2894302</a>

Result language

angličtina

Original language name

Low-Noise Orthogonal Fluxgate Using Flipped Current Joule Annealing

Original language description

It has been shown that annealing of amorphous magnetic wire used as a core for orthogonal fluxgates in the fundamental mode can significantly decrease the noise of the sensors in the 1/f region. This is due to an increase in the circumferential anisotropy due to the dc current flowing through the wire during annealing. This method, however, presents some drawbacks: first, it requires an infrared furnace and precise compensation of the magnetic field inside it. Second, it is very slow, because it requires the cooling of the whole furnace before removing the wire. Most importantly, while the 1/f noise decreases, the noise floor increases. In this paper, we present a method that allows the simultaneous reduction of 1/f noise and noise floor. This method is based on Joule annealing by means of a very large current in the wire. The current is periodically flipped with 0.25 Hz frequency in order to avoid an excessive increase in the offset. The annealing is performed in a four-layer shielding to avoid the presence of an external dc field. Annealing for 1 min, 1 wire-based sensor returned a considerable noise reduction both in the 1/f regions from 2.5 to 1.5 pT/root Hz) while the noise floor was unchanged at 650 fT/root Hz. For larger annealing time, however, the noise floor rose. We tried to compensate this problem by increasing the number of wires to four, but also in this case, we achieved the best noise reduction (from 1.7 to 0.75 pT/root Hz at 1 Hz and from 470 to 350 fT/root Hz noise floor) with 1 min annealing. By the use of thermocamera, we discovered that the problem of long-time annealing was that the sensor head support was warming up too much. Therefore, we repeated the experiment by annealing 21 min as a series of 1 min annealing followed by 3 min of no current for 21 times to let the sensor head totally cool to room temperature after every annealing period. In this way, we achieved the lowest noise of 630 fT/root Hz at 1 Hz and 400 fT/root Hz noise floor.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

20201 - Electrical and electronic engineering

Project

<a href="/en/project/GJ16-10591Y" target="_blank" >GJ16-10591Y: Magnetic gradiometer based on fundamental mode orthogonal fluxgate</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2019

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

IEEE Transactions on Magnetics

ISSN

0018-9464

e-ISSN

1941-0069

Volume of the periodical

55

Issue of the periodical within the volume

7

Country of publishing house

US - UNITED STATES

Number of pages

6

Pages from-to

—

UT code for WoS article

000472632500001

EID of the result in the Scopus database

2-s2.0-85065190143