High Sensitivity Magnetometers pp 63-102 | Cite as

# Orthogonal Fluxgate Magnetometers

## Abstract

Orthogonal fluxgate is a particular type of fluxgate, which recently gained popularity. As all fluxgate sensors it is based on the gating of magnetic flux in a ferromagnetic core; however, in orthogonal fluxgates the excitation field and the measured field are orthogonal. This leads to different sensor structure, most notably to the absence of an excitation coil, making the construction of an orthogonal fluxgate very simple. In this chapter we will first analyse the principle of operation of orthogonal fluxgates in order to explain the mechanism which generates the output signal. Then, we will examine how the sensor is build, especially the structure of the core and the techniques typically used in order to minimize the amplitude of excitation current. Next, a particular type of orthogonal fluxgate—the so-called coil-less fluxgate—is presented: its name comes from the lack of the pick-up coil, for the output voltage is derived directly from the core’s termination thanks to helical anisotropy of the core. The most important part of the chapter is however focused on fundamental mode orthogonal fluxgate; in this type of sensor a large dc bias is added to the excitation current in order to suppress the Barkhausen noise, that is the main source of noise in fluxgates. The resulting output has very low noise: we show how, properly designing the core geometry and modifying the anisotropy by annealing we can achieve noise as low as 1 pT/√Hz at 1 Hz. Another part of the chapter is focused on magnetic gradiometers based on orthogonal fluxgates, typically used when the sensor has to be used in noisy environment and the magnetic field to be measured has large gradient and small amplitude. Finally a comparison with similar sensors, such as wire-based GMI, is presented: we show similarities and differences, especially regarding the methods for signal extractions and we explain why orthogonal fluxgates perform better.

## Keywords

Circumferential Direction Wire Core Excitation Field Magnetic Noise Composite Wire## References

- 1.Alldredge, USA Patent 2,856,581, 1952Google Scholar
- 2.F. Primdahl, The fluxgate mechanism, Part I: the gating curves of parallel and orthogonal fluxgates. IEEE Trans. Magn.
**MAG-6**(2), 376–383 (1970)Google Scholar - 3.M. Butta, P. Ripka, Two-domain model for orthogonal fluxgate. IEEE Trans. Magn.
**44**(11), 3992–3995 (2008)Google Scholar - 4.J.P. Sinnecker, K.R. Pirota, M. Knobel, L. Kraus, AC magnetic transport on heterogeneous ferromagnetic wires and tube. J. Magn. Magn. Mater.
**249**(1–2), 16–21 (2002)Google Scholar - 5.P. Ripka, X.P. Li, F. Jie, Orthogonal fluxgate effect in electroplated wires. IEEE Sens. (2005) Google Scholar
- 6.X.P. Li, Z.J. Zhao, T.B. Oh, H.L. Seet, B.H. Neo, S.J. Koh, Current driven magnetic permeability interference sensor using NiFe/Cu composite wire with a signal pick-up LC circuit. Phys. Status Solidi A
**201**, 1992–1995 (2004)CrossRefGoogle Scholar - 7.M. Butta, P. Ripka, G. Infante, G.A. Badini-Confalonieri, M. Vázquez, Bi-metallic magnetic wire with insulating layer as core for orthogonal fluxgate. IEEE Trans. Magn.
**45**(10), 4443–4446 (2009)Google Scholar - 8.X.P. Li, J. Fan, J. Ding, H. Chiriac, X.B. Qian, J.B. Yi, A design of orthogonal fluxgate sensor. J. Appl. Phys.
**99**(8), Article number 08B313 (2006). ISSN 0021-8979Google Scholar - 9.X.P. Li, J. Fan, J. Ding, X.B. Qian, Multi-core orthogonal fluxgate sensor. J. Magn. Magn. Mater.
**300**(1), e98–e103 (2006)Google Scholar - 10.P. Ripka, X.P. Li, F. Jie, Multiwire core fluxgate. Sens. Actuators, A
**156**(1), 265–268 (2009). ISSN 0924-4247Google Scholar - 11.P. Ripka, M. Butta, F. Jie, X.P. Li, Sensitivity and noise of wire-core transverse fluxgate. IEEE Trans. Magn.
**46(**2), 654–657 (2010). ISSN 0018-9464Google Scholar - 12.F. Jie, N. Ning, W. Ji, H. Chiriac, X.P. Li, Study of the noise in multicore orthogonal fluxgate sensors based on Ni-Fe/Cu composite microwire arrays. IEEE Trans. Magn.
**45**(Sp. Iss. SI), 4451–4454 (2009). ISSN 0018-9464Google Scholar - 13.Y. Terashima, I. Sasada, Magnetic domain Imaging using orthogonal fluxgate probes. J. Appl. Phys.
**91**(10), 8888–8890 (2002). ISSN 0021-8979Google Scholar - 14.J. Kubik, L. Pavel, L. Ripka, P. Kaspar, Low-power printed circuit board fluxgate sensor. IEEE Sens. J.
**7**(2), 179–183Google Scholar - 15.E. Delevoye, A. Audoin, A. Beranger, R. Cuchet, R. Hida, T. Jager, Microfluxgate sensors for high frequency and low power applications. Sens. Actuators, A
**145**(SI), 271–277 (2008)Google Scholar - 16.M. Butta, P. Ripka, S. Atalay, F.E. Atalay, X.P. Li, Fluxgate effect in twisted magnetic wire. J. Magn. Magn. Mater.
**320**(20), E974–E978 (2008)Google Scholar - 17.M. Butta, P. Ripka, G. Infante, G.A. Badini-Confalonieri, M. Vázquez, Magnetic microwires with field induced helical anisotropy for coil-less fluxgate. IEEE Trans. Magn.
**46**(7), 2562–2565 (2010)CrossRefGoogle Scholar - 18.P. Ripka, M. Butta, M. Malatek, S. Atalay, F.E. Atalay, Characterization of magnetic wires for fluxgate cores. Sens. Actuators, A
**145**(special issue), 23–28 (2007)Google Scholar - 19.M. Butta, P. Ripka, J.P. Navarrete, M. Vázquez, Double coil-less fluxgate in bridge configuration. IEEE Trans. Magn.
**46**(2), 532–535 (2010)Google Scholar - 20.S. Atalay, V. Yagmur, F.E. Atalay, N. Bayri, Coil-less fluxgate effect in CoNiFe/Cu wire electrodeposited under torsion. J. Magn. Magn. Mater.
**323**(22), 2818–2822 (2011)Google Scholar - 21.S. Atalay, P. Ripka, N. Bayri, Coil-less fluxgate effect in (Co
_{0.94}Fe_{0.06})_{72.5}Si_{12.5}B_{15}amorphous wires. J. Magn. Magn. Mater.**322**(15), 2238–2243(2010)Google Scholar - 22.M. Butta, P. Ripka, M. Vazquez et al., Microwire electroplated under torsion as core for coil-less fluxgate. Sens. Lett.
**11**(1, SI), 50–52 (2013)Google Scholar - 23.I. Sasada, Orthogonal fluxgate mechanism operated with dc biased excitation. J. Appl. Phys.
**91**(10), 7789–7791 (2002). ISSN 0021-8979Google Scholar - 24.D. Jiles,
*Introduction to Magnetism and Magnetic Materials*(Chapman & Hall, London, 1991). ISBN 0-412-38640-2 Google Scholar - 25.E. Paperno, Suppression of magnetic noise in the fundamental-mode orthogonal fluxgate. Sens. Actuators, A
**116**(3), 405–409 (2004). ISSN 0924-4247Google Scholar - 26.E. Paperno, E. Weiss, A. Plotkin, A tube-core orthogonal fluxgate operated in fundamental mode. IEEE Trans. Magn.
**44(**11), 4018–4021 (2008)Google Scholar - 27.I. Sasada, H. Kashima, Simple design for orthogonal fluxgate magnetometer in fundamental mode. J. Magn. Soc. Jpn.
**33**, 43–45 (2009)Google Scholar - 28.M. Butta, I. Sasada, Method for offset suppression in orthogonal fluxgate with annealed wire core. Sens. Lett.
**12**, 1295–1298 (2014)CrossRefGoogle Scholar - 29.M. Butta, S. Yamashita, I. Sasada, Reduction of noise in fundamental mode orthogonal fluxgates by optimization of excitation current. IEEE Trans. Magn.
**47**(10), 3748–3751 (2011)CrossRefGoogle Scholar - 30.M. Butta, I. Sasada, Sources of noise in a magnetometer based on orthogonal fluxgate operated in fundamental mode. IEEE Trans. Magn.
**48**(4), 1508–1511 (2012)Google Scholar - 31.C. Dolabdjian, B. Dufay, S. Saez, A. Yelon, D. Menard, Is low frequency excess noise of GMI induced by magnetization fluctuations? in
*International Conference on Materials and Applications for Sensors and Transducers (ICMAST)*, 2013, Prague, Czech RepublicGoogle Scholar - 32.F. Johnson, H. Garmestani, S. Y. Chu, M.E. McHenry, D.E. Laughlin, Induced anisotropy in FeCo-based nanocrystalline ferromagnetic alloys (HITPERM) by very high field annealing. IEEE Trans. Magn.
**40**(4), 2697–2699 (2004) Google Scholar - 33.P. Butvin, M. Janosek et al., Field annealed closed-path fluxgate sensors made of metallic-glass ribbons. Sens. Actuators, A
**184**, 72–77 (2012)CrossRefGoogle Scholar - 34.I. Sasada, Symmetric response obtained with an orthogonal fluxgate operating in fundamental mode. IEEE Trans. Magn.
**38**(5), 3377–3379 (2002)Google Scholar - 35.Eyal W., Eugene P. Noise investigation of the orthogonal fluxgate employing alternating direct current bias. J. Appl. Phys.
**109**, 07E529 (2011)Google Scholar - 36.P. Ripka (ed.),
*Magnetic Sensors and Magnetometers*(Artech House, Norwood, MA, 2001). ISBN: 1580530575Google Scholar - 37.M. Butta, I. Sasada, M. Janosek, Temperature dependence of offset and sensitivity in orthogonal fluxgate operated in fundamental mode. IEEE Trans. Magn.
**48**(11), 4103–4106 (2012)Google Scholar - 38.A. Moldovanu, E.D. Diaconu, C. Ioan, E. Moldovanu, Magnetometric sensors with improved functional parameters. J. Magn. Magn. Mater.
**157**(158), 442–443 (1996)CrossRefGoogle Scholar - 39.Y. Nishio, F. Tohyama, N. Onishi, The sensor temperature characteristics of a fluxgate magnetometer by a wide-range temperature test for a Mercury exploration satellite. Meas. Sci. Technol.
**18**(8), 2721–2730 (2007)Google Scholar - 40.A. Cerman, J.M.G. Merayo, P. Brauer et al., Self-compensating excitation of fluxgate sensors for space magnetometers, in
*IEEE Instrumentation And Measurement Technology Conference*, vols. 1–5, pp. 2059–2064 (2008)Google Scholar - 41.M. Butta, I. Sasada, Effect of terminations in magnetic wire on the noise of orthogonal fluxgate operated in fundamental mode. IEEE Trans. Magn.
**48(**4), 1477–1480 (2012)Google Scholar - 42.Shoumu Harada, Ichiro Sasada, Feng Hang, Development of a one dimensional fluxgate array and its application to magnetocardiogram measurements. IEEJ Trans. Fundam. Mater.
**133**(6), 333–338 (2013)CrossRefGoogle Scholar - 43.I. Sasada, S. Harada, Fundamental mode orthogonal fluxgate gradiometer. IEEE Trans. Magn.
**50**(11) (2014)Google Scholar - 44.M. Malatek, B. Dufay, S. Saez, C. Dolabdjian, Improvement of the off-diagonal magnetoimpedance sensor white noise. Sens. Actuators, A
**204**, 20–24 (2013)CrossRefGoogle Scholar - 45.B. Dufay, S. Saez, C. Dolabdjian, A. Yelon, D. Ménard, Characterization of an optimized off-diagonal GMI-based. IEEE Sens. J.
**13**(1), 379–388 (2013)CrossRefGoogle Scholar - 46.D. Ménard, D. Seddaoui, L.G.C. Melo, A. Yelon, B. Dufay, S. Saez, C. Dolabdjian, Perspectives in giant magnetoimpedance magnetometry. Sens. Lett.
**7**(3), 339–342 (2009)CrossRefGoogle Scholar - 47.K. Goleman, I. Sasada, A triaxial orthogonal fluxgate magnetometer made of a single magnetic wire with three U-Shaped branches. IEEE Trans. Magn.
**43**(6), 2379–2381 (2007) Google Scholar - 48.B. Dufay, S. Saez, C. Dolabdjian, D. Seddaoui, A. Yelon, D. Ménard, Improved GMI sensors using strongly-coupled thin pick-up coils. Sens. Lett.
**7**(3), 334–338 (2009)CrossRefGoogle Scholar - 49.L. Kraus, Off-diagonal magnetoimpedance in stress-annealed amorphous ribbons. J. Magn. Magn. Mater.
**320(**20), E746–E749 (2008)Google Scholar - 50.K. Knobel, M. Vázquez, L. Kraus,
*Giant Magneto Impedance, Handbook of Magnetic Materials*, vol. 15 (Elsevier, K.H.J. Buschow, 2003)Google Scholar