**10. Acknowledgment**

The author thanks the Japanese Society for Promotion of Science (JSPS) for support under the framework of the JSPS PostDoc fellowship program. This work was supported by a kakenhi grant 22・00376.

### **11. References**

### **Print books**

Jiles, D. (1991). *Introduction to Magnetism and Magnetic Materials*. Chapman & Hall, ISBN: 0- 412-38640-2, London

### **Edited books**


### **Patents**

40 Magnetic Sensors – Principles and Applications

These efforts strongly improved the performances of orthogonal fluxgates, making this

However, even if sensors like orthogonal fluxgates in a fundamental mode already achieved

Currently, we still do not have extensive information about the long-term offset stability of orthogonal fluxgates as well as the temperature dependence of both offset and sensitivity,

Another important field, which has to be investigated, is the dependence of the orthogonal fluxgate's performance on the geometrical dimensions of the core. So far, different structures have been proposed, but a comprehensive study that explains the effect of different core sizes on sensitivity and noise has yet to be reported. In particular, the effects of the demagnetization factor have not been properly investigated, mainly due to the fact that the excitation field is applied to a circumferential direction facing a toroidal shape, which is not affected by the demagnetizing effect. Nevertheless, a measured field is applied in the axial direction over a finite length specimen so that the internal field distribution will be affected by the demagnetizing effect. This applies especially to multi-core orthogonal fluxgates. Indeed, when operated out of resonance, the output sensitivity will strongly depend on the distance between the wires, because it affects the demagnetization factor. A detailed study on the core's size dependence of orthogonal fluxgates' parameters will be also useful to optimize the geometry of micro-fluxgates, where the small dimension strongly affects the

Finally, further steps should be made towards developing manufacturing techniques for the production of magnetic wires to be used as the core of orthogonal fluxgates, as a means of assuring mass production of cores with very similar parameters. Such efforts are an

The author thanks the Japanese Society for Promotion of Science (JSPS) for support under the framework of the JSPS PostDoc fellowship program. This work was supported by a

Jiles, D. (1991). *Introduction to Magnetism and Magnetic Materials*. Chapman & Hall, ISBN: 0-

Ripka, P. (Ed.). (2001). *Magnetic Sensors and Magnetometers*. Artech House., ISBN:

Knobel, M.; Vázquez, M. & Kraus, L. (2003). *Handbook of Magnetic Materials*, Vol. 15, pp. 497-

important requirement for the industrialization of this type of sensor.

sensor competitive in the field of magnetic measurement at room temperature.

noise levels similar to cheap parallel fluxgates, other issues have to be faced.

which are critical points for many magnetometers.

achieved sensitivity and noise.

**10. Acknowledgment** 

kakenhi grant 22・00376.

412-38640-2, London

1580530575, Norwood, MA

**11. References** 

**Print books** 

**Edited books** 

563

Alldredge, L.R. (1958). Magnetometer. *US Patent 2,856,581*. (October 1958)


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**0**

**3**

*France*

**Induction Magnetometers Principle,**

**Modeling and Ways of Improvement**

Induction sensors (also known as search coils), because of their measuring principle, are dedicated to varying magnetic field measurement. Despite the disadvantage of their size, induction magnetometer remains indispensable in numerous fields due to their sensitivity and robustness whether for natural electromagnetic waves analysis on Earth Lichtenberger et al. (2008), geophysics studies using electromagnetic toolsHayakawa (2007); Pfaffling (2007), biomedical applications Ripka (2008) or space physic investigations Roux et al. (2008). The knowledge of physical phenomena related to induction magnetometers (induction, magnetic amplification and low noise amplification) constitutes a strong background to address design

Let us describe the magnetic field measurement in the context of space plasma physics. AC and DC magnetic fields are among the basic measurements you have to perform when you talk about space plasma physics, jointly with electric fields measurements and particle measurements . The magnetic field tells us about the wave properties of the plasma, as the electric field also does. At the current time, several kinds of magnetometers are used onboard space plasma physics missions: most often you find a fluxgate to measure DC fields and a searchcoil to measure AC fields. The searchcoil is better than the fluxgate above coarsely 1 Hz. In-situ measurements of plasma wave in Earth environment have been performed since many years by dedicated missions (ESA/CLUSTER (2002), NASA/THEMIS (2007)) and will continue with NASA/MMS mission, a 4 satellites fleet, which will be launched in 2014 with induction magnetometer (see Fig. 1) onboard each spacecraft. Earth is not the only planet with a magnetic field in the solar system. Search coils are for space plasmas physics and how

*<sup>e</sup>* <sup>=</sup> <sup>−</sup>*d*<sup>Φ</sup>

−→*<sup>B</sup>* −→*dS* is the magnetic flux through a coil over a surface (*S*).

of other types of magnetometers and their application.

Induction sensor principle derives directly from the Faraday's law:

their development still is a challenge.

**2. Induction sensor basis**

(*S*)

where Φ = '

**1. Introduction**

Christophe Coillot and Paul Leroy *LPP Laboratory of Plasma Physics*

*dt* (1)

Zorlu, O.; Kejik, P. & Popovic, R.S. (2006). An orthogonal fluxgate-type magnetic microsensor with electroplated Permalloy core. *Sensors and Actuators A-Physical*, Vol. 135, Iss. 1, (March 2007), pp. 43-49, ISSN 0924-4247

#### **Papers in conference proceedings**

