Amorphous wire and CMOS IC-based sensitive micro-magnetic sensors (MI sensor and SI sensor) for intelligent measurements and controls

doi:10.1016/S0304-8853(02)00558-9

Journal of Magnetism and Magnetic Materials

Volume 249, Issues 1–2, August 2002, Pages 351-356

https://doi.org/10.1016/S0304-8853(02)00558-9 Get rights and content

Abstract

New sensitive, quick response and low power consumption micro-magnetic sensors named the magnetoimpedance (MI) sensor utilizing the MI effect in zero-magnetostrictive amorphous wires and the stress impedance (SI) sensor utilizing the SI effect in negative-magnetostrictive amorphous wires are presented. The field detection resolution of the CMOS IC type MI sensor is about 1 μOe for AC fields and 100 μOe for a DC field with the full scale of ±3 Oe using a 2 mm long sensor head; the possible response speed is about 1 MHz, and the power consumption is about 10 mW. The high density fabricated MI sensor has just been developed by the Aichi Steel Co. for mass production. The stress detection resolution of the SI sensor is about 0.1 Gal in acceleration sensing which is suitable for detection of micro-displacement in the medical field. More than 100 themes are proposed for application of MI and SI sensors.

Introduction

Recently sensitive micro-magnetic sensors are strongly required to grade up technologies for automation, motorization, computerization, and bio-engineering through intelligent measurement and control systems. A new sensitive micro-magnetic field sensor named the magnetoimpedance (MI) sensor [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21] has been developed as listed in Table 1 in comparison with conventional magnetic sensors of Hall sensor, the magnetoresistive (MR) sensor, the giant magneto-resistive (GMR) sensor, and the fluxgate sensor. The MI sensor has both advantageous features of the high sensitivity of the fluxgate sensor with the field detection resolution of about 1 μOe for AC uniform fields and about 100 μOe for a DC field and the quick response and low power consumption of the Hall sensor and the MR, GMR sensors with about 1 MHz and about 10 mW, respectively. The sensor head length of the MI sensor is about 1 mm which is about $120$ of the fluxgate sensor head length due to being free from the demagnetizing field in the head. Therefore, the resolution for detection of localized magnetic-pole field is more than 20 times higher in the MI sensor than that in the fluxgate sensor.

The MI sensor is a new micro-magnetic sensor integrating five essential technologies listed as follows:

(1)
Amorphous wire which is cold drawn to about 30 μm diameter and then tension annealed to induce a circumferential anisotropy made by UNITIKA LTD.
(2)
The MI effect that was found in amorphous wires in 1993 [1], [2], [3].
(3)
CMOS transistor sensor circuit utilizing the pulse current response MI effect found in 1997 [4].
(4)
Negative and positive feedback loops in the sensor electronic circuits for high-resolution linear sensors and stable switch-type sensors, respectively [4], [11].
(5)
Micro-machined MI chips developed by the Aichi Steel Co. on 2001 [21].

In this paper, the five essentials and some typical applications of the MI and SI sensors are summarized.

Section snippets

Principle of MI and SI effects

The impedance of a wire-shaped magnetic material having a radius and a length l magnetized with an AC wire current with the angular frequency ω is expressed using Bessel's functions as follows [2]: $Z= 12 R_{dc} kaJ_{0} (ka)/J_{1} (ka),k=(1−j)/δ, δ(skin depth)=(2ρ/ωμ)^{1/2},R_{dc} =ρl/πa^{2},$ where ρ is the resistivity and μ is the circumferential maximum differential permeability. The magnitude of Z is changed with an external magnetic field H_ex applied parallel to the wire axis utilizing the strong skin effect (δ⪡a) as

MI and SI sensor circuits

Fig. 2 illustrates typical CMOS IC multivibrator type MI sensor circuits for stable and low power consumption linear micro-magnetic sensors: impedance detection type [4] in (a), and inductance detection type [10] in (b). Fig. 2(a) represents an MI sensor having a pair of 2 mm long amorphous wires with the pulse bias circuit in the balanced circuit. A pulse current with the rising time of about 10 ns is generated through a differential circuit of R_d and C_d differentiating a square voltage of a

Application of MI and SI sensors

Various sensitive and intelligent measurements have been developed using the MI sensors and SI sensors combined with micro-computers. More than 100 themes for necessary development using the MI and SI sensors are listed in Table 2.

Conclusions

The MI integrated circuit (MIIC) has been just developed by Aichi Steel Co., Japan on October 2001. Many applications would start immediately.

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Amorphous wire and CMOS IC-based sensitive micro-magnetic sensors (MI sensor and SI sensor) for intelligent measurements and controls

Abstract

Introduction

Section snippets

Principle of MI and SI effects

MI and SI sensor circuits

Application of MI and SI sensors

Conclusions

Mater. Sci. Eng. A

Sensors Actuators A

J. Magn. Magn. Mater.

J. Appl. Phys. Lett.

IEEE Trans. Magn.

IEEE Trans. Magn.

J. Magn. Soc. Japan

IEEE Trans. Magn.

IEEE Trans. Magn.