Abstract
We analyzed and organized the reasons why the amorphous wire CMOS IC magneto-impedance sensor (MI sensor) has rapidly been mass-produced as the electronic compass chips for the smart phones, mobile phones, and the wrist watches. Comprehensive advantageous features regarding six terms of (1) microsizing and ultralow power consumption, (2) high linearity without any hysteresis for the magnetic field detection, (3) high sensitivity for magnetic field detection with a Pico-Tesla resolution, (4) quick response for detection of magnetic field, (5) high temperature stability, and (6) high reversibility against large disturbance magnetic field shock are based on the magneto-impedance effect in the amorphous wires. We have detected the biomagnetic field using the Pico-Tesla resolution MI sensor at the room temperature such as the magneto-cardiogram (MCG), the magneto-encephalogram (MEG), and the self-oscillatory magnetic field of guinea-pig stomach smooth muscles (in vitro) that suggest the origin of the biomagnetic field is probably pulsive flow of Ca2+through the muscle cell membrane.
Highlights
We have found a new electromagnetic phenomenon in the amorphous wire in 1993 and named it as “the magnetoimpedance effect” [1], in which the impedance of the amorphous wire sensitively changed with a small external applied magnetic field when a high-frequency current was applied through the wire as a carrier
We developed further a reliable amorphous wire CMOS IC multivibrator magneto-impedance sensor in 1999 using the analog switches instead of the Schottky diodes for realization of high temperature stability [7] and developed various stable and sensitive micromagnetic sensors [8, 9]
We developed an amorphous wire CMOS IC multivibrator type microlinear magnetic field sensor for industrial usage MI sensor chip as illustrated in Figure 4 [7]
Summary
We have found a new electromagnetic phenomenon in the amorphous wire in 1993 and named it as “the magnetoimpedance effect” [1], in which the impedance of the amorphous wire sensitively changed with a small external applied magnetic field when a high-frequency current was applied through the wire as a carrier. We invented a practical sensitive linear micromagnetic sensor electronic circuit in 1997 on the basis of the magneto-impedance effect using a zero-magnetostrictive amorphous wire with a pickup coil and CMOS IC multivibrator pulse voltage generator applying the pulse current via the Schottky diode to the amorphous wire instead of the high-frequency current [5, 6]. We developed further a reliable amorphous wire CMOS IC multivibrator magneto-impedance sensor in 1999 using the analog switches instead of the Schottky diodes for realization of high temperature stability [7] and developed various stable and sensitive micromagnetic sensors [8, 9]. Electronic compasses have been developed and massproduced by Aichi Steel Co., Japan, supported by the Japan Science and Technology Agency (JST) using the 3-axis amorphous wire MI sensor chips for the mobile phones since. We have developed a highly sensitive magnetic sensor with 1 Pico-Tesla resolution MI sensor and applied it to detect the biomagnetic field at the room temperature such as for an in vitro biopsy fragment of guinea-pig stomach [10], the human magneto-cardiogram, the human back magnetocardiogram, and the human magneto-encephalogram [11, 12]
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