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ABSTRACT: The authors have presented a pulse frequency modulation (PFM) amorphous wire CMOS IC magneto-impedance (MI) sensor for the purpose of omitting the A/D converter in the electronic compass for mobile phone application by counting the output square wave voltage width with the number of timing pulses of the microprocessor. Elimination of A/D converters is useful for downsizing, speed up and cost cutting in the mobile phone electronic compass. However, output stability of the PFM-MI sensor should be improved by canceling the fluctuation of sensor circuit parameter (R, C) with temperature variation. They recently constructed a pulsewidth modulation (PWM) amorphous wire CMOS IC MI sensor on the basis of the PFM-MI sensor detecting the pulse duty ratio proportional to the applied magnetic field strength, in which the sensor circuit parameter (R, C) are canceled in the sensor output equation for the improvement of the magnetic field sensing stability to temperature variation.
IEEE Transactions on Magnetics 12/2008; · 1.36 Impact Factor
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ABSTRACT: We summarize the achievement of development of the magneto-impedance sensor (MI sensor) using amorphous wires and CMOS IC since the discovery of a new principle for a sensitive micro magnetic sensor utilizing the sensitive magneto-impedance effect in a 30 μm diameter zero-magnetostrictive FeCoSiB amorphous wire on 1993, the invention of a CMOS IC inverter multi-vibrator type sensitive micro magnetic sensor using the pulse magneto-impedance effect in the amorphous wire on 1997, a further invention of a highly stable micro magnetic sensor for temperature variation introducing analog switches on 1999, the development of an electronic compass IC chip for mobile phones using two-axis MI geomagnetic field sensors for Telson Co., on 2003 and LG Co., on 2004, and the advanced development of a new direction and motion sensor IC chip combining a three-axis MI electronic compass with a two-axis MI inclination and acceleration sensors (5-dimensional motion sensor chip) for Vodafone Ltd., mobile phones by Aichi Steel Corporation on 2005. We also introduce a further advanced development of a 6-dimensional motion sensor chip on 2006 for mobile phones and various motion control systems.
Sensor Letters 02/2007; 5(1):267-270. · 0.82 Impact Factor
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ABSTRACT: An accurate stationary low-speed and torque control system for induction motors (IM) with a secondary current (I<sub>2</sub>) signal feedback loop is presented, in which a sensitive and stable micromagnetic (MI) sensor is set inside a drilled shaft hole to detect a slip frequency (sf) magnetic field proportional to an endring circular current. A finite impulse response digital low-pass filter (FIR-DLPF) is introduced to separate the I<sub>2</sub> signal from slightly higher frequency drive current I<sub>1</sub> signal at a low speed IM operation for such as the steel sheet rolling spread control. Accurate stationary low speed (45 r/min) control with error less than 1.11% and stationary torque (1.3 Nmiddotm at 45 r/min) control with error less than 0.76% for a 1.5 kW, 4-pole IM through 83 min operation were obtained, respectively
IEEE Transactions on Magnetics 11/2006; · 1.36 Impact Factor
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Magnetics Conference, 2000. INTERMAG 2000 Digest of Technical Papers. 2000 IEEE International; 05/2005
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Magnetics Conference, 2000. INTERMAG 2000 Digest of Technical Papers. 2000 IEEE International; 05/2005
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ABSTRACT: We investigated the magnetic-field behavior of the off-diagonal impedance in Co-based amorphous wires under sinusoidal (50 MHz) and pulsed (5 ns rise time) current excitations. For comparison, we measured the field characteristics of the diagonal impedance as well. In general, when an alternating current is applied to a magnetic wire, the voltage signal is generated not only across the wire but also in a pickup coil wound on it. These voltages are related to the diagonal and off-diagonal impedances, respectively. We demonstrate that these impedances have a different behavior as functions of axial magnetic field: the diagonal impedance is symmetrical, whereas the off-diagonal one is antisymmetrical with a near-linear portion within a certain field interval. For the off-diagonal response, the dc bias current is necessary to eliminate circular domains. In the case of the sinusoidal excitation without a dc bias current, the off-diagonal response is very small and irregular. In contrast, the pulsed excitation, combining both high- and low-frequency harmonics, produces the off-diagonal voltage response without additional biasing. This behavior is ideal for a practical sensor circuit design. We discuss the principles of operation of a linear magnetic sensor based on a complementary metal-oxide-semiconductor transistor circuit.
IEEE Transactions on Magnetics 12/2004; · 1.36 Impact Factor
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ABSTRACT: A new frequency-modulation-type magnetoimpedance (MI) sensor using amorphous wire and a complimentary metal-oxide-semiconductor (CMOS) multivibrator is presented. The normal switching mode (mode I) with the alternative saturation and off states in the p-MOSFET and n-MOSFET maintains a stable multivibrator oscillation and simultaneous CMOS unsaturation state mode (mode II) generates a sensitive MI effect. A 50%/Oe change in the oscillation frequency versus external dc magnetic field was obtained. A linear sensor characteristic is obtained using a negative feedback through a frequency-voltage converter.
IEEE Transactions on Magnetics 02/2004; · 1.36 Impact Factor
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ABSTRACT: Summary form only given. The MI sensor, originally discovered by Mohri et al. (1992), has 10,000 times the sensitivity of the MR sensor. Mass-production of an amorphous wire sensor without loss of characteristics during bonding of the amorphous wire has been a considerable challenge. Here, the successful mass production of an amorphous wire type MI sensor is introduced. A summary of the sensor performance, and the technical points important to mass production are given.
01/2002;
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ABSTRACT: A figure of merit (FOM) for the magneto-impedance (MI) effect is
defined by the product of the MI ratio and the cut-off frequency for ac
field detection as
(|∂Z/∂Hex|/Z<sub>0</sub>)·f<sub>cutoff</sub>. The FOM
for almost zero-magnetostrictive amorphous wire of 30 μm diameter was
about improved 2.5 times by twisting and flash annealing using a pulse
current of 80 mA, 1 second. A sensitive, quick response, and low power
consumption wireless FM type MI sensor is constituted using the high FOM
amorphous wire head combined with all CMOS IC sensor circuit. The
wireless MI sensor is successfully applied to a torque sensor fixed on
an automobile power steering steel
IEEE Transactions on Magnetics 08/2001; · 1.36 Impact Factor
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ABSTRACT: Time series reflecting human brain activities in mental and
emotional states was detected using a sensitive micro acceleration
sensor composed of a CoSiB magnetostrictive amorphous wire connected
with a CMOS IC circuit with the resolution of about 0.1 Gal. A small
sensor head of a glass specimen of 0.16 mm thick, 3 mm wide, and 15 mm
long on which a CoSiB amorphous wire of 20 μm diameter and 5 mm long
and an inertia mass of 0.1 gr are adhered was fixed on the center of
forehead of a subject. Detected waveforms of the sensor output for
several subjects with both eyelids closed were different from the
conventional microvibration and were classified into four kinds
representing the states at rest or lightly sleeping, passively stressed,
actively stressed, and pleasant imaging. We named these signals as the
mechano-encephalogram separating from the microvibration
IEEE Transactions on Magnetics 08/2001; · 1.36 Impact Factor
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ABSTRACT: Sensitive, quick response and low power consumption micro-magnetic
sensors have been developed utilizing the magneto-impedance (MI) and
stress-impedance (SI) effects in zero-magnetostrictive (zero-λ)
and negative-magnetostrictive amorphous wires connected with CMOSFET IC
sensor circuits. The MI magnetic field sensor using zero-λ
amorphous wires of 30 μm diameter and 2 mm length represents the
resolution of about 1 μG for AC fields and about 100 μG for the DC
field with ±3 G in the full scale, the cut-off frequency of about
1 MHz, and low power consumption of about 10 mW for the CMOS MI sensor.
The SI sensor using a 20 μm diameter negative-λ amorphous wire
shows the gauge factor of about 4000 for stress (strain) sensors and the
resolution of 0.1 Gal for acceleration sensors. The principles, basic
features, and applications of MI and SI sensors are summarized
Micromechatronics and Human Science, 2001. MHS 2001. Proceedings of 2001 International Symposium on; 02/2001
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ABSTRACT: This paper reports experimental results to obtain a sensitive and
asymmetrical MI effect in crossed anisotropy sputtered films magnetized
with a DC-biased AC or pulse current. The sensitive and asymmetrical MI
effect occurs, because the crossed anisotropy films induce spiral
magnetic anisotropy. The crossed anisotropy film
(Co<sub>72</sub>Fe<sub>8</sub>B<sub>20</sub>) was made on a glass
substrate using DC sputtering with two layers having 4.5 μm thickness
each applying a DC field of 21 kA/m along with a designed anisotropy
direction. A linear MI characteristic with a field detection sensitivity
of 0.15%/(A/m) (12%/Oe) was obtained, which realizes a sensitive linear
field sensor without any DC bias field
IEEE Transactions on Magnetics 10/2000; · 1.36 Impact Factor
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ABSTRACT: A highly sensitive and quick response acceleration sensor has been
constructed using the stress-impedance (SI) element of 20 μm diameter
CoSiB amorphous wires combined with a CMOS IC multivibrator. The
resolution of the acceleration sensor is 10<sup>-3</sup> Gal(=0.01 m/s
<sup>2</sup>) for repetitive vibration and 0.1 Gal for nonrepetitive
motion. The high sensitivity is based on the ultrahigh values of the
gauge factor of about 4000 in the CoSiB amorphous wire SI element. The
power consumption is about 6 mW due to the pulse magnetization
circuitry. Basic properties of the acceleration sensor and application
to the sensing of road bridge seismovibration due to car passing are
presented
IEEE Transactions on Magnetics 10/2000; · 1.36 Impact Factor
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ABSTRACT: An asymmetrical magneto-impedance (MI) effect in almost zero
magnetostrictive amorphous wires is obtained using torsion annealing and
then magnetizing with a high frequency current biased with a DC current.
A highly sensitive MI characteristic showing a field detection
sensitivity of more than 100%/Oe was realized in the wire annealed with
450 turn/m torsion at 500°C, inducing a spiral anisotropy. The
change of the torsion direction from clockwise to anti-clockwise inverts
the asymmetrical MI effect. A sensitive linear field sensor is
successfully constructed using a pair of the asymmetrical MI heads
without bias coils
IEEE Transactions on Magnetics 10/1999; · 1.36 Impact Factor
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ABSTRACT: Accurate controls for the speed and the torque of induction motors
(IM) are realized using the detected secondary current (I<sub>2</sub>)
signal with the inverter having a constant ratio of the primary voltage
over the driving frequency (V<sub>1</sub>/f). A new method for detecting
I<sub>2</sub> is presented setting a MI sensor head inside a drilled
hole through a shaft of an actuator type IM, in which an almost pure I
<sub>2</sub> signal having the slip frequency is stably detected, An
accurate and reliable control system for the IM is constructed using the
I<sub>2</sub> feedback loop with the inverter
IEEE Transactions on Magnetics 10/1999; · 1.36 Impact Factor
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ABSTRACT: A new highly stable magneto-impedance (MI) micro magnetic sensor
with a pair of zero-magnetostrictive amorphous wires is presented. The
sensor picks up a first pulse in an induced oscillatory pulse voltage at
a wire coil using an analog switch. High temperature stability in the MI
sensor is established in which zero drift for temperature variation from
20°C to 80°C is 0.6%/FS (0.01.%/FS°C). The highly stable MI
sensor will be useful for application to automobile controls
IEEE Transactions on Magnetics 10/1999; · 1.36 Impact Factor
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ABSTRACT: New sensitive stress sensors having a both ends fixed double beam
and a diaphragm on which a pair of 20 μm diameter CoSiB amorphous
wires are adhered as the stress-impedance (SI) element connecting with a
CMOS IC multivibrator circuit. The SI characteristics are quantitatively
analyzed using a magnetization rotation model and measured BH hysteresis
loops. Detection of a blood vessel pulsation is also carried out
IEEE Transactions on Magnetics 10/1999; · 1.36 Impact Factor
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Magnetics Conference, 1999. Digest of INTERMAG 99. 1999 IEEE International; 06/1999
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Magnetics Conference, 1999. Digest of INTERMAG 99. 1999 IEEE International; 06/1999
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ABSTRACT: Two approaches for obtaining asymmetrical magnetoimpedance (MI) characteristics in Co-based negative magnetostrictive amorphous wires are analyzed in terms of the surface impedance tensor , which is expressed in the form of orthogonal expansions in Bessel functions in a general case of a helical magnetization. The asymmetry in MI behavior with respect to an axial dc magnetic field can be related to either a certain asymmetric arrangement of the dc magnetic configuration or a contribution to the wire voltage due to the ac cross-magnetization process (represented by the off-diagonal component of ). The first case is realized in a wire having a helical anisotropy and subjected to an ac current superposed with a dc current. In the other approach, the asymmetric voltage response can be obtained by applying the ac current in series through the wire and the coil mounted on it. No helical anisotropy is required in this case. These kinds of asymmetrical MI are especially important for developing autobiased linear MI sensors. © 1999 American Institute of Physics.
Journal of Applied Physics 04/1999; 85(8):5444-5446. · 2.17 Impact Factor
