L.P. Shen

Sensitive micro magnetic sensor family utilizing magneto-impedance (MI) and stress-impedance (SI) effects for intelligent measurements and controls

Abstract Recent development in the field of highly sensitive, quick response and small power consumption micro magnetic sensor family (MI sensors and SI sensors) utilizing the magneto-impedance (MI) and stress-impedance (SI) effects mainly in amorphous wires is summarized. The MI and SI sensors are constituted with CMOS inverter IC and MI and SI heads magnetized with the sharp pulse current generating the skin effect, which realize the application specified integrated circuits (ASIC) sensors. Various pocketable or handy micro sensors have been developed, such as the handy terrestrial field sensor and the electronic compass for automobiles using the amorphous zero-magnetostrictive (FeCoSiB) wire MI chips combined with the CMOS IC circuit. Highly sensitive micro stress (strain) sensors and micro acceleration sensors are also developed using the amorphous magnetostrictive (CoSiB) wire SI elements combined with the CMOS IC circuit. Various small oscillatory motions in human bodies, such as the finger tip blood vessel pulsation (FTP) and the mechano-encephalogram, and road bridge oscillation during car passing are sensitively detected using the SI acceleration sensor.

Amorphous wire and CMOS IC-based sensitive micromagnetic sensors utilizing magnetoimpedance (MI) and stress-impedance (SI) effects

New sensitive quick-response and low-power-consumption micromagnetic sensors, namely, 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 I /spl mu/Oe for ac fields and 100 /spl mu/Oe for a dc field with the full scale of /spl plusmn/3 Oe using a 2- or 0.5-mm-long amorphous wire with 30- or 15-/spl mu/m diameter as a sensor head. The possible response speed is about 1 MHz, and the power consumption is about 10 mW. The magnetoimpedance integrated circuit (MIIC sensor was developed in 2002 by the Aichi Steel Company, Japan, 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 microdisplacement in the medical field. More than 100 themes are proposed for application of MI and SI sensors.

Sensitive Stress-impedance Micro Sensor Using Amorphous Magnetostrictive Wire

A giant stress-impedance (GSI) effect with the strain-gauge factor more than 1200 was found in negative magnetostrictive amorphous CoSiB wires of 30-/spl mu/m diameter magnetized with a high frequency current or a sharp pulse current. A sensitive stress sensor is constructed using a CMOS IC multivibrator circuit in which the amorphous wire is magnetized with a sharp pulse train current. The amorphous wire GSI sensor will be applied for detection of such as pressure, tension, stream speed for liquid and gases and mechano-cardiogram with the sensitivity of 5-6 times higher than that of the semiconductor stress sensors utilizing the piezo-resistance effect showing a gauge factor of about 200.

Amorphous wire MI micro sensor using C-MOS IC multivibrator

A family of sensitive, stable and low power consumption MI micro magnetic sensors are constructed using a CMOS IC multivibrator circuit, in which a sharp pulse train current is applied to an amorphous wire to cause the skin effect. A micro field sensor having a resolution of 10/sup -6/ Oe with a full scale (FS) of /spl plusmn/1.5 Oe and a nonlinearity of less than 0.2%, a cut-off frequency of /spl sim/200 kHz, and a power consumption in the oscillation circuit of 0.5/spl sim/5 mW is obtained using a zero-magnetostrictive FeCoSiB amorphous wire of 30 /spl mu/m diameter and 2 mm length. A differential field sensor is also constructed using a pair of amorphous wires suitable for detection of a localized held with the resolution of 10/sup -4/ Oe cancelling uniform disturbance fields such as terrestrial field. Non-contact sensing of a magnetic card surface field was demonstrated.

Sensitive acceleration sensor using amorphous wire si element combined with CMOS IC multivibrator for emvironmental sensing

A highly sensitive and quick response acceleration sensor has been constructed using the stress-impedance (SI) element of 20 /spl mu/m diameter CoSiB amorphous wires combined with a CMOS IC multivibrator. The resolution of the acceleration sensor is 10/sup -3/ Gal(=0.01 m/s/sup 2/) 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.

Mechano-encephalogram based on amorphous wire micro SI acceleration sensor

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 /spl mu/m 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.

Sensitive stress sensor using amorphous magnetostrictive wires on both ends fixed double beam and diaphragm

New sensitive stress sensors having a both ends fixed double beam and a diaphragm on which a pair of 20 /spl mu/m 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.

Detection of finger-tip blood vessel pulsation using CoSiB thin amorphous wire CMOS-IC SI sensor

Finger-tip blood vessel pulsation (FTP) with a capillary blood vessel pressure of few milligrams was accurately detected using a CoSiB amorphous wire stress-impedance (SI) sensor which shows a giant strain-gauge factor of about 4000. The incisura in a FTP waveform was clearly observed for young aged subjects, while the incisura slightly appeared in the FTP waveform for older subjects after sports. The blood vessel pulsation speed was measured between the elbow and the wrist V/sub ew/, and also between the wrist and the finger-tip V/sub wf/, and the authors found that V/sub ew/ was faster than V/sub wf/. It is concluded that the FTP sensing will be useful for diagnosis of the circulatory system and the health state.

Sensitive stress sensor using amorphous magnetostrictive wires on beam with both ends built in and diaphragm

Introductioq The authors have obtained giant straingauge factors of about 2W0 and 1200 using cold drawn and then tension annealed CoSiB amorphous wires (a-wire, for short) with 20 I UI and 30 p diameters respectively (made by UNlTlKA LID.). The wires are magnetized with a high frequency current or a sharp pulse current to generale the stress-impedance (SI, for short) effect [1][2]. We have also reported stress sensors using a pair of amorphous CoSiB wires fixed to a plastic cantilever beam combined with a CMOS IC multivibrator circuit (31. This type sensor has a high sensitivity and a high linearity in the range of -0.75-1.25 gr with a resolution of 2.5 mgr. However, the cantilever type sensor is not applicable lo detect distributed stresses as gas and liquid, because that two a-wires must be fixed on both sides of the plate. In this paper, new stress sensors with a beam with both ends built in and a diaphragm are presented in which a pair of a-wires are fixed on a single side of the substrates. A blood vessel pulsation is stably detected using the diaphragm type SI sensor with a CMOS IC multivibrator. Exoeriments and discuss ion Fig. 1 illustrates a beam with both ends built in type stress sensor head with induced stress distribution. When a weight (W) is loaded on the center of the beam, the a-wire@ (CoSiB with U) p diameter and 7 mm length) fixed on the central area of the plastic plate ( 45 X 15 X 0.4 mm) receives a compressive stress in longitudinal direction, while the a-wire @ fixed on a edge area receives a tensile stress in longitudinal direction. Fig. 2 shows measured results of SI characteristics of the a-wire @ and @set in a CMOS IC multivibrator sensor circuit as shown in Fig. 3. The rising time of the pulse current applied through @and @is 15 ns which corresponds to a sinusoidal current with about 30 MHz for the magnetization. Fig. 4 shows the output voltage Eout versus weight W characteristics of the SI sensor which shows a resolution of about 10 mgr in a linear range of -1-4 gr. Fig. 5 represents a detection of blood vessel pulsations of wrist artery in (a), and carotid artery in (b) using a flexible diaphragm.

Simultaneous detection of blood vessel pulsation waves at temple and finger tip using CoSiB amorphous wire CMOS IC Si sensor

Summary form only given. Detection of blood vessel pulsation (BVP) waves are important for estimation of circulatory system functions and diagnosis for circulatory organs. We have developed a highly sensitive stress sensor having a 4000 gauge factor named SI sensor using a 20 /spl mu/m diameter CoSiB amorphous wire and CMOS IC multivibrator utilizing the stress-impedance effect and applied to detect the finger-tip BVP waves in which effects of smoking and drinking are clearly detected. In this paper, a simultaneous detection of BVP waves at the temple and the finger-tip of a healthy subject using a pair of SI sensors for investigation of their relation on sleeping and awaking in which the temple BVP precedes except during deep sleep.