• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.244-252
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• 2015

This paper describes design and construction results of the measurement system developed on the purpose of measuring properties of AC magnetic field sensors used in the weapon system. The system for measuring the properties of AC magnetic field sensors consist of 3-axis helmholtz coil, signal generator, signal amplifier, sensor data acquisition unit and AC magnetic field sensor property measurement & analysis equipment including the operating software. By using this system, we can measure various properties of AC magnetic field sensor such as sensitivity, linearity and dynamic response in the frequency from 1 Hz to 10 kHz. Finally we also verified its performance by measuring the property of a MAG 639, standard magnetic field sensor of bartington instruments, with the developed measurement system.

• Korean Journal of Optics and Photonics
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• v.2 no.3
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• pp.139-148
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• 1991

A fiber-optic magnetic sensor system for the detection of small ac magnetic field(200Hz-2 kHz) was constructed. Magnetic field sensing part was fabricated by bonding a section of optical fiber to amorphous metallic glass(2605SC) having large magnetostriction effect. And with the directional coupler, all fiber type Mach-Zehnder interferometer was constructed to measure the variation of the external magnetic field by translating it into the optical phase shift in the interferometer. The signal fading problem of the interferometer, which is due to random phase drifts originated from the environment, i.e., temperature fluctuation, vibrations, etc., was elliminated by feedback phase compensation. This allows the sensitivity to be maintained at the maximum by keeping the interferometer in quadrature phase condition. The frequency response of metallic glass was found to be nearly flat in the range of 90 Hz-2 kHz and dc bias field for the maximum ac response was 3.5 Oe. The interferometer output showed good linearity over the range $\pm$0.5 Oe. For 1 kHz ac magnetic field the scale factor S and the minimum detectable magnetic field were measured to be 8.0 rad/Oe and $3X10^{-6} Oe/\sqrt{Hz}$at 1 Hz detection bandwidth respectively.

• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.125-130
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• 1998

13Cr-1.5Nb-Fe alloy powder was fabricated by water atomization method, and ring-shape specimen of this composition was fabricated by oil press, and then sintered in the vacuum furnace. Powder shape, size distribution, composition (C, N, O, S) analysis and saturation magnetization of as-prepared 13Cr-1.5Nb-Fe alloy powder were investigated. Ac permeability and power loss was measured after forming and sintering process. Saturation magnetization and contents of oxygen of the alloy powder is160 emu/g and about 6000 ppm, respectively. 50 % volume fraction indicate particle size of 70$\mu$m. The ac permeability of sintered specimen increases with increasing sintering temperature and forming pressure. The power loss is 107 W/cc at sintering temperature of 1200 $^{\circ}C$, 12 ton/$\textrm{cm}^2$ forming pressure, and 20 KHz. It is the lowest among the prepared specimen.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.48-52
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• 2005

This paper describes a current sensor for precision current measurement of an electronic watt-hour meter that is going to install in houses in the future. As the current sensor is based on an cored principle (the Rogowski principle) it is not subject to usual limitations of saturation and non-linearity of general current transformers. An advantage of the developed current sensor is that non-linearity error in low current range is improved and the construction can be kept simple using an air core. We present a magnetic field analysis of the sensor using a finite-element solver. We compared the measured values versus the calculated values.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.11-17
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• 1993

We have constructed an acceleration sensor which is based on the maximum magnetic induction changes of amorphous wire as a measurand. The frequency bandwith of the constructed sensor depends on the mass of a sensing element. For $Co_{72.5}Si_{12.5}B_{15}$ amorphous wire, the bandwith is DC-700 Hz for $1{\times}10^{-3}kg$ sensing element and DC-200 Hz for $5{\times}10^{-3}kg$. The linearity of the acceleration sensor was less than 1% within the acceleration of 5 g.

• Journal of the Korean Magnetics Society
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• v.6 no.6
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• pp.388-396
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• 1996

Magnetic properties of sintered Fe-79Ni-4Mo cores made of centrifugal atomized powders were investigated. $H_{c}$ and $\mu_{a}$ of the cores sintered at $1350^{\circ}C$ for 2 hours measured at 60 Hz at a magnetic field of 10 Oe showed the best properties. Particularly the properties of $H_{c}$ and $\mu_{a}$ measured at low field (< 0.2 Oe) were found to increase with increasing the particle size of the core samples. It resulted from the domain wall motion depending on the grain size of sintered bodies. The best D, C magnetic properties of $H_{c}$ and $\mu_{max}$ were 0.085 Oe and 40000, respectively. A, C properties of the same cores showed the $\mu_{a}$ of 11000. The magnetic properties of sintered cores always exhibited an enhanced AC/DC performance by using the powders mixed with two different particle sizes. Those properties of cores are expected to apply for current transformer.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.304-308
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• 1995

In order to measure magnetic field difference, we have constructed a fluxgate magnetometer which is based on the measurement of apparent coreci ve field strength from the magnetizing current of two sensors. 'Co-based amorphous ribbon, which has square shape of ac hysteresis loop, was used as core material. Two sensors have 315 turns of the primary and the secondary windings respectively, and core size of 2 mm wide and 30 mm long. The primary windings are connected parallel to measure external magnetic field difference and the secondary windings serieally for the averaged magnetic induction of the cores. The constructed magnetometer could measure magnetic field difference with sensitivity of $1.6{\times}10^{6}V/T$ and resolution of 1 nT at 1 Hz bandwidth.

• Journal of the Korean Magnetics Society
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• v.23 no.3
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• pp.94-97
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• 2013

Orthogonal fluxgate sensor was fabricated with cylinder-shaped NiZn ferrite core, Cu wire through the core and pickup coil wound on the core, and the bias current effect on the output sensitivity of it was investigated. The output ($$\sim_\sim$$ sensitivity) of the sensor was largely dependent on the operation frequency, and the tendency of sensor output was similar to that of the impedance of pickup coil. The maximum output was obtained by adding the DC bias current of which value was over 50% of the excitation current. The output was saturated when the DC bias current was larger than 50% of the excitation current.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.434.1-434.1
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• 2014

최근 자성 나노 입자를 이용한 온열치료가 주목을 받고 있다. 자성을 띄는 나노 입자를 암 세포에 보내, 교류 자기장을 걸어주어 회전에 의한 마찰손실로 인한 열을 이용하여 암 조직만을 국소 가열하는 원리이다. 본 실험은 유도 자기장을 사용한 자성 나노 파우더의 가열을 목적으로 시행하였다. 나선형 코일위에 세라믹, 유리 등 절연체 원판 위에 자기장이 발생되도록 휴대용 평판형 자기장 발생장치를 제작하였다. 자기장 발생 장치는 평판형 나선형 코일에 특정 주파수를 가진 전원을 인가하여 자기장을 발생시킨다. 평판형 나선형 코일은 내경 40 mm, 외경 140 mm, 2 mm 동선으로 제작하였다. 제작한 자기장 발생장치를 자기장 측정 센서(Hall sensor 등)을 원판 위에 설치하여 거리별 자기장의 크기를 측정하였다. 자기장은 나선형 코일 위 원판 중심에서 최대로 발생되어 중심에서 멀어질수록 크기가 감소하였다. 자기장 발생장치 위에 자성 나노 파우더($Fe_3O_4$와 $CoFe_2O_4$)를 혼합한 용액 시료를 위치시키고 자기 쌍극자 모멘트와 자기장간의 상호작용을 유도한다. 이때 자성 나노 파우더별로 발생하는 열을 열전쌍(TC)이나 Optical fiber를 사용한 Thermometer로 측정하여 비교분석하였다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.5
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• pp.474-482
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• 1992

This paper describes the speed control system of an induction type ac servomotor drive on the vector control basis of slip frequency and constant secondary flux control for a quick torque response. The system is composed of a digital controller using a SCB-V50 microprocessor and a PWM inverter with power MOSFETs for high speed switching. And, for the measurement of actual instantaneous currents, MDCS A070-051 hall sensors are employed. The rising time of step responce by this system through the test of a 600[W] ac servomotor is 30[ms]. Overall experimental result shows that the drive performance of the system is similar to that of a separately excited armature current control of a dc motior.