• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.575-585
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• 2015

Magnetic field in magnetic bearings is the physical medium to realize magnetic levitation, the distribution of the magnetic field determines the operating performance of magnetic bearings. In this paper, a thin-slice Fiber Bragg Grating-Giant Magnetostrictive Material magnetic sensor used for the air gap of magnetic bearings was proposed and tested in the condition of dynamic magnetic field. The static property of the sensor was calibrated and a polynomial curve was fitted to describe the performance of the sensor. Measurement of dynamic magnetic field with different frequencies in magnetic bearings was implemented. Comparing with the finite element simulations, the results showed the DC component of the magnetic field was detected by the sensor and error was less than 5.87%.

• Journal of Magnetics
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• v.13 no.1
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• pp.34-36
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• 2008

For the measurement of the magnetic field distribution with high spatial resolution and high accuracy, the magnetic field sensing probe must be non-magnetic, but the MFM probe and sub-millimeter-meter size Hall probe use a ferromagnetic tip and block, respectively, to increase the sensitivity. To overcome this drawback, we developed a micro-size search coil magnetometer which consists of a single turn search coil, Terfenol-D actuator, scanning system, and control software. To reduce the noise generated by the stray ac magnetic field of the actuator driving coil, we employed an even function $\lambda$-H magnetostriction curve and lock-in technique. Using the developed magnetometer, we were able to measure the magnetic field distribution with a magnetic field resolution of 1 mT and spatial resolution of $0.1mm{\times}0.2mm$ at a coil vibration frequency of 1.8 kHz.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.3114-3120
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• 2023

A high-accuracy magnetic field measurement device based on a cyclotron is being developed for accelerator mass spectrometry (AMS). In this study, a magnetic field measurement device consisting of a Hall probe sensor, piezo-motor, and step motor was developed to measure the magnetic field of the AMS cyclotron magnet. The Hall probe sensor was calibrated to achieve positional accuracy by using polar coordinates. The measurement results between the ratchet gear and piezo-motor, which are the instruments used for driving the measurement device, were analyzed. The measurement result of the device with a piezo-motor exhibits a difference of 5 Gauss (0.04%) as compared with the simulation result.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.263-268
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• 2008

The measurement of magnetic field is performed AC magnetic field emission density in driver cab and saloon's compartment of rolling stock. In order to measure magnetic-field emission, a three-axial magnetic-field sensor is used and connected to data process system. The AC magnetic field is checked and analysis through BNC output, DAQ cad and notebook PC. The spectral analysis is performed by short time Fourier transform(STFT) for time-domain emission signal.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1637-1639
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• 2005

The measurement of magnetic field is performed about DC and AC magnetic field in test track of depot. The test point is cap, on the converter/inverter box, on the traction motor, on the APSE and on the line filter, the height of measurement is bottom and 50 cm height. In case of AC magnetic field, the selected specific frequency is measured on the converter/inverter box. The AC magnetic field is checked and analysis through RS-232C and notebook PC. The DC magnetic field is measured by using the Hall Probe, test result is saved and analysis by PXI system. On the line filter, the maximum value is 1.4 mT in case of DC magnetic field and 0.044 mT in case of AC magnetic field at 50 Hz.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.465-472
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• 2013

Since 1990, Agency for Defense Development is operating the non-magnetic laboratory for the development of key technology for the underwater magnetic stealth part, the research of the magnetic application weapons and the technical support for Korean Navy. Recently, we installed the new three-axis earth magnetic field simulator and the measurement system in the non-magnetic laboratory which is replacing the existing outdated facility. In this paper, we deal with the detailed design result of the earth magnetic field simulator and the measurement system. Also, we describe the effective method to separate the permanent and the induced magnetic field from the measured data for a scaled model ship using the earth magnetic field simulator and the measurement system.

• 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.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.1001-1009
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• 1994

The present paper deals with a new developed sensor for measuring the time-varying magnetic fields and describes the experimental results of trasient magnetic field that takes place during the operations of electric appliance. The operation principle of the self-integrating magnetic field sensor by using coaxial cable is analyzed and a calibration investigation is carried out. The frequency bandwidth of the magnetic field measurement system is from 40 Hz to about 300 kHz. The magnetic field induced by the starting and/or operation of electric appliance mainly includes the odd harmonics such as the third, the fifth and the seventh harmonics. The magnetic field intensity caused during the operation of ultrasonic washer is inversely proportional to distance, this correspodns to induction component. As a result, it was known that the odd harmonics of magnetic field in the desing of electromagnetic shield employed for protecting electronic circuit and control devices have to be considered.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.28-32
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• 2015

Nowadays the magnetic field mapping is widely used in the design and analysis of the NMR/MRI magnet system, and the accuracy of mapping result has become more and more important. There are several factors affecting the accuracy of the mapping such as the mapping method, the precision of the sensor, the position of the measurement points, the calculation accuracy, and so on. In this paper the error due to the misalignment of the measurement points was discussed. The magnetic field in the central volume was mapped using an indirect method in an MRI magnet system and the magnetic field was fitted to a polynomial. Considering the misalignment between the original measurement points and the practical measurement points, there must be some errors in the mapping calculation and we called it positioning error. Several comparisons of the positioning error have been presented through the theoretical estimates and the exact magnetic field values. Finally, the allowable positioning errors were suggested to guarantee the accuracy of the magnetic field mapping within a certain degree for an example case.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.553-562
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• 2007

In this paper, we designed and implemented the system for telemetering ELF(Extremely Low Frequency) magnetic field intensity. The magnetic field measurement system used a 3-axis magnetic field sensor to measure the magnetic field with isotropy and the equalizer to compensate the frequency characteristic in band. By multiplexing three output signals of the magnetic field sensor in time domain, we got the uniform gain and frequency characteristic among three axes. This system was designed that the magnetic field measurement level range was $0.01{\sim}10.0\;uT$ and the measurement frequency band was $40{\sim}180\;Hz$. The control system would access to the magnetic field measurement system with RF and the maximum access distance was 1.0 km. We confirmed that the measurement level error of the fabricated system was within 5 %. The fabricated system was installed to a golf practice range where a high voltage power transmission line was crossed.