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손대락(Derac Son) 한국자기학회 2020 韓國磁氣學會誌 Vol.30 No.3
Mines have been used to protect army from enemy with cost effectively. In opposite site, quick detection and remove of mines are very important for movement of armed force. Measure and remove of UXO (UneXploded Ordnance) is one of very important problems for safety of peoples living that area after war. To countermeasure mine and UXO, EMI (ElectroMagnetic Impedance), EMI(ElectroMagnetic Induction), Magnetometer, and GPR (Ground Penetrating Radar) methods have been used. In this work, we introduced magnetic field measuring method to find location of mine and UXO because they are made by iron steel and earth magnetic field is distorted by them. The conditions of magnetometers and research trends, which are applicable to unmanned vehicle such as UGV, UAV, USV, and UUV are introduced.
손대락(Derac Son) 한국자기학회 2014 韓國磁氣學會誌 Vol.24 No.3
Toroidal cores made of metallic powder requires large magnetic field strength up to few decade kA/m to obtain major hysteresis loop. To overcome thermal heat generation problem from large exciting current during measurement, we have employed a real time hysteresis loop tracer which can digitize and calculate B-H signals in personal computer as real time. For example, when we magnetize specimen at 10 Hz frequency, we could display hysteresis loops 10 times per second. Using the real time hysteresis loop tracer, we could measure major hysteresis loop of toroidal shape metallic powder core at maximum flux density or maximum magnetic field strength to be measured within 5 second not to significant increasement of specimen temperature due to the heat dissipation from coil windings. For the constructed hysteresis loop tracer, we could measure hysteresis loop at magnetic field strength higher than 50 kA/m for the toroidal shape specimen.
손대락(Derac Son) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.2
Feed-back type 3-axis flux-gate magnetometer using Co-based amorphous ribbon (Metglass<sup>®</sup>2714A) was constructed in this work. Measuring range of magnetic field and frequency were ± 100 μT and dc~10 Hz respectively. For the interface to computer, microcontroller and 24 bit ADC (Analog to Digital Converter) were employed and resolution of digital output was 0.1 nT. Magnetometer noise of analog output was 5 pT/ at 1 Hz. Digital output of the magnetometer showed linearity of 1 × 10?4 and the offset drift was smaller than 0.2 nT during 1 h.
자기장크기 측정이 가능한 3-축 Flux-gate 마그네토미터 제작
손대락(Derac Son) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.5
Magnetic field measurement under vibration and rotation condition of the magnetometer, total field measuring magnetometers have been used, because orthogonality error and scale factor differene of the 3-axis magnetometer can not measure total magnetic field with high precission. In this study, we developed total magnetic field sensor by orthogonality correction for the 3-axis flux-gate magnetometer. To correct orthogonality and scale factor, 24 bit 3-channel simultaneous digitizing ADC and DSP were used. To demonstrate the performance of the developed magnetometer under condition of vibration, the magnetometer was installed on dron and measured magnetic anormality of passenger cars. We can measure total magnetic field with resolution of 1 nT for the developed orthogonality corrected 3-axis flux-gate magnetometer.
손대락(Derac Son) 한국자기학회 2014 韓國磁氣學會誌 Vol.24 No.1
North indicating azimuth angle sensors have been used in airplanes, ships traditionally and nowadays employed in smart phones. For the azimuth and roll angle measurement of the sensor, 3-axis acceleration sensor was added to the 3-axis magnetic field sensor. In this work, we have constructed a measuring system for the measurement of the magnetic field and the angle uncertainty of the magnetic field sensors. Measuring system could be useful not only in non-magnetic laboratory but also in normal laboratory, we constructed small size of 3-axis Helmholtz coils for the compensation environment magnetic field (Earth magnetic field and magnetic field from building) and the generation of magnetic field for the test of magnetic field sensor. The constructed measuring system could compensate environment magnetic field below 10 nT level and generate 3-dimensional magnetic field with magnitude uncertainty of 0.2 % and angle error of 0.2° within the volume of ± 30 mm diameter at center of Helmholtz coils. For the conformation of developed measuring system, We tested commercially available 3-axis magnetometer and heading sensor.
인공위성의 자세제어용 3-축 Flux-gate 마그네토미터 제작
손대락(Derac Son) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.3
In this work, we have constructed 3-axis flux-gate magnetometer for the attitude control of satellite. The constructed magnetometer shows uncertainty of ±1%, noise level of 0.2nT/√㎐ at 1 ㎐ under 1W power consumption. Environment test for satellite component, acceleration test and thermal cycle test were carried out. For the acceleration test, magnetometer was vibrated frequency ranging from 10 ㎐ to 1 ㎑ at 15 g (g : gravitational acceleration at earth), and for thermal cycle test, 4 times of thermal cycle were carried out temperature ranging from -55℃ to +80℃ under vacuum of 1×10?? Torr.
Tendon의 인장응력에 따른 자기이력특성 변화의 측정
강선주(Sunju Kang),손대락(Derac Son),조창빈(Changbin Joh),이정우(Jungwoo Lee) 한국자기학회 2015 韓國磁氣學會誌 Vol.25 No.4
The iron is an element having a high yield strength, mechanical hardness, good electrical conductivity, and also it has been used in various fields because of ease machining. In bridges have been used tendon made of a steel wire for large loads and light weight. Tension measurement of tendon employed in PreStressed Concrete (PSC) bridge is very important for the bridge safety check. NDT (Non-Destructive Testing) is essential for the safety check, however, magnetic NDT is difficult to apply due to the non-linear magnetization curve and hysteresis loop in the magnetic properties. In this work, for basic study of magnetic NDT application, we have constructed a B-H loop measuring system for 7-strand tendon of which diameter is 15.5 mm, and which can apply tensile stress up to 2.0 GPa. We have measured hysteresis loops of two kinds of tendons under different tensile stress. Amplitude permeability and maximum magnetic induction near knee show the most sensitive and high linearity depends on tensile stress. Relative amplitude permeability was decreased from 500 to 200 and maximum magnetic flux density changed 0.6 T.