• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.874-880
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• 2000

In this paper, a DC potential drop measurement system was used to find the position of the flaw on a simple thin plate. Four-point probe test was evaluated and used for this study. In the four-point probe test, the more distance between current pins provides the more measurable scope, the less voltage difference, and the more voltage difference rate. In the other hand, the more distance between voltage pins provides the less voltage difference and the less voltage difference rate. An optimized four-point probe was applied to measure the relation between voltage and the relative position of flaw to the probe. The Maxwell 21) simulator was used to analyze the electromagnetic field, and it showed that the analytical result was similar to the experimental result within 11.4% maximum error.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.391-395
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• 1999

In this paper, we have obtained the Electron Energy Distribution Function(EEDF) in plasma by using two differentiators and investigated the EEDFs by sawtooth and triangle waveform voltages with the working pressures and the positions of single probe. It is found that as the working pressure is decreased, the EEDFs approach to theMaxwellian distribution independent of the waveforms of probe voltage. On the otherhand, as the position of probe is moved from the center of the plasma to its edge, the EEDF of sawtooth waveform probe voltage approaches to the Maxwellian distribution, but the EEDF of triangle waveform probe voltage deviates from the Maxwellian distribution.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.60-64
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• 2010

This paper introduces reliability improvement and time saving in eddy current inspection by signal characteristic optimization of multi-coil eddy current array probe. In the past, Multi-coil array probe and single probe were used for the gas turbine rotor surface inspection & defect evaluation. The multi-coil array probe was used for the broad area inspection. But the signal deviations among multi-coil array probe are maximum 28% in commercial probe. This differences were considered to impedance differences among coils, so it is very difficult to evaluate exact defect size. The signal deviations among multi-coil array probe are maximum 28% in commercial probe. So, single coil inspection was used for exact defect sizing. The purpose of this study is to improve signal deviations of multi-coil array probe. The introduced new technology can improves this deviation by adjusting input voltage in each coil. At first, apply same voltage in each coil and collect signal amplitude of each coil. And calculate new input voltage based on signal amplitude of each coil. If the signal amplitude deviation is within 5% among multi-coil array probe, the signal amplitude of multi-coil array probe is reliable. The proposed technology gives 2% signal deviation among multi-coil array probe. The proposed new technology gives reliability improvement and inspection time saving in eddy current inspection.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1087-1091
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• 2005

Four-probe device of single ZnO nanowire was fabricated by electron beam lithography. Electrical characterizations in a two-probe and a four-probe configuration with a back-gate were carried out to clarify the relative contribution of the contact and the intrinsic part in a ZnO nanowire. I-V characteristic in four-probe measurement showed an ohmic behavior with a high conductivity, 100 S/cm, which was better than those of two-probe measurement by 10 times. At the same values of the current between two-probe and four-probe, the net voltage applied inside the nanowire were extracted with calculated voltages at the contact. Four-probe current-gate voltage characteristics showed bigger tendencies than those of two-probe measurement at low temperatures, indicating the reduced gate dependence in two-Probe measurements by the existence of the contact resistance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.1
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• pp.85-89
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• 2008

An objective of this paper is to develop a partial discharge (PD) measurement device for monitoring gas insulated switches installed in power distribution system. A capacitive voltage probe was studied and designed to detect PD pulse without an electrical connection. The PD measurement device consists of the capacitive voltage probe attached outside of a bushing, a coupling network which attenuates AC voltage by 270 dB, and a low noise amplifier with the gain of 40 dB in ranges of 500 kHz${\sim}$20 MHz. The sensitivity of the prototype device calculated by a calibrator was 1.98 m V /pc. An application experiment was carried out in a 25.8 kV gas insulated switch and the peak pulse of 76.7 pC was detected. From the experimental results, it is expected that the PD measurement device can be applied to online monitoring system of gas insulated switches.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1111-1114
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• 2003

In this paper, electrical characteristics of inductively coupled plasma in an electrodeless fluorescent lamp were investigated using a Langmuir probe with a variation of argon gas pressure. The RF output was applied in the range of $5{\sim}50W$ at 13.56MHz. The internal plasma voltage of the chamber and the probe current were measured while varying the supply voltage to the Langmuir probe in the range of $-100V{\sim}+100V$. When the pressure of argon gas was increased, electric current was decreased. There was a significant electric current increase from l0W to 30W. Also, when the RF power was increased, electron density was increase. This implies that this method can be used to find an optimal RF power for efficient light illumination in an electrodeless fluorescent lamp.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.11
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• pp.508-511
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• 2003

In this paper, electrical characteristics of inductively coupled plasma in an electrodeless fluorescent lamp were investigated using a Langmuir probe with a variation of argon gas pressure. The RF output was applied in the range of 5 ∼ 50 (W) at 13.56 (MHz). The internal plasma voltage of the chamber and the probe current were measured while varying the supply voltage to the Langmuir probe in the range of -100 (V) ∼+100 (V). When the pressure of argon gas was increased, electric current was decreased. There was a significant electric current increase from l0W to 30 〔W〕. Also, when the RF power was increased, electron density was increase. This implies that this method can be used to find an optimal RF rower for efficient light illumination in an electrodeless fluorescent lamp.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.269-274
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• 1997

Langmuir probe was housed in the sounding rocket to test the probe's performance and to find the environmental parameters at the F layer of the ionosphere. The gold plated cylindrical probe had a length of 14㎝ and a diameter of 0.096 ㎝. The applied voltage to the probe consisted of 0.9 sec fixed positive bias followed by 0.1 sec of down/up sweep. This ensured that the probe swept through the probe's current-voltage characteristic at least once during 1 second quiescent periods enabling the electron temperature to be measured during the undisturbed times of the flight. The experimental results showed good agreement of the temperature distribution with IRI model at the lower F layer. In the upper layer, the experimental temperatures were 100-200K lower than the IRI model's because of the different geomagnetic conditions: averaged conditions were used in IRI model and specific conditions were reflected in the experiment.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.167-180
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• 2015

Herein, we discuss the in situ measurement of the electron temperature in the ionosphere/plasmasphere by means of DC Langmuir probes. Major instruments which have been reported are a conventional DC Langmuir probe, whose probe voltage is swept; a pulsed probe, which uses pulsed bias voltage; a rectification probe, which uses sinusoidal signal; and a resonance cone probe, which uses radio wave propagation. The content reviews past observations made with the instruments above. We also discuss technical factors that should be taken into account for reliable measurement, such as problems related to the contamination of electrodes and the satellite surface. Finally, we discuss research topics to be studied in the near future.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.506-511
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• 1996

This paper deals with an inexpensive, simple and fast Langmuir probe sweeping circuit and its application. This sweeper completes a probe trace in a 1 ms order. Futhermore, the circuit drives a maximum probe voltage of $\pm$30V and has a maximum probe current capability of a few amperes. The plasma parameters are successfully determined using the fast Langmuir probe method.