• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.3
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• pp.283-288
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• 2005

A portable primary inductance standard set that includes a Maxwell-Wien bridge and a 10 mH standard inductor installed in a thermostat has been developed at KRISS. Two auxiliary resistance capacitance networks (analogous to a 'Wagner ground') provide excellent stability of the bridge balance and impose less strict requirements on the components of these networks. Removable capacitance and ac-dc resistance standards used in the bridge arms made it possible to reproduce 10 mH and 100 mH inductance values in the frequency range of 500 Hz to 3 kHz. From investigations of this standard and preliminary comparison with VNIIM (D. I. Mendeleyev Institute for Metrology), the results have demonstrated that the bridge can be used as a part of the transportable inductance standard with a measurement uncertainty within (1-3) $\mu$H/H at frequencies of 1 kHz and 1.6 kHz. The application of the bridge as a constituent part of the transportable standard gives us an opportunity to eliminate the influence of the standard inductors.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.201-206
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• 2004

The AC-DC magnetic field standard systems were constructed for the calibration of magnetometers for low magnetic field and the tests for low magnetic field characteristics of sensors and materials. In the range of 1 mT, the expanded uncertainty of dc is 8${\times}$10$\^$-6/, ac uncertainties are 0.16% in 0.1～1 kHz, 0.26% in 1～5 kHz, and 0.44% in 5～20 kHz. We have been participated in international key comparison(KC) to achieve the equality and the mutual agreement between standard institutes for the results of calibrations and tests. KRISS participating in ac-dc magnetic flux density of KC got equal level of uncertainty results compare with the advanced nations. It confirm that measurement ability of magnetic flux density is high level in the world.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.51-54
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• 2013

This paper deals with harmonic components of the voltage on high temperature superconducting wire carrying an alternating current. HTS wire is used to manufacture superconducting power applications carrying an alternating current. Typically, international standard, IEC 61788-3 is used for critical current measurement. Thus, it is not ideal that critical current criteria in dc are adapted to superconducting power devices to decide the operating current of the devices. In this paper, we confirmed odd harmonic voltage on HTS wires carrying an AC. The ratio between harmonic components and fundamental component can be significant clues to decide the critical current criteria for HTS wire and its power applications in AC circumstance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.6
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• pp.313-316
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• 2006

A method for evaluation of the linearity of both the ratio error and phase angle error in the current transformer(CT) comparison measurement equipment has been developed by employing the standard resistors with negligible AC-DC resistance difference less than $10^{-5}$. The non-reactive standard resistors for the linearity check of the system are used as the external burden connected with the secondary of CT under test. These burdens consist of nine standard resistors, with the nominal resistance of $0.01{\Omega},\;0.1{\Omega},\;0.2{\Omega},\;0.4{\Omega},\;0.6{\Omega},\;1{\Omega},\;2{\Omega},\;4{\Omega}$, and $10{\Omega}$. For linearity check, the developed method has been applied in the CT comparison measurement equipment belonging to the industry.

• Journal of Sensor Science and Technology
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• v.7 no.6
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• pp.401-408
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• 1998

A dual-channel automatic ac-dc voltage transfer error measurement system in which the output voltages of two thermal voltage converters which are ac voltage standard are directly measured at the same time to reduce the output voltage drift is described. Forward-reverse measurement method by using a two-channel scanner is used to cancel the offset voltage of the voltmeters. The agreements of the 4-V TVC comparison results between other national standards institute and Korea Research Institute of Standards and Science were less than about ${\pm}2\;ppm$ in the frequency range of $40\;Hz{\sim}100\;kHz$, and were less than about ${\pm}4\;ppm$ at $200\;kHz{\sim}1\;MHz$. Measurement uncertainty is reduced significantly from ${\pm}4\;ppm$ of manual system to ${\pm}3\;ppm$ of new system(up to 100 kHz) typically and great increase in comparison efficiency has been achieved by this system.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.187-193
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• 2015

Purpose: This study was aimed to investigate effects of increased breath alcohol concentration (BrAC) which is the standard measurement of alcohol consumption in sobriety test under current laws on visual acuity and values of objective refraction. Methods: For twenty three males in 20s (average age $21.17{\pm}2.19$ years, body mass index (BMI) $22.09{\pm}2.16$) were selected. Distance and near visual test was performed at BrAC of 0%, 0.05% and 0.08%, and objective refraction with open-field auto-refractometer was also performed at different BrAC. Results: As breath alcohol concentration is increased, distance visual acuity was decreased, which was statistically significant, but near visual acuity was not changed. Also, values of objective refraction tended to be increased towards minus as breath alcohol concentration is increased. Conclusions: As breath alcohol concentration is increased, corrected visual acuity is decreased and refractive power is towards minus, it is necessary that visual acuity test and refraction measurement should be conducted under sober condition.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.203-208
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• 2023

In this study, we propose a method to improve the precision of contact resistance measurement circuits using constant current method and voltage drop method, and implement a dashboard that monitors the measured data of contact resistance measurement systems through MQTT broker server. The contact resistance measurement system measures the resistance value and transmits the measured value to the MQTT broker server using wireless communications. This developed dashboard uses Node-RED and Node-RED-Dashboard to receive the resistance values of up to four contact resistance measurement systems and show them to user's monitor screen. Users can manage multiple measurement data using a single dashboard and easily interface with other devices through the MQTT broker server. Through the experimental results from real data measurements, the relative standard deviation about precision is improved to average 40.37% and maximum 64.73% respectively.

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.23-26
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• 1999

The Langmuir adsorption isotherm at the $(Pt)/0.1M\;H_2SO_4$ electrolyte interface has been qualitatively analyzed using the ac impedance measurement and phase-shift method. The phase shift $(\phi)$ depends on both the cathode potential (E<0) and frequency (f) and is inversely proportional to the factional surface coverage $(\theta)$. At an intermediate frequency band (ca. $1\~100$ Hz), the phase-shift profile $(\phi\;vs.\;E)$ can be related to the fractional surface coverage $(\theta\;vs.\;E)$. The phase-shift profile $(\phi\;vs.\;E)$ can be used as an experimental method to estimate and analyze the Langmuir adsorption isotherm $(\theta\;vs.\;E)$. The equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the adsorbed hydrogen atom $(H_{ads})\;and\;3\times10^{-4}$ and 20.1 kJ/mol, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.422-429
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• 2009

Meridian which used as the basic theory of acupuncture treatment, is an important functional connection system of acupuncture point in oriental medicine. Yangdorak and EAV have lack of precision because of using 2-electrode method, occurring high non-uniformed current density and electrode contact status on electrode placement spot. Therefore we implemented a meridian impedance measurement system for measuring meridian impedance using 4-electrode method. In order to confirm the precision of developed system, we made an constant current characteristic experiment using standard resistor. As a results of clinical study with 18 subjects, the meridian impedance showed that reproductivity and repeatability of HT7 acupuncture point are $0.515[k{\Omega}]{\pm}0.000$(mean${\pm}$standard deviation) and $0.515[k{\Omega}]{\pm}0.002$, respectively. And reproductivity and repeatability of PC7 are $0.521[k{\Omega}]{\pm}0.000$ and $0.521[{\Omega}]{\pm}0.001$ respectively. The proposed system was stable and reliable. Therefore this study proved AC impedance method to valid in measuring meridian impedance, and also verified precision and repeatability of the proposed meridian impedance measurement system. The proposed system will serve as more effective method of measuring meridian phenomena as a bioelectric signal in clinical practice.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.1
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• pp.1-5
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• 2008

The output voltage value of AC high voltage source has been usually obtained by multiplying low voltage value measured at both terminals of low voltage resistor by the dividing ratio of the high voltage capacitive divider. From the dividing ratio determined of each 200 kV capacitive divider, we have developed step-up method for measuring the output voltage up to 400 kV using two same type of 200 kV capacitive dividers connected in series. The theoretical dividing ratio of 400 kV capacitive dividers connected in series coincides with that of manufacturer's certification within measurement uncertainty. Thus, this developed step-up method makes it possible to extend the range of output voltage from 200 kV to 400 kV. Furthermore, The dividing ratio of divider under test obtained using this step-up method is consistent with that obtained using one 200 kV high voltage divider within corresponding uncertainties.