• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.147-153
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• 2008

Improvement of the selectivity of nonenzymatic glucose based on mesoporous platinum ($H_1$-ePt) by using A.C. impedance is reported. The idea of the present work is based on the novel effect of the mesoporous electrode that the apparent exchange current due to glucose oxidation remarkably grows although the reaction kinetics on the surface is still sluggish. It is expected that the enlarged apparent exchange current on the mesoporous electrode can raise the sensitivity of admittance in A.C. impedance to glucose concentration. At a low frequency, A.C. impedance could become more powerful. The admittance at 0.01 Hz is even more sensitive to glucose than to ascorbic acid while amperometry exhibits the inverse order of sensitivity. This is the unique behavior that is neither observed by A.C. impedance on flat platinum electrode nor obtained by amperometry. The study shows how the combination of A.C. impedance and nano-structured surface can be applied to the detection of sluggish reaction such as electrochemical oxidation of glucose.

• Agricultural and Biosystems Engineering
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• v.2 no.2
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• pp.63-68
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• 2001

The objective of this study was to develop a real-time soil moisture meter using RF impedance. The impedance suchas capacitance and resistance (or conductance) was analyzed using parallel cylinder type capacitance probe(C-probe) and Q-meter (HP4342). The capacitance and conductance of soil increased as volumetric water content increased. The 5 MHz of modified Colpitts type crystal oscillator was designed to detect the capacitance change of the C-probe with moist soil. A third order polynomial regression model was proposed to describe the relationship between RF impedance and volumetric water content. The prototype real time moisture meter consisted of the C-probe, sample container, oscillator, frequency counter and related signal processing units. The calibration equation for measurement of volumetric moisture content of soil was developed and validated. The correlation coefficient and root mean square error between measured volumetric water content by oven method and predicted values by prototype moisture meter for unknown soil samples were 0.984 and 0.032$cm^3$$cm\^3$, respectively.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.469-470
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• 2007

In this paper, we propose a simple and relative electrode contact monitoring method. By exploiting the power line interference, which is regarded as one of the worst noise sources for bio-potential measurement, the relative difference in electrode impedance can be measured without a current or voltage source. Substantial benefits, including no extra circuit components, no degradation of the body potential driving circuit, and no electrical safety problem, can be achieved using this method. Furthermore, this method can be applied to multi-channel isolated bio-potential measurement systems and home health care devices under a steady measuring environment.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.8
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• pp.374-379
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• 2002

In this study, we developed a new human arm movement detection system using electrical bio-impedance method with several skin-electrodes. The correlation coefficients of the joint angle and the impedance change from human arm movement was obtained using a goniometer and impedance measurement system developed in this study. The correlation coefficients of the wrist and the elbow movements were 0.94 and -0.99, respectively. This system was applied to control a robotic arm by converting the measured impedance to joint angle to confirm the validity of the proposed system. In conclusion, we confirmed that this system can control the robotic arm according to arm movement without any limitation of movement. This system showed possibility that upper arm movement could be easily measured by impedance measurement system with a few skin-electrodes.

• Journal of Sensor Science and Technology
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• v.13 no.6
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• pp.462-472
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• 2004

In this study, we measured the blood flow on arm by non-invasive method and implemented a system to measure variation of the blood flow by estimating bio-electrical impedance and arterial pressure according to cuff pressure. The implemented system measured impedance variation according to pressure variation applied by artificial cuff pressure on the measuring position. The system consisted of pressure measuring part and impedance measuring part using 4-electrode method. Pressure measuring part was composed of semiconductor pressure sensor and electronic circuit for signal processing of sensor output signal. In addition, impedance measuring part was composed of constant current source circuit and lock-in amplifier for detecting impedance signal. We conducted experiments of impedance measuring part using standard resistance for performance evaluation of the implemented system. In addition we experimented to estimate variation of the blood flow by measuring impedances of the experimental group. We estimated ratio of the blood flow resistance using mean arterial pressure and variation of the blood flow. As a result the ratio of the blood flow resistance and variation of blood flow were in an inverse relationship with each other and the correlation coefficient was -0.96776.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.197-198
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• 2008

본 논문은 Impedance plethysmography를 이용하여 당뇨병 및 동맥경화의 비침습적이고 고통없는 조기 진단을 위한 시스템 구성의 초기 단계로, 하지 동맥의 기계적 특징인 혈량 변화를 비침습적으로 측정하였다. 혈량과 혈압의 변화는 각각 Impedance plethysmograph와 mercury spbygmomanometer를 이용하여 측정되는데 탄성도는 혈량 변화값을 맥압(수축기압)의 변화량으로 나누어 계산한다. 이 논문에서는 하지 동맥의 탄성도를 비침습적으로 측정하기 위한 전초 단계로서 하지 동맥에서의 임피던스 변화만을 측정하였다. 회로는 50kHz Wien bridge 발진 회로, demodulation, 50kHz band past filter, 0.1Hz high pass filter, 20Hz low pass filter와 증폭기로 구성하였고, 생체 신호 획득 및 처리 과정을 거쳐 임피던스 변화량을 관찰하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.230-234
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• 2005

Fabrication of MEA is important factor for proton exchange membrane fuel cell (PEMFC). MEA of PEMFC with hot pressing and direct coating method were prepared, and performances were evaluated and compared each other. The effect of MEA preparation methods, hot pressing methods and direct coating methods, on the cell performance was analyzed by impedance spectroscopy and SEM. The performance of PEMFC with direct coating method was better than with hot pressing method because membrane internal resistance and membrane-interfacial resistance were reduced by elimination of hot pressing process in MEA fabrication. In addition the micro structure of MEA with direct coating method reveals uniform interface between membrane and catalyst layer.

• Korean Journal of Acupuncture
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• v.29 no.4
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• pp.563-572
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• 2012

Objectives : The aim of this study was to suggest a new method to estimate the resistance by acupoint compositions by using the multi-frequency bioelectrical impedance analysis(MF-BIA) of 5 kHz, 50 kHz and 200 kHz within 2 cm of acupoints as a local segment. Moreover, we try to confirm the relation to between measured resistance at skin surface and measured resistance by various manual acupuncture needle insertion depth. Methods : Ten male subjects participated in this study. We measured the resistance at left/right ST36 at skin surface and various manual acupuncture needle insertion depth(skin, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm and 30 mm). Results : It was also observed that the all measured resistances were the highest at 5 kHz and the lowest at 200 kHz. There were significant differences at 5 kHz, 50 kHz and 200 kHz between measured resistance at skin surface and measured resistance by various manual acupuncture needle insertion depth(p<0.05). There was no significant difference in the left and right identical acupoints under the identical condition(p>0.05). Conclusions : We conclude that the measured resistance at skin surface has limitation as to reflect the information of tissue. However, the measured resistance at each frequency was changed as similar pattern by different insertion depth. Hence, we confirmed the possibility of assumption on information of tissue which was expected to locate an acupoint.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.9-14
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• 2023

In this work, we developed a Nafion polymer-coated impedance sensor with two gold electrode configurations to measure the ion concentration in solution samples. The gold electrodes were fabricated through the sputtering process, followed by surface modification using Nafion polymer. The resulting sensors enable the prevention of the polarization phenomenon on the electrode surface, resulting in stable measurement of electrochemical signals. Spectroscopy and scanning electron microscopy measurements revealed that the thin film of Nafion was coated uniformly onto the surface of the gold electrode. The Nafion-coated sensor exhibited more stable impedance signals than the conventional gold electrode. It showed a highly reliable calibration curve (R² = 0.983) of the impedance sensor using a standard sodium chloride solution. In addition, a comparison experiment between the impedance sensor and a commercial conductivity sensor was performed to measure the ion concentration of artificial tears, showing similar results for the two sensors.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.6
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• pp.1070-1074
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• 2008

Body fat correlation formula induced by using optical method was used white light LED source and electrical method used BIA(Bio-electrical Impedance Analysis) method measured at same time. In the case of BIA method confirmed phase difference of 6 degree and voltage drop of 2.7V at 5V and 50kHz's input signal. In the case of optical method confirmed that optical intensity increased by order of the biceps, the fleshy inside of the thigh and the triceps. We obtained percent body fat of 20% with the body fat correlation formula induced by photo-electricity method.