• 전기화학회지
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• 제11권3호
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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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• 제2권2호
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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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.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권8호
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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.

• 센서학회지
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• 제13권6호
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 학술대회 논문집 정보 및 제어부문
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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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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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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• 제29권4호
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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.

• 공업화학
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• 제34권1호
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• pp.9-14
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• 2023

본 논문에서는 용액의 이온 농도 측정이 가능한 나피온 폴리머(Nafion polymer) 코팅 기반 2상 금 전극의 임피던스(Impedance) 센서를 개발하였다. 스퍼터링(Sputtering) 공정을 통해서 제작된 금 전극의 표면을 나피온 폴리머를 사용하여 표면 개질 하였다. 상기 제작된 전극은 분극 현상 제어가 가능하여 전기화학적 신호를 안정적으로 측정할 수 있도록 하였다. 분광학과 전자주사현미경 관찰을 통하여 박막의 나피온 폴리머 코팅을 확인하였다. 나피온 코팅이 된 전극은 기존 금 전극에 비해 안정적인 임피던스 신호를 보여 주었으며, 표준 염화나트륨(NaCl) 용액 사용 시 임피던스 센서의 신뢰성 높은 검정 곡선(R² = 0.983)을 나타내었다. 또한, 임피던스 센서는 상용화 전도도 장치와 인공 눈물의 이온 농도 측정 비교 실험을 진행하였으며, 유사한 결과값을 확인하였다.

• 한국정보통신학회논문지
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• 제12권6호
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• pp.1070-1074
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• 2008

광학적 방식은 백색광 LED광원을, 전기적 방식은 BIA(Bio-electrical Impedance)방식을 이용하여 동시에 측정할 수 있는 광전기적 지방측정에 관한 상관식을 유도하였다. 실험을 통해서 BIA 방식의 경우 5V 및 50kHz의 입력 교류 신호에 대해 6도의 위상차와 2.7V의 전압 강하를 확인하였다. 광학적 방식의 경우 이두박근, 허벅지, 삼두박근의 순으로 광강도가 높아지는 것을 확인하였다. 측정된 광전 방식의 값은 상관식에 의해서 20%의 퍼센트 비만도를 얻었다.