• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1163-1168
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• 2013

The maximum allowable value of loop impedance($Z_s$) to secure the operation of overcurrent protective devices and the safety for indirect contact is a very important in TN-C-S system. The loop impedance is divided into inner loop impedance which consumer can adjust and external loop impedance($Z_e$) which only electric operator can adjust. Thus, an external loop impedance which limits to less than a certain value is a very important factor for human body protection against electric shock in TN-C-S system. The concept of loop impedance($Z_s$) is recently introduced to the domestic, the study about external loop impedance is yet insufficient. However, the study about the reference impedance as specified by the IEC 60725 standard to improve the quality and reliability of the power supply is being made. In this paper, reference value of external loop impedance($Z_e$) to meet domestic environment will be proposed by the nationwide measurement and statistical analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1194-1197
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• 2004

High temporal-resolution and accurate measurement of skin impedance locus provides useful data for the identification of the physiological/psychological changes and also the identification of acupuncture point. An impedance spectroscopy method using digitally constructed current waveform consisting of many frequency components (multiples of 1Hz) was reported3. The time resolution of the method depends on the lowest frequency used in the waveform construction, and therefore, the measurement would be faster if the lowest frequency is the higher. However, it was not clear that how many and how low frequencies must be used for the estimation of the skin impedance parameters from which the impedance locus can be drawn. This study shows the relationship between the estimation error of the impedance parameters and the frequency coverage of the spectroscopy. The results of this study are expected to serve as the reference of the frequency selection in the impedance spectroscopy.

• Journal of information and communication convergence engineering
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• v.15 no.2
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• pp.123-130
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• 2017

The early detection of intravenous (IV) infiltration is necessary to minimize the injury caused by the infiltration, which is one of the most important tasks for nurses. For detecting early infiltration in patients receiving invasive vein treatment, bioelectrical impedance was measured using multi-frequency bioelectrical impedance. The impedance decreased significantly at infiltration, and then decreased gradually over time after infiltration. The relative impedance at 20 kHz decreased remarkably at infiltration, and then gradually decreased thereafter. In addition, the impedance ratio increased temporarily at infiltration and then gradually decreased over time. Furthermore, the impedance at each frequency decreased quantitatively over time. This indicates that IV solution leaking from the vein due to infiltration accumulates in the subcutaneous tissues. Moreover, slopes of log Z vs. log f differently decreased with increasing log f, indicating that the impedance exhibits different responses depending on the frequency.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.46-48
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• 2007

In this study, we determined the optimum electrode pair for measuring the abdominal pressure using bio-impedance method. Because impedance changes differ from a weight, a height, contractile force, volume of muscle and blood other or whatever of individuals, it was quantified using values of impedance change, correlation coefficient and SNR. Our results showed the optimum electrode pair (1, 9) which could detect impedance changes due to an increase of the intensity of the abdominal pressure. The correlation coefficient and quadratic function between the RMS values of EMG and the impedance changes were 0.87 and $y=0.0014x^2$+0.0620x+0.6958, respectively. It demonstrated that the abdominal pressure could be measured non-invasively and simply using bio-impedance method. We propose that this optimum electrode configuration would be useful for future studies involving the convenient measurement of abdominal pressure by ambulatory urodynamics monitoring study.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1159-1175
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• 2015

In this study, the effect of temperature variation on the wireless impedance monitoring is analyzed for the tendon-anchorage connection of the prestressed concrete girder. Firstly, three impedance features, which are peak frequency, root mean square deviation (RMSD) index, and correlation coefficient (CC) index, are selected to estimate the effects of temperature variation and prestress-loss on impedance signatures. Secondly, wireless impedance tests are performed on the tendon-anchorage connection for which a series of temperature variation and prestress-loss events are simulated. Thirdly, the effect of temperature variation on impedance signatures measured from the tendon-anchorage connection is estimated by the three impedance features. Finally, the effect of prestress-loss on impedance signatures is also estimated by the three impedance features. The relative effects of temperature variation and prestress-loss are comparatively examined.

• Smart Structures and Systems
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• v.22 no.1
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• pp.1-11
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• 2018

This study presents early crack detection of steel fiber-reinforced concrete (SFRC) under varying temperature and humidity conditions using an instantaneous electrical impedance acquisition system. SFRC has the self-sensing capability of electrical impedance without sensor installation thanks to the conductivity of embedded steel fibers, making it possible to effectively monitor cracks initiated in SFRC. However, the electrical impedance is often sensitively changed by environmental effects such as temperature and humidity variations. Thus, the extraction of only crack-induced feature from the measured impedance responses is a crucial issue for the purpose of structural health monitoring. In this study, the instantaneous electrical impedance acquisition system incorporated with SFRC is developed. Then, temperature, humidity and crack initiation effects on the impedance responses are experimentally investigated. Based on the impedance signal pattern observation, it is turned out that the temperature effect is more predominant than the crack initiation and humidity effects. Various crack steps are generated through bending tests, and the corresponding impedance damage indices are extracted by compensating the dominant temperature effect. The test results reveal that propagated cracks as well as early cracks are successfully detected under temperature and humidity variations.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.5
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• pp.345-352
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• 2004

Currently, high data rate PLC(Power Line Communications), up to 100 Mbps, which use frequency bandwidth between 2 MHz and 30 MHz is investigated very hard, and commercial PLC modem for low voltage powerline network (indoor) is coming soon into communication market. For the purpose of developing a fit communication system which has little distortion of signal and attenuation, it is surely necessary to know about channel environments of powerline. Especially, the impedance measurement of the powerline and impedance matching are very important. As is known, since medium-voltage powerline (22.9 ㎸) is still working, it is not so simple to measure the powerline impedance. In our study, a portable impedance measurement equipment is developed. It consists of coupling capacitor, a drain coil and impedance matching transformer. The equipment is easily connected to medium voltage line and impedance of power line is measured using a network analyzer. Also, measurement results are used for impedance matching of PLC signal. In fact, matching transformer with several different impedances are used. The matching transformer is connected between coupling capacitor and signal port. In this paper, the developed portable impedance measurement equipment and impedance measurement results are presented. Also impedance matching technique using matching transformers will be explained. We showed the result of the improved performance by the impedance matching.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2887-2890
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• 2003

This paper describes the possibility of analyzing gait pattern from the variation of the lower leg electrical impedance. This impedance is measured by the four-electrode method. Two current electrodes are applied to the thigh, knee, and foot, and two potential electrodes are applied to the lateral, medial, and posterior position of lower leg. The correlation coefficients of the joint angle and the impedance change from human leg movement was obtained using electrogoniometer and 4ch impedance measurement system developed in this study. We found the optimal electrode position for ankle, knee and hipjoint movements based on high correlation coefficient, least interference, and maximum magnitude of impedance change. The correlation coefficients of the ankle, knee, and the hip movements -0.87, 0.957 and 0.80. respectively. From such features of the lower leg impedance, it has been made clear that different movement patterns exhibit different impedance patterns and impedance level. This system showed possibility that lower leg movement could be easily measured by impedance measurement system with a few skin-electrodes.

• Structural Monitoring and Maintenance
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• v.1 no.3
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• pp.339-356
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• 2014

This study has been motivated to evaluate the practicality of numerical simulation of impedance monitoring for damage detection in steel column connection. In order to achieve the objective, the following approaches are implemented. Firstly, the theory of electro-mechanical (E/M) impedance responses and impedance-based damage monitoring method are outlined. Secondly, the feasibility of numerical simulation of impedance monitoring is verified for several pre-published experimental examples on steel beams, cracked aluminum beams, and aluminum round plates. Undamaged and damaged steel and aluminum beams are simulated to compare to experimental impedance responses. An aluminum round plate with PZT patch in center is simulated to investigate sensitive range of impedance responses. Finally, numerical simulation of the impedance-based damage monitoring is performed for a steel column connection in which connection bolts are damaged. From the numerical simulation test, the applicability of the impedance-based monitoring to the target steel column connection can be evaluated.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1979.05a
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• pp.4.2-4
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• 1979

Since Metz had employed the impedance audiometry in 1946, scholars have carried out many investigation. Brook, Jeger, Cooper reported and evaluated the clinical studies of impedance audiometry and its screening test. Recently, in Korea, a studies of impedance audiometry have been reported. We analysed 100 children aged between 7-16 years old who visited OPD of E.N.T. department with the complaints of the nasal obstruction and hard of hearing from Nov. 77-Feb. 79. Through the use of otoscope and impedance audiometry, we evaluated the types of tympanogram, static compliance and the acoustic reflex. This paper is dealing with the statistical study of impedance audiometric result and its literature.