• 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 KIEE Conference
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• 1990.07a
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• pp.215-220
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• 1990

A.C. impedance properties of $RuO_2$ based thick film resistors which having different resistivity value (DuPont 1721 : $100{\Omega}$/ sq., 1741 : $10K{\Omega}$/sq.) were investigated using by impedance analyzer. In case of lower resistivity 1721 system, the complex impedance was composed nearly R component for all speciman sintered at above $600^{\circ}C$, and the frequency dependancy on impedance was not affected very much up to 5MHz and again gradually increase with increasing the frequency. In case of higher resistivity 1741 resistor system, impedance properties were very depandant on sintering temperature. When sintering temperature was $600^{\circ}C$, the complex impedance plot shows a vertical line, which correspond to lone capacitance equivalant circuit, and the impedance linearly decreased with increasing frequency. In case of speciman sintered at $700-900^{\circ}C$, the complex impedance plot shows semi-circular are correspond to a lumped RC combination, and the impedance shows constant value to 5MHz, again decreased with increasing frequency. But the complex impedance behavior of speciman sintered at $1000^{\circ}C$ was shows the equivalent circuit correspont to parallel combined LCR component, and the impedance was not varied with frequency.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.387-389
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• 1998

For the continuous and exact measurement of load impedance of AC power system on the electric railway, this paper presents a method to show the load area to resistance(R)-reactance(X) plane of impedance plane. The load area is presented in terms of impedance which is in the ratio of voltage and current continuously measured and impedance plane indicates the protection area of fault locator. The proposed method is verified its reasonability by computer simulation, and using this method we will develop the power system impedance analyser which is available actual application.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.12
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• pp.1366-1371
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• 2011

In ultra precision machining, it is necessary to adjust the horizontality and reference position of a workpiece in a noncontact manner. For this, a simple process by measuring impedance between a tool tip and a workpiece which are connected to impedance analyzer is proposed. As the distance between the tool and the workpiece gets closer, the reduction rate of impedance becomes higher over all frequency ranges. By setting threshold value of impedance reduction rate at specific frequencies through preliminary experiments, the distance between the tool and the workpiece can be predicted and it directly enables us to horizontalize the workpiece and to set the tool to the desired reference position.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.137-138
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• 2006

In this paper, we study the algorithm for the multiport measurements using the 2port VNA(Vector network Analyzer). We explain the conversion algorithm which the open impedance to the matched impedance(50 ohm), and then we apply this algorithm to the 4 port VNA measurement. Finally, we discuss the reliability of this algorithm.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.243-248
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• 2011

The purpose of this study is to develop a sensing system to measure the capacitance of a pre-developed engine oil deterioration detection sensor integrated with an oil filter. To measure the capacitance of engine oil in the sensor, it is used the way measuring the electric charging time in a capacitor by impressing DC volt. This method has merits on cost and signal stability. The measured capacitance is compensated by comparison with the one measured by an impedance analyzer. Also, using the dielectric constant gained by an impedance analyzer, the calculating equation of the dielectric constant of engine oil related with the currently developed sensor is decided. Finally, the degradation degree of engine oil is estimated according to the change rate of dielectric constant between green oil and used oil. The newly developed personal controller is to control a series of the processes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.872-879
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• 2017

This work presents a cable fault monitoring system based on the differential frequency domain reflectometry using a compact impedance analyser which is composed of a direct digital synthesizer, an op amp and a gain/phase detector with a micro controller. The proposed system can replace expensive vector network analysers for frequency domain reflectometry and therefore be deployed in sensor networks for long term multi-point cable monitoring. Effectiveness of the system is experimentally confirmed by diagnosing the status of the power cable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.265-271
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• 2018

This paper presents a method for detecting damage to a structure at low cost using its impedance. The impedance technique is a typical method to detect local damage for structural health monitoring. This is a common technique for estimating damage by monitoring the electro-mechanical admittance signal of the structure. To apply this technique, an expensive impedance analyzer is generally used. On the other hand, it is necessary to develop a low-cost variant to effectively disseminate the technique. In this study, a method based on the transfer impedance using a function generator and digital multimeter, which are generally used in the laboratory instead of an impedance analyzer, was developed. That is, this technique estimates the damage by comparing the damage index using the amplitude ratio of the output voltage measured in the healthy and damaged state. A transfer impedance test was carried out on a steel specimen. By comparing the damage index, the presence of damage could be assessed reasonably. This study is a basic investigation of an impedance-based low-cost damage detection method that can be used effectively for structural health monitoring if supplemented with future research to estimate the damage location and severity.

• Proceedings of the Korean Magnestics Society Conference
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• 1993.11a
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• pp.16-17
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• 1993

• Journal of Radiation Protection and Research
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• v.38 no.4
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• pp.202-207
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• 2013

Bioimpedance involves a lot of information related to living tissue. If there is alteration in bio tissue, its electrical characteristics also change. It is to study electrical characteristics of pork tenderlion in using a HP-4194A Impedance/Gain-phase analyzer instrument and electrical characteristics changes by graded radiation exposure dose. The results were as follow 1. Electrical characteristics of pork tenderlion in repeated measurement had high precision within ${\pm}5$% of coefficiency of variability. 2. During the measurement impedance absolute value and phase alteration did not show statistically significant difference.(p>0.05) 3. While impedance phase of electrical characteristics associated with frequency change was almost stable, impedance absolute value was in inverse proportion to frequency that means high inverse correlation of -0.096(r). 4. Impedance absolute value dropped in radiation exposure dose. The alteration of the value did not show statistically significant difference in 1 Gy, 2 Gy and 4 Gy.(p>0.05) However in radiation exposure dose of 10 Gy, the decrease of impedance absolute value was significantly different.(p<0.05) 5. Impedance phase according to radiation exposure dose change did not show statistically significant difference in 1 Gy, 2 Gy, 4 Gy, and 10 Gy(p>0.05).