• Proceedings of the KIEE Conference
• /
• 2005.10b
• /
• pp.75-77
• /
• 2005

When measuring impedance of electronic component and so on, even the small size can reject the interference to shielding object. But, the interference through human body is grown when measuring bioimpedance without establishing shield specially. Consequently, when measuring bioimpedance in this paper, it proposed impedance measurement method to take advantage of spread spectrum technology, so that can reject the interference without establishing shield specially. Spread spectrum impedance measurement method to propose in this paper can reject the interference signal that occurring from medical instruments in the human body, the interference signal that is flowed in from surrounding environment when measuring impedance. It improved SJR(signal to jamming ratio) about 22dB than conventional method that actually realize and experiment spread spectrum impedance measurement method.

• Smart Structures and Systems
• /
• v.4 no.3
• /
• pp.305-318
• /
• 2008

The development of a digital signal processor based prototype is described in relation to continuing efforts for realizing a fully self-contained active sensor system utilizing impedance-based structural health monitoring. The impedance method utilizes a piezoelectric material bonded to the structure under observation to act as both an actuator and sensor. By monitoring the electrical impedance of the piezoelectric material, insights into the health of the structured can be inferred. The active sensing system detailed in this paper interrogates a structure utilizing a self-sensing actuator and a low cost impedance method. Here, all the data processing, storage, and analysis is performed at the sensor location. A wireless transmitter is used to communicate the current status of the structure. With this new low cost, field deployable impedance analyzer, reliance on traditional expensive, bulky, and power consuming impedance analyzers is no longer necessary. A complete power analysis of the prototype is performed to determine the validity of power harvesting being utilized for self-containment of the hardware. Experimental validation of the prototype on a representative structure is also performed and compared to traditional methods of damage detection.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.6
• /
• pp.100-108
• /
• 2008

The transient ground impedance depending on configuration, size, and material of grounding electrodes as well as the shapes of impulse currents, has a significant affect on the performance of the grounding system. This paper presents experimental results in regard to the analysis method of transient ground impedance using the lightning impulse and variable frequency currents. Also a new estimation method to replace the effective surge impedance for transient ground impedance was proposed. The ground electrodes used in this experiment are virtual ground electrodes including both resistance and inductance components, carbon ground electrode with 1[m] length, copper electrode with 9[m] length and counterpoise with 40[m] length. Ground impedances using the proposed method were measured respectively. Comparing with the ground impedance using variable frequency current the conventional ground impedance($Z_1$) calculated from the peak values of impulse voltage and impulse current is observed more correct method for evaluating the performance of ground electrode than the effective surge impedance.

• The Journal of Information Technology
• /
• v.8 no.3
• /
• pp.25-33
• /
• 2005

This paper describe a method for measuring line impedance as a function of frequency for an energized powerline in normal operation. A small sinusoidal signal of a powerline communication utility frequency 30khz$\sim$1Mhz band is continuously injected into the line, and a implemented impedance analyzer calculates the indoor powerline channel impedance from the measured magnitude and phase of resulting voltage and current. The impedance measurement is executed over a range of frequencies to produce a wideband impedance versus frequency characteristic. Implemented impedance analyzer can analysis powerline communication environments measuring line impedance due to load caused in indoor. And measured analysis information through the database can use to evaluate performance of modem and to decide test environment standard.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.297-300
• /
• 2004

Perforated elements are extensively used in mufflers for the intake and exhaust systems of various fluid machines. Perforated elements are usually exposed to grazing flow or cross flow. For analyzing performances of mufflers, the impedance of perforated elements with mean flow is very important. The impedance of perforates under both conditions are measured with different experimental setups. Even if there is no flow, the preceding experimental method for grazing flow shows different values with both theoretical ones and measured under cross flow setup. Using high-order analysis considering phase differences, the experimental method for grazing flow can be modified. The acoustical impedance of perforated impedance contains interaction effects between orifices. After correcting these effects, the measured impedance with grazing flow setup show similar results with both theoretical impedance and measured ones under cross flow setup.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.2E
• /
• pp.46-50
• /
• 2001

The characteristics of radiation impedance are analyzed by algorithms which consists of Finite Element Method (FEM) and Hybrid type Infinite Element Method. The changes of radiation impedance for piston source according to the size and the material properties of baffles are studied. The results of the radiation impedance for rigid finite baffle coincide with other reports. The more the material properties of baffle that comes across the acoustic medium, the more the calculation results of radiation impedance approach the ones without baffle. Therefore, these results can be applied to the design and the radiation characteristics analysis of acoustic transducers.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.7
• /
• pp.503-507
• /
• 1999

Quartz crystal in contact with viscoelastic medium was described directly in terms of the electrical equivalent circuit of the system. Stearic acid was used as viscoelastic medium and deposited on the surface of quartz crystal using the Langmuir-Blodgett(LB) method. Impedance properties of quartz crystal coated with LB films which were investigated by using admittance diagram and $Ζ-\theta$ plot a method of impedance analysis. When stearic acid LB film was deposited on the surface of quartz crystal, resonant frequency of quartz crystal was changed about 100 Hz/layer. This result illustrates the ability of the sensor system to detect small amounts of special gas in air.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.6
• /
• pp.60-67
• /
• 2014

Power system fault analysis is commonly based on well-known symmetrical component method, which describes power system elements by positive, negative and zero sequence impedance. The majority of fault in transmission lines is unbalanced fault, such as line-to-ground faults, so that both positive and zero sequence impedance is required for fault analysis. When unbalanced fault occurs, zero sequence current flows through earth and ground wires in overhead transmission systems and through cable sheaths and earth in underground transmission systems. Since zero sequence current distribution between cable sheath and earth is dependent on both sheath bondings and grounding configurations, care must be taken to calculate zero sequence impedance of underground cable transmission lines. In this paper, EMTP-based sequence impedance calculation method was described and applied to 345kV cable transmission systems. Calculation results showed that detailed circuit analysis is desirable to avoid possible errors of sequence impedance calculation resulted from various configuration of cable sheath bonding and grounding in underground cable transmission systems.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.1
• /
• pp.41-44
• /
• 2005

A new method to reduce the computation time in power/ground-plane analysis is proposed. The existing method using the two dimensional infinite series summation take a lot of computation time. The proposed method is based on the approximation of impedance in the frequency domain through the Mobius transform. This method shows the good accuracy and the high speed in computing. In the case of impedance calculation for 9'x4' board, the proposed method takes 0.16 second of computing time whereas the existing method takes 2.2 second. This method can be applied to the analysis and design of power/ground-plane that need a lot of computation steps.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.2
• /
• pp.342-346
• /
• 2012

This paper presents a loop impedance(inner loop impedance & external impedance) measurement method in TN system. When the measurement of a loop impedance then the measurement result have a some error by load condition. In this paper suggest the loop impedance measurement on actual loading condition by two experiment. one was laboratory condition and the other was the actual measurement on site. Analysis result, measuring error by load condition has not effect on measuring loop impedance.