• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1084-1087
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• 2002

The guard-ring type 3-terminal parallel plate electrodes proposed by ASTM D 150-81 and IEC 250 have been widely used for measurement of dielectric constants of solid dielectrics. However the method using this electrodes causes many uncertainty associated with the measurement errors of the diameter of the guarded electrode. the gap between guarded and guard-ring electrode. the distance of two active electrodes(the thickness of specimen), the roughness and contamination of surface of electrode and specimen. close adherence grade of electrode and specimen. In this paper. a new electrode system of cross capacitance type based on Thompson-Lampard theorem is designed and is employed for the measurement of dielectric constant. The results of simulation of guard-ring electrode and cross capacitance electrode using FEM program show that distance measurement between two electrodes in guard-ring electrode produces large uncertainty. on the other hand this effect in cross capacitance electrode is negligible. Furthermore. the air gap effects in the cross capacitance electrode is 5.6 times less sensitive than that in guard-ring electrode by assuming air gap of $50{\mu}m$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.482-483
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• 2007

For measurement of dielectric constants, the commercial parallel plate electrodes system with guard-ring electrode have been widely used up to now. The capacitance derived from the parallel plate electrodes capacitor with guard-ring electrode is calculated by the equation of ($C={\epsilon}\;{\cdot}\;\frac{area\;of\;electrod}{distance\;between\;electrodes}$). Therefore, in parallel plate electrode capacitor, the diameter of the guarded electrode, the gap size between guarded electrode and guard ring, and distance between two active electrode should be measured precisely to calculate dielectric constants from the measured capacitance. Consequently their mechanical measurement uncertainties are directly contributed. Especially the air-gap between the electrodes and dielectric specimen at the system must be existed and the measurement error derived from the air-gap is impossible to evaluate as measurement uncertainties. In this study, we analyze the uncertainty of the commercial dielectric constant test cell using 3 kinds CRMs.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.9
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• pp.443-448
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• 2006

Non-contacting capacitive sensor based on Thompson-Lampard theorem have been fabricated and characterized for measuring of 때 order displacements. To overcome disadvantages of the existed capacitive sensors of parallel plate type with 2-electrodes and 3-electrodes, the developed new sensor was designed to have 4-electrodes with a constant gap of 0.2mm between the electrodes. Two of the electrodes were used as a high potential electrode and a low one, the other two electrodes were used as guard electrodes. These electrodes were made from copper using RF sputtering system on a sapphire plate with diameter 17 mm and thickness 0.7 mm. This sensor can be used for measuring the distance not only between the sensor and metallic target connected to ground potential but also non-metallic target without ground connection.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.1285-1286
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• 2005

• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.214-219
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• 2002

The influence of ultraviolet (UV) irradiation and corona on the surface degradation of high temperature vulcanized (HTV) silicone rubber used for outdoor insulation through measuring surface voltage decay after corona charging, surface resistivity, contact angle and X-ray photoelectron spectroscopy (XPS) analysis was studied. The surface resistivity calculated by the surface voltage decay was compared with a value directly obtained from the three electrode method having the guard ring electrode. A good agreement between the two methods for surface resistivity was obtained. UV treated specimens showed the slower decrease of surface voltage decay, while the corona exposed specimens showed a dramatically faster decrease. Although both artificial treatments cause the same oxidative products, which was confirmed with XPS, we could distinguish the difference between the reactions of the two treatments by monitoring the surface voltage decay on corona-charged specimen. In addition, we could derive the specific surface states of the silicone rubber treated by accelerated artificial aging factors and the degradation process.

• Progress in Medical Physics
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• v.15 no.2
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• pp.59-62
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• 2004

We developed very small parallel plate radiation detector by using our existing experience of mating radiation dosimeter and capability of analyzing characteristics of dosimeter. The radiation detector was consisted of microfilm and carbon electrode. The detector was parallel plate type of all-filled ionization chamber. The ionization chamber had been fabricated using an acrylic plate for the air cavity and carbon coated microfilm for electrical configuration. The alr gap between two electrodes was 0.48 mm. The diameters of collect electrode and guard electrode were 3.3 mm, 5 mm respectively. The diameter of high voltage electrode was 5 mm. Nominal sensitive volume of the chamber was 0.016 ㎤. The major parameters of the chamber characteristics such as leakage current, reproducibility, dose rate effect, and polarity effect were measured. The experimental results were as followings. Leakage current was 0.1 pA. Standard deviation of reproducibility was less than 0.1%. Dose rate effect was less than 1.5%. Polarity effect was less than 2.4%. These data were comparable to those of commercially available dosimetric system for QA-purpose. As the result, we found that the radiation detector consisting of the ionization chamber, microfilm and carbon electrode, was satisfactory for the purpose of the small field dosimetry in size and characteristics. In the future, We will try to refine the dosimeter for use in very small volume.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.384-398
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• 1996

An improved multi-channel Impedance Void Meter (IVM) is developed to measure an area-averaged void fraction. It consists of a main sensor, a reference sensor and a signal processor. The sensor was designed to be flush-mounted to the inner wall of the test section to avoid the flow disturbances. Guard electrodes are used to obtain evenly distributed electrical field in a measuring volume. A reference sensor is also installed to eliminate the drift in void signal caused by the changes in electrical properties of working fluid. The signal processor with three channels is specially designed so as to minimize the inherent error due to the phase difference between channels. As an example of applications, the mean and fluctuating components of void fraction are measured for bubbly and slug flow regime, and it is shown that IVM has good dynamic resolution which is required to investigate the structural developments of bubbly flow and the propagation of void waves in a flow channel.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.9
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• pp.1085-1094
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• 1992

A variable-spacing cesium thermionic energy conversion test station is designed and fabricated for the study of power generation. The diode is in the form of a guard-ringed plane-parallel geometry in which a polycrystalline rhenium emitter of 2 cmS02T area faces a radiation-cooled polycrystalline rhenium collector of 1.9 cmS02T area. The emission of plasma from heated refractory electrode metal is the driving reaction in the direct conversion of heat to electricity by thermionic energy conversion. The plasma is produced from electrons and positive ions formed simultaneously by thermionic emission and surface ionization of cesium atoms incident on the hot emitter from the cesium vapor in the diode. And high plasma density causes plasma multiplication within the gap due to volume ionization that results in high power output. The variation of the saturation current of a Knudsen converter is investigated at an emitter-collector gap of 0.1 mm and an emitter temperatures. A maximum power output of 13.47 watta/cmS02T is observed at a collector temperature of 963 K and a cesium reservoir temperature of 603 K.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.768-771
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• 2001

Non-contacting capacitive sensor, based on principle of the cross capacitor, for measuring of $\mu\textrm{m}$-order displacements have been fabricated and characterized. To overcome disadvantages of the existed capacitive sensors of parallel type with 2-electrodes and 3-electrodes, the developed new sensor was designed to have 4-electrodes, two of them used high and low electrode the other two used as guard electrodes, on a sapphire plate with diameter 17 mm and thickness 0.7 mm, and are symmetrically situated with a constant gap of 0.2 mm between the electrodes. This sensor can be used for measuring the distance between sensor and target not only the metallic but also non-metallic target without ground connection.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.1
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• pp.53-56
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• 2008

The commercial parallel plate electrodes system with guard-ring electrode have been widely used for measurement of dielectric constants of solid materials. And the specification of the electrodes system is about 1 % of measurement uncertainty. This measurement uncertainty is only estimated the error come from mechanical measurements such as the area of the electrodes and the gap between the electrodes except the error come from the air gap between the electrodes and dielectric specimen. Because it is impossible to measure the air gap. This study analyze the total measurement uncertainties of the commercial dielectric constant test cell using 3 kinds of Standard Reference Materials. As a results, the total measurement uncertainty is much bigger than 1 % and the most of the uncertainty can be reduced by compensation of the error values evaluated in this study.