• 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 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 KIEE Conference
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• 2007.07a
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• pp.1287-1288
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• 2007

The cross capacitor electrode system applied Thompson-Lampard theorem for precise and accurate measurement of dielectric constants is studied in this study. The capacitance derived from cross capacitor is calculated by the equation of ($C=\frac{{\epsilon}ln2}{\pi}{\cdot}$ effectivelength of electrode) which is very different from the equation of capacitance derived from parallel plate capacitor. From above mentioned reason, the capacitance measurement uncertainty of cross capacitor can be reduced then that of the parallel plate capacitor. the measurement dielectric constant measured by cross capacitor electrode method is one order more accurate and precise than that of 3-electrode method.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.33-38
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• 2002

To establish the national standard of capacitance, four main electrodes of the cross capacitor which were evaluated to linearity and roundness less the $\pm 1 \mu m$ respectively have to be adjusted symmetrically in an inner cylinder. Four LM shafts with diameter of 5 mm were installed between main electrodes of the cross capacitor, and the electrodes were adjusted, as the first step, by means of the measured capacitance. In the second step, the symmetrical adjustment up to $\pm 1.2\mu m$ was performed by using a ball sensor, ball-type movable sensor, non-contacting capacitive sensor and upper guard sensor which were developed in this project.