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    Item type:Publication,
    Analysis of capacitive variation using parallel-plates method
    (2009-12-01)
    Tanachaikhan, Lerdlekha
    ;
    Sriratana, Witsarut
    Capacitive variation of capacitive sensor was analyzed by using two parallel plates coated by 0.4 mm- thick nylon and fixed together by resin to maintain the distance of those two plates at 2.5 mm and 5 mm. In this study, stainless and copper were used for development of capacitive sensor. In this paper Ethel alcohol solution is used as a case study. Ethel alcohol solution with the concentration ranging from 95% to 5% with 10% step decrease of concentration diluted by distilled water was experimented under the controlled temperature of 23°C and the frequency was varied from 100 Hz to 2 kHz with 500 Hz interval. The capacitive variation analyzed from the equivalent circuit which was obtained from the developed sensor was then compared to the electrical circuit obtained from the Good Will R-L-C instrument model CRT to analyze for the appropriate material and the distance between two parallel plates (d) of the sensor. This proposed methodology was developed with consideration of the simple design for easy fabrication and low costs with high accuracy and reliability of the results. ©2009 IEEE.
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    Item type:Publication,
    Design of capacitive sensor for concentration measurement
    (2006-12-01)
    Thong-un, Natee
    ;
    Sriratana, Witsarut
    ;
    Tanachaikhan, Lerdlekha
    This paper presents the analysis of ideal equivalent circuit of the developed concentration sensor probe for chemical solutions by regarding to reasonable costs and reliability of device. The designed sensor probe consists of 2 parallel electrode plates that are coated by Nylon with 0.4 mm thick and mounted together by Resin with 2.5 mm of gap (0.09 times greater than electrode width). Any capacity changes will be compared with the electric circuit that is obtained from the Good Will R-L-C standard instrument, model CTR, at the frequency extending from 100Hz to 2 kHz. From the experiments, it was found that the sensor designed for Ethyl Alcohol solution within concentration of 5% to 95% and 10% concentration interval, at room temperature of 23°C and frequency of 100 Hz, can provide the results with high linearity as well as high resolution of capacity change which is 2 pF per 1% of concentration. © 2006 ICASE.