Design of Capacitive Sensor for Concentration Measurement

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 100 Hz 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 degC 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