Design and construction of capacitive sensor for monitoring different liquid mixtures

In this paper design and operation of a capacitive cell sensor for liquid mixturemonitoring is reported. The capacitive effect of small drop of different liquids in tap water wasstudied using this capacitive sensor. A small percentage of contaminating agents such as oil in tapwater is determined with a good sensitivity. Important factors concerning operation of the sensorsuch as the precision, reproducibility, and stability are reported. Output variation of the measuredvalues with the temperature (27-73.5 ˚C) is also investigated for tap water and different watermixtures. An averaged variation of 0.8348 μF/˚C in output measurement for tap water isobtained. Our results indicate an averaged variation of 0.4324 μF/˚C for the fresh oil and avariation of 0.5121 μF/˚C for the used water oil mixture. An averaged variation of 0.4840 μF/˚Cfor methanol, 0.5048 μF/˚C for the ethanol, and 0.8250 μF/˚C for water antifreeze mixtures areobtained. For water + salt mixture our data shows that the sensitivity change exhibits a factor of12.69 increases in sensitivity when temperature increases from 24.7 ˚C to 40.0˚C. Hence todetermine a trace impurity, this methodology provides more accurate results at low temperatures(room temperature) and requires less temperature compensation for calibration.

Keywords:

Water Mixture , Monitoring , Sensor , Capacitance , Resistance