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http://dx.doi.org/10.12791/KSBEC.2021.30.1.027

Quantification of Rockwool Substrate Water Content using a Capacitive Water Sensor  

Baek, Jeong-Hyeon (Department of Agriculture and Life Science, Graduate School, Korea National Open University)
Park, Ju-Sung (Department of Electronics Engineering, Pusan National University)
Lee, Ho-Jin (Department of Environmental Horticulture, Graduate School, The University of Seoul)
An, Jin-Hee (Department of Agriculture and Industries, Kangwon National University Graduate School)
Choi, Eun-Young (Department of Agricultural Science, Korea National Open University)
Publication Information
Journal of Bio-Environment Control / v.30, no.1, 2021 , pp. 27-36 More about this Journal
Abstract
A capacitive water sensor was developed to measure the capacitance over a wide part of a substrate using an insulated electrode plate (30 cm × 10 cm) with copper and Teflon attached on either side of the substrate. This study aimed to convert the capacitance output obtained from the condenser-type capacitance sensor into the substrate water content. The quantification experiment was performed by measuring the changes in substrate water weight and capacitance while providing a nutrient solution and by subsequently comparing these values. The substrate water weight and capacitance were measured every 20 to 30 seconds using the sensor and load cell with a software developed specifically for this study. Using a curve-fitting program, the substrate water content was estimated from the output of the capacitance using the water weight and capacitance of the substrate as variables. When the amount of water supplied was increased, the capacitance tended to increase. Coefficient of variation (CV) in capacitance according to the water weight in substrate was greater with the 1.0 kg of water weight, compared with other weights. Thus, the fitting was performed with higher than 1.0 kg, from 1.7 to 6.0 kg of water weight. The correlation coefficient between the capacitance and water weight in substrate was 0.9696. The calibration equation estimated water content from the capacitance, and it was compared with the substrate water weight measured by the load cell.
Keywords
condenser-type capacitance sensor; CurveExpert; electrode plate; load cell;
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