Abstract
Moisture measurements in a hydroponic medium with growing carrot and in a rough-rice medium using ECH2O probes (EC-5, ECH2O-TE; Decagon De-vices) have been conducted as case studies on applications of the probes to the environmental control field in biology. In the hydroponics, it was difficult to apply directly EC-5 sensor to moisture measurement in the medium due to the effect of conductive nutrient solution on EC-5 output voltage. To eliminate the effect, a correction method that may be acceptable for known and stable electrical conduc-tivity condition was proposed and examined. The results showed that the correction method was useful for estimat-ing relationship between volumetric water content in the medium and the output voltage under various conductiv-ity conditions. For the rough-rice medium, the moisture decline in the drying process was confirmed by the mea-surements using EC-5 and ECH2O-TE sensors. From the experiments, we could obtain non-linear functions that are highly relating the moisture in the rough-rice medium to output voltage or relative permittivity.
