Abstract
Recently in the field of agriculture, demands for convenient measurement of water contents in rockwool and sand, concentration of nutrient solution, and plant physiological information with the change of environments, are increasing. This paper shows the characteristics and applications of resistance-capacitance meter composed of two resonant circuits, which is developed to solve these problems. By this resistance-capacitance meter, capacitance and resistance of specimen can be measured by both zero method and deflection method, and small changes in resistance can be measured by deflection method. Measurement sensitivity can be changed freely by fitting values of circuit elements (capacitor) adequately. Since circuit composition of this measurement instrument is very simple, demands for the one of small size and portability are satisfied. Measurement of capacitance and resistance corresponding to the water contents of sand including electrolyte were shown as the applications, and continuous measurement of water status in rice, though it has been regarded as difficult, and the effect of magnetic field on capacitance and resistance of the leaf of plants were shown as the example for detecting plant physiological information.
