RESONANCE-CAPACITANCE SOIL MOISTURE METER

Abstract

IN DETERMINING SOIL MOISTURE CONTENT, THE METHOD THAT TREATS CAPACITANCE AS A FUNCTION OF MOISTURE CONTENT IS NONLINEAR, IS SUITABLE ONLY IN A NARROW RANGE OF LOW SOIL MOISTURE CONTENT, AND IS LESS PRECISE THAN ONE DESCRIBED IN THIS PAPER. AN EMPIRICAL EXPRESSION ORIGINALLY USED FOR POROUS BUILDING MATERIALS, IN WHICH THE PARAMETERS ARE MOISTURE CONTENT AND EMPIRICAL CONSTANTS EXPRESSING THE NATURE OF SOIL, TEMPERATURE, AND OTHER FACTORS, IS COMBINED WITH AN EQUATION FOR THE REASONANCE FREQUENCY OF A CIRCUIT TO DERIVE A FREQUENCY EQUATION WHOSE CONSTANTS HAVE TO BE CALIBRATED APPROXIMATELY. A COMMERCIAL GRID-DEEP METER WAS USED FOR LABORATORY EXPERIEMTS WITH SOIL COLUMNS. THE METHOD OF OPERATION AND CALIBRATION IS EXPLAINED BRIEFLY. IN ADDITION TO MEASURING SOIL MOISTURE CONTENT, THE METHOD HAS SUCCESSFULLY EVALUATED MOISTURE DISTRIBUTION DURING INFILTRATION OF A NONCONSTANT INITIAL MOISTURE CONTENT, AND HAS ALSO BEEN APPLIED TO DETERMINE MOISTURE IN BUILDING MATERIALS.