DEVELOPMENT OF THE FUNCTIONS FOR AUTOMATED DENSITY CORRECTION AND MOISTURE GRADIENT MEASUREMENT OF HIGH FREQUENCY MOISTURE METER

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Development of the functions for density correction and moisture gradient measurement of high frequency moisture meter was investigated.In order to evaluate the moisture gradient, an electrode scanning method was proposed. In this method, the capacitance change in function of electrode distance was measured. The capacitance curve pattern showed good correlation with the moisture gradient pattern.The capacitance change due to electrode scanning C (d) was defined as the following integral equation, C (d)=* S (d, x) U (x) dx, where S (d, x) is a weight function and U (x) is a moisture gradient. In order to solve this equation, a linear simultaneous equation was introduced. The weight function was experimentally determined from model specimens with different moisture gradient.Simulation research was made to investigate the relationship between the capacitance curve and the moisture gradient. The following results were obtained : (1) In these high frequency moisture meter, the capancitance is sensitive very much to the moisture condition near electrodes. (2) The capacitance decreases exponentially with increase of the electrode distance. (3) As the electrode distance increases, relative sensibility of deep position increases. (4) The inverse solution of moisture gradient was not stable, and the reproduce of the moisture gradient was insufficient. Father mathematical treatment should be required. (5) Practical application of the results is to classify the spectrum patterns of the capacitance curves.Wood density affects very much on the measurement of a high frequency moisture meters. In this research, a simultaneous determination of a density and moisture content was proposed, and the following algorism was examined. The Kollmann's density-moisture content figure was combined with the result of the reading of a moisture meter. These values converged in two or three times of iteration, and the propriety of the proposed algorism was confirmed.