DETERMINATION OF DRY ENDING POINT

摘要

PURPOSE:To determine the dry ending point of an object to be dried, by measuring a plate current (IP) of a high frequency oscillation tube for heating the object being dried at each fixed time to obtain a difference between the preceding IP measured value and the current IP measured value when the resulting value is below a fixed value. CONSTITUTION:A plate voltage is applied to a high frequency oscillation tube TU to start high frequency oscillation and an oscillation output thereof is applied to electrode plates 1 and 2 through a coupling circuit 25 to perform a high frequency induction heating of an object 3 to be dried. As the water content of the object 3 being dried lowers, the decreasing current IP of the oscillation tube TU is measured at each fixed time and a difference is determined between the preceding current IP measured value and this current IP measured value when the resulting value is below a fixed value. Thus, the dry ending point is given at the point of time at which the difference becomes smaller than a preset value. In other words, the time at which the decrease per a fixed time of the water content of the object 3 being dried falls below a fixed value is determined to be the dry ending point and hence this enables the ending of drying when the water content of the object being dried reaches a low level close to an equilibrium water content previously obtained for material thereof.