TERMINAL POINT DETECTION METHOD FOR VACUUM DRYING AND VACUUM DRYING DEVICE

PROBLEM TO BE SOLVED: To enable a drying terminal point to be detected as fast as possible even if a pressure within a drying tank is measured by a first vacuum meter such as a barrier membrane pressure gauge and a second vacuum meter such as Pirani vacuum meter and the like when a vacuum frozen drying is carried out, and when a time in which a difference between the measured indicated values at the first vacuum meter and the second vacuum meter is small and converged is judged as a drying terminal point, the drying terminal point can be detected as fast as possible even if a pressure in the drying tank is varied in reference to the type or volume of items to be dried.SOLUTION: A terminal point detection method of vacuum drying in accordance with this invention is carried out in such a way that when a pressure measured by the second vacuum meter 5b is once turned to increase while a pressure in the drying tank is being decreased as an interior of the drying tank 1 is drawn in vacuum, an index value is calculated under application of one inflection point and another inflection point when it is turned to descend and this calculated index value is judged while being converted to the measured indicated value of the second vacuum meter.SELECTED DRAWING: Figure 2 【課題】真空凍結乾燥の際、乾燥槽内の圧力を隔膜圧力計などの第１の真空計とピラニ真空計などの第２の真空計とで測定し、第１及び第２の両真空計での測定指示値の差が小さく収束する時点を乾燥終点と判断する場合に、被乾燥物の種類や量によって乾燥槽内の圧力が変動している場合でも可及的速やかに乾燥終点を検知できるようにする。【解決手段】本発明の真空乾燥の終点検知方法では、乾燥槽１内の真空引きに伴って当該乾燥槽内の圧力が下降している間で第２の真空計５ｂで測定した圧力が一旦上昇に転じる場合にその一の変曲点と、次に下降に転じるときの他の変曲点とを用いて指標値を求め、この求めた指標値を第２の真空計の測定指示値に置き換えて判断する。【選択図】図２