Internal pressure determining method and system for hermetically sealed containers using electromagnetic induction

摘要

An internal pressure inspecting method and system for determining the degree of unevenness of the surface of an elastic cover of each of one or more hermetically sealed containers, the unevenness being produced according to the internal pressure. The distance from a fixed position exterior of the hermetically sealed container to said cover surface is determined by measuring the change in inductance utilizing the action of electromagnetic induction, at a plurality of points i.e. the center and peripheral portions thereof. A value is derived by calculation of the difference between a mean value of both measured values at any one point in the peripheral portion and at the position on the diametric line which is in symmetrical relation therewith with the center of the container cover as the center of symmetry, and the measured value at the center of the container cover. The internal pressure of said hermetically sealed container is determined from this value.