Ageing indicator

摘要

An ageing indicator compares a closed sachet of one or more closed tubes of a material which is slightly permeable to a fluid contained in the sachet or tube. The rate of permeation of the fluid through the sachet-like assembly tube wall depends upon temperature and time of exposure to that temperature so the quantity of fluid loss is indicative of temperature and time; the ageing capable of then being detected either by measuring a column of the liquid in a tube or by observing the appearance or disappearance of printed indicia in the sachet.