Patent ID: 7475653
Filing Date: 2009-01-13
Classification: G01K

Abstract:
1. An apparatus that indicates whether an object has been exposed to a predetermined critical temperature T below the freezing point of the object, comprising: a) an impermeable housing having a reservoir portion and a capillary tube portion in fluid connection with said reservoir portion; b) a first fluid contained within said reservoir portion; c) a second fluid contained within said capillary portion; d) a barrier located intermediate said first fluid and said second fluid, said barrier comprising a liquid that is immiscible with said first and second fluids and preventing said first and second fluids from intermixing until said apparatus is exposed to the critical temperature T and then allowing at least a portion of said second fluid to mix with said first fluid when said apparatus is exposed to the critical temperature; wherein an observable characteristic of one of said fluids irreversibly changes when said apparatus is exposed to the critical temperature; and, wherein said impermeable housing completely encapsulates said fluids and barrier within said housing and prevents evaporation of said fluids and barrier from said housing.