Patent ID: 6339960
Filing Date: 2002-01-22
Classification: G01F,G01L,G01N

Abstract:
A method for determining an internal pressure of a sealed container, comprising:exciting a lid of the sealed container so as to create at least two modes of vibration having separate frequencies, wherein said frequencies are fundamental, f1, and a second frequency, f2; detecting the vibration resulting from said exciting to determine f1, and f2; using f2, which is indicative of internal pressure, to calculate a first value for internal pressure using a first mathematical model that is calibrated to the lid on the sealed container; using f1, which is indicative of volume of contents, to calculate the volume of contents in the sealed container using a second mathematical model that is calibrated to the lid on the sealed container; wherein a natural frequency of said lid is a function of internal pressure and volume of contents; and compensating for said volume of contents to determine a second value for internal pressure, wherein said second value for internal pressure is more reliable than said first value for internal pressure.