Patent ID: 6944570

Claim:
A system for displaying liquid volume of a cryogenic fluid stored in a cryogenic tank, the fluid stored within the tank, the tank containing a liquid space and a head space, the system comprising: a differential pressure sensor coupled to the head space and to the liquid space for sensing a differential pressure between the liquid space and head space and generating a differential pressure signal as a function of the differential pressure; a pressure sensor coupled to the head space for sensing a pressure of the head space; an operator input interface for entering the dimensions of the tank and the type of cryogenic fluid; a nonvolatile memory coupled to the operator input interface, for storing the dimensions of the tank, the type of cryogenic fluid, tank dimension formulas, a look-up table containing liquid density conversion constants for each of plural tank dimensions, and a look-up table containing cryogenic fluid densities for each of plural liquid types and plural pressure ranges; a micro-controller coupled to the pressure sensor, the differential pressure sensor and the nonvolatile memory, said micro-controller reading from said nonvolatile memory a selected liquid density conversion constant corresponding to said stored dimensions of the container; said micro-controller calculating an estimated average pressure as a difference between said head space pressure and said liquid density conversion constant, and reading from said nonvolatile memory a selected liquid density corresponding to said estimated average pressure and said liquid type; said micro-controller calculating a liquid volume based upon the dimensions of the tank, the type of cryogenic fluid, the tank dimension formulas, and the cryogenic fluid densities; and a display coupled to the micro-controller for displaying the liquid volume.