Patent ID: 7966878
Filing Date: 2011-06-28
Classification: G01F

Abstract:
1. A method of measuring a level of liquid cryogen, comprising: providing a cryogen level probe comprising a length of superconductive material, means for applying a current to the superconductive material, a heater for heating the superconductive material and means for measuring the voltage across the superconductive material; dipping the liquid cryogen level probe in a liquid cryogen; applying a propagation current to the heater to heat a part of the superconductive material above the critical temperature, thereby causing a normal resistive front to propagate along the superconductive material; removing the propagation current from the heater; applying a measurement current to the superconductive material; and measuring a voltage across the superconductive material thereby to determine the level of the liquid cryogen; wherein the magnitude of voltage across the superconductive material is monitored while the propagation current is being applied; and the propagation current is removed from the heater in response to detection of a voltage across the superconductive material which exceeds a certain threshold level.