The Hydrogen Quartector®-A New Phase Detector for Exotic Liquid-Gas Systems

The problem of an instrument to discriminate automatically between liquid and gaseous hydrogen has been solved. The principle of operation involves the dependence of acoustic radiation resistance upon density of the medium. The instrument comprises a quartz piezoelectric vibrator immersed in the medium and developing at its terminals a radiation resistance, and an electronic unit external to the medium, which automatically converts this resistance to a signal for measurement or control. The system is suitable for use with most fluids, including hydrogen, oxygen, and kerosene. Hydrogen is of particular interest because low density provides a less distinct interface, particularly at high pressure. The radiation resistance of practicable sensor configurations is analyzed for a number of fluids and experimental data are presented for conditions of liquid, gas, and wet in gas. An electronic technique for precise conversion of radiation resistance to a control signal is described. A stable negative resistance is generated, and maintenance of oscillation is the criterion for radiation resistance greater or less than the prescribed value of negative resistance. This negative resistance is chosen to be intermediate in value between the values which obtain for liquid and gas phases. Stable radiation resistance resolution of a few per cent has been obtained easily without encountering any limiting condition. An example of equipment designed for missile environmental conditions is described.