| 摘要 |
The depth of a cryogenic liquid in a Dewar may be ascertained by inserting a measurement probe into the container. The measurement probe includes a hollow tube having a proximal end and an open distal end, a heater operationally connected within the tube and positioned substantially adjacent the distal end, a pressure sensor operationally connected within the tube and positioned substantially adjacent the proximal end, and a microcontroller in electric communication with the heater and with the pressure sensor. The distal end of the measurement probe is placed against the bottom of the container, liquid from the container enters the tube, and is evaporated by the heater. The gas pressure in the tube between the heater and the pressure sensor is increased, until the gas pressure in the tube is equal to the pressure exerted by the liquid in the Dewar. A quasi-equilibrium condition (dependent upon continued heat supplied from the heater) is achieved between the gas pressure in the tube and the pressure from the liquid in the Dewar. A voltage output signal is generated from the pressure sensor proportional to the gas pressure in the tube and is correlated with a liquid depth value. The liquid depth value is then output.
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