| 摘要 |
PROBLEM TO BE SOLVED: To provide a gas-protecting device that detects the generation of re-liquefaction, obtains a stable flow-rate value, and can prevent a protection function from malfunctioning. SOLUTION: In the gas-protecting device having an ultrasonic measurement part consisting of an ultrasonic sensor 1 and a channel 2, a cutoff vale 3 for shielding gas when failure occurs, and a control circuit 7 for judging whether the used state of gas is normal or not, a re-liquefaction detection means 11 for detecting a re-liquefaction phenomenon where a gas pressure fluctuates irregularly, and a re-liquefaction time counting means 12 for averaging a measurement flow-rate value that fluctuates when re-liquefaction occurs are provided, thus detecting that re-liquefaction has occurred based on the pattern of a flow-rate measurement value that fluctuates when the re-liquefaction phenomenon occurs and obtaining a stabilized flow-rate value by averaging the flow-rate values.
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