| 摘要 |
PROBLEM TO BE SOLVED: To activate effectively a lithium battery without increasing cost by using an ultrasonic oscillator as not only a flow meter but also a temperature detecting device. SOLUTION: In the gas meter having a lithium battery 9, measuring the flow rate of a gas to be measured passing through a gas conduit 52 by using a pair of ultrasonic oscillators 5a, 5b arranged in the gas conduit 52, and having a solenoid cutoff valve 8, a present temperature is calculated based on an arrival time of an ultrasonic wave between the ultrasonic oscillators 5a, 5b, thereby activating the lithium battery 9 at a proper timing of detecting a low temperature.
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