| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a gas shutoff device that improves safety and convenience in using gas. <P>SOLUTION: The gas shutoff device includes an amplifying unit 15 for receiving an ultrasonic signal detected by an ultrasonic transducer 31 and amplifying it to a prescribed level; a transmission/reception switching unit 14 for alternately connecting a transmission unit 13 and the amplifying unit 15 to the ultrasonic transducers 31 and 32; an amplification comparison unit 17 for comparing and determining amplification factors detected by the amplifying unit 15; a transmission time detection unit 16 for detecting a transmission time period from the ultrasonic signal amplified by the amplifying unit 15; a flow rate calculation unit 18 for converting the obtained transmission time period into a flow rate; and an abnormality determination unit 19 for determining whether a difference in the amplification factors obtained by the amplification comparison unit 17 is not less than a prescribed value, when a current within a prescribed range continues for a prescribed time period or more. <P>COPYRIGHT: (C)2012,JPO&INPIT</p> |
