To measure the flow with good accuracy from a large flow region (e.g. a flow rate of 160m3/h) to a very small flow region (very small leakage flow region such as 5L.h).
The ultrasonic flowmeter is formed by a first flow passage 1 including a pair of ultrasonic transducers 2 for detecting the flow of the large flow region, a changeover valve 5 for opening and closing the first flow passage 1, and a second flow passage 3 bypassing the upstream side and the downstream side of the changeover valve 5 and including a pair of ultrasonic transducers 4 for detecting a small flow region. In the case of measuring the large flow region, the changeover valve 5 is opened to make a measurement by a first ultrasonic flow measuring part 6, and in the case of measuring the small flow region, the switching valve 5 is closed to make a measurement by a second ultrasonic flow measuring part 7. The changeover valve 5 is driven by an ultrasonic motor having good responsiveness.
Tomoyasu Sakaguchi
Hiroki Naito