| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter which prevents erroneous outputs against abrupt pressure change due to stoppage of fluid flow or the like, without impairing excellent sensitivity at a small flow rate. <P>SOLUTION: An ultrasonic flowmeter comprises a flow velocity calculation part 44 which calculates flow velocity from the difference in propagation time of ultrasonic wave, a sonic velocity calculation part 45 which calculates sonic velocity of the ultrasonic wave with the calculation of the flow velocity, a memory 46 which sequentially stores the flow velocity and the corresponding sonic velocity at a predetermined number of times, and a flow velocity correction part 47 which obtains variation in the sonic velocity corresponding to the flow velocity and corrects the flow velocity on the basis of the variation in the sonic velocity. On the basis of a first sonic velocity calculated by the sonic calculation part 45 and a second sonic velocity calculated prior to a predetermined number of times, the flow velocity correction part 47 obtains the variation in the sonic velocity of the first sonic velocity relative to the second sonic velocity. In the case that the variation in the sonic velocity is equal to or larger than a predetermined threshold of the variation in sonic velocity, the flow velocity corresponding to the first sonic velocity is replaced by the flow velocity corresponding to second sonic velocity so as to be held for a predetermined period. After a lapse of the predetermined time, the hold is released. <P>COPYRIGHT: (C)2013,JPO&INPIT |
