Patent ID: 7980142

Claim:
An ultrasonic flow rate measuring device comprising: a measurement passage through which a fluid flows, the measurement passage having a rectangular cross-section defined in part by a pair of opposing walls; a plurality of pairs of ultrasonic flow rate sensors having ultrasonic wave propagation paths running across the measurement passage between the pair of opposing walls, wherein the plurality of pairs of ultrasonic flow rate sensors are arranged such that their ultrasonic wave propagation paths run respectively at different angles with respect to the flow direction of the measurement passage; and layers of partitioning plates provided substantially in parallel to each other in the measurement passage so as to divide the measurement passage into layers of mutually parallel flat passages, wherein the ultrasonic wave propagation paths run respectively through different flat passages, wherein the plurality of pairs of ultrasonic flow rate sensors are selectively used according to a flow rate to measure the flow rate of the fluid flowing in the measurement passage.