| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter that enables a highly sensitive ultrasonic wave transmission and reception with sufficiently small acoustic impedance, which is matched with gas being an emission medium of ultrasound, and also comprises a acoustic matching layer that can improve rising responsiveness of signals. SOLUTION: The ultrasonic flowmeter is provided with a flow measurement part where the fluid to be measured flows; a pair of ultrasound transducer, which is arranged in the flow measurement part, for transmitting and receiving ultrasound signals; a measurement circuit for measuring an ultrasound propagation time between the ultrasound transducers; and a flow rate arithmetic circuit for computing the flow rate on the basis of signals from the measurement circuit. Each of the pair of ultrasound transducer has a piezoelectric layer 4 and the acoustic matching layer 1 arranged on the piezoelectric layer 4. The acoustic matching layer 1 has a first acoustic matching layer 2 of which density is within a range of 50 kg/m<SP>3</SP>to 500 kg/m<SP>3</SP>and a second acoustic matching layer 3 of which density is within a range of 400 kg/m<SP>3</SP>to 1,500 kg/m<SP>3</SP>. Also, the density of the first acoustic matching layer 2 is smaller than that of the second acoustic matching layer 3, and the second acoustic matching layer 3 is arranged at the side of the piezoelectric layer 4. COPYRIGHT: (C)2004,JPO
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