| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a thermal flowmeter which has high measurement accuracy and durability, and can easily execute signal processing. SOLUTION: A sensor 12 arranged in a pipe body 11, in which fluid flows, includes a piezoelectric plate 14 composed of crystal adhered onto a substrate 13, and four pillar 15 for supporting the substrate 13. A laser beam radiated from a laser source irradiates the central portion of the piezoelectric plate 14 after passing through a hole 18 of a flange 17. A laser absorbing film for absorbing the laser beam is formed at the central portion of the piezoelectric plate 14. A plurality of comb shape electrodes are formed on both sides of the laser absorbing film. When the flow rate is measured, the laser beam irradiates the laser absorbing film of the piezoelectric plate 14, for example, for a predetermined time. The piezoelectric plate 14 shows a temperature variation characteristic curve according to cooling by a mass flow rate of the fluid. The oscillation frequency of the piezoelectric plate 14 varies following the temperature variation. The flow rate is measured according to this temperature variation characteristic.</p> |
