| 摘要 |
PURPOSE:To improve the sensitivity of concentration measurement by placing a diaphragm in bending vibration by a ring-shaped piezoelectric vibrator fixed on at least one surface of the diaphragm. CONSTITUTION:Fluid 12 flows in a cavity 9 of a transducer through a cylinder body 5 and a cavity 10 through a through hole 6c. When a detecting circuit 7 is powered on, the bottom part 1a of the vibration body 1 enters bending vibration in the directions of the cylinder body axis. The piezoelectric vibrator 20 consists of an annular discoid substrate 20a, an annular filmy electrode 20b provided on its reverse surface, an annular filmy electrode 20c provided on its top surface, and an electrode 20d. Further, the vibrator 20 has the electrode 20b fixed on the internal surface of the bottom part 1a of the vibration body 1. The mass of the mechanical vibration part 21 consisting of the vibrator 20 and vibration body 1 is smaller than the mass of a mechanical vibration part using a discoid piezoelectric vibrator. The resonance frequency of a composite vibration system 22, therefore, increases and the variation rate of the concentration rho of liquid 12 of the resonance frequency to be measured increases above that of a conventional vibration system, so the sensitivity of the concentration measurement is improved.
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