| 摘要 |
PURPOSE:To achieve a stable measurement of humidity with the oscillation of a vibrator stopped at a desired humidity by specigying the thickenss of a film of a hygroscopic material coated on a piezo-electric vibration plate to ensure a proper combination with the required vibration mode at a given humidity. CONSTITUTION:A hygroscopic material such as polymide is applied on the surface of an electrode 2 provided on the surface and the back of a rectangular piezo- electric vibration plate to 1 form a hygroscopic material film 4. Changing the thickness of the elctrode 2 reduces the main vibration frequency of the vibration plate 1 in proportion to the thickness thereof, so that the frequency in the unwanted vibration mode little changes. On the other hand, absorbing the humidity with the film 4 substantially changes the thickness of the electrode 2. Therefore, when the thickness of the hygroscopic film 4 is selected so that the main vibration mode is properly combined with the undesired vibration mode, a hmidity according to the film 4 increases the euivalent resistance of the vibration plate 1 so suddenly to halt the vibration thereby assuring a stable measurement of humidity. |
