| 摘要 |
The device comprises a thin vibratable plate to be introduced into the substances whose density is to be measured, and the plate is held by a holder at a holding point and is vibrated by at least one vibration exciter in operative engagement with the plate. The vibrations of the plate are detected by at least one vibration detector operatively associated with the plate at a point spaced from the point or points at which vibrations are imparted to the plate. An electronic unit is connected to the vibration exciters and the vibration detector and forms therewith an oscillator having an input from the vibration detector and an output supplied to the vibration exciters. The vibration exciters are so positioned with respect to the plate, and so energized by the electronic unit, that the plate vibrates in a manner such that two nodal lines intersect in the range of each holding point at which the plate is supported by a holder. While the plate may have various configurations, it is preferably circular and is so energized that the nodal lines extend diametrically of the plate and intersect at its center, with the center forming the holding point at which the holder supports the plate. The electronic unit includes a meter measuring the periods of the vibration.
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