Measuring and testing – Specific gravity or density of liquid or solid
Patent
1987-12-07
1990-10-09
Williams, Hezron E.
Measuring and testing
Specific gravity or density of liquid or solid
G01L 908
Patent
active
049613456
ABSTRACT:
The apparatus of the present invention detects the resonant frequency of a vibratory member in contact with the fluid in order to determine the density or pressure of the fluid. The vibratory member is disposed in a housing to form a cavity with no flow communication between the side of the vibratory member facing into the cavity and the other side of the vibratory member. The vibratory member is vibrated by an annular piezoelectric device which may be attached to one or both sides of the vibratory member. An amplifier and feedback circuit regulate the frequency of oscillation of the piezoelectric device to that of the resonant frequency. The piezoelectric device may be comprised of several separate sections or several sections with partial interruptions in the piezoelectric material. Instead of the vibratory member and the piezoelectric transducer combination, the vibratory member may be constructed from a single fixed piezoelectric device with another piezoelectric disc mounted thereon. In this configuration one of the devices is used to mechanically excite the other and through a feedback circuit establish the resonant frequency of the two laminated piezoelectric devices.
REFERENCES:
patent: 4435986 (1984-03-01), Choffat
patent: 4644804 (1987-02-01), Ramm et al.
Japanese Patent Application No. 139786/86; filed 6/16/86 by Tsuruoka et al.
Kounosu Naohiro
Machida Masashi
Nakagawa Wataru
Tsuruoka Michihiko
Arana Louis M.
Fuji Electric & Co., Ltd.
Williams Hezron E.
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