US 5,176,031 A · Viscously coupled dual beam accelerometer

Abstract

A viscously coupled dual beam accelerometer. An accelerometer (60) includes a first proof mass (32') and a second proof mass (42'), which are respectively connected by flexures (36' and 46') to a first base (34') and a second base (44'). The first and second bases are clamped between a top enclosure (62) and a bottom enclosure (64), between which is defined a cavity (66) in which the first and second proof masses are disposed. A quartz crystal resonator (38') extends between the first proof mass and the first base; similarly, a quartz crystal resonator (48') extends between the second proof mass and second base. The quartz crystal resonators experience tension/compression in a push-pull mode when the accelerometer is subjected to acceleration along an acceleration-sensitive axis (26') that extends transversely through the proof masses. A fluid within the cavity couples the first and second proof masses together through a "squeeze film damping," due to their closely-spaced relationship to each other. As a result of this dynamic mutual damping of out-of-phase motion of the first and second proof masses, tracking errors in the signals produced by the quartz crystal resonators are minimized when the accelerometer is subjected to vibration at a frequency close to the resonant frequency of the proof masses.

Claims20

Dependent claims

An accelerometer comprising:

a. an enclosure including a first and a second damping plate disposed at generally opposite ends of the accelerometer, said enclosure defining a cavity between the first and second damping plates;
b. a first pendulous mass integrally connected to a first fixed base by a first flexure, said first pendulous mass being pivotable about said first flexure in response to an acceleration;
c. a second pendulous mass integrally connected to a second fixed base by a second flexure, said second pendulous mass being generally in parallel alignment with and closely spaced apart from said first pendulous mass, and being pivotable about said second flexure in response to the acceleration;
d. a first sensor connected between said first fixed base and said first pendulous mass so as to sense rotational movement of the first pendulous mass due to the acceleration and to produce a first signal in response thereto;
e. a second sensor connected between said second fixed base and said second pendulous mass so as to sense rotational movement of the second pendulous mass due to the acceleration and to produce a second signal in response thereto;
and
f. a fluid disposed within the cavity, between said first and second pendulous masses, wherein said first and second pendulous masses are spaced sufficiently close to each other so that the fluid interposed between them defines a coupling force and damps out a resonant oscillation tracking error of said first and second pendulous masses when they are subjected to vibrations at their resonant frequency, thereby minimizing a common mode rejection error in the first and the second signals caused by resonant oscillation of the first and second pendulous masses.

4 more elements

A viscously coupled accelerometer comprising:

a. an enclosure defining an elongate cavity filled with a fluid;
b. first acceleration sensing means having a resonant frequency, mounted within the cavity, for producing a first signal in response to an acceleration;
and
c. second acceleration sensing means having a resonant frequency, mounted within the cavity closely adjacent the first acceleration sensing means, for producing a second signal in response to the acceleration, said second acceleration sensing means being coupled to said first acceleration sensing means by the fluid within the cavity defining a coupling force so as to damp out-of-phase resonant oscillation of the first and the second acceleration sensing means, thereby minimizing common mode rejection errors in the first and second signals when the first and the second acceleration sensing means are subjected to vibrations at their resonant frequency.

1 more element

Dependencies are inferred from the claim text.

Viscously coupled dual beam accelerometer

Life of this patent

Viscously coupled dual beam accelerometer

Life of this patent

Abstract

Claims20