Elastic wave accelerometer
First Claim
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1. An elastic wave accelerometer comprising:
- (a) a piezoelectric substrate thin wafer;
(b) support means for mounting said wafer and including at least one seismic mass, said support means delimiting two portions on the surface of said wafer;
(c) surface acoustic wave transducer means disposed on at least one face of said wafer, for forming an acoustic delay line or filter on each portion of said two portions, with the waves on said portions propagating in opposite directions, said waves being effected by the component of an acceleration applied to the accelerometer in the direction of propagation of the elastic waves, said two portions being deformed in said direction one by extension and the other by compression;
(d) means for measuring said extension and compression in each portion of said delay line or filter, including oscillators having amplifier means connected to said delay lines or filters for forming oscillations in each portion in accordance with said extension and compression;
(e) frequency subtraction means for giving the difference of frequency of the two oscillators corresponding to said two delay lines or filters, said frequency difference being proportional to the acceleration parallel to said propagation direction of said two waves.
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Abstract
The invention discloses an elastic wave accelerometer for measuring acceleration at least in one direction.
The device comprises a solid support, a seismic mass and a piezoelectric wafer embedded in the seismic mass and in the solid support. An acceleration in one direction in the plane of the wafer produces an extension in one portion of the wafer and a compression in the other. Elastic waves are excited in the two portions of the wafer. Two oscillators are obtained by means of amplifiers and the frequency difference between the two oscillators is proportional to the acceleration.
The invention applies to accelerometers for inertial navigation.
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Citations
22 Claims
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1. An elastic wave accelerometer comprising:
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(a) a piezoelectric substrate thin wafer; (b) support means for mounting said wafer and including at least one seismic mass, said support means delimiting two portions on the surface of said wafer; (c) surface acoustic wave transducer means disposed on at least one face of said wafer, for forming an acoustic delay line or filter on each portion of said two portions, with the waves on said portions propagating in opposite directions, said waves being effected by the component of an acceleration applied to the accelerometer in the direction of propagation of the elastic waves, said two portions being deformed in said direction one by extension and the other by compression; (d) means for measuring said extension and compression in each portion of said delay line or filter, including oscillators having amplifier means connected to said delay lines or filters for forming oscillations in each portion in accordance with said extension and compression; (e) frequency subtraction means for giving the difference of frequency of the two oscillators corresponding to said two delay lines or filters, said frequency difference being proportional to the acceleration parallel to said propagation direction of said two waves. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification