Low thermal response time surface acoustic wave sensors
First Claim
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1. A pressure sensor comprising:
- a generally cylindrical body made of two halves joined along an axial plane;
an axially extending channel formed in each half to face that of the other, each channel having a bottom and walls, said channels forming a sealed cavity enclosed by said body;
an axially extending flat formed at the bottom of each channel; and
a respective SAW device formed on each flat;
wherein one of the halves has a flat exterior surface which reduces the radial thickness of the body adjacent the flat to thereby make the thermal responses of the two SAW devices more equal than in the absence of said exterior flat surface.
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Abstract
Disclosed is an externally loaded pressure sensor using a pair of SAW devices formed on the wall of an interior cavity. The difference frequency of these devices is used as a temperature-compensated measure of hydrostatic pressure on the sensor exterior. The termal response time of the sensor is shortened by matching to each other the sensor wall thicknesses adjacent the two SAW devices, e.g., by making these wall thicknesses approximately the same by means of forming an external flat on the sensor body.
18 Citations
18 Claims
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1. A pressure sensor comprising:
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a generally cylindrical body made of two halves joined along an axial plane; an axially extending channel formed in each half to face that of the other, each channel having a bottom and walls, said channels forming a sealed cavity enclosed by said body; an axially extending flat formed at the bottom of each channel; and a respective SAW device formed on each flat; wherein one of the halves has a flat exterior surface which reduces the radial thickness of the body adjacent the flat to thereby make the thermal responses of the two SAW devices more equal than in the absence of said exterior flat surface. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A pressure sensor comprising:
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a generally cylindrical body having a sealed cavity which has a cavity wall; and at least two SAW devices formed on said cavity wall; wherein said body has an exterior flat radially adjacent to one of said SAW devices. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A pressure sensor system comprising:
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a sensor body enclosing a sealed cavity which has a cavity wall; at least two SAW devices coupled with the cavity wall and having frequency characteristics which vary with pressure externally applied on the sensor body, said variation differing as between respective SAW devices; wherein the thicknesses of the sensor body at the respective SAW devices are matched to reduce the difference between the respective thermal response times of said devices; a well logging tool and means for mounting the sensor body therein; and means for logging the pressure in a borehole with said tool and sensor body. - View Dependent Claims (17, 18)
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Specification