Method of reducing the drift rate of accelerometer and accelerometer with reduced drift rate

• US 20080092653A1
• Filed: 10/18/2006
• Published: 04/24/2008
• Est. Priority Date: 10/18/2006
• Status: Abandoned Application

• Current Assignee: Scintrex Ltd. (LaCoste & Romberg Scintrex, Inc.)
• Original Assignee: Scintrex Ltd. (LaCoste & Romberg Scintrex, Inc.)
• Inventors: Mihajilovic, Djordje, Seigel, Harold O., Brcic, Ivo, Ehrat, Rolf, Mistry, Dhirejlal
• Application Number:
  US11/582,392
• Publication Number:
  US 20080092653A1
• Time in Patent Office: Days
• US Class Current: 73/514.01
• CPC Class Codes: G01P 1/006 used for thermal compensation
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01V 1/181 Geophones

Abstract

An accelerometer comprises a chamber and a proof mass supported by an elastic element within the chamber. The elastic element is formed of fused silica. A sensor senses displacement of the proof mass. Means to inhibit interaction of water vapour with the elastic element is provided.

Claims

1. An accelerometer comprising:

a chamber;

a proof mass supported by an elastic element within said chamber, said elastic element being formed of fused silica;

a sensor sensing displacement of said proof mass; and

means inhibiting interaction of water vapour with said elastic element.

2. An accelerometer according to claim 1 wherein said elastic element is formed of fused silica.

3. An accelerometer according to claim 2, wherein said inhibiting means comprises a desiccant in said chamber, said desiccant adsorbing water vapour in the chamber.

4. An accelerometer according to claim 3, wherein said desiccant comprises a molecular sieve material.

5. An accelerometer according to claim 4, wherein said molecular sieve material has pore spaces large enough to adsorb water molecules but small enough to reject molecules of a larger diameter.

6. An accelerometer according to claim 5 wherein said chamber is gas filled and wherein the constituents of said gas other than water vapour include only non-polar molecules, or polar molecules larger than the diameter of water molecules.

7. An accelerometer according to claim 2, wherein said inhibiting means comprises a vacuum pump evacuating said chamber.

8. An accelerometer according to claim 2, wherein said inhibiting means comprises a treated surface of said elastic element.

9. An accelerometer according to claim 8 wherein said surface is treated by preheating the elastic element to a temperature of about 850°

C., treating the elastic element in a stream of dry chlorine gas at a temperature in the range of from about 600 to 1000°

C., and then consolidating the elastic element at a temperature of about 1250°

C.

10. An accelerometer according to claim 1 employed in a gravimeter.

11. An accelerometer according to claim 1 employed in a seismometer.

12. An accelerometer comprising:

a chamber;

a proof mass supported by a fused silica elastic element within said chamber;

a sensor sensing displacement of said proof mass; and

a substantially water vapour free environment surrounding said elastic element.

13. An accelerometer according to claim 12, further comprising a desiccant in said chamber, said desiccant adsorbing water vapour in the chamber.

14. An accelerometer according to-claim 13, wherein said desiccant comprises a molecular sieve material.

15. An accelerometer according to claim 14, wherein said molecular sieve material has pore spaces large enough to adsorb water molecules but small enough to reject molecules of a larger diameter.

16. An accelerometer according to claim 12, further comprising a vacuum pump evacuating said chamber thereby to create said water vapour free environment.

17. An accelerometer according to claim 13, further comprising a vacuum pump evacuating said chamber thereby to create said water vapour free environment.

18. An accelerometer according to claim 12 employed in a gravimeter.

19. An accelerometer according to claim 12 employed in a seismometer.

20. A method of reducing the drift rate of an accelerometer comprising a chamber housing a fused silica elastic member, said method comprising:

reducing the interaction of the elastic member with water vapour in the chamber.

21. The method of claim 20, wherein said reducing comprises evacuating gas in the chamber.

22. The method of claim 20, wherein said reducing comprises placing a desiccant, with selective affinity for water vapour, in the chamber.

23. The method of claim 22, wherein said desiccant is a molecular sieve.

24. The method of claim 20, wherein said reducing comprises treating the surface of the elastic member to prevent its interaction with water vapour.

25. The method of claim 24, wherein said treating comprises:

preheating the elastic member to a temperature of about 850°

C.;

treating the elastic member in a stream of dry chlorine gas at a temperature in the range of from about 600 to 1000°

C.; and

consolidating the elastic member at a temperature of about 1250°

C.

26. The method of claim 21, wherein said reducing further comprises placing a desiccant, with selective affinity for water vapour, in the chamber.

27. The method of claim 21 wherein said reducing further comprises treating the surface of the elastic member to prevent its interaction with water vapour.

28. The method of claim 27, wherein said treating comprises:

preheating the elastic member to a temperature of about 850°

C.;

treating the elastic member in a stream of dry chlorine gas at a temperature in the range of from about 600 to 1000°

C.; and

consolidating the elastic member at a temperature of about 1250°

C.

29. The method of claim 22, wherein said reducing further comprises treating the surface of the elastic member to prevent its interaction with water vapour.

30. The method of claim 29, wherein said treating comprises:

preheating the elastic member to a temperature of about 850°

C.;

treating the elastic member in a stream of dry chlorine gas at a temperature in the range of from about 600 to 1000°

C.; and

consolidating the elastic member at a temperature of about 1250°

C.

31. The method of claim 29, wherein said reducing further comprises evacuating gas in the chamber.