CONTAMINANT DEPOSITION CONTROL BAFFLE FOR A CAPACITIVE PRESSURE TRANSDUCER

• US 20040226382A1
• Filed: 05/16/2003
• Published: 11/18/2004
• Est. Priority Date: 05/16/2003
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Lischer, D. Jeffrey, Traverso, Robert
• Granted Patent: US 6,993,973 B2
• Time in Patent Office: Days
• US Class Current: 73/724
• CPC Class Codes: G01L 19/0636 using particle filters
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

The disclosed transducer includes a housing, a diaphragm, an inner conductor, an outer conductor, and a first baffle. The housing defines an interior volume. The diaphragm is disposed in the housing and divides the interior volume into a first chamber and a second chamber. The diaphragm flexes in response to pressure differentials in the first and second chambers. The inner conductor is disposed in the first chamber. The outer conductor is disposed in the first chamber around the inner conductor. The first baffle is disposed in the second chamber and defines an inner region, a middle region, and an outer region. The inner region underlies the inner conductor. The middle region underlies the outer conductor. The outer region underlies neither the inner conductor nor the outer conductor. The first baffle defines apertures in at least two of the inner, middle, and outer regions.

Claims

1. A transducer, comprising:

A. a housing defining an interior volume;

B. a diaphragm disposed in the housing and dividing the interior volume into a first chamber and a second chamber, the diaphragm flexing in response to pressure differentials in the first and second chambers;

C. an inner conductor disposed in the first chamber;

D. an outer conductor disposed in the first chamber around the inner conductor; and

E. a first baffle disposed in the second chamber, an inner region of the first baffle underlying the inner conductor, a middle region of the first baffle underlying the outer conductor, an outer region of the first baffle underlying neither the inner conductor nor the outer conductor, the first baffle defining apertures in at least two of the inner, middle, and outer regions.

2. A transducer according to claim 1, the first baffle defining apertures in each of the inner, middle, and outer regions.

3. A transducer according to claim 1, a total area of all the apertures in the inner region being substantially equal to a total area of all the apertures in the middle region.

4. A transducer according to claim 1, a total area of all the apertures in the inner region being greater than a total area of all the apertures in the middle region.

5. A transducer according to claim 1, a total area of all the apertures in the inner region being less than a total area of all the apertures in the middle region.

6. A transducer according to claim 1, the inner region of the first baffle being larger than the inner conductor.

7. A transducer according to claim 1, the inner region of the first baffle being smaller than the inner conductor.

8. A transducer according to claim 1, the middle region of the first baffle being smaller than the outer conductor.

9. A transducer according to claim 1, the middle region of the first baffle being larger than the outer conductor.

10. A transducer according to claim 1, a first unit area of the first baffle defining a first set of apertures, a second unit area of the first baffle defining a second set of apertures, a total area of the apertures in the first set being substantially equal to a total area of the apertures in the second set regardless of where the first and second unit areas are located.

11. A transducer according to claim 1, the first baffle comprising a sintered metal element.

12. A transducer according to claim 1, the transducer including an inlet tube, the inlet tube providing an opening into the second chamber.

13. A transducer according to claim 12, further including a second baffle disposed between the opening and the first baffle, a central region of the second baffle defining no apertures and being larger than the opening, the central region being disposed to prevent particles traveling through the opening in a direction parallel to the inlet tube from passing through the second baffle without first contacting the central region, a peripheral region of the second baffle being disposed around the central region and defining a plurality of apertures.

14. A transducer according to claim 13, further including a third baffle disposed between the first baffle and the second baffle, a central region of the third baffle defining no apertures, peripheral openings being provided between the third baffle and the housing, the third baffle being spaced apart from the second baffle by a gap, apertures in the peripheral region of the second baffle being separated from the peripheral openings by a length, the length being at least ten times greater than the gap.

15. A transducer according to claim 1, the inner conductor being circular, the outer conductor being annular, the inner and outer conductors being disposed generally parallel to the diaphragm.

16. A transducer according to claim 1, wherein the diaphragm is entirely metallic.

17. A transducer, including:

A. a housing defining an interior volume;

B. a diaphragm disposed in the housing and dividing the interior volume into a first chamber and a second chamber, the diaphragm flexing in response to pressure differentials in the first and second chambers;

C. an inlet tube providing an opening into the second chamber;

D. an inner conductor disposed in the first chamber, the inner conductor and at least a portion of the diaphragm being characterized by an inner capacitance;

E. an outer conductor disposed in the first chamber around the inner conductor, the outer conductor and at least a portion of the diaphragm being characterized by an outer capacitance;

F. a first baffle disposed in the second chamber, an inner region of the first baffle underlying the inner conductor, a middle region of the first baffle underlying the outer conductor, an outer region of the first baffle underlying neither the inner conductor nor the outer conductor, the first baffle defining apertures in at least two of the inner, middle, and outer regions;

G. a second baffle disposed between the opening and the first baffle, a central region of the second baffle defining no apertures and being larger than the opening, the central region being disposed to prevent particles traveling through the opening in a direction parallel to the inlet tube from passing through the second baffle without first contacting the central region, a peripheral region of the second baffle being disposed around the central region and defining a plurality of apertures; and

H. a third baffle disposed between the first baffle and the second baffle, a central region of the third baffle defining no apertures, peripheral openings being provided between the third baffle and the housing.

18. A transducer according to claim 17, the first baffle defining apertures in each of the inner, middle, and outer regions.

19. A transducer, comprising:

A. a housing defining an interior volume;

B. a diaphragm disposed in the housing and dividing the interior volume into a first chamber and a second chamber, the diaphragm flexing in response to pressure differentials in the first and second chambers;

C. an inner conductor disposed in the first chamber, the inner conductor being generally parallel to and spaced apart from the diaphragm, an inner portion of the diaphragm being proximal to the inner conductor;

D. an outer conductor disposed in the first chamber, the outer conductor being generally parallel to and spaced apart from the diaphragm, a middle portion of the diaphragm being proximal to the outer conductor, an outer portion of the diaphragm extending around the middle portion of the diaphragm; and

E. a first baffle disposed in the second chamber, the first baffle defining an inner region, a middle region, and an outer region, the first baffle defining apertures in at least two of the inner, middle, and outer regions, the first baffle being disposed so that;

i. a majority of molecules passing through apertures in the inner region of the first baffle towards the diaphragm contact the inner portion of the diaphragm before contacting any other part of the transducer;

ii. a majority of molecules passing through apertures in the middle region of the first baffle towards the diaphragm contact the middle portion of the diaphragm before contacting any other part of the transducer; and

iii. a majority of molecules passing through apertures in the outer region of the first baffle towards the diaphragm contact the outer region of the diaphragm before contacting any other part of the transducer.

20. A transducer, comprising:

A. a housing defining an interior volume;

B. a diaphragm disposed in the housing and dividing the interior volume into a first chamber and a second chamber, the diaphragm flexing in response to pressure differentials in the first and second chambers;

C. a first conductor disposed in the first chamber;

D. a second conductor disposed in the first chamber; and

E. a first baffle disposed in the second chamber, a first region of the first baffle being proximal to the first conductor, a second region of the first baffle being proximal to the second conductor, a third region of the first baffle underlying neither the first conductor nor the second conductor, the first baffle defining apertures in at least two of the first, second, and third regions.

21. A transducer according to claim 20, the first baffle defining apertures in each of the first, second, and third regions.

22. A transducer according to claim 20, wherein the diaphragm is entirely metallic.