Optical temperature probe assembly

• US 5,355,423 A
• Filed: 07/16/1992
• Issued: 10/11/1994
• Est. Priority Date: 07/16/1992
• Status: Expired due to Term

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Phillips, Richard W.
• Primary Examiner(s): FONT, FRANK G
• Application Number:
  US07/914,796
• Time in Patent Office: 817 Days
• Field of Search: 385/12, 385/13, 385/31, 385/51, 385/78, 385/84, 356/43, 356/44, 374/131
• US Class Current: 385/12
• CPC Class Codes: G01K 11/20 using thermoluminescent materials G01K11/32 takes precedence

Abstract

A temperature probe includes a sensor material optically communicating with a waveguide, and a sheath having a sheath coefficient of thermal expansion substantially matched to a thermal expansion coefficient of the waveguide. The waveguide has first and second ends secured proximate corresponding sheath ends. In another aspect of the invention, waveguide ends are secured near the sheath ends, the sheath is bent at one or more locations so that it is noncylindrical, and a midsection of the waveguide is loosely held within the bent sheath. In still another aspect of the invention, a metallic tube with the sensor material disposed therein is secured to the waveguide by direct attachment to a metallic coating on the waveguide.

Claims

1. A temperature probe, comprising:

a sheath having a first and second sheath end, and further having a sheath coefficient of thermal expansion;

a waveguide having a first waveguide end secured proximate the first sheath end and a second waveguide end secured proximate the second sheath end, the waveguide having a waveguide coefficient of thermal expansion; and

a sensor material having a thermally responsive characteristic, and in optical communication with the second waveguide end;

wherein the sheath coefficient is substantially matched to the waveguide coefficient.

2. The temperature probe as recited in claim 1, wherein the sheath coefficient is not greater than 25 times the waveguide coefficient.

3. The temperature probe as recited in claim 1, wherein a ratio of the sheath coefficient to the waveguide coefficient has a magnitude between 10 and 1/10.

4. The temperature probe as recited in claim 1, wherein a ratio of the sheath coefficient to the waveguide coefficient has a magnitude between 5 and 1/5.

5. The temperature probe as recited in any one of claims 1, 2, 3, or 4, wherein the waveguide includes a light-guiding core comprising silica, and wherein the waveguide coefficient is substantially equal to a thermal expansion coefficient of silica.

6. The temperature probe as recited in claim 5, wherein the sheath comprises a material selected from the group consisting of platinum, platinum-rhodium alloy, and iron-nickel alloy.

7. The temperature probe as recited in claim 1, wherein the sensor material comprises a luminescent material, and wherein the characteristic is a luminescent lifetime.

8. The temperature probe as recited in claim 1, further comprising:

a mating member connecting the first waveguide end to the first sheath end, the mating member having a bore for receiving the first waveguide end.

9. The temperature probe as recited in claim 1, further comprising:

a metallic tube held at the second waveguide end and containing the sensor material;

wherein the metallic tube attaches to the sheath.

10. The temperature probe as recited in claim 9, wherein the metallic tube attaches to the sheath by a braze, weld, or solder joint.

11. The temperature probe as recited in claim 9, wherein the tube has a tube coefficient of thermal expansion which is substantially matched to the waveguide coefficient.

12. The temperature probe as recited in claim 1, wherein the sheath is adapted to malleably bend into a noncylindrical shape.

13. The temperature probe as recited in claim 12, further comprising:

a buffer layer disposed between the waveguide and the sheath.

14. The temperature probe as recited in claim 13, wherein the buffer layer is porous.

15. The temperature probe as recited in claim 14, wherein the buffer layer includes braided fibrous sleeving.

16. A temperature probe, comprising:

a sensor material having a thermally responsive characteristic;

a waveguide having an outside surface and a waveguide end which is in optical communication with the sensor material;

a metallic coating covering at least a portion of the waveguide outside surface; and

a metallic tube attached to the metallic coating with the sensor material disposed therein, the metallic tube being held to the waveguide proximate the waveguide end;

wherein the waveguide has a waveguide coefficient of thermal expansion, the metallic tube has a tube coefficient of thermal expansion, and the tube coefficient is substantially matched to the waveguide coefficient.

17. The temperature probe as recited in claim 16, wherein the tube coefficient is not greater than 25 times the waveguide coefficient.

18. The temperature probe as recited in claim 16, wherein the ratio of the tube coefficient in the waveguide coefficient has a magnitude between 10 and 1/10.

19. The temperature probe as recited in claim 16, wherein a ratio of the tube coefficient to the waveguide coefficient has a magnitude between 5 and 1/5.

20. The temperature probe as recited in any one of claims 16, 17, 18, or 19, wherein the waveguide includes a light-guiding core comprising silica, and wherein the waveguide coefficient is substantially equal to a thermal expansion coefficient of silica.

21. The temperature probe as recited in claim 20, wherein the metallic tube comprises a material selected from the group consisting of platinum, platinum-rhodium alloy, and iron-nickel alloy.

22. The temperature probe as recited in claim 21, wherein the metallic coating comprises gold.

23. The temperature probe as recited in claim 21, wherein the metallic coating comprises nickel.

24. The temperature probe as recited in claim 16, further comprising:

a sheath in which the metallic coating, metallic tube, and waveguide are disposed, the sheath having a sheath coefficient of thermal expansion;

wherein the sheath coefficient is substantially matched to the waveguide coefficient.

25. The temperature probe as recited in claim 24, wherein the sheath is adapted to malleably bend into a noncylindrical shape.

32. The temperature probe as recited in any one of claims 16, 29, 30 or 31, wherein the metallic tube is a unitary metallic tube.

26. A temperature probe, comprising:

a sheath having a first and second sheath end;

a waveguide having a first waveguide and secured proximate the first sheath end, a second waveguide end secured proximate the second sheath end, and waveguide midsection; and

a sensor material having the thermally responsive characteristic, and in optical communication with the second waveguide end;

wherein the sheath has a noncylindrical shape, and the waveguide midsection is loosely held within the sheath.

27. The temperature probe as recited in claim 26, further comprising:

a buffer layer disposed between the waveguide midsection and the sheath.

28. The temperature probe as recited in claim 27, wherein the buffer layer comprises braided silica sleeving.

29. A temperature probe, comprising:

a sensor material having a thermally responsive characteristic;

a waveguide having an outside surface and a waveguide end which is in optical communication with the sensor material;

a metallic coating covering at least a portion of the waveguide outside surface; and

a metallic tube attached to the metallic coating with the sensor material disposed therein, the metallic tube being held to the waveguide proximate the waveguide end;

wherein the sensor material is a luminescent powder tightly packed between the metallic tube and the waveguide, and wherein the characteristic is a lifetime of luminescence.

30. A temperature probe, comprising:

a sensor material having a thermally responsive characteristic;

a waveguide having an outside surface and a waveguide end which is in optical communication with the sensor material;

a metallic coating covering at least a portion of the waveguide outside surface;

a metallic tube attached to the metallic coating with the sensor material disposed therein, the metallic tube having a first open tube end held to the waveguide and a second open tube end; and

an end cap substantially sealing the second open tub end to prevent escape of the sensor material from the metallic tube, the end cap having a reflective surface adjacent the sensor material.

31. A temperature probe, comprising:

a sensor material having a thermally responsive characteristic;

a waveguide having an outside surface and a waveguide end which is in optical communication with the sensor material;

a metallic coating covering at least a portion of the waveguide outside surface;

a metallic tube attached to the metallic coating with the sensor material disposed therein, the metallic tube being held to the waveguide proximate the waveguide end; and

a metallic plating substantially covering the metallic coating and the metallic tube.