Validation and calibration apparatus and method for nuclear density gauge

• US 6,050,725 A
• Filed: 04/16/1999
• Issued: 04/18/2000
• Est. Priority Date: 06/12/1997
• Status: Expired due to Term

• Current Assignee: InstroTek, Inc.
• Original Assignee: InstroTek, Inc.
• Inventors: Regimand, Ali
• Primary Examiner(s): Porta, David P.
• Application Number:
  US09/293,113
• Time in Patent Office: 368 Days
• Field of Search: 378/53, 378/54, 378/56, 378/86, 378/88, 378/89, 378/90, 378/207, 250/252.1, 250/390.01, 250/390.04
• US Class Current: 378/207
• CPC Class Codes: G01N 23/06 and measuring the absorption

Abstract

A cost effective, field-usable validation and calibration apparatus and method for nuclear density gauges comprises an absorption element, where the absorption element is capable of simulating at least one known density when subjected to analysis using the nuclear density gauge. The absorption element may be positioned inside an enclosure, which also may include an insertion hole capable of receiving a source rod from a nuclear density gauge. The absorption element also can be capable of simulating a plurality of densities, both in backscatter and direct transmission modes. A method of validating and re-calibrating a nuclear density test gauge is also provided, where only a single block of a known density, either a reference block or a field block with a simulated density, is required.

Claims

1. A field block for use with a nuclear density gauge comprising an absorption element, wherein said absorption element is capable of simulating at least one known density when subjected to analysis using the nuclear density gauge, and, wherein the nuclear density gauge comprises a source rod and detector and said field block is configured to receive said source rod therein, and wherein in operation when subject to analysis using the nuclear density gauge, said source rod and said detector define a detection radiation path having an associated spatial volume therebetween, and wherein said absorption element is configured to extend about a portion of the radiation path to thereby leave a remaining portion of the radiation path free.

2. A field block according to claim 1, wherein said absorption element is mounted to said field block such that it is translatable from a first operative position to a second operative position.

3. A field block according to claim 2, wherein the nuclear density gauge will perceive two simulated density readings, one corresponding to said absorption element positioned in said first operative position and the second corresponding to said absorption element positioned in said second operative position.

4. A field block according to claim 3, wherein said translatable positions are at substantially the same depth in said field block, the translation of said absorption element thereby providing two different simulated material density readings at a single source depth.

5. A field block according to claim 2, wherein said absorption element is rotatably mounted within said field block to rotate said absorption element such that it presents a first profile in the radiation path in the first operative position and a second profile in the radiation path in the second operative position.

6. A field block according to claim 5, wherein said rotation is in response to a motorized input.

7. A field block according to claim 5, wherein said rotation is in response to manual movement of a lever.

8. A field block according to claim 2, wherein said absorption element is linearly translatable within said field block along the radiation path.

9. A field block according to claim 8, wherein said linear translation is in response to rotation of lever mounted on said field block such that it is externally accessible.

10. A field block according to claim 1, wherein said remaining free portion of the radiation path is a major portion of the spatial volume extending within said field block between the source rod and the detector.

11. A field block according to claim 1, wherein said absorption element is configured within said radiation path such that an air gap space extends proximate to each side of said absorption element within said field block along the radiation path.

12. A field block according to claim 1, wherein said absorption element is mounted within said field block to present a first profile in a first radiation path in a first operative position and a second profile in a second radiation path in a second operative position.

13. A field block for use with a nuclear density gauge comprising an absorption element, wherein said absorption element is capable of simulating at least one known density when subjected to analysis using the nuclear density gauge, wherein said field block further comprises an enclosure, and wherein said absorption element has an outer surface contour, and wherein said enclosure is substantially hollow and has an inner surface contour, and wherein said enclosure inner surface contour is dissimilar to said absorption element outer surface contour.

14. A field block according to claim 13, wherein the nuclear density gauge comprises a source rod and detector, and wherein in operation when subject to analysis using the nuclear density gauge, said source rod and said detector define a radiation path therebetween, and wherein said absorption element is configured and sized to be discontinuous in the radiation path.

15. A field block according to claim 13, wherein said absorption element is mounted to said field block such that it is translatable from a first operative position to a second operative position.

16. A field block according to claim 15, wherein the nuclear density gauge detects two simulated density readings, a first reading corresponding to said absorption element positioned in said first operative position and a second reading corresponding to said absorption element positioned in said second operative position.

17. A field block according to claim 16, wherein said first and second operative positions are at substantially the same source depth in said field block, the translation of said absorption element thereby providing two different simulated material density readings at a single source depth.

18. A field block according to claim 16, wherein said enclosure inner surface contour and said absorption element outer surface contour are configured in spaced-apart relationship to define a major air space volume therebetween.

19. A field block according to claim 16, wherein said dissimilar enclosure inner surface contour and absorption element contour are configured such that an air gap volume extends within said field block to define a void space proximate the perimeter of said absorption.

20. A field block according to claim 19, wherein said absorption element is linearly translatable within said field block along the radiation path.

21. A field block according to claim 20, wherein said linear translation is in response to rotation of a lever attached to said absorption element and mounted on said field block such that it is externally accessible.

22. A field block according to claim 13, wherein said field block includes a radiation path extending between the detector positioned on an upper surface of said enclosure and the source rod longitudinally extending within said enclosure such that it is transversely and longitudinally spaced apart from the detector, wherein said absorption element has a first profile in a first radiation path corresponding to a first operative position and a second profile different from said first profile in a second radiation path corresponding to a second operative position.

23. A field block according to claim 22, wherein said absorption element profile which is presented to the radiation path changes as said absorption element translates within said enclosure corresponding to the first and second operative positions.

24. A field block according to claim 23, wherein said absorption element is rotatably mounted within said field block to rotate said absorption element such that it presents the first profile in the radiation path in the first operative position and the second profile in the radiation path in the second operative position.

25. A field block according to claim 24, wherein said rotation is in response to a motorized input.

26. A field block according to claim 24, wherein said rotation is in response to manual movement of a lever attached to said absorption element.

27. A field block according to claim 22, wherein said absorption element profile which is presented to the radiation path changes while said absorption element remains substantially stationary within said enclosure.

28. A field block for use with a nuclear density gauge having a source rod and a detector, said field block comprising an absorption element and an upper support platform having opposing outer and inner surfaces defining a thickness therebetween, wherein said absorption element is capable of simulating at least one known density when subjected to analysis using the nuclear density gauge, and wherein, in position for operation, the nuclear density gauge is supported by said field block upper support platform surface, and the source rod and detector define a detection radiation path having an associated spatial volume therebetween, and wherein said absorption element is configured to extend about a portion of the radiation path to thereby leave a major portion of the radiation path free.

29. A field block according to claim 28, wherein said major free portion includes an air space extending between the upper platform inner surface and the outer contour of said absorption element.

30. A field block according to claim 28, wherein said absorption element is mounted to said field block such that it is translatable from a first operative position to a second operative position.

31. A field block according to claim 28, wherein the nuclear density gauge detects two simulated density readings, a first reading corresponding to said absorption element positioned in said first operative position and a second reading corresponding to said absorption element positioned in said second operative position.

32. A field block according to claim 30, wherein said first and second operative positions are at substantially the same depth in said field block, the translation of said absorption element thereby providing two different simulated material density readings at a single source depth.

33. A field block according to claim 28, wherein said absorption element has an outer surface contour, and wherein said absorption element contour and said platform inner surface are configured in spaced-apart relationship to define a major air space volume therebetween.

34. A field block according to claim 33, wherein said upper support platform is provided by the upper portion of an enclosure, and wherein the upper portion of the field block enclosure and said absorption element contour define an air gap volume therebetween which extends proximate to a major portion of the perimeter of said absorption element within said field block.

35. A field block according to claim 28, wherein said field block includes a radiation path extending between the detector positioned on an upper surface of said platform and the source rod longitudinally extending within said field block and transversely and longitudinally spaced apart from the detector, wherein said at least one air gap volume is configured to extend around the portion of the perimeter of said absorption element which is positioned in the radiation path.

36. A field block according go claim 35, wherein said absorption element has a perimeter portion with a profile which is presented to the radiation path, and wherein said profile changes as said absorption element moves from one operative position to another.

37. A field block according to claim 36, wherein said absorption element is rotatably mounted within said field block to rotate said absorption element such that it presents a first profile in the radiation path in the first operative position and a second profile in the radiation path in the second position.

38. A field block according to claim 37, wherein said rotation is motorized.

39. A field block according to claim 37, wherein said rotation is in response to movement of an externally accessible manual lever in communication with said absorption element within said field block.

40. A field block according to claim 28, wherein said absorption element is linearly translatable within said field block along the radiation path.

41. A field block according to claim 40, wherein said linear translation is in response to rotation of a lever attached to said absorption element and mounted on said field block such that it is externally accessible.

42. A field block according to claim 41, wherein said linear translation is motorized.

43. A field block for use with a nuclear density gauge comprising an absorption element, wherein said absorption element is capable of simulating at least one known density when subjected to analysis using the nuclear density gauge, wherein said field block further comprises an enclosure, and wherein said absorption element is translatable from a first operative position to a second operative position, and wherein said enclosure includes a substantially hollow region configured to allow said absorption element to translate in one or more of a linear or rotatable manner within said enclosure.

44. A field block according to claim 43, wherein the nuclear density gauge detects two backscatter measurements, a first measurement corresponding to said absorption element positioned in said first operative position and a second measurement corresponding to said absorption element positioned in said second operative position.

45. A field block according to claim 44, wherein the nuclear density gauge detects two different measurements, a first measurement corresponding to a direct transmission measurement with said absorption element positioned in said first operative position, and a second measurement corresponding to a backscatter measurement with said absorption element positioned in said second operative position.

46. A field block according to claim 43, wherein said absorption element is mounted to said field block such that it is translatable from a first operative position to a second operative position in response to an externally accessible lever.