초록 ▼

An optical absorption gas sensor includes a radiation source, detector and radiation guide which has a rectangular cross section and curves around a side of the cross section. Locating elements locate a support element relative to the radiation guide to align the radiation source and detector with t

An optical absorption gas sensor includes a radiation source, detector and radiation guide which has a rectangular cross section and curves around a side of the cross section. Locating elements locate a support element relative to the radiation guide to align the radiation source and detector with the guide. Radiation from the reference radiation source may be transmitted through a transparent measurement radiation source. Radiation from a reference radiation source may be directed around the measurement reference source. A light emitting diode may generate radiation which is detected by a photodiode and the photodiode may be driven to generate radiation having a different emission spectrum detectable using the light emitting diode, in another operating mode. Two or more abutting L-shaped radiation guide portions may form the radiation guide.

대표청구항 ▼

1. A gas sensor comprising a radiation source, a detector operable to detect radiation emitted by the radiation source and a radiation guide operable to guide radiation between the radiation source and the detector, the radiation guide comprising a curved portion having a substantially rectangular c

1. A gas sensor comprising a radiation source, a detector operable to detect radiation emitted by the radiation source and a radiation guide operable to guide radiation between the radiation source and the detector, the radiation guide comprising a curved portion having a substantially rectangular cross section, wherein the curved portion of the radiation guide curves around an axis parallel to one of the sides of the rectangular cross section; wherein the radiation guide has an inward facing surface formed from a material operable to reflect radiation emitted by the radiation source, which material absorbs at least 1% of incident radiation. 2. A gas sensor according to claim 1, wherein the substantially rectangular cross section is a substantially oblong cross section having a major and a minor dimension. 3. A gas sensor according to claim 2, wherein the curved portion of the radiation guide curves around an axis parallel to the major dimension of the substantially rectangular cross section. 4. A gas sensor according to claim 1, wherein the radiation guide comprises a collimator operable to at least partially collimate radiation emitted by the radiation source. 5. A gas sensor according to claim 4, wherein the radiation guide comprises a major dimension and radiation emitted by the radiation source is generally collimated by the collimator predominantly in a single direction parallel to the major dimension of the radiation guide. 6. A gas sensor according to claim 4, wherein the collimator comprises a parabolic reflector. 7. A gas sensor according to claim 1, wherein the radiation guide comprises a condenser operable to condense radiation onto the detector. 8. A gas sensor according to claim 7, wherein the radiation guide comprises a major dimension and radiation entering the condenser from the radiation guide is predominantly condensed onto the detector in a single direction parallel to the major dimension of the radiation guide. 9. A gas sensor according to claim 7, wherein the condenser comprises a parabolic reflector. 10. A gas sensor according to claim 1, wherein the radiation source and the detector are adjacent to each other. 11. A gas sensor according to claim 1, wherein the shortest path length of radiation between the radiation source and the detector along the radiation guide is at least ten times the spacing between the radiation source and the detector. 12. A gas sensor according to claim 1, wherein the radiation source and the detector are in thermal communication with each other. 13. A gas sensor according to claim 1, wherein the radiation guide comprises first and second curved portions which curve in opposite senses. 14. A gas sensor comprising a radiation source, a detector operable to detect radiation emitted by the radiation source and a radiation guide operable to guide radiation between the radiation source and the detector; the radiation guide comprising a curved portion having a substantially rectangular cross section, wherein the curved portion of the radiation guide curves around an axis parallel to one of the sides of the rectangular cross section; wherein: the radiation guide comprises a plurality of said curved portions; the radiation guide comprises first and second curved portions which curve in opposite senses; and the radiation guide comprises a first curved portion which curves in a first sense and then a second curved portion, further along the radiation guide than the first curved portion (measured from the radiation source to the detector) which curves in a second opposite sense, and a third curved portion, further along the radiation guide than the second curved portion (measured from the radiation source to the detector) curved in the first sense. 15. A gas sensor according to claim 14, wherein the first and third curved portion each curve in the first sense by at least 10° and the second curved portion, curves in the opposite sense with a substantially constant curve for at least 180°. 16. A gas sensor according to claim 14, wherein the radiation guide has a plane of symmetry. 17. A gas sensor according to claim 14, which changes the mean direction of radiation between the radiation source and the detector by at least 90°. 18. A gas sensor according to claim 14, wherein the integral of the magnitude of the curvature of the radiation guide is at least 90° and less than 720°. 19. A gas sensor according to claim 14, wherein the radiation guide has a recess adjacent the radiation source and/or detector, the radiation source and/or detector having a radiation guide facing surface and an electrical connection on the respective radiation guide facing surface. 20. A gas sensor according to claim 14, wherein the radiation source and the detector are adjacent to each other. 21. A gas sensor comprising a radiation source, a detector opera detect radiation emitted by the radiation source and a radiation guide operable to guide radiation between the radiation source and the detector, the radiation guide comprising a curved portion having a substantially rectangular cross section, wherein the curved portion of the radiation guide curves around an axis parallel to one of the sides of the rectangular cross section; wherein the gas sensor comprises a radiation guide element comprising or consisting of the said radiation guide, and a support element comprising the radiation source and/or the detector, wherein the radiation guide element or the support element may comprise a plurality of locating elements configured to locate the support element relative to the radiation guide element to thereby align the detector and radiation source with the radiation guide. 22. A gas sensor according to claim 21, wherein the radiation guide or the support element comprises three locating elements. 23. A gas sensor according to claim 21, wherein the radiation guide or the support element comprises a biasing means to bias the support element towards the radiation guide element. 24. A gas sensor comprising a support element and a radiation guide element, the support element comprising a radiation source and a detector operable to detect radiation emitted by the radiation source; the radiation guide element comprising a radiation guide operable to guide radiation between the radiation source and the detector; wherein the support element or the radiation guide element comprises a plurality of locating elements configured to locate the support element relative to the radiation guide element to thereby align the radiation source and the detector with the radiation guide. 25. A gas sensor according to claim 24, wherein the gas sensor comprises three locating elements. 26. A gas sensor according to claim 24, wherein the gas sensor comprises a biasing means to bias the support element towards the radiation guide element. 27. A gas sensor comprising a radiation source, a detector operable to detect radiation emitted by the radiation source and a radiation guide operable to guide radiation between the radiation source and the detector, wherein the detector is operable to emit radiation having a different wavelength spectrum to that emitted by the radiation source, and the radiation source is operable to detect radiation emitted by the detector. 28. A gas sensor according to claim 27, further comprising an electronic circuit operable to cause the radiation source and the detector to operate in two modes such that in a first mode the radiation source emits radiation and said radiation is detected by the detector to provide a measurement signal, and in a second mode the detector emits radiation and said radiation is detected by the radiation source to provide a reference signal. 29. A gas sensor according to claim 27, wherein radiation emitted by the detector and detected by the radiation source provides a reference signal and the radiation emitted by the radiation source and detected by the detector provides a measurement signal. 30. A gas sensor according to claim 27, wherein the detector and radiation source emit radiation with different peak wavelengths. 31. A gas sensor according to claim 27 wherein the radiation guide comprises a curved portion having a substantially rectangular cross section, wherein the curved portion of the radiation guide curves around an axis parallel to one of the sides of the rectangular cross section. 32. A gas sensor comprising a first radiation source, a second radiation source, a detector operable to detect radiation emitted by the first radiation source and the second radiation source, and a radiation guide operable to guide radiation from the first radiation source and the second radiation source to the detector, wherein radiation emitted from the second radiation source is guided along a path extending either or both around or through the first radiation source. 33. A gas sensor according to claim 32, wherein the second radiation source emits radiation with a different wavelength spectrum to the first radiation source. 34. A gas sensor according to claim 32, wherein radiation emitted from the second radiation source is guided along a path extending through the first radiation source. 35. A gas sensor according to claim 34, wherein at least 1% of the radiation emitted by the second radiation source is transmitted through the first radiation source. 36. A gas sensor according to claim 32, wherein the substantial majority or all of the radiation from the second radiation source which reaches the detector passes through the first radiation source. 37. A gas sensor according to claim 32, wherein radiation emitted from the second radiation source is transmitted around the first radiation source. 38. A gas sensor according to claim 32, wherein the first and second radiation sources are mounted to opposite sides of a printed circuit board, the printed circuit board comprising a bore therethrough, the first and second radiation sources being located at opposite ends of the bore. 39. A gas sensor according to claim 32, wherein the gas sensor comprises an electronic circuit operable to pulse the first and second radiation sources alternately such that radiation from either the first radiation source or the second radiation source may be detected by the detector. 40. A gas sensor according to claim 32 wherein the radiation guide comprises a curved portion having a substantially rectangular cross section, wherein the curved portion of the radiation guide curves around an axis parallel to one of the sides of the rectangular cross section. 41. A gas sensor comprising a radiation source, a detector operable to detect radiation emitted from the radiation source and a radiation guide having a plurality of reflective walls, wherein the radiation guide is defined by two abutting radiation guide portions having substantially L-shaped reflective surfaces. 42. A method of manufacturing an optical absorption gas sensor comprising two or more L-shaped radiation guide comprising at least one reflective surface and bonding the two or more L-shaped radiation guide portions to form a radiation guide such that the reflective surface of the two or more L-shaped radiation guide portions forms the interior surface of the radiation guide. 43. A gas sensor comprising a support element and a radiation guide element, the support element comprising a radiation source and a detector operable to detect radiation emitted by the radiation source, the radiation guide element comprising a radiation guide having a conductive surface, the radiation source and/or detector having a radiation guide facing surface with an electrical connection on the radiation guide facing surface, the radiation guide comprising a support element facing surface which forms at least part of the conductive surface, and a recess in the support element facing surface adjacent to the radiation source and/or a recess in the support element facing surface adjacent to the detector.