WO2014164505A2

WO2014164505A2 - Gas sensor for breath alcohol and other analytes

Info

Publication number: WO2014164505A2
Application number: PCT/US2014/022634
Authority: WO
Inventors: John S. Laudo; Joseph D. Dennis
Original assignee: Battelle Memorial Institute
Priority date: 2013-03-11
Filing date: 2014-03-10
Publication date: 2014-10-09
Also published as: WO2014164505A3

Abstract

Systems, methods, and devices for sensing a gaseous analyte are disclosed. A system for gaseous analyte detection generally includes a gas sensor and a processor. The gas sensor may be embodied as a sensor device including a flow tube, a primary mirror, a mosaic plate, a broadband infrared (IR) source, and a detector. The gas sensor may also be embodied as a sensor device including a mixing chamber including a sensor ring and a common source for producing a homogenous signal and a relay mirror attached to mixing chamber. A method for detecting a gaseous sample may include projecting a broadband infrared (IR) source into a gaseous sample, reflecting the IR source between a primary mirror and at least one mini-facet mirror, collecting the IR source at a detector, and calculating the concentration of at least one gas analyte in real time.

Description

GAS SENSOR FOR BREATH ALCOHOL AND OTHER ANALYTES

BACKGROUND

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 61/775,963, filed March 1 1 , 2013. The entirety of that application is fully incorporated by reference herein.

[0002] The present disclosure relates to systems, methods, and devices for sensing gas analytes. Generally, the system may be used for the detection and discrimination of ethanol, Benzene, Toluene, EthylBenzene, and Xylene (BTEX) and/or methane in water at the parts-per-billion (ppb) concentration range. Methods to detect the presence of a gas analyte are also disclosed. The device may be a portable, low-cost sensor for accurate, real-time detection and discrimination of one or more gas analytes.

[0003] An optical absorption sensor device traditionally includes a light source, a detector, and an absorption cell including a sample volume and one or more mirrors. The light source may be transmitted multiple times through the absorption cell (or multipass cell) by reflecting the light source between mirrors on either end. These multiple reflective passes increase the path length over which the light source travels. According to the Beer-Lambert Law, a detected absorption reading is directly proportional to the product of path length and concentration. Multi-pass cells increase the path length of the light source and thereby allow a lower concentration of gas analyte to be determined without changing the magnitude of the detected absorption signal.

[0004] Current low cost, smaller-sized sensor devices have a number of recognized limitations. First, they use relatively expensive laser-based technology as the light source. To discriminate between multiple different gases, these sensors may employ multiple laser-based technology sources, with each additional source driving up cost and complexity of the sensor. Second, they may have an active surface that is used for detection of a chemical change. Before another measurement can be performed, the active surface must be heated to remove trace reactants and/or products from the prior chemical reaction. Active surfaces require a downtime (or dwell time) of approximately thirty seconds or more between each concentration determination. This prevents the sensor from taking real-time measurements with only sub-second lag times, which is a necessary ability for determining ethanol levels in human breath.

[0005] It would be desirable to provide systems, methods, and devices for low-cost, real-time detection of gas analytes. It would be advantageous to provide a portable sensor device which efficiently channels a broadband IR source and enables the detection of a plurality of gas analytes at ppb concentration range. The device may be used in the transportation sector as a low cost, compact, accurate drunk driving sensor which is competitive with state-of the art sensors. The device may also act as a monitor for the detection and discrimination of BTEX in the transportation and chemical processing industries. The device may alternatively be used to detect methane diffusing out of a liquid sample.

BRIEF DESCRIPTION

[0006] In one embodiment, a system for gaseous analyte detection includes a gas sensor for detecting an infrared absorption signal and a processor for calculating concentration of a gaseous sample from the detected infrared absorption signal in realtime.

[0007] In another embodiment, a sensor device for sensing a gaseous analyte includes a flow tube having a first end and a second end, wherein the flow tube receives a gaseous sample, a primary mirror attached to the first end, a mosaic plate attached to the second end and including at least one mini-facet mirror, a broadband infrared (IR) source removably attached to the mosaic plate, the IR source generating a beam of infrared light, and a detector removably attached to the mosaic plate.

[0008] In yet another embodiment, a sensor device for sensing a gaseous analyte includes a mixing chamber which receives a gaseous sample and includes a sensor ring and a common source for producing a homogenous signal, and a relay mirror attached to the mixing chamber. The relay mirror directs the homogenous signal to a particular sensor in the sensor ring.

[0009] In a different embodiment, a method for detecting a gaseous sample includes projecting a broadband infrared (IR) beam into a gaseous sample, reflecting the IR beam between a primary mirror and at least one mini-facet mirror, collecting the IR beam at a detector, and calculating the concentration of at least one gas analyte in real time.

[0010] In another embodiment, a method for detecting a gaseous sample includes mixing a broadband infrared (IR) signal in a region with equal path length to produce a homogenous common source output, relaying the common source output to at least one sensor or detector, and calculating the concentration of at least one gas in real-time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following is a brief description of the drawings, which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same.

[0012] FIG. 1 is an overview diagram of a system for gaseous analyte sensing.

[0013] FIG. 2 is a side view of a first exemplary embodiment of a gaseous analyte sensor device.

[001 ] FIG. 3 is a perspective view of the sensor device of FIG. 2.

[0015] FIG. 4 is a view of the primary mirror and mini-facet mirrors from the sensor device of FIG. 2.

[0016] FIG. 5 is a rear left perspective view of a second exemplary embodiment of a gaseous analyte sensor device. Compared to FIG. 2, the flow tube has been widened in width and shortened in length. A machinable, low-cost mosaic back plate has also been added for support and arrangement of the mini-facet mirrors;

[0017] FIG. 6 is a front right perspective view of the sensor device of FIG. 5.

[0018] FIG. 7 is an X-Z plane cross-sectional view of the sensor device of FIG. 5, showing the interior surface of the mosaic back plate.

[0019] FIG. 8 is an X-Z plane cross-sectional view of the sensor device of FIG. 5, showing a close-up view of the interior surface of the mosaic back plate and labeling the mini-facet mirrors.

[0020] FIG. 9 is an external perspective view of an I R source component.

[0021] FIG. 10 is an external perspective view of another IR source component.

[0022] FIG. 11 is an external perspective view of a detector assembly according to one embodiment of the present disclosure. [0023] FIG. 12 is an external perspective view showing only the butterfly mount from the detector assembly of FIG. 11.

[0024] FIG. 13 is a diagram showing different views of the butterfly mount of FIG. 12.

[0025] FIG. 14 is a perspective view of a mounted detector crystal.

[0026] FIG. 15 is a perspective view of a non-mounted detector crystal.

[0027] FIG. 16 is a perspective view of a mount board for the detector crystal of FIG.

15.

[0028] FIG. 17 is a diagram showing different views of the mount board of FIG. 16.

[0029] FIG. 18 is an external perspective view of a third exemplary embodiment of a gaseous analyte sensor device. In this embodiment, the flow tube has been widened in width and shortened in length relative to the first and second exemplary embodiments. Fewer mini-facet mirrors are employed, and they are not arranged in a circular pattern.

[0030] FIG. 19 is an external perspective view of a fourth exemplary embodiment of a gaseous analyte sensor device. In this embodiment, a detector/sensor ring is present at one end of a mixing chamber. The beam of infrared light passes through gas in the mixing chamber and bounces off of a relay mirror that directs the beam of infrared light to one of the sensors in the detector/sensor ring. This construction permits the path length to each sensor to remain equal so that it does not affect calculation of the results. This construction also permits the signal from the devices of FIG. 2, FIG. 5, and FIG. 18 to be distributed to multiple sensors in the detector/sensor ring.

[0031] FIG. 20 is a flow diagram for one embodiment of a method for real-time sensing of a gaseous analyte.

[0032] FIG. 21 is a flow diagram for another embodiment of a method for real-time sensing of a gaseous analyte.

[0033] FIG. 22 is a graph showing fractional ppm precision over a 1 minute time frame with a steady state concentration at 0.07772 mg/dL.

[0034] FIG. 23 is a graph showing fractional ppm precision over a 1 minute time frame with a steady state concentration at 0.131 mg/dL. DETAILED DESCRIPTION

[0035] A more complete understanding of the processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the existing art and/or the present development, and are, therefore, not intended to indicate relative size and dimensions of the assemblies or components thereof.

[0036] Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.

[0037] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0038] As used in the specification and in the claims, the term "comprising" may include the embodiments "consisting of and "consisting essentially of." The terms "comprise(s)," "include(s)," "having," "has," "can," "contain(s)," and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients/steps and permit the presence of other ingredients/steps. However, such description should be construed as also describing compositions or processes as "consisting of and "consisting essentially of" the enumerated ingredients/steps, which allows the presence of only the named ingredients/steps, along with any impurities that might result therefrom, and excludes other ingredients/steps.

[0039] Numerical values in the specification and claims of this application should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0040] All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (for example, the range of "from 2 grams to 10 grams" is inclusive of the endpoints, 2 grams and 10 grams, and all the intermediate values). The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and/or values.

[0041] As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about" and "substantially," may not be limited to the precise value specified, in some cases. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. The modifier "about" should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression "from about 2 to about 4" also discloses the range "from 2 to 4." The term "about" may refer to plus or minus 10% of the indicated number. For example, "about 10%" may indicate a range of 9% to 11%, and "about 1" may mean from 0.9-1.1. Other meanings of "about" may be apparent from the context, such as rounding off, so, for example "about 1" may also mean from 0.5 to 1.4.

[0042] With reference to FIG. 1 and FIG. 2, a system 100 for sensing gaseous analytes centers around a gas analyte sensor 110, which may be mobile or stationary, and of pocket-sized dimension or scaled up for industrial-sized applications. The sensor may include a light source, detector, and plurality of mirrors (not shown). The sensor may be a multi-pass cell optical absorption cell. Mount 101 is removably attachable to the sensor and may include: a handle for gripping a smaller-sized sensor 110, a shaft for sending sensor 110 into drilled holes for oil and gas sensing applications, a stationary flat surface mount for stationary applications, an adhesive mount for attachment to chemical equipment or the like so that the sensor 110 may serve as a passive monitor of the chemical environment, and other mount applications as known by one having ordinary skill in the art. Sample input 102 includes any means for inputting the sample into the gas sensor, such as an inhaler, manual injection point, automatic input fan, etc. Fan 104 may serve as an input, output, or mixing point for gaseous samples within the gas sensor 110. [0043] The sensor 110 is removably attachable to a processor 106. The processor 106 may be digitally embodied as a single-core processor, dual core processor (or more generally by a multiple-core processor), a digital processor and cooperating math coprocessor, a digital controller, or the like. The digital processor 106 includes memory for storing instructions, wherein the instructions enable calculation of the concentration of multiple gaseous analyte components in real time according to a detected magnitude of absorbance, fixed path length of the sensor, and the Beer-Lambert Law, shown as: = - log₁₀(^) = £(c)(L) EQN. 1 where A is the absorbance, lo is the intensity of the incident light at a given wavelength, I is the intensity of the transmitted light, £ is a constant (the extinction coefficient), c is the concentration of the substance and L is the path length. Therefore, for a fixed path length the transmitted light intensity is proportional to the concentration. The concentration, c, can be determined from the magnitude of detected absorbance.

[0044] Display 108 is in digital communication with the processor 106 and can display the output of concentration calculations for view by a user. The display may consist of LCD, OLED materials, or other display technologies known by one having ordinary skill in the art. In one embodiment, the processor 106 and display 108 are integrated into the sensor 110.

[0045] With reference to FIG. 2, the first exemplary embodiment of the gaseous analyte sensor device 210 includes a flow tube 212 with a first end 211 and second end 213. The flow tube 212 may be between approximately 7 and 8 inches in length with a diameter between approximately 1 and 3 inches. In one embodiment, flow tube 212 is a cylinder with a compact design at 1 inch diameter and 7 inch length. In the first exemplary embodiment, the flow tube 212 has a diameter of 23-25 mm. A primary mirror 214 is located on the first end 211 of flow tube 212 for reflecting light projected from an IR source 230 back towards one or more mini-facet mirrors 222. The IR source 230 and mini-facet mirrors 222 are located on a second end 213 of the flow tube 212.

[0046] The IR source 230 consists of a laser-based technology or non-laser based broadband IR source. In one embodiment, the IR source 230 is an Intex INT20-1000. In another embodiment, the source is a high temperature Hawkeye IR18 1200 degree C Silicon Nitride emitter. The IR source 230 may emit IR radiation in the 2-15 micron regime of the mid-infrared spectrum. The size of the mini-facet mirrors 222 depends on the type of IR source 230 used and the associated diameter of the IR source beam. In this exemplary embodiment, the mini-facet mirrors 222 are 3.3 x 3.3 mm in size.

[0047] With reference to FIG. 3, energy from IR source 230 first travels to the primary mirror 214, where it is reflected to a single mini-facet mirror 222 at the second end 213 of the flow tube 212. The first mini-facet mirror 222 reflects this energy laterally to an adjacent mini-facet mirror 222 which then reflects the energy back to the primary mirror 214 as incident energy. The primary mirror 214 can subsequently reflect the incident energy to a third mini-facet mirror 222, and the process of lateral shifting and end-to-end reflections continues until the IR energy reaches a detector 240 located on the second end 213 of flow tube 212. In transiting the tube, the energy may be expanded to fill the primary mirror 214 at the first end 211 and focused to an image at or near the mini-mirror facets 222 on the second end 213.

[0048] In the first exemplary embodiment, the mini-facet mirrors 222 are located at approximately the center of the curvature of the primary mirror 214 by design. This design allows for a low power, low cost, small IR source 230 to be used, as opposed to costly scanned infrared laser systems. Use of a broadband IR source 230 not only reduces cost, it also allows for a broadband spectrum of interrogation by source 230. For example, hydrocarbons such as alcohol can be interrogated as well as C0₂ by the same source— as opposed to multiple laser sources to cover the same range (3.2-4.2 microns). The broadband IR source also allows for a burst of IR absorption which, in combination with an appropriate detector 240, allows for real-time measurement of gas analyte concentration. In one embodiment, the final reflection of energy lands on the detector 240 where the energy is spread across four square detectors of 1 x 1 mm each. The detectors may be MIRA4 sensors from CalSensors, Inc. in Santa Rosa, CA.

[0049] With reference to FIG. 4, a total of 28 reflections occur in the sensor device 210 according to the exemplary embodiment using 18 mini-facet mirrors 222 and a single primary mirror 214. More or fewer mini-facet mirrors 222 may be used to increase or decrease, respectively, the desired path length of IR light through the flow tube 212. The transmission of energy through the sensor device 210 is determined by the quality of coatings on each mirror. For example, a 98% to 99.5% reflectance per mirror would yield approximately 23% to 28% transmission of IR energy through the sensor device 210 from the IR source 230 to the detector 240.

[0050] To ensure that the mini-facet mirrors 222 are properly reflecting IR source 230 energy back towards the center of the primary mirror 214, the mirrors 222 have a pre-determined pitch and yaw angle. Table 1 indicates the optimum geometry for the mini-facet mirrors for the exemplary embodiment of sensor device 210:

Table 1

Element X Y Z A (deg) B (deg) C (deg) Name

Geometry.Mirror 3. Back

15 -1.712 -1.750 0.212 0.000 -45.000 0.000 Surface

Geometry.Mirror 3. Edge

16 -1.500 -1.750 0.000 0.000 -45.000 0.000 Curve

17 -1.500 -1.750 0.000 0.000 -45.000 0.000 Geometry.Mirror 3. Edge

18 -1.500 1.500 0.000 45.000 0.000 0.000 Geometry.Mirror 4

Geometry.Mirror

19 -1.500 1.500 0.000 45.000 0.000 0.000 4. Reflecting Surface

Geometry.Mirror 4. Back

20 -1.500 1 .288 0.212 45.000 0.000 0.000 Surface

Geometry.Mirror 4. Edge

21 -1.500 1.500 0.000 45.000 0.000 0.000 Curve

22 -1.500 1.500 0.000 45.000 0.000 0.000 Geometry.Mirror 4.Edge

23 -1.500 4.650 0.000 -45.500 0.000 0.700 Geometry.Mirror 5

Geometry.Mirror

24 -1.500 4.650 0.000 -45.500 0.000 0.700 5. Reflecting Surface

Geometry.Mirror 5. Back

25 -1.503 4.864 0.210 -45.500 0.000 0.700 Surface

Geometry.Mirror 5.Edge

26 -1.500 4.650 0.000 -45.500 0.000 0.700 Curve

27 -1.500 4.650 0.000 -45.500 0.000 0.700 Geometry.Mirror 5. Edge

28 1.500 -5.000 0.000 0.000 45.000 0.000 Geometry.Mirror 6

Geometry.Mirror

29 1.500 -5.000 0.000 0.000 45.000 0.000 6. Reflecting Surface

Geometry.Mirror 6. Back

30 1.712 -5.000 0.212 0.000 45.000 0.000 Surface

Geometry.Mirror 6. Edge

31 1.500 -5.000 0.000 0.000 45.000 0.000 Curve

32 1.500 -5.000 0.000 0.000 45.000 0.000 Geometry.Mirror 6.Edge

33 -1.250 -5.250 0.000 0.000 -45.350 2.800 Geometry.Mirror 7

Geometry.Mirror

34 -1.250 -5.250 0.000 0.000 -45.350 2.800 7. Reflecting Surface

Geometry.Mirror 7. Back

35 -1.463 -5.260 0.2 1 0.000 -45.350 2.800 Surface Element X Y Z A (deg) B (deg) C (deg) Name

Geometry.Mirror 7.Edge

36 -1.250 -5.250 0.000 0.000 -45.350 2.800 Curve

37 -1.250 -5.250 0.000 0.000 -45.350 2.800 Geometry.Mirror 7.Edge

38 1.500 4.565 -1.000 0.000 -45.000 0.000 Geometry.Mirror 8

Geometry.Mirror

39 1.500 4.565 -1.000 0.000 -45.000 0.000 8. Reflecting Surface

Geometry.Mirror 8. Back

40 1.288 4.565 -0.788 0.000 -45.000 0.000 Surface

Geometry.Mirror 8. Edge

41 1.500 4.565 -1.000 0.000 -45.000 0.000 Curve

42 1.500 4.565 -1.000 0.000 -45.000 0.000 Geometry.Mirror 8. Edge

43 4.450 5.000 -1.000 0.000 45.600 2.600 Geometry.Mirror 9

Geometry.Mirror

44 4.450 5.000 -1.000 0.000 45.600 2.600 9. Reflecting Surface

Geometry.Mirror 9. Back

45 4.664 5.010 -0.790 0.000 45.600 2.600 Surface

Geometry.Mirror 9. Edge

46 4.450 5.000 -1.000 0.000 45.600 2.600 Curve

47 4.450 5.000 -1.000 0.000 45.600 2.600 Geometry.Mirror 9. Edge

48 -4.750 -2.000 0.000 -45.400 0.000 0.200 Geometry.Mirror 10

Geometry.Mirror

49 -4.750 -2.000 0.000 -45.400 0.000 0.200 10. eflecting Surface

Geometry.Mirror 10. Back

50 -4.751 -1.786 0.21 1 -45.400 0.000 0.200 Surface

Geometry.Mirror 10. Edge

51 -4.750 -2.000 0.000 -45.400 0.000 0.200 Curve

52 -4.750 -2.000 0.000 -45.400 0.000 0.200 Geometry.Mirror 10. Edge

53 -4.500 -4.750 0.000 45.100 -2.400 0.000 Geometry.Mirror 11

Geometry.Mirror

54 -4.500 -4.750 0.000 45.100 -2.400 0.000 11.Reflecting Surface

Geometry.Mirror 11.Back

55 -4.509 -4.963 0.212 45.100 -2.400 0.000 Surface

Geometry.Mirror 11.Edge

56 -4.500 -4.750 0.000 45.100 -2.400 0.000 Curve Element X Y Z A (deg) B (deg) C (deg) Name

57 -4.500 -4.750 0.000 45.100 -2.400 0.000 Geometry.Mirror 11 .Edge

58 4.500 1.900 0.000 -45.000 -3.800 0.000 Geometry.Mirror 12

Geometry.Mirror

59 4.500 1.900 0.000 -45.000 -3.800 0.000 12. Reflecting Surface

Geometry.Mirror 12. Back

60 4.486 2.112 0.212 -45.000 -3.800 0.000 Surface

Geometry.Mirror 12. Edge

61 4.500 1.900 0.000 -45.000 -3.800 0.000 Curve

62 4.500 1.900 0.000 -45.000 -3.800 0.000 Geometry.Mirror 12. Edge

63 4.750 -0.750 0.000 45.000 6.700 0.000 Geometry.Mirror 13

Geometry.Mirror

64 4.750 -0.750 0.000 45.000 6.700 0.000 13. Reflecting Surface

Geometry.Mirror 13. Back

65 4.775 -0.962 0.211 45.000 6.700 0.000 Surface

Geometry.Mirror 13. Edge

66 4.750 -0.750 0.000 45.000 6.700 0.000 Curve

67 4.750 -0.750 0.000 45.000 6.700 0.000 Geometry.Mirror 13. Edge

68 -4.950 1.000 0.000 47.000 -4.000 0.000 Geometry.Mirror 14

Geometry.Mirror

69 -4.950 1.000 0.000 47.000 -4.000 0.000 14. Reflecting Surface

Geometry.Mirror 14. Back

70 -4.964 0.781 0.204 47.000 -4.000 0.000 Surface

Geometry.Mirror 14. Edge

71 -4.950 1.000 0.000 47.000 -4.000 0.000 Curve

72 -4.950 1.000 0.000 47.000 -4.000 0.000 Geometry.Mirror 14. Edge

73 -4.900 3.750 -0.100 -43.500 0.000 -0.800 Geometry.Mirror 15

Geometry.Mirror

74 -4.900 3.750 -0.100 -43.500 0.000 -0.800 15. Reflecting Surface

Geometry.Mirror 15. Back

75 -4.897 3.956 0.1 18 -43.500 0.000 -0.800 Surface

Geometry.Mirror 15. Edge

76 -4.900 3.750 -0.100 -43.500 0.000 -0.800 Curve

77 -4.900 3.750 -0.100 -43.500 0.000 -0.800 Geometry.Mirror 15. Edge Element X Y Z A (deg) B (deg) C (deg) Name

78 1.250 1.250 0.000 180.000 0.000 0.000 Optical Sources.Source 1

79 7.000 -8.500 -9.000 0.000 0.000 0.000 Geometry.Detector

Geometry.Detector.Refle

80 7.000 -8.500 -9.000 0.000 0.000 0.000 cting Surface

Geometry.Detector.Back

81 7.000 -8.500 -8.900 0.000 0.000 0.000 Surface

82 7.000 -8.500 -9.000 0.000 0.000 0.000 Geometry.Detector.Edge

83 7.000 -15.000 -9.000 90.000 0.000 0.000 Geometry.Detect-can1

Geometry.Detect-

84 7.000 -15.000 -9.000 90.000 0.000 0.000 canl .Reflecting Surface

Geometry.Detect-

85 7.000 -21.500 -9.000 90.000 0.000 0.000 canl .Back Surface

Geometry.Detect-

86 7.000 -15.000 -9.000 90.000 0.000 0.000 canl .Edge

Geometry.Subassembly

87 7.000 -12.000 0.000 0.000 0.000 0.000 1.Detect-can 2

Geometry.Subassembly 1. Detect-can 2. Reflecting

88 7.400 -1.600 2.000 0.000 0.000 0.000 Surface

Geometry.Subassembly 1. Detect-can 2. Back

89 7.400 -1.600 8.000 0.000 0.000 0.000 Surface

Geometry.Subassembly

90 7.400 -1.600 2.000 0.000 0.000 0.000 1.Detect-can 2. Edge

Geometry.Subassembly

91 6.400 -1.600 1 .000 0.000 0.000 0.000 1.Det-1

Geometry.Subassembly

92 6.400 -1.600 1.000 0.000 0.000 0.000 1.Det-1.Surface 1

Geometry.Subassembly

93 6.400 -1.600 1.100 0.000 0.000 0.000 1.Det-1.Surface 2

Geometry.Subassembly

94 6.150 -3.600 1 .000 0.000 0.000 0.000 1. Det-1. Edge Curve

Geometry.Subassembly

95 6.150 -3.600 1.000 0.000 0.000 0.000 1. Det-1. Edge Element X Y Z A (deg) B (deg) C (deg) Name

Geometry.Subassembly

96 7.400 -1.600 1.000 0.000 0.000 0.000 1.Det- 2

Geometry.Subassembly

97 7.400 -1.600 1.000 0.000 0.000 0.000 1.Det- 2.Surface 1

Geometry.Subassembly

98 7.400 -1 .600 1.100 0.000 0.000 0.000 1.Det- 2.Surface 2

Geometry.Subassembly

99 10.725 -3.600 1.000 0.000 0.000 0.000 1.Det- 2.Edge Curve

Geometry.Subassembly

100 10.725 -3.600 1.000 0.000 0.000 0.000 1.Det- 2.Edge

Geometry.Subassembly

101 7.400 -0.600 1.000 0.000 0.000 0.000 1.Det- 3

Geometry.Subassembly

102 7.400 -0.600 1.000 0.000 0.000 0.000 1.Det- 3.Surface 1

Geometry.Subassembly

103 7.400 -0.600 1.100 0.000 0.000 0.000 1.Det- 3.Surface 2

Geometry.Subassembly

104 10.725 0.975 1.000 0.000 0.000 0.000 1. Det- 3. Edge Curve

Geometry.Subassembly

105 10.725 0.975 1.000 0.000 0.000 0.000 1.Det- 3.Edge

Geometry.Subassembly

106 6.400 -0.600 1.000 0.000 0.000 0.000 1.Det- 4

Geometry.Subassembly

107 6.400 -0.600 1.000 0.000 0.000 0.000 1.Det- 4.Surface 1

Geometry.Subassembly

108 6.400 -0.600 1.100 0.000 0.000 0.000 1.Det- 4.Surface 2

Geometry.Subassembly

109 6.150 0.975 1.000 0.000 0.000 0.000 1. Det- 4. Edge Curve

Geometry.Subassembly

110 6.150 0.975 1 .000 0.000 0.000 0.000 1.Det- 4.Edge

1 1 1 7.006 -9.002 -1.899 18.561 77.372 17.862 Geometry. Plus 1

Geometry.Plus

112 7.006 -9.002 -1.899 18.561 77.372 17.862 1.Reflecting Surface

Geometry.Plus I .Back

113 7.104 -9.004 -1 .878 18.561 77.372 17.862 Surface Element X Y z A (deg) B (deg) C (deg) Name

Geometry.Plus I .Edge

114 7.006 -9.002 -1.899 18.561 77.372 17.862 Curve

115 7.006 -9.002 -1.899 18.561 77.372 17.862 Geometry.Plus I .Edge

116 8.801 -9.002 -2.025 1 1.522 -69.612 -1 1.098 Geometry.Plus 2

Geometry.Plus

1 17 8.801 -9.002 -2.025 11.522 -69.612 -1 1.098 2. Reflecting Surface

Geometry.Plus 2. Back

118 8.707 -9.004 -1.990 1 1.522 -69.612 -1 1.098 Surface

Geometry.Plus 2. Edge

1 19 8.801 -9.002 -2.025 1 1.522 -69.612 -1 1.098 Curve

120 8.801 -9.002 -2.025 1 1.522 -69.612 -11.098 Geometry.Plus 2. Edge

121 8.250 -9.651 -2.031 1 1.555 69.620 100.849 Geometry.Plus 3

Geometry.Plus

122 8.250 -9.651 -2.031 1 1.555 69.620 100.849 3. Reflecting Surface

Geometry.Plus 3. Back

123 8.252 -9.557 -1.997 1 1.555 69.620 100.849 Surface

Geometry.Plus 3. Edge

124 8.250 -9.651 -2.031 1 1.555 69.620 100.849 Curve

125 8.250 -9.651 -2.031 1 1.555 69.620 100.849 Geometry.Plus 3. Edge

126 8.259 -7.805 -1.903 18.589 -77.360 71.831 Geometry.Plus 4

Geometry.Plus

127 8.259 -7.805 -1.903 18.589 -77.360 71.831 4.Reflecting Surface

Geometry.Plus 4. Back

128 8.260 -7.903 -1 .882 18.589 -77.360 71.831 Surface

Geometry.Plus 4. Edge

129 8.259 -7.805 -1.903 18.589 -77.360 71.831 Curve

130 8.259 -7.805 -1.903 18.589 -77.360 71.831 Geometry.Plus 4. Edge

131 0.000 0.000 -197.500 0.000 0.000 0.000 Geometry.GAS

132 0.000 0.000 -197.500 0.000 0.000 0.000 Geometry.GAS. Surface 1

133 0.000 0.000 -2.500 0.000 0.000 0.000 Geometry.GAS. Surface 2

134 0.000 0.000 -197.500 0.000 0.000 0.000 Geometry. GAS. Edge

135 0.000 0.000 -197.000 0.000 0.000 0.000 Geometry.Plane

136 0.000 0.000 -197.000 0.000 0.000 0.000 Geometry. Plane. Surface Element X Y z A (deg) B (deg) C (deg) Name

137 1.500 1 .500 2.750 180.000 0.000 0.000 Optical Sources.Source 2

138 7.000 0.000 4.000 0.000 0.000 0.000 Geometry. Plane 1

Geometry.Plane

139 7.000 0.000 4.000 0.000 0.000 0.000 1.Surface

Geometry.Subassembly

140 0.400 7.400 7.000 0.000 0.000 0.000 1

141 5.000 -4.000 -1 .000 0.000 -45.000 0.000 Geometry.Mirror 16

Geometry.Mirror

142 5.000 -4.000 -1 .000 0.000 -45.000 0.000 16. Reflecting Surface

Geometry.Mirror 16. Back

143 4.788 -4.000 -0.788 0.000 -45.000 0.000 Surface

Geometry.Mirror 16. Edge 44 5.000 -4.000 -1.000 0.000 -45.000 0.000 Curve

145 5.000 -4.000 -1 .000 0.000 -45.000 0.000 Geometry.Mirror 16. Edge

146 7.500 -3.750 -1.000 0.000 45.200 -2.600 Geometry.Mirror 17

Geometry.Mirror

47 7.500 -3.750 - .000 0.000 45.200 -2.600 17. Reflecting Surface

Geometry.Mirror 17. Back

148 7.713 -3.760 -0.789 0.000 45.200 -2.600 Surface

Geometry.Mirror 17. Edge

149 7.500 -3.750 -1.000 0.000 45.200 -2.600 Curve

150 7.500 -3.750 -1.000 0.000 45.200 -2.600 Geometry.Mirror 17. Edge

151 -8.000 3.850 -0.750 -44.300 0.000 -0.750 Geometry.Mirror 18

Geometry.Mirror

152 -8.000 3.850 -0.750 -44.300 0.000 -0.750 18. Reflecting Surface

Geometry.Mirror 18. Back

153 -7.997 4.060 -0.535 -44.300 0.000 -0.750 Surface

Geometry.Mirror 18. Edge

154 -8.000 3.850 -0.750 -44.300 0.000 -0.750 Curve

155 -8.000 3.850 -0.750 -44.300 0.000 -0.750 Geometry.Mirror 18. Edge

156 -8.000 1.000 -1.000 46.100 -5.600 0.000 Geometry.Mirror 19

Geometry.Mirror

157 -8.000 1.000 -1.000 46.100 -5.600 0.000 19. Reflecting Surface Element X Y z A (deg) B (deg) C (deg) Name

Geometry.Mirror 19. Back

158 -8.020 0.784 -0.793 46.100 -5.600 0.000 Surface

Geometry.Mirror 19. Edge

159 -8.000 1.000 -1.000 46.100 -5.600 0.000 Curve

160 -8.000 1.000 -1.000 46.100 -5.600 0.000 Geometry.Mirror 19. Edge

161 0.000 0.000 0.000 0.000 0.000 0.000 Geometry.Paraboloid

Geometry.Paraboloid.Sur

162 0.000 0.000 0.000 0.000 0.000 0.000 face

163 1.500 1 .500 4.000 0.000 0.000 0.000 Geometry.lR-Source

Geometry.lR-

164 1.500 1.500 4.000 0.000 0.000 0.000 Source.Outer Wall

Geometry. I R-

165 1.500 1.500 6.125 0.000 0.000 0.000 Source.Front End

Geometry.lR-

166 1.500 1.500 1.875 180.000 0.000 180.000 Source. Back End

167 8.050 -1.200 7.000 0.000 0.000 0.000 Geometry.Detector-A

Geometry.Detector-

168 8.050 -1.200 7.000 0.000 0.000 0.000 A.Outer Wall

Geometry.Detector-

169 8.050 -1.200 8.575 0.000 0.000 0.000 A.Front End

Geometry.Detector-

170 8.050 -1.200 5.425 180.000 0.000 180.000 A.Back End

171 8.050 -1.200 7.000 0.000 0.000 0.000 Geometry.Detector-A 1

Geometry.Detector-A

172 8.050 -1.200 7.000 0.000 0.000 0.000 1. Outer Wall

Geometry.Detector-A

173 8.050 -1.200 7.350 0.000 0.000 0.000 1. Front End

Geometry.Detector-A

174 8.050 -1.200 6.650 180.000 0.000 180.000 LBack End

175 11 .000 -1.100 3.000 0.000 90.000 0.000 Geometry.Detector-b1

Geometry.Detector-

176 1 1.000 -1.100 3.000 0.000 90.000 0.000 b1.Outer Wall

Geometry.Detector-

177 .350 -1.100 3.000 0.000 90.000 0.000 b1. Front End Element X Y z A (deg) B (deg) C (deg) Name

Geometry. Detector-

178 10.650 -1.100 3.000 0.000 -90.000 0.000 bl .Back End

179 11.000 -1.100 3.000 0.000 90.000 0.000 Geometry.Detector-b

Geometry.Detector-

180 11.000 -1.100 3.000 0.000 90.000 0.000 b.Outer Wall

Geometry. Detector-

181 12.575 -1.100 3.000 0.000 90.000 0.000 b. Front End

Geometry Detector-

182 9.425 -1.100 3.000 0.000 -90.000 0.000 b.Back End

183 8.000 0.000 3.000 0.000 -45.000 0.000 Geometry.Bmspltr

Geometry.Bmspltr.Surfac

184 8.000 0.000 3.000 0.000 -45.000 0.000 e 1

Geometry.Bmspltr.Surfac

185 7.505 0.000 3.495 0.000 -45.000 0.000 e 2

Geometry.Bmspltr. Edge

186 8.000 0.000 3.000 0.000 -45.000 0.000 Curve

187 8.000 0.000 3.000 0.000 -45.000 0.000 Geometry.Bmspltr.Edge

[0051] Each mini-facet mirror 222 (3.3 x 3.3 mm) is placed in position, including tip and tilt of the facet 222, to optimize the incident radiation onto the facet 222, to minimize conflicts with adjacent mini-facet mirrors 222, and to ensure that the redirected beam from the mirror 222 will land on the central portion of the primary mirror 214, for those mini-facet mirrors 222 directing energy to that element. Tilt angles for each facet 222 were derived from a single ray trace method where the source 230 ray was reflected from the facet 222 so that it intersected the central portion of the primary mirror 214. This ensures the highest throughput of energy through the sensor device 210 is maintained as the beam reflects from the first end 211 to the second end 213 of flow tube 212. Tilt angles on each mini-mirror facet 222 were created in the first exemplary embodiment by a laser-assisted fabrication process.

[0052] With reference to FIG. 5 and FIG. 6, the second exemplary embodiment of the gaseous analyte sensor device 310 includes a flow tube 312 with ventilation slits 316 present in the circumferential sidewall of the flow tube, and generally spaced evenly around the circumference thereof. The slits 316 allow for the gaseous sample to enter and mix within the flow tube 312. Slits 316 also provide structural rigidity while allowing flow though ability for gas to exchange. Slits 316 create passive air flow in and out of sensor 310. Slits 316 may be covered with a screen (not shown) to filter dust particles out of incoming air. A primary mirror 314 is located at a first end 311 of flow tube 312. A mosaic back plate 320 is located on a second end 313 of flow tube 312. An IR source 330 and detector 340 are removably attachable to the exterior surface of the mosaic back plate 320 located on second end 313.

[0053] The second exemplary embodiment of the gaseous analyte sensor 310 differs from the first exemplary embodiment 210 primarily in the inclusion of the back plate 320, which is a low-cost, metal machinable part for easily attaching and arranging mini-mirror facets 322 (not shown, projecting from interior surface and further described below in FIG. 7 and FIG. 8). Additionally, the diameter of flow tube 312 is also greater in diameter with approximately a half of a centimeter increase in width. The width of flow tube 312 in the exemplary embodiment is approximately 28 mm in diameter.

[0054] With reference to FIG. 7 and FIG. 8, the interior surface of the mosaic back plate 320 is shown in greater detail by showing an X-Z plane cross-sectional view of sensor 310. Mini-facet mirrors 322 are circularly arranged around the outside (circumferential) edge of the back plate 320. Energy from IR source 330 is reflected from the primary mirror 314 to a mini-facet mirror 322. The mini-facet mirror 322 can reflect this energy laterally to an adjacent mini-facet mirror 322 (illustrated for example, with pairs A-B) which then reflects it back to the primary mirror 314 as incident energy. The primary mirror 314 may subsequently reflect the incident energy to another mini- facet mirror 322 pair (for example, pair C-D) and the process of lateral shifting and end- to-end reflections continues until the energy reaches a detector 340 located on the second end 313 of the flow tube 312.

[0055] The 18 mini-facet mirrors 322 may be diced out of a single wafer and attached to the machined mosaic back plate 320. The mini-facet mirrors 322 may be adjusted in pitch and yaw to allow incident source energy to be relayed to the center of the primary mirror. Adjustment parameters may be discovered through computational modeling in raytrace software or other in silico methods known to one having ordinary skill in the art. The geometry of mini-facet mirrors 322 on the mosaic back plate 320 allows for efficient relay of IR energy through the flow tube 312 and thereby enables the sensor device 310 to maintain detection sensitivity in the parts-per-billion concentration range. The number and placement of mirrors is dependent upon the desired path length from the IR source 330 to the detector 340. For example, for a 1-2 mm diameter source 330, each mini-facet mirror 322 sees an incident energy beam of at least 1-2 mm diameter, and usually larger with aberrations experienced during multiple passes through the flow tube 312. In this second exemplary embodiment, the mini-facet mirrors 322 are 3.3 mm x 3.3 mm. Furthermore, there are 18 mirrors in the second exemplary embodiment, enabling the source to travel a 3.96 meter path length after being relayed through all 18 mini-facet mirrors.

[0056] With reference to FIG. 9, the broadband IR source 330 allows for interrogation of gas analytes over a broadband spectrum. Illustrated in FIG. 9 is an Intex INT20-1000 source. This source includes a modulatable silicon membrane which can achieve 750 degree c temperatures and 0Hz or greater duty cycles using 6-7 volt operation and <149 mAmp drive currents. This source can be built with a reflector to improve directionality of the emission in the forward direction, or in a surface mount format for ease of integration onto electronic boards.

[0057] With reference to FIG. 10, the source 330 may alternatively be a high temperature Hawkeye IR18 1200 degree C Silicon Nitride emitter. This source operates at high temperatures, has a parabolic reflector to improve directionality, is larger in diameter and extent, requires higher operating power than the Intex source and is less able to be modulated with direct drive currents and is more amenable to DC or constant current applications with weak signals. Similar sources as those known to one having ordinary skill in the art are contemplated.

[0058] With reference to FIG. 11, a source signal 341 enters detector 340 after the process of lateral shifting between mini-facet mirrors 322 and end-to-end reflections between the primary mirror 314 and mini-facet mirrors 322. The signal may first be split by a beam splitter 344 located at the bottom of a detector mount 342. The beam then travels to metallized spherical mirrors 346, before being sent to a detector crystal (not shown here) which is mounted at the bottom of the butterfly mount. Additional filtering can be implemented by applying filter crystal 348 on top of the detector components. The spherical mirrors 346 focus the radiation from the sensor section onto the active areas of the detectors, providing higher signals that would be otherwise lost. This allows the use of longer wavelength filters, or custom filters to spectrally filter the radiation in the 8-15 micron region where additional unique spectral lines exist. This affords the ability to select spectral operation independently from the main gas sensing geometry 212 and flow conditions of the system.

[0059] The beam splitter may be a reflective beam divider type device (Optometries 4-2430 for example) with faceted mirror grooves which run along one direction of the surface. The facets are arranged in a sawtooth pattern with alternating facets reflecting the incident beam to alternating angular directions such that incident radiation is alternatively directed to one of the two detector channels. The dimensional scale of these facets can be -0.1 to 1 mm approximately, and their angles are determined by the designer to afford the proper angular spread to the detector geometry. If the butterfly mount is not used, a multiple band detector such as the Cal Sensors MIRA4 can be used, replacing the butterfly mount with another integrated detector package 340. The detector 340 preferably monitors infrared spectral bands in the 3-5 micron region over four or more detection channels. The 3-5 micron region can be chosen to maximize the signal response per band with the strongest absorption and greatest spectral widths. In the second exemplary embodiment, the detector includes four channels. Having four channels minimizes costs, as additional sources are not needed to probe different gas analytes. To increase accuracy of detection, one of the four channels may be dedicated to measuring the background absorption of the system in a spectral window that has no other information. This background channel acts as a baseline for ratioing the remaining 3 channels. For example, in ethanol detection, at least 2 bands are expected in the 3.3-3.5 micron region, with the remaining two bands above and below this region.

[0060] The water content of the air may be read via a dedicated sensor band or, to save a channel for measurement, by an external relative humidity sensor. CO₂ may be measured by a band dedicated at 4.2 micron region, which leaves a band for background measurement. The CO₂ band is helpful in calibrating the sensor 310 for use in detecting human breath alcohol, as this band correlates to the exhaled breath volume. Additionally, methane can be sensed by simply changing one or more of the filters used on the detector 340.

[0061] With reference to the diagram set forth in FIG. 12 and FIG. 13, the mount 342 may be a butterfly mount for resting filters 346, 348 at the appropriate angles. The butterfly mount may be CNC machined part which orients the beam splitter, the filters and the detectors in one block. The filters may be ~1 mm thick windows that are cut to size and placed on the transverse bars in the middle of the butterfly block. The filters are chosen by the designer for their appropriate isolation of a spectral region of interest. The butterfly mount may be 1 inch in width and height nominally with access voids for insertion of the components and adjustment of their orientation during assembly. A port feature on the top of the butterfly mount mates the block directly to the baseplate of the mosaic back plate 320 at the detector position 340.

[0062] With reference to FIG. 14, a mounted detector crystal 350 is illustrated. Here, the detector crystal 354 is mounted upon the mount board 358. Thermopile detectors with integrated ASIC amplification architectures can be used which have pre-attached filter crystals. These devices are on the order of 3.8 x 3.8 mm and when mounted on the electronic board as shown are approximately 1cm x 1cm, which affords ease in integration of several detectors in the butterfly or other geometries.

[0063] With reference to FIG. 15, a detector crystal 354 is illustrated in greater detail. For example, Heimann thermopile sensors with ASIC architectures are low cost, pre- filtered detectors that offer amplified outputs which can be utilized by the sensor to support the detection of multiple gas species in the butterfly geometries described above.

[0064] With reference to FIG. 16 and FIG. 17, the mount board 358 includes electrical connections oriented for interfacing with a detector crystal 354. Mount board 358 enables the detector crystal 354 to be mounted in the butterfly geometry of FIG. 12 and FIG. 13. The butterfly mount provides egress for the electronic board pins and their connection through the open sections in the butterfly part.

[0065] With reference to FIG. 18, a third exemplary embodiment of gaseous sensor 410 includes flow tube 412 having six ventilation slits 416. Primary mirror 414 is located at the first end 411 of flow tube 412, while mini-facet mirrors 422 are attached to a mosaic back plate 420 located at a second end 413 of flow tube 412. An IR source and detector (both not shown) are located on the second end 413.

[0066] The third exemplary embodiment of the gaseous analyte sensor 410 differs from other exemplary embodiments 210, 310 primarily in the increased ability to capture the infrared source energy by use of the larger diameter primary mirror 414. Additionally, the diameter of flow tube 412 is also greater in diameter at approximately three inches. Due to the smaller length of flow tube 412, the sensor 410 has relatively less path length for the IR energy to travel. However, with less pass length there is also more total energy received by the detector, as there are also less optical reflection losses along the flow tube 412. The third embodiment, also referred to as the "drum," makes a tradeoff between receiving more energy from the source 430 but with less path length in the flow tube 412. The squat flow tube 412 design of sensor 410 improves sensitivity by increasing the amount of light moving through the device. The increase in signal strength affords higher signal to noise ratio performance by increasing the signal relative to the electronic noise limits. Mini-facet mirrors 222 are arranged so that there is improved efficiency in capturing energy from the source 412, while moving the energy through a smaller yet still significant path length.

[0067] With reference to FIG. 19, a fourth exemplary embodiment of the gaseous sensor 510 includes a mixing chamber 512 having a common source 530 and sensor/detector ring 540. A relay mirror 514 is removably attached to the mixing chamber and acts to direct IR energy from the common source 530 to different sensors and/or detectors on the sensor ring 540.

[0068] In further detail, it is contemplated that the gas to be sampled will be present in the mixing chamber. IR energy passes through the mixing chamber 512 and then exits the mixing chamber through the common source 530, so that a homogenous IR signal is sent to any sensor in the sensor ring 540. The relay mirror 510 directionalizes the common source 530 output to the ring 540 of sensors and detector channels with even illumination to each channel which is constructed on or about a 10 degree angle from the source axis. In one embodiment, the detector channels in ring 540 may contain reference gas mixtures of various concentrations to act as calibration standards. In another embodiment, one or more of the ring 540 channels may act as a flow-through cell for sample gas testing. The benefit of having one common source 530 of IR energy to be fed to all channels is that there is an equal path length in the mixing chamber 512 for each sensor. This equal path length eliminates source amplitude noise in the measurement, and reduces the potential variability of channel measurements with unequal path lengths that are subject to uneven amounts of interfering absorption in the ambient air. It is noted that the flow tubes of FIG. 2, FIG. 5, and FIG. 18 could be combined with the mixing chamber to distribute their IR signal to different sensors in the sensor ring 540.

[0069] With reference to FIG. 20, a method for real-time sensing of gaseous analytes S100 starts at S101. At S102, a gaseous sample is input into a sensor device. At S104, a single broadband IR source projects IR energy into the gaseous sample. At S106, the IR energy is reflected between a primary mirrors and at least one mini-facet mirror. At S108, the IR energy is reflected between a pair of mini-facet mirrors and a central portion of a primary mirror. At S110, the IR energy, is collected at a detector. At S112, the concentration of at least one gas analyte is calculated in real-time. At S114, the concentration of a plurality of gases is calculated in real-time.

[0070] With reference to FIG. 21, a method for sensing gaseous analytes using a common source S200 starts at S101. At S202, broadband IR energy is sent into a mixing chamber to produce a homogenous common signal. At S204, the common signal is output to at least one of a sensor or detector. At S206, the common signal is relayed to a calibration reference channel. At S208, the common signal is relayed to a flow through cell for sample gas testing. At S210, the concentration of at least one gas analyte is calculated in real-time. At S212, the concentration of a plurality of gas analytes is calculated in real-time.

Examples

Expected Performance In Silico Modeling

[0071] The expected performance from the first embodiment of the gaseous sensor device 210 was modeled in raytrace software for the case of ethanol absorption in the cell. At a level of 1 part per million ethanol (1 ppm) the transmittance of the cell changed from 0.363337 to 0.3630732. Using the Cal Sensors detectors and a 1200 deg C source (Hawkey IR18) along with a bias circuit with modest gain of 35,000 with a 1 MegaOhm resistor, a 94 microvolt input change was expected to a Mosaic 24/7 DAQ for a 1 ppm change in ethanol in the presence of 65% relative humidity water content in ambient air. Using a realistic DAQ resolution of 20.5 bits over a 2.5 volt scale, this yields a minimum signal change of about 1.68 microvolts. A 1/55^th change for 1 ppm was the expected limit of detection, which is equivalent to 18 parts per billion. This detection limit is useful for the projected low cost of the sensor device 210. The coating reflectance for the mirror was modeled at 98%, however higher reflectance coatings are available in the community (ECl, Inc. 640IR coating for 3-5 micron region on silicone substrate).

Experimental Data on Sensor Stability

[0072] With reference to FIG. 21, a static repeatability test using ethanol detection was performed on the sensor 310 (second exemplary embodiment). Real-time measurement, sensitivity, and stability of the sensor 310 has been demonstrated with ethanol on the order of sub-ppm concentration. Readings were continuous, with precision calculated at 1 second integration. The dotted lines indicate ± 1 standard deviation. A steady state concentration of 0.07772 mg/dL ethanol was obtained. While detecting ethanol concentration in the 181-184 ppm concentration level, the sensor 310 demonstrated between 0.5 - 0.75 ppm accuracy over a lengthy 50 second interval.

[0073] With reference to FIG. 22, a second static repeatability test using ethanol detection was performed on the sensor 310 (second exemplary embodiment). Realtime measurement, sensitivity, and stability of the sensor 310 was once again demonstrated with ethanol on the order of sub-ppm concentration. Readings were continuous, with precision calculated at 1 second integration. The dotted lines indicate ± 1 standard deviation. A steady state concentration of 0.131 mg/ dL ethanol was obtained. While detecting ethanol concentration in the 300 - 314 ppm concentration level, the sensor 310 demonstrated 0.5 - 0.75 ppm accuracy over a lengthy 78.4 second internal. [0074] It should be noted that the sub-ppm accuracy for ethanol detection at 181- 184 and 300-314 ppm concentration levels demonstrated in FIG. 21 and FIG. 22, respectively, may meet the NHTSA requirements for devices which may act as a breath alcohol sensor in the transportation industry.

[0075] The present disclosure has been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

CLAIMS:

1 . A sensor device (310, 410) for sensing a gaseous analyte, comprising: a flow tube (312, 412) having a first end (311 , 411) and a second end

(313, 413), wherein the flow tube receives a gaseous sample;

a primary mirror (314, 414) at the first end of the flow tube; a mosaic back plate (320, 420) at the second end of the flow tube that includes at least one mini-facet mirror (322) on an interior surface of the mosaic back plate;

a broadband infrared (IR) source (330) removably attached to the mosaic back plate that generates a beam of infrared light; and

a detector (340) removably attached to the mosaic back plate.

2. The sensor device (310, 410) of claim 1 , wherein the flow tube includes evenly spaced ventilation slits (316, 416) in a circumferential sidewall between the first end and the second end.

3. The sensor device (310, 410) of either of claims 1 or 2, wherein the mosaic back plate has a plurality of mini-facet mirrors (322, 422) placed around an outside edge to create a continuous light path between the primary mirror and the plurality of mini-facet mirrors.

4. The sensor device (310, 410) of claim 3, wherein the mini-facet mirrors are oriented such that the beam of infrared light is redirected to a central region of the primary mirror (314, 414).

5. The sensor device (310, 410) of any of claims 1-4, wherein the detector is a multi-channel detector (340) capable of detecting infrared light signals corresponding to a plurality of analytes.

6. The sensor device (310, 410) of any one of claims 1-5, wherein the detector (340) has a detection sensitivity below 1 part per million.

7. The sensor device (310, 410) of any one of claims 1-6, wherein the flow tube (312) has a diameter of about 1 inch to about 3 inches, and has a length of about 4 inches to about 8 inches.

8. The sensor device (310, 410) of any one of claims 1-7, wherein the detector is connected to a mixing chamber (512) that includes a sensor ring (540) surrounding a common source (530), wherein the beam of infrared light exits the flow tube through the common source and bounces off of a relay mirror (514) to the detector (340).

9. The sensor device (310, 410) of any one of claims 1-7, wherein the detector comprises a butterfly mount (342) that receives the beam of infrared light at a top end of the butterfly mount, a beam splitter (344) located at a bottom end of the butterfly mount, at least one mirror (346) located on a transverse bar of the butterfly mount, and a detector crystal (354).

10. The sensor device (310, 410) of claim 9, further comprising a filter crystal (348) between the mirror (346) and the detector crystal (354).

11. A system (100) for sensing at least one gaseous analyte, comprising: the sensor device (310, 410) of any of claims 1-8 for producing an infrared absorption signal; and

a processor (106) for calculating the concentration of the at least one gaseous analyte from the infrared absorption signal.

12. The system (100) of claim 11 , wherein the processor (106) further calculates the concentration of a plurality of gaseous analytes from the infrared absorption signal in real-time.

13. The system (100) of either of claims 11 or 12, further including a display (108) digitally connected to the processor (106), wherein the display (108) indicates the concentration of at least one gaseous sample.

14. The system (100) of any of claims 11 -13, further including a mount (101 ) for supporting the sensor device (310, 410).

15. The system (100) of claim 14, wherein the mount (101) is a handle, a shaft, a flat surface mount, or an adhesive mount.

16. The system (100) of any one of claims -15, further including a sample input (102) attached to the sensor (110) for receiving a breath sample.

17. The system (100) of any one of claims 1 1- 6, further including a fan.

18. The system (100) of any one of claims 1 1-17, further comprising:

a mixing chamber (512) that includes a sensor ring (540) and a common source (530) from which the infrared absorption signal is emitted;

a relay mirror attached to the mixing chamber that directs the infrared absorption signal to a particular sensor in the sensor ring (540).

19. The sensor device (510) of claim 18, further including at least one calibration channel in the sensor ring (540).

20. The sensor device (510) of either of claims 18 or 19, further including at least one sample channel in the sensor ring (540).