Abstract: A method of infrared-optically determining the concentration of at least one analyte in a liquid sample, wherein the infrared absorption of the analyte(s) is measured and compared with a standard, which is characterized in that the liquid sample is sampled with an infrared radiation of high light density, wherein the infrared radiation has a sharp intensity peak at at least one wave length, as well as an arrangement for the infrared-optical transmission determination of the concentration of at least one analyte in a liquid sample, with a sample cuvette flowed through by the sample liquid, the sample cuvette being arranged in the radiation path between a radiation source for providing the infrared radiation and a detector for measuring the infrared absorption induced by the analyte in the sample cuvette.

Abstract: In a sensor for detecting a carbon dioxide gas in an expiration gas of a living body, an airway case is adapted to be disposed below nostrils of the living body, and formed with an airway passage extending across an optical axis of a light beam emitted from a right emitter of the sensor. A mouth guide is adapted to be disposed in front of a mouth of the living body so as to define a space communicated with the airway passage. The mouth guide is pivotably supported on the airway case. A retainer is adapted to retain an oxygen supply tube on the airway adapter body in such an attitude that an oxygen gas supplied from prongs of the oxygen supply tube is not directly injected into the nostrils.

Abstract: A gas sensor, whose chamber uses filters and choppers in either a semicircular geometry or annular geometry, and incorporates separate infrared radiation filters and optical choppers. This configuration facilitates the use of a single infrared radiation source and a single detector for infrared measurements at two wavelengths, such that measurement errors may be compensated.

Abstract: An infrared absorption measurement method including: (a) measuring infrared absorption of a target component in a sample gas while decompressing the sample gas so that an absorption area in a peak region of the target component in the infrared absorption shown in a graph is within a predetermined range, the graph showing the relationship between the wave number and absorbance of the sample gas; and (b) calculating the concentration of the target component in the sample gas based on the absorption area and pressure of the decompressed sample gas.

Abstract: A gas detection device includes a light source, a light sensor element, and a shield plate arranged in a single package. The shield plate protects the light sensor element from light beams that travel from the light source directly to the light sensor element. The gas detection device further includes a reflector plate arranged so that light beams emitted from the light source are reflected off the reflector plate and travel to the light sensor element. The light sensor element detects a degree of light absorption by gas provided in a space between the reflector plate, the light source, and the light sensor element.

Abstract: The sensitivity adjusting equipment applied to a photoelectric smoke detector is provided. The photoelectric smoke detector includes a luminous component for providing an input light and a detecting component for receiving an even output light. The sensitivity adjusting equipment includes a light-scattering device having a scattering component and an adjustable hole for scattering the input light evenly and adjusting an intensity of the input light so as to output the even output light to the detecting component. The sensitivity adjusting equipment also includes a movable platform having a first brace connected to the photoelectric smoke detector and a supporting base having a second brace connected to the light-scattering device. The movable platform is moved to make the photoelectric smoke detector and the light-scattering device combined to adjust the sensitivity of the photoelectric smoke detector.

Abstract: A rigid redundant light source for obtaining down hole near infrared data in a NIR data acquisition instrument is provided having a plurality of lamps positioned in close proximity and symmetrically about a common optical axis. A lens system for capturing and collimating the light is provided. The structure is arranged and dimensioned so that a single collimating lens can be used for a plurality of light sources. A switch and sensor is provided for turning on an alternate light source when a first light source burns out. A filter is rotated 90 degrees with respect to the light sources to minimized off axis error when switching between light sources.

Abstract: A transmission meter (1) and a method for measuring the transmittance of a fluid, the meter (1) comprises an analysis chamber for passage of the fluid therethrough, means for receiving an electromagnetic source (9) within said chamber and three sensors (D1, D2 and D3) each configured to measure the output from said source (9), wherein each of the three sensors (D1, D2 and D3) are located at different distances from the source (9). The transmission meter may be used in a disinfection system either to measure the transmittance of the untreated water or to measure the transmittance of the water as it is purified.

Abstract: A leak detector using an infrared emitter and pyroelectric sensor to form an instrument for identifying the presence and concentration of a selected material type gas compound, such as a refrigerant gas compound within a given sample, such as a sample of ambient air. For the detection, a radiation flux coming from an infrared emitter penetrates the sample, which is analyzed spectrally, and results in a wave length-specific signal being generated at the output of the detector. By controlling the type of optical filter, the radiation energy is controlled at a selected wavelength, to ensure coverage of all selected compounds. For refrigerants, the selected wavelength can be between approximately 8 to approximately 10 microns in the wavelength range. This selected wavelength obscures other signals, thus minimizing false alarms. By not chopping or pulsing the emitter, the leak detector has a faster response time with no adverse impacts on the accuracy of the compound material being detected.

Abstract: Apparatus and method for in situ measurements of at least one property of a liquid contained within a vessel.

Abstract: Method and apparatus for providing real-time data indicative of the isotopic composition of formation fluids during drilling. The method includes the steps of: (a) providing a reference fluid having a known isotopic composition in a reference cell; (b) capturing a sample of formation; (c) providing at least one laser beam; (e) passing a beam through the reference fluid, measuring the reference-measurement beam before and after it passes through the reference fluid; (f) and passing a beam through the sample, measuring the beam before and after it passes through the sample, and calculating a first isotope concentration from those measurements. The measurements can provide information relating to the carbon isotopic composition of individual compounds in hydrocarbon gas mixtures, with the individual compounds including methane, ethane, propane, iso- or normal butane, or iso- or normal pentane.

Abstract: An optical detector 1 wherein detection elements 11, 12, 13 and 14 are provided in a sealed case 4 whose opening portion 3 is blocked with a window material 2 for transmitting light such as an infrared and an ultraviolet ray therethrough, the detection elements being formed opposite to the window material; and optical filters 21, 22, 23 and 34 are disposed between the window material 2 and the detection elements 11, 12, 13 and 14 and used for selecting and causing only light composed of a predetermined band of wavelengths to be transmitted by thin optical films in connection with the detection elements 11, 12, 13 and 14.

Abstract: The present invention relates to apparatuses for use in performing a quantitative analysis of a turbid pharmaceutical sample, e.g. a tablet, a capsule or a similar sample forming a pharmaceutical dose. A pharmaceutical, turbid sample (24, 57, 67) is irradiated with an excitation beam (20, 53, 64) of radiation, e.g. near infrared radiation. The intensity of emitted radiation (30) from the sample (24, 57, 67) is detected as function of both the wavelength of the emitted radiation and the photon propagation time through said sample (24, 57, 67). Optionally, the intensity of the emitted radiation (30) from the sample (24, 57, 67) is also detected in a spatially resolved manner.

Abstract: The invention provides a spectrometer (10) which includes a filter arrangement (16,18), in addition to any option filters (20) for limiting an operational wavelength range of the spectrometer, the filter arrangement (16,18) comprising a plurality of broadband optical filters or broadband optical filter areas each of known transmission and being located or selectively locatable in a path of collected incident spectral radiation (44). The spectrometer further includes at least one detector (24) arranged to measure the spectral radiation passing through at least one of the broadband filters located in the path of collected incident spectral radiation, and signal-processing means (34) for recovering the spectrum of the collected spectral radiation from measurements by the detector (24).

Abstract: A method of quantitative measurement of fat in a liquid sample by an infrared attenuated technique is disclosed. The fat is present in the form of an emulsion of particles causing Christiansen's effect, i.e. the combined effect of light-scattering and anomalous dispersion. The method comprises transmitting infrared radiation through the sample, determining the infrared absorption of the sample in at least one measurement waveband exhibiting the Christiansen's effect, and with reference to a reference waveband. The wavebands are selected such that the fat determination is essentially independent of the Christiansen's effect. The wavebands are preferably selected such that the fat absorbance, i.e.

Abstract: A specimen sensing apparatus according to the present invention includes a specimen container which is vertically positioned by a container holder of a columnar rack type and conveyed by a belt conveyor, an infrared CCD camera configured to pick up an infrared image of the specimen container, a visible image converter which converts the infrared image picked up by the infrared CCD camera into a visible image, an image signal processing unit which processes and converts one of the infrared image and the visible image into a signal that is suitable to measure a specimen amount, and a specimen amount measuring unit which measures an amount of specimen contained in the specimen container in response to the signal processed by the image signal processing unit.

Abstract: The invention relates to a transmission sensor (1) for measuring the turbidity of a fluid, comprising a first and a second measuring section (2, 3). A transmitter (6) emits electromagnetic radiation into the two measuring sections (2, 3). A first receiver (14) is allocated to the first measuring section (2) and a second receiver (15) is allocated to the second measuring section (3). The transmitter (6) is inserted into a transmitter carrier (8) in such a way that the transmitter (6) is forced to adopt a predetermined oriented position. The receivers (14, 15) are inserted into a receiver carrier (18) in such a way that each of said receivers (14, 15) is forced to adopt a predetermined oriented position. A transmitter carrier holder (9) forcibly positions the transmitter carrier (8) in a predetermined location and a receiver carrier holder (19) forcibly positions the receiver carrier (18) in a predetermined location.

Abstract: An apparatus for measuring the concentration of a substance in a specimen. The apparatus includes a housing that defines a chamber for the specimen. A radiation source mounted to the housing emits radiation at a wavelength at which the radiation is absorbed by the substance. Two spaced apart receivers are mounted to the housing. Both receivers detect radiation at the wavelength at which it is absorbed by the specimen. Two concave mirrors are disposed in the housing. The mirrors are positioned to split the radiation emitted by the source into two beams, each of the beams being directed to a separate one of the receivers and so that the paths of travel of the beams from the source to the separate receivers are of different lengths. The concentration of the substance is determined by based on the difference in radiation detected by the receivers.

Abstract: A device for utilizing an optical infrared emitter/detector to sense substances of interest is provided. The infrared emitter/detector comprises a single crystal semiconductor, photonic band gap structure which functions both as an infrared emitter, a narrow-band filter, and as a broad-band infrared bolometer detector to exert wavelength control directly on the active element emitter/detector surface using the periodic symmetry of the photonic band gap structure to produce narrow wavelength “forbidden” optical transmission bands or modes to sense the presence of a specified substance in the environment. A system and method for sensing specific substances using the optical infrared emitter/detector of this invention in a sensor device is also provided. Finally, a method of manufacturing the infrared emitter/detectors of the present invention is also provided.

Abstract: A thermopile-based detector for monitoring and/or controlling semiconductor processes, and a method of monitoring and/or controlling semiconductor processes using thermopile-based sensing of conditions in and/or affecting such processes.

Abstract: A gas sensor of the type that detects the presence of a specific gas by monitoring the absorption of optical radiation transmitted through a chamber containing a sample of gas under test comprises an optical source for emmiting radiation therefrom and a detector sensitive to radiation emitted from the source at opposing ends of a circumferential chamber, having optically reflective surfaces, extending around the periphery of a sensor housing The optical pathway between the source and detector may include a radial portion as well as a circumferential portion to allow one or other of the source and detector to be located in a central chamber of the sensor housing.

Abstract: A method for applying a sample film to a sample carrier for subsequent spectroscopic analysis is described, comprising providing a quantity of sample in liquid state, providing a sample carrier having at least one sample position, applying the quantity of sample in liquid state on the at least one sample position in a plurality of partial quantities of the quantity of sample in such a manner that the partial quantities on the at least one sample position are not in contact with one another before being dried, drying the quantity of sample to form the sample film.

Abstract: A thermopile-based detector for monitoring and/or controlling semiconductor processes, and a method of monitoring and/or controlling semiconductor processes using thermopile-based sensing of conditions in and/or affecting such processes.

Abstract: A device for measuring the concentration of a gas contained in a cavity and for checking the operation of a catalytic element in an exhaust line in an automobile vehicle. A first emitter (E1) composed of an optical pumped micro-cavity and for which the emission spectrum is within the gas absorption band emits a first radiation that passes through the cavity. A second emitter emits a second radiation that passes through the cavity. A receptor measures the optical intensity (I) of the radiation that passed through the cavity.

Abstract: An interference filter transmission wavelength scanning photometer operable to determine the concentration of an interesting component in a sample without interference from coexisting components by measuring the light absorption of the interesting component. An angle of inclination of an interference filter varies periodically and is centered at the maximum absorption wavelength of the interesting component. The wavelength of a transmitted light is modulated due to the periodical variation of the angle of inclination. Variation in the intensity of the light transmitted through a sample is extracted by an infrared sensor as an electric signal. The time between rise and fall zero cross points of an AC component of the electric signal is determined by a microprocessor. A ratio is calculated from a full period and a half period of the AC component. The concentration of the interesting component is determined from a variation in the calculation of the ratio.

Abstract: An amplifier-enhanced optical analysis system and method to optically analyze a molecular component of a gas, liquid, or solid. The amplifier-enhanced optical system comprises a laser, a light amplifier, and an optical analysis means, all optically coupled so that light at a predetermined wavelength in the near-infrared spectrum is transported from the laser, through the light amplifier, and to the optical analysis means, wherein the predetermined wavelength corresponds to an absorption feature of the molecular component. Optical analysis means preferably comprises photoacoustic analysis equipment.

Abstract: Disclosed is a method of infrared-optically determining the concentration of at least one analyte in a liquid sample, wherein the infrared absorption of the analyte(s) is measured and compared with a standard, which is characterized in that the liquid sample is sampled with an infrared radiation of high light density, wherein the infrared radiation has a sharp intensity peak at at least one wave length, as well as an arrangement for the infrared-optical transmission determination of the concentration of at least one analyte in a liquid sample, with a sample cuvette flowed through by the sample liquid, the sample cuvette being arranged in the radiation path between a radiation source for providing the infrared radiation and a detector for measuring the infrared absorption induced by the analyte in the sample cuvette.

Abstract: Using at least one surface mount resistor as an infrared light emitter in an analytical instrument provides low cost, long life and high reliability.

Abstract: A system and method are disclosed for the detection of water vapor in a natural gas background. The system includes a light source operating in a wavelength range such as, 1.877-1.901 &mgr;m, 2.711-2.786 &mgr;m, or 920-960 nm, passes through the natural gas to be detected by a detector. In one embodiment, the light source is a tunable diode laser and the moisture level is determined by harmonic spectroscopy. In other embodiments, a VCSEL laser is utilized.

Abstract: The invention relates to a method for the analysis of the qualitative and/or quantitative composition of fluids with at least one light source, one interaction space area in which the light interacts with the fluid, and one detection device for detecting the interaction between the fluid and the light. The device and the method are characterised in that a photonic the gap structure is provided creating a greater reduced group velocity in the interaction space area and thus an increased dwell time for the light in the interaction space area. This means that the interaction space area can be considerably reduced in size, which allows a compact design of the device.

Abstract: A sample cell, which is a component of a gas monitoring system, includes a sample cell body and a sample cell core installed therewith. The sample cell is coupled to a sampling tube that communicates with an airway of a patient. Gas from the sampling tube passes through the sample cell such that the flow profile remains substantially undisturbed. Within the sample cell, at least one optical aperture permits radiation to be emitted, pass through the gas in the sample cell core, and detected. In this manner, measurements of the partial pressure or concentration of a gas of interest are determined.

Abstract: A method and apparatus for temperature-independent determination of a concentration of a probe gas in a sample over a selected temperature range between a low temperature TL corresponding to a lowest temperature expected or found in the sample and a high temperature TH corresponding to a highest temperature expected or found in the sample. In accordance with the method, a probe temperature function of the probe gas is determined over the temperature range using a first spectroscopic technique. Then, a second spectroscopic technique is selected, a reference gas is identified and a reference temperature function of the reference gas is determined using the second spectroscopic technique over the temperature range. In particular, the reference gas is identified such that a ratio of the probe temperature function and the reference temperature function is substantially constant over the temperature range.

Abstract: An apparatus and method for detecting at least one component gas in a sample includes a radiation source for providing radiation along an optical path in a pre-selected spectral band having at least one absorption line of the component gas to be detected and an optical detector for detecting radiation at the optical path. A sample chamber is positioned in the optical path between the source and the optical detector to contain a quantity of a sample gas. At least one gas cell enclosing an amount of the gas to be detected is fixedly positioned in the optical path in series with the gas chamber. A mathematical relationship is determined between the detected radiation and the concentration of a sample gas filling the sample chamber.

Abstract: The invention relates to a method for detecting a test gas that may be present at a measuring location, using an infrared gas analyser (1) that comprises a cuvette (2), an infrared light source (3), an infrared detector (4), and two gas lines (15, 17). Said gas lines supply gases to the infrared gas analyser and one of said lines is adapted to take up a measuring gas at a measuring location that may contain a test gas. The second line (17) is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location. In order to improve the sensitivity of the analyser it comprises only one cuvette (2) and the measuring gas taken up at the measuring location and the reference gas are fed to the cuvette of the infrared gas analyser in such a manner that they are alternately present in the cuvette.

Abstract: A method for spectroscopically determining the concentration of alcohols with 1 to 5 carbon atoms, especially ethanol, in liquid probes, especially alcohol-containing food products, healing preparations, cosmetic products and the like. The absorption of light by the probe is measured at at least one wave length in the range of 1100 nm to 1300 nm, and preferably in the range of 1150 nm to 1250 nm. The alcohol concentration is determined from the measured absorption with the help of a calibration. The alcohol content of a liquid probe can be determined in a simple and fast manner and over a large concentration range.

Abstract: The invention comprises UV/visible spectroscopic analysis of polycarbonate composition. The method comprises determination of the concentration of Fries products, as either total Fries products or as separate determinations of linear and branched components. The method also allows for simultaneous determination of uncapped phenolic end-groups. Determinations may be performed at a single wavelength or over the entire absorption band. The method is suitable for measuring of Fries products in samples ranging in size from small scale combinatorial formats to production scale reactors. The method is independent of reaction variables such as polymer molecular weight, reactor type, and reaction temperature.

Abstract: A robust gas sensor can be manufactured in a simple manner and at low cost, and have no movable optical components. A measured gas cell (3) has a wall defining a cylindrical space with a measured gas inlet. The measured gas cell (3) is limited in the longitudinal axial direction by a reflective, flat first cover element (1) and by a reflective, flat second cover element (5) arranged at a spaced location from and in parallel to the first cover element (1). The height of the measured gas cell (3) corresponds approximately to 1 to 3 times the diameter of the cover elements (1, 5). The second cover element (5) accommodates a radiation source (6) and two detector elements (23, 24) with at least one measuring detector and one reference detector. The radiation source (6) is arranged displaced by 30% to 60% of the radius of the second cover element (5) from the center of the second cover element (5).

Abstract: An infra red spectrometer incorporates a flow cell connected to a process line containing sugar to provide continuous sugars measurements. The optical components and lamp are selected to operate in the range of 1800 nm to 2500 nm. The absorption at two wavelengths are used to calculate sucrose concentration. Absorbance at one of the wavelengths is independent of sugars concentration so that the difference between the two is indicative of sugar concentration. The method is applicable to both beet and cane sugars as well as any food processing system which requires monitoring of sugar concentrations.

Abstract: A method and system for identifying and calculating the percentages of gases, such as the automotive and other commercial refrigerant gases, in a gas mixture using infrared spectroscopy is disclosed. The novel system is compact, relatively inexpensive and has greater accuracy than those systems of the prior art.

Abstract: A multi-component gas analyzer includes a light source system, a cassette-type light path system, an optical folding system, and an infrared detecting system. The light source system has an infrared light source and a reflector for providing a parallel infrared light beam. The cassette-type light path system has a cassette, an optical absorption chamber, and a set of concave mirrors. A vent hole set is provided having a plurality of vent holes enclosed by an O-ring for sealing the gas between the stacked-up cassettes. The optical absorption chamber includes a highly reflective coating film coated on the inner wall surface thereof that is employed for introducing the gases to be analyzed and provides a space for contact between the gases and the infrared light.

Abstract: A mobile gas detector comprising a laser transmitter and signal analyser carried on a vehicle, the vehicle having an exterior, a laser absorption cell carried on the exterior of the vehicle, a light guide connecting light from the laser transmitter into the laser absorption cell, a photo-detector mounted with the laser absorption cell exterior to the vehicle to convert light that has traversed the laser absorption cell into electrical signals, and a cable connecting the photodetector to the signal analyser.

Abstract: An optical absorption measuring instrument for determining the percentage of a component in a fluid shall be improved such that changes in the measuring radiation caused by drift or temperature have only a limited effect on the measuring result. Provisions are made for deflecting the measuring beams (10, 11) from a radiation source (4) to a detector (5) by at least two plane mirrors (71, 72), which are positioned such that the measuring beams (10, 11) emitted by the radiation source (4) are deflected to the detector (5). The surface of each plane mirror (71, 72) is dimensioned to be such that its illuminated surface in the area of the detector (5) is larger than the receiving surface (12) of the detector (5).

Abstract: A sensitivity adjusting equipment applied to a photoelectric smoke detector is provided. The photoelectric smoke detector includes a luminous component for providing an input light and a detecting component for receiving an even output light. The sensitivity adjusting equipment includes a light-scattering device having a scattering component and an adjustable hole for scattering the input light evenly and adjusting an intensity of the input light so as to output the even output light to the detecting component. The sensitivity adjusting equipment also includes a movable platform having a first brace connected to the photoelectric smoke detector and a supporting base having a second brace connected to the light-scattering device. The movable platform is moved to make the photoelectric smoke detector and the light-scattering device combined to adjust the sensitivity of the photoelectric smoke detector.

Abstract: The present invention provides a miniaturized infrared gas analyzing apparatus, which is composed of various kinds of micro elements (e.g., infrared light source, tunable filter, and thermal detector) fabricated by means of silicon micromachining technology so as to meet the requirements of low power consumption and low cost and apply to qualitative and quantitative analysis of infrared absorption spectra of various kinds of gases. The miniaturized infrared gas analyzing apparatus comprises an infrared emitting unit, an infrared collimator, a bandpass and spatial filter, a tunable filter unit, a sensing unit, and a microprocessing unit. The infrared emitting unit utilizes the blackbody radiation principle of thermo-resistive filament to radiate out a wide infrared spectrum and serves as a point light source. The infrared collimator converts the infrared emitting unit into a collimated infrared light beam.

Abstract: An infrared spectrophotometer is described wherein an infrared source is provided for emitting infrared energy. A sample cell is provided for containing gases to be analyzed and is positioned in the path of infrared energy emitted by the source. A detector assembly includes first, second and third thermopile detectors mounted in thermal proximity to each other and being responsive to impinging infrared energy to produce an electrical response. The first and second detectors are positioned in the path of infrared energy emitted by the source and the third detector is positioned out of the path of infrared energy emitted by the source. The spectrophotometer further comprises a narrow band filter corresponding to an absorption wavelength band for a gas of interest and a narrow band reference filter corresponding to a reference wavelength band.

Abstract: An optical gas sensor has a compact design and without movable optical elements, with at least one radiation source (8), at least one measuring detector (9, 12) and a reference detector (11). The reflecting measuring cuvette is designed as an annular space (1) between a first, inner cylinder section (6) and a second, outer cylinder section (2) that is concentric thereto. The annular space (1) is limited by a cover element (5) and a bottom element (7) arranged at a spaced location therefrom in the direction of the longitudinal axis. The cover element (5) is permeable to the measuring gas. The bottom element (7) accommodates the radiation source (8).

Abstract: The invention relates to an infrared gas analyser (1), especially for use as a gas detector for leak detection using a sampling probe. Said gas analyser comprises a vessel (test vessel 2), through which a test gas flows, and an infrared light source (4, 5, 42) which produces an infrared light that shines through the test vessel (2). The analyser further encompasses a detector (35) that facilitates measurement of the infrared light absorption in the test gas. The aim of the invention is to provide at low costs an analyser that is apt for every day use. To this end, a reference vessel (3) through which a reference gas flows is provided in addition to the test vessel (2) through which the test gas flows. A reference gas is sucked from the environment of the test gas suction area. The same or an additional light source (4, 5, 42) and the same detector (35) are allocated to said reference vessel.

Abstract: An isotope gas measuring apparatus for measuring concentrations of components in a sample gas includes two sample cells through which the sample gas passes; a control cell filled with a gas having no absorbance at a wavelength of infrared light to be measured; a light source irradiating infrared light to the sample cells and the control cell; an optical coupler for coupling light permeated from the sample cells and the control cell; a first interference filter disposed between one sample cell and the optical coupler; a second interference filter disposed between the other sample cell and the optical coupler; and an optical detector for detecting infrared light from the optical coupler. The apparatus can minimize an influence of drift, and have a simple structure.

Abstract: A method and apparatus are described for determining the safety of a gas mixture containing flammable components such as methane together with ethane or other hydrocarbon, together with a diluent gas. The method comprises the filtered infrared spectroscopy of the gas mixture in a gas cell (10) using a filter (16). The peak transmission wavelength (&lgr;max) and bandwidth of the filter (16) are so chosen to provide an output, when an infrared light source (42) having a flat wavelength distribution is used, indicative of the %LEL of the gas mixture, within a predetermined tolerance. The filter may be a gas correlation filter containing a mixture of methane and ethane, together with a diluent gas.

Abstract: A photo expansion gas detector includes a radiation emitter, a sample gas, an expansion gas hermetically sealed in a chamber, and a capacitive diaphragm for sensing pressure changes. The radiation emitter may be constant or may be cycled on and off. Radiation passes through the sample and into the expansion gas. The expansion gas expands according to the intensity of the radiation received. The capacitive diaphragm is impacted directly by the expansion gas. The capacitive diaphragm deflects relative to a fixed capacitive plate, resulting in changes in capacitance representing expansion and contraction of the expansion gas. The electrical signal generated by the changes in capacitance represent changes in the gas composition of the sample. The electrical signals are then processed to activate control systems.