Abstract: The present invention is to provide a thin type vacuum chamber device, wherein two hollow slabs are fastened by a claw fastener to form a thin type simple structure that can maintain a high vacuum state, and wherein the air inside the chamber is pumped out to attain a vacuum state with a high pressure suction activity. The thin-chamber design of the present invention can decrease the number of the components and reduce the cost. The special assembly design of the vacuum chamber of the present invention can effectively decrease the length of the transmission cable and thus can reduce signal attenuation and noise interference. The present invention has the advantage of convenient operation and is very suitable to a two-dimensional infrared sensor.

Abstract: A system for certifying a concentration of gas in a cylinder includes a gas cell configured to receive a sample gas from a cylinder, and an FTIR module coupled to the gas cell for scanning the sample gas and forming a beam spectrum. A processor is coupled to the FTIR module for calculating an intensity response of the sample gas based on the beam spectrum. A storage device is included for storing data points of a plot of intensity response of a known gas versus concentration levels. The processor is configured to interpolate between the stored data points of the plot to determine an interpolated data point corresponding to the intensity response of the sample gas. The processor provides to the user a concentration level of the sample gas, based on the interpolated data point.

Abstract: A detecting apparatus for detecting information of a liquid object or sample includes a transmission path, a THz wave supplying unit, a THz wave detecting unit, and an infiltrative holding member for infiltration and holding of a liquid object. The supplying unit supplies an electromagnetic wave in a frequency range between 30 GHz and 30 THz to the transmission path. The detecting unit detects the THz wave transmitted through the transmission path. The infiltrative holding member is set at a location containing at least a portion in which an electric field distribution of the THz wave propagating along the transmission path extends.

Abstract: Concentrations of a target analyte in a gas mixture containing one or more background analytes having potentially interfering spectral absorption features can be calculated by compensating for background analyte absorption at a target wavelength used to quantify the target analyte. Absorption can be measured at a reference wavelength chosen to quantify the concentration of the background analyte. Using a background gas adjustment factor or function, the absorption measured at the reference wavelength can be used to calculate absorption due to the background analyte at the target wavelength and thereby compensate for this background absorption to more accurately calculate the target analyte concentration in real or near real time. Additional background analytes can optionally be compensated for by using one or more additional reference wavelengths.

Abstract: Disclosed is a method and apparatus for detecting the type of anesthetic gas. The method comprises the steps of: generating a light with a plurality of wavelengths, the light being able to be separated to a plurality of light beams whose central frequencies correspond to the plurality of wavelengths; passing said light through a gas chamber, wherein, the gas chamber being filled with said anesthetic gas, said anesthetic gas having absorption characteristic with respect to said plurality of light beams; detecting the light intensity of the attenuated light beams transmitted from the gas chamber respectively, to obtain the relative absorption characteristic of said attenuated light beams, which attenuated light beams having been absorbed by said anesthetic gas; and determining the type of said anesthetic gas based on the relative absorption characteristic between said attenuated light beams.

Abstract: Devices and methods for measuring the fraction of a liquid in a wet gas flow are described, the device including one or more light sources emitting at a first wavelength at which the liquid is highly absorbing and emitting at a second wavelength close to the first wavelength and at which the liquid is not highly absorbing; and one or more sensor for detecting the transmittance of the light at the first and second wavelengths through said gas flow, the device further including processing means for determining a liquid fraction of the liquid in the wet gas flow by correcting the transmittance measured at the first wavelength for the effects of scattering using the transmittance measured at the second wavelength. By making use of cross-correlations or know flow rate meters the device can be used as a flow meter.

Abstract: This invention relates to a compact cavity ring down spectrometer for detection and measurement of trace species in a sample gas using a tunable solid-state continuous-wave mid-infrared PPLN OPO laser or a tunable low-power solid-state continuous wave near-infrared diode laser with an algorithm for reducing the periodic noise in the voltage decay signal which subjects the data to cluster analysis or by averaging of the interquartile range of the data.

Abstract: A light emission section spread-spectrum modulates a base band signal at a chip frequency f to thereby generate a primary modulated signal, modulates the primary modulated signal at a frequency 2f to thereby generate a secondary modulated signal, and emits a near-infrared light beam having a specific wavelength into a living organism on the basis of the secondary modulated signal. A light detection section receives a reflected light beam from the interior of the living organism in an effective detection band 2f, converts it to an electrical detection signal, and converts the detection signal to a digital signal at a sampling frequency 4f. The light detection section then demodulates the digital signal at the frequency 2f to thereby generate a primary demodulated signal, and demodulates the primary demodulated signal through spectrum despreading to thereby generate a secondary demodulated signal. Thus, a biological information signal representing biological information is output.

Abstract: A system for analyzing a bulk material including a tube for transporting a stream of a bulk material, a plurality of illuminators for directing radiation through the stream and arranged about a circumference of the tube, a plurality of detectors arranged substantially opposite the illuminators, and at least one spectrometer for receiving and analyzing data from the plurality of detectors.

Abstract: The present invention is to provide a thin type vacuum chamber device, wherein two hollow slabs are fastened by a claw fastener to form a thin type simple structure that can maintain a high vacuum state, and wherein the air inside the chamber is pumped out to attain a vacuum state with a high pressure suction activity. The thin-chamber design of the present invention can decrease the number of the components and reduce the cost. The special assembly design of the vacuum chamber of the present invention can effectively decrease the length of the transmission cable and thus can reduce signal attenuation and noise interference. The present invention has the advantage of convenient operation and is very suitable to a two-dimensional infrared sensor.

Abstract: The invention relates to a microstructured sensor, having at least one measurement chip in which there is formed a first measurement area having a first measurement structure and a second measurement area having a second measurement structure, the measurement areas being offset to one another in a lateral direction, one cap chip that is fastened in vacuum-tight fashion to the measurement chip in a connecting area, one intermediate space, formed between the measurement chip and the cap chip, that is sealed outwardly by the connecting area and in which the measurement areas are situated, and at least one contact area, formed on the measurement chip, and left exposed by the cap chip, for the contacting of the measurement chip. The sensor can be in particular a gas sensor for measuring a gas concentration, or an acceleration sensor.

Abstract: A gas measurement system of this invention includes a housing adapted to be mounted on an airway adapter, and a luminescence quenching gas measurement assembly disposed in the housing. The luminescence quenching gas measurement assembly includes a source disposed in a first plane, and at least one detector also disposed in the first plane.

Abstract: This invention relates to a compact cavity ring down spectrometer for detection and measurement of trace species in a sample gas using a tunable solid-state continuous-wave mid-infrared PPLN OPO laser or a tunable low-power solid-state continuous wave near-infrared diode laser with an algorithm for reducing the periodic noise in the voltage decay signal which subjects the data to cluster analysis or by averaging of the interquartile range of the data.

Abstract: A gas sensor comprises a cavity for containing a gas, means for generating radiation which is transmitted through the cavity and includes one or more wavelengths which is absorbed in use by a gas to be detected; and a detector for detecting radiation which has passed through the cavity. The walls of the cavity are sufficiently reflective to the radiation that the cavity is substantially uniformally illuminated with the radiation.

Abstract: The obstruction detection device for an infrared intruder detection system comprises at least one transparent facet having a roughened surface; a light emitter arranged for emitting light towards the roughened surface; a light detector arranged for detecting the intensity of light, which is transmitted or reflected or diffracted by the roughened surface into a specific direction of space; and an output device for outputting an alarm-signal, when an absolute difference between the intensity of the detected light and a reference value exceeds a threshold value. A liquid or spray applied onto the roughened surface changes its scattering patterns. This change triggers the alarm-signal.

Abstract: A gas sensor usable in harsh environments includes a multiple chamber radiant energy transmission path which extends between a multi-channel emitter and a multi-channel detector. Chamber length and gas selection are establishable using a movable element with an aperture. The element is located between the emitter and the detector on the transmission path. Radiant energy from the emitter is reflected between the emitter and the element, prior to passing through the element to impinge on the detector.

Abstract: A device and method for measuring the relative amounts of 235U and 238U in the gaseous phase of UF6 using tunable diode laser spectroscopy (TDLS). The invention is a faster, more accurate method for making such measurement. The improved method involves using methane (CH4) or acetylene (C2H2) as a calibration gas, and using a Fabry-Perot interferometer to calibrate the laser frequency, to determine the relative amounts of 235U and 238U in UF6 gas within ±0.27% accuracy, for example 7.00%±0.27%. The sample time required for such measurement is about one second.

Abstract: A system for detection of gas leakage sources. An open-path FTIR detection system is located before the return filter of recirculating air of a factory to detect gas composition of recirculating air and transmits the result to a data server through a communication network. A multi-port extractive FTIR system is located in the factory to collect and detect gas sample of local area air using pipelines located in different areas and transmits the result of gas composition to the data server through the communication network. An IR monitor system obtains the gas composition from the data server through the communication network. A process exhaust management system obtains the gas composition from the IR monitor system through the communication network for the analysis of a gas leakage source.

Abstract: The present invention relates to a method for determining the condition of a biological fluid by recording the IR spectrum of a sample of the biological fluid. To this end, the biological fluid can be examined in its native form. The method of the invention is usable, for example, for detecting pathological conditions in organisms.

Abstract: A fluid sensor is provided which contains a fluid cell (1) to enclose a volume of fluid (7), i.e., a gas or liquid, to be analyzed, in addition to a method for producing such a fluid sensor. An electromagnetic energy source (3) is arranged to transmit electromagnetic waves (4) into the fluid cell (1) with at least one detector (5) arranged to detect electromagnetic waves passing through the fluid cell (1) and at least one opening (2) situated for inlet or outlet of the fluid (7) to be analyzed. A circuit board (8, 10, 11, 12, 13, 14, 15, 16) is arranged to evaluate intensity of electromagnetic waves reaching the detector (5) and/or provide circuitry for the electromagnetic energy source (3). At least part of the fluid cell (1) is incorporated into the substrate of the circuit board (8, 10, 11, 12, 13, 14, 15, 16).

Abstract: A pressure sensor having a diaphragm which is differently deformable or locally changeable by pressure differences is described. A construction advantageously usable even in poorly accessible spaces having high temperatures is obtained in that at least one functional section of the diaphragm has a material which has the properties of a black-body radiator or has an emissivity used for detection in the spectral radiation range corresponding to the temperature of the diaphragm under its conditions of use, and a radiation receiver unit, which detects at least a portion of the emitted radiation, having at least one infrared radiation sensor, is assigned to the diaphragm.

Abstract: An infrared gas detector includes an infrared light source for emitting infrared light, an infrared sensor for detecting the infrared light from the infrared light source, and a housing having a gas cell which accommodates the infrared light source and the infrared sensor. The internal surface of the gas cell is defined as an ellipsoidal surface. The positions of the infrared light source and the infrared sensor are respectively determined based on two different focal points of the ellipsoidal surface of the gas cell to efficiently focus the infrared light from the infrared light source on the infrared sensor.

Abstract: An apparatus and method for detecting wood eating insect infestations. For trees, a baseline air sample is taken outside of the tree to determine a baseline CO2 concentration. A second CO2 sample is taken from underneath the bark of the tree. The results of the sample taken from underneath the bark of tree are compared to the baseline sample. An increased CO2 indicates a hidden wood eating insect infestation somewhere in the tree, even though the location of the infestation may be far removed from the place of sampling. For a shipping container, a baseline sample of air near the CO2 container is taken, then a sample is taken from the bottom of a shipping container. A shipping container need not be filled with wood products, rather wood products only be present as packing or support materials. The comparison is made between the baseline CO2 with the CO2 sample taken from inside the shipping container.

Abstract: Described herein are methods for optimizing petroleum reservoir analysis and sampling using a real-time component wherein heterogeneities in fluid properties exist. The methods can help predict the recovery performance of oil such as, for example, heavy oil, which can be adversely impacted by fluid property gradients present in the reservoir.

Abstract: A gas measurement system of this invention includes a housing adapted to be mounted on an airway adapter, and a luminescence quenching gas measurement assembly disposed in the housing. The luminescence quenching gas measurement assembly includes a source disposed in a first plane, and at least one detector also disposed in the first plane.

Abstract: A device for use in monitoring optical markers present in a liquid flowing in a conduit comprises a transparent tube 7 connectable in the conduit by pipe couplers (not shown) contained in housings 8, 9, and two optical tranceivers 1, 2 mounted on a segmented printed circuit board 3, 4 wrapped around the tube 7 such that the tranceivers 1, 2 face one another. In use, the tranceivers 1,2 produce infra-red radiation and detect infra-red radiation transmitted and/or reflected by any optical markers, e.g. bubbles, present in the liquid. The tranceivers 1, 2 are connected to a digital signal processor (not shown) programmed to determine, from the signals, a selected property, e.g. carbonation level, of the liquid.

Abstract: The present invention relates to a semiconductor processing system that employs infrared-based thermopile detector for process control, by analyzing a material of interest, based on absorption of infrared light at a characteristic wavelength by such material. In one embodiment, an infrared light beam is transmitted through a linear transmission path from an infrared light source through a sampling region containing material of interest into the thermopile detector. The linear transmission path reduces the risk of signal loss during transmission of the infrared light. The transmission path of the infrared light may comprise a highly smooth and reflective inner surface for minimizing such signal loss during transmission.

Abstract: A gas sensor of the type having a housing defining a chamber within which light is transmitted from a source to a detector through an optical path, includes internal mirror portions having part ellipsoidal shape. Light is transmitted from a source to a detector via the reflective portions. The detector is arranged to sense light only from a limited range of angles, such that only light transmitted through a defined optical path reflected off the two reflective portions from the source reaches the sensor. This ensures that there is a constant optical path from the source to the detector, which improves the signal to noise ratio of the device.

Abstract: A gas concentration measuring apparatus utilizing a gas correlation method capable of measuring concentrations of a plurality of analyte gases simultaneously and at high sensitivity uses an infrared light source (2) such as an infrared semiconductor diode or a quantum cascade semiconductor laser to increase the intensity of collimated infrared light (5) and to lessen infrared light unnecessary for measurement, thereby improving the S/N ratio while achieving a rise in sensitivity. A plurality of analyte gases are simultaneously measured by means of a gas correlation filter comprising a reference gas cell (6a) filled with all of the analyte gases and a plurality of probe gas cells (6b) each individual of which is filled with all such analyte gases other than one of the analyte gases which is of its particular interest.

Abstract: An apparatus and method for detecting carbonate scale. An energy emitting device transmits energy through one optical window, through a fluid stream, and out through a second optical window where the energy is detected by an energy receiving device. As scale, such as that due to carbonate present in the fluid, accumulates on the wetted surface of the optical windows, the transmission of the energy through the optical windows is obscured. The optical windows may optionally be coated and electrically charged to promote the formation of carbonate scale on the wetted surface of the window. The optical windows can be cleaned by reversing their polarity. By correlating the rate of energy intensity reduction to carbonate scale formation, the concentration of carbonate in the fluid stream can be determined. The carbonate detector can be used to alarm, shutdown, or control operation of equipment that may be adversely affected by the presence of carbonate in the fluid stream.

Abstract: A measuring device for determining the concentrations of gases by radiation absorption. The device includes at least one radiation source for generating radiation, a measuring cell, which is arranged downstream of the radiation source and in which the medium to be measured is located and at least one radiation detector, which is reached by the radiation after it has been sent through the measuring cell. A radiation guide device is provided by which the radiation is guided to the radiation detector. The radiation guide device includes a main optical unit, which has, on the one hand, an optical element (4), so that the punctiform radiation source is imaged in a bar-shaped radiation spot (5) extending along a preferred direction (1), and which has, on the other hand, parallel reflection surfaces (7, 7?), which extend at right angles to the preferred direction and at the inner surfaces of which the radiation is totally reflected between the optical element (4) and the radiation detector (3, 3?).

Abstract: A method of detecting gas conveyed in a drilling fluid (M) returning from a well (26), which method comprises the steps of: (a) extracting gas from said drilling fluid (M); (b) transmitting infra-red radiation through said gas; and (c) detecting with a detector (50) infra-red red radiation that has passed through said gas and providing an output signal representative thereof; characterised by the step of: (d) examining the intensity of a portion of the infra-red spectrum within a range of approximately 3.1 ?m and 3.6 ?m to estimate whether or not said gas comprises any light or heavy hydrocarbons.

Abstract: A terahertz spectroscopy system includes a source of terahertz radiation, a detector of terahertz radiation, a source of sample gas, and a sample cell that can be cooled to cryogenic temperatures. The sample cell may be configured to receive the sample gas, received terahertz radiation from the source of terahertz radiation, provide the terahertz radiation to the detector after the terahertz radiation has passed through the sample gas, and facilitate cryogenic cooling thereof. The sample cell may be cryogenically cooled to freeze the sample gas and subsequently warmed either continuously or in steps in temperature so that individual components or groups of components of the sample gas may evaporate and thus have absorption spectra formed therefor. Enhanced resolution of absorption spectra is provided when a gas sample contains a large number of components of different gases.

Abstract: A device for conducting a transmission measurement includes a system for generating a light wave consisting of a first and a second wavelength fraction, in addition to an optical channel guiding the light wave to a sample tube with a sample, wherein the light wave permeates the sample tube with a sample. The device also has a motion unit for producing a relative movement of the light wave along the sample tube. A receiver for receiving and separating the first and second wavelength fragments after the light wave has permeated the sample tube with a sample is also provided. A converter converts the first wavelength fraction into a first digital measuring value describing the degree of transmission in the first wavelength and converts the second wavelength fraction into a second digital measuring value describing the degree of transmission in the second wavelength.

Abstract: There is disclosed a gas sensor comprising an electromagnetic radiation source, a detector which is sensitive to radiation from the source and a waveguide which comprises at least a part of an optical path from the source to the detector through a gas sample, the waveguide comprising a first waveguide portion which extends from the radiation source and a reflector which is arranged to change the direction of and laterally displace radiation conducted from the source through the first waveguide portion into a second waveguide portion which is separate to the first waveguide portion and which conducts received radiation towards the detector. The gas sensor can be formed as a layered structure. A convoluted passage allows gas access to the optical path.

Abstract: A laser mark which will be the positioning mark for a secondary charged particle image in the charged particle beam apparatus is applied by moving the sample processing/observation area in the charged particle beam apparatus so as to come into the view field while performing an observation by an infrared microscope, and by a using a laser optical system disposed coaxially with an optical observation system, the mark made at the periphery of the processing/observation object area. Next, by a superposition of an infrared transmission image and a CAD data, the processing/observation object area and the laser mark are registered onto the CAD data. And, by a correlation of the registered data read from the charged particle beam apparatus and the secondary charged particle image, it is possible to accurately and easily determine the processing position.

Abstract: An optical gas sensing apparatus for sensing gas includes a tubular housing member, a column light source member, a column light sensing element member and an adhesive. The tubular housing member has a light-reflecting inner surface. The column light source member is provided to a first end portion of the housing member, wherein the light source member has a light source, which emits light. The column light sensing element member is provided to a second end portion of the housing member, wherein the light sensing element member has a light sensing element, which senses the light emitted by the light source. The adhesive connects the housing member to at least one of the light source member and the light sensing element member.

Abstract: The invention relates to a device for monitoring the oxygen concentration in an aircraft tank. The device includes an absorption measuring section equipped with a laser or laser diode (6), a photodiode (7), a temperature sensor (8) and a reflector (5) for carrying out laser spectroscopy on a gas volume to be measured inside the tank. The conducting components of the device are positioned outside the tank and its reflector (5) is positioned in the tank in the gas volume to be measured, the components and reflector being optically coupled by a window (3) that is situated in the tank wall (2). The absorption measuring section is mainly located in the chamber containing the gas to be measured.

Abstract: A multi-pass gas cell that operates with reflected radiation pass through a gas, the reflected radiation transmitted and received by first and second fiber optic ports that are subject to an alignment adjustment, and a mirrored viewing window having a inner reflective surface exposed to an interior of the elongated cell body for reflecting the radiation within the cell body, an outer viewing surface, and a transmittance characteristic that permits a portion of the radiation to pass through the mirrored window, from the inner reflective surface to the outer viewing surface, as a visual indicator of the alignment condition of the reflected radiation relative to the first and second fiber-optic ports.

Abstract: The present invention provides a method for measuring a lubricant's total basicity by measuring one or more preselected infrared absorption bands of a lubricant and correlating the measured bands to the basicity. Preferably, the measured bands are due to carbonate or sulfate species in the lubricant.

Abstract: An infrared gas sensing apparatus for sensing gas includes an infrared source for emitting infrared light, a wavelength tunable filter for selectively allows passage of the infrared light at a specific wavelength, an infrared detector for detecting the amount of the filtered infrared light, and a control circuit for controlling the wavelength tunable filter. The control circuit has a check circuit that checks whether the wavelength tunable filter selects a collect wavelength. The check circuit controls the wavelength tunable filter so that the wavelength tunable filter allows passage of the infrared light at a wavelength within a wavelength range where atmospheric gases do not absorb the infrared light. The check circuit checks whether the wavelength tunable filter operates normally by comparing the amount of the filtered infrared light with a reference value.

Abstract: A spectroscopic detection system is described for monitoring ambient air for toxic chemical substances. The system can be a compact, portable multiple gas analyzer capable of detecting and discriminating a broad range of chemical constituents including various nerve and blister agents as well as toxic industrial chemicals at low or sub part per billion (ppb) levels. The system minimizes false alarms (e.g., false positives or negatives), features high specificity, and can operate with response times on the order of a few seconds to a few minutes, depending on the application. The system can be an entirely self-contained analyzer, with a Fourier Transform Infrared (FTIR) spectrometer, a gas sample cell, a detector, an embedded processor, a display, power supplies, an air pump, heating elements, and other components onboard the unit with an air intake to collect a sample and an electronic communications port to interface with external devices.

Abstract: This invention provides devices and apparatuses comprising the same, for windowless optical detection of particle-laden samples, for example aerosols or fluid suspensions. The devices make use of passive sheath flow as a mechanism for containing aerosol/fluid suspension flow. The operation of the device reduces particle loss inherent to conventional windowless optical detection schemes. Methods of optical detection and/or analysis of or the particles in a sample using devices of this invention are described.

Abstract: A chemical reactor includes two substrates that are joined along a surface and a chemical reaction chamber formed between the substrates. The chemical reaction chamber has a hollow interior and one or more light reflectors located along walls of the hollow interior. The chemical reaction chamber has one or more inputs to transport fluid into the hollow interior and an output to transport fluid out of the hollow interior. The one or more light reflectors cause light rays to make multiple crossings of the hollow interior as a result of reflections off the one or more reflectors.

Abstract: A gas measurement system of this invention includes a detector assembly having a beamsplitter adapted to separate infrared radiation into a first beam and a second beam and a mirror adapted to receive the first beam from the beamsplitter. The first and second beams are directed to first and second detectors that are disposed in a common plane. In one embodiment, the optical elements are provided on or in an optical block. In another embodiment, the gas measurement system includes a housing that contains an infrared absorption gas measurement assembly, a luminescence quenching gas measurement assembly, and a processor that is programmed to measure gas constituents of a gas flow based on an output of the infrared absorption gas measurement assembly and the luminescence quenching gas measurement assembly.

Abstract: Method and apparatus for detecting, by absorption spectroscopy, an isotopic ratio of a sample, by passing first and second laser beams of different frequencies through the sample. Two IR absorption cells are used, a first containing a reference gas of known isotopic ratio and the second containing a sample of unknown isotopic ratio. An interlacer or reflective chopper may be used so that as the laser frequencies are scanned the absorption of the sample cell and the reference cell are detected alternately. This ensures that the apparatus is continuously calibrated and rejects the baseline noise when phase sensitive detection is used.

Abstract: The amount of water vapor in natural gas at different levels, including at levels below 10 ppmv, is measured by directing a light from a quantum cascade laser at a frequency in the 5.01 to 5.03 micron or the 5.07 to 50.9 micron wavelength range through natural gas containing water vapor. A detector is configured to detect the intensity of light transmitted through the natural gas from the laser; and an analyzer is coupled to the detector for determining the level of water vapor in the natural gas.

Abstract: A sidestream sampling system includes a sidestream gas measurement assembly and a sample cell configured to be assembled therewith. The sidestream gas measurement assembly includes a receptacle for removably receiving at least a portion of the sample cell. The sample cell is coupled to a sampling tube that is configured to communicate with an airway of an individual. When the sample cell is assembled with the sidestream gas measurement assembly, a window of the sample cell is oriented toward a corresponding source and/or detector of the sidestream gas measurement assembly to facilitate monitoring of an amount of at least one gas or vaporized material in an individual's respiration.

Abstract: A mixture ratio detecting apparatus comprises: a light source which emits light including light of an infrared region; a first light detecting unit which detects the light of the infrared region from the light source; a second light detecting unit which detects light of a region having a range different from that of the first light detecting unit; and a control unit which outputs a signal pertaining to a mixture ratio based on signals from the first light detecting unit and the second light detecting unit, and controls the light source, the first light detecting unit, and the second light detecting unit.

Abstract: Concentrations of a target analyte in a gas mixture containing one or more background analytes having potentially interfering spectral absorption features can be calculated by compensating for background analyte absorption at a target wavelength used to quantify the target analyte. Absorption can be measured at a reference wavelength chosen to quantify the concentration of the background analyte. Using a background gas adjustment factor or function, the absorption measured at the reference wavelength can be used to calculate absorption due to the background analyte at the target wavelength and thereby compensate for this background absorption to more accurately calculate the target analyte concentration in real or near real time. Additional background analytes can optionally be compensated for by using one or more additional reference wavelengths.