Abstract: Gases such as pollutants are discerned in a sample, preferably using a laser to emit an infrared light beam along a sight path for illuminating the gases. The beam is directed along the sight path and collects light from the gases. An optical tunable filter selects a particular optical wavelength or band, and the filtered wavelength is focused on a detector coupled to an analyzer. The analyzer can include a processor that can pulse the laser or coordinate collection of data from sample gases and from a reference cell containing known gases, e.g., using an optical chopper wheel. The processor analyzes the light levels as a function of wavelength to discriminate for the presence of selected gases by determining a characteristic pattern of light absorption and light emission by the gases. The tunable filter has an acousto-optical crystal of Tl.sub.3 AsSe.sub.3, in which an RF acoustic wave is generated for varying diffraction of light by the filter, thereby selecting a wavelength.

Abstract: An absorption cell of the type used to measure gas concentrations by pressure fluctuations of the concentrated gas in an IR radiation field, wherein the IR radiation through the field is affected by the pressurized gas fluctuations to thereby provide an electrical measurement of gas concentration. The sensitivity, linearity and accuracy of the measured gas concentration is improved by controlling the surface roughness of the interior walls of the measurement cell; the wall roughness is preferably controlled to between 15 and 70 microinches.

Abstract: A spectroscopy device comprises a laser diode/lens assembly driven by a periodic stepped laser diode drive current. Each period of the stepped laser diode drive current has a plurality of constant current intervals: a left baseline interval, a left skirt interval, a peak interval, a right skirt interval, and a right baseline interval. The left and right skirt constant current intervals are used to lock the laser radiation emitted from the laser diode onto a preselected absorption line. The left and right baseline constant current intervals are used to subtract baseline absorption measurements from peak constant current interval absorption measurements. A high frequency common mode noise rejection circuit rejects noise common to a monitor radiation detector and a radiation detector which detects radiation passing through a sample cell. A serial line locking cell is provided to allow locking when little or no absorbing material is present in the sample cell.

Abstract: A method is provided for precisely and concurrently measuring dynamic engine oil consumption and fuel consumption within an internal combustion engine on a real-time basis. Nonradioactive organo- bromine or chlorine compounds are added to the oil in small amounts in their natural isotopic abundance or enriched. Upon complete combustion, the bromine or chlorine is converted into hydrogen bromide (HBr) or hydrogen chloride (HCl), respectively. A tunable diode laser spectrometer is used to determine the trace amounts of the resultant HBr or HCl in the exhaust gases, which continuously flows through a sample cell by the use of a sample line that allows the unimpeded transport of samples, reduces the pressure of the exhaust gas and maintains it at a suitable level for analysis, and prevents the condensation of water vapor in the exhaust gas so as to prevent the dissolution of the tracer compounds in the water condensate.

Abstract: This invention provides a means for detecting local atmospheric contaminants from safe distances. The invention means of a detector system comprise a pulsed laser, a sensitive photo-detector, various optical filters, and necessary digital control circuitry. The detector system employs laser technology in combination with a sensitive photo-detector to achieve detection of any hazardous gas elements or other pollutants remotely located from personnel who may subsequently be exposed. In operation, a pulsed laser or a tunable dye laser is employed as an excitation source for the contaminant or pollutant to achieve excitation of the contaminant or pollutant. When the excited molecule of the contaminant or pollutant returns to ground-state it emits a photon at a given (measurable) frequency. A sensitive photo-detector is filtered to permit detection of only the frequency at which a harmful gas (as an example of a contaminant or pollutant) fluoresces.

Abstract: A miniaturized NDIR gas sensor is manufactured using semiconductor micromachining techniques from a semiconductor material such as Si or GaAs. The NDIR gas sensor comprises an optical waveguide, a light source at one end of the waveguide, at least one light detector at the end of the waveguide opposite the light source, a diffusion type gas sample chamber formed within the waveguide and interposed in the optical path between the light source and light detector so that the light source and light detector are thermally isolated from the gas sample, and a separate bandpass filter interposed between the light source and each light detector. Because the NDIR sensor is fabricated out of a semiconductor material, the source driver and signal processing electronics may be added directly to the sensor using integrated circuit fabrication techniques. Particles and smoke and dust may be kept out of the sample chamber by application of a gas permeable membrane over apertures in the sample chamber walls.

Abstract: A compact infrared gas analyzer capable of reducing the quantity of heat generated from a radiation source and the effects of temperature on samples is provided. A shutter is provided between the radiation source and the sample cell and/or between the sample cell and a detector with the shutter in a closed position. The shutter is opened and closed during measurement. A resistor comprising a resistance element made of one of RuO.sub.2, W, SnO.sub.2, FeCrAlY, Pt, Pt-Rh and Pt-Pd, formed on an AlN substrate, may be used as the radiation source, with the radiation source and the shutter being interrelatedly controlled.

Abstract: Improvements in non-invasive detection methods for glucose and other constituents of interest in a sample have been developed. The apparatus and methods of the invention provide an analog of color perception of human vision, preferably in the near infrared region, replacing spectrophotometers and narrow band sources used in other non-invasive near infrared detection methods. A plurality of detector units are used, each covering a broad and overlapping region of the detected spectrum, paralleling color perception and colorimetry. The improvements are primarily concerned with improving the signal-to-background (or noise) ratio such that the data stream is improved. These improvements use congruent sampling, comparison of different data streams from different sample portions or filter sets, using an interrogation system with sufficient speed to allow testing of arterial blood, and using a filter with a spectral structure. In some circumstances, a neural net is used for analysis, allowing the system to learn.

Abstract: A non-dispersive infrared gas analyzer, with improved linearity in output concentration signal especially in measuring gas species of high concentration, includes a measuring cell into which a gas to be measured is fed, a non-selective infrared radiation sensor disposed on one side of the measuring cell, an optical band-pass filter disposed between the measuring cell and the infrared radiation sensor, and a nonselective infrared radiation source, disposed on the other side of the measuring cell and having an infrared radiation transmission window, wherein the radiation source further includes a gas filled therein at a predetermined partial pressure and the filled gas has at least a common partial molecular structure with the gas to be measured.

Abstract: A spectral analyzer has a high efficiency optical collector having a first concave reflector portion and an opposed second concave reflector portion providing an exit passage therethrough, and a light emitting source of a predetermined wavelength range is positioned in the collector so that the light is collected and directed to the exit passage. A specimen holder is positioned adjacent the exit passage and has windows at its entrance and exit ends. An elongated reverse non-imaging optical member which has a peripheral wall reflecting light rays entering through the exit window of the holder reduces the angle of the rays relative to the optical axis of the optical member as they pass therethrough. The light passing through the exit end of the optical member enters a detector assembly including at least one photo detector sensitive to a predetermined wavelength of light, and at least one optical filter disposed between the optical member and the photodetector to pass light of the predetermined wavelength.

Abstract: A method uses near-infrared radiation to optimize the removal or separation of normal paraffins from a kerosene feed stream. The absorptivity of a feed stream and/or sievate is determined for at least one near-infrared wavelength. The weight percent of the normal paraffins in the feed stream and/or sievate is determined from the absorptivity. The determined weight percent is used to control the removal or separation of normal paraffins from the kerosene feed stream.

Abstract: A new non-invasive non-spectrophotometric method for measuring the blood concentration of analytes such as glucose has been developed. The apparatus and methods of the invention exploit analogies with colorimetry and color perception to extract concentration measurements from the global structure of the intensity versus wavelength absorbance or transmission profile. A plurality of broad spectrum filters transmit distinguishably coded beams of radiation in overlapping portions of the spectrum to the sample. Radiation reflected or transmitted by the sample is detected and decoded. LED's may be used instead of the broad spectrum radiation generating device and the filters. Further, a scanning interferometer can be used as the illuminating and coding device. In a preferred mode, congruent illumination is utilized. The coded signals are analyzed by analogy to colorimetry and visual processing and can be converted into concentration measurements.

Abstract: A calibration device, method and apparatus is provided for checking calibration of a breath alcohol measuring instrument. A silicon wafer with an anti-reflective silicon monoxide coating on both sides is used to attenuate the infrared radiation in the range of 3.35 to 3.80 microns wavelength in a manner to simulate the attenuation caused by a breath sample containing 0.10 BrAC. A comparison of the signal generated by the attenuation at a wavelength of approximately 3.48 microns is made to the baseline signal obtained before placing the calibration disk in the IR beam path and accurately simulates the breath sample. The related breath alcohol measuring method and apparatus provides for the positioning of the composite disk in the path between the infrared source and receiver. A computer compares the signals and performs the calibration check, as well as the actual BrAC analysis.

Abstract: A system (10) for detecting nitric oxide (NO) within an exhaust plume (14) includes a source (18) for generating an optical beam (20) and for directing (22, 24) the optical beam through the exhaust plume, the optical beam having wavelengths within a predetermined band of wavelengths within the infrared (IR) radiation spectrum. The system includes a sensor (32)/filter (30) assembly having a first channel for determining a measured NO transmission value for a first predetermined band of wavelengths; a second channel for determining a measured water transmission value for a second predetermined band of wavelengths; a third channel for determining a measured reference transmission value for a third predetermined band of wavelengths selected so as not to be significantly absorbed by the exhaust plume; and a fourth channel for determining a measured combustion by-product transmission value for a fourth predetermined band of wavelengths.

Abstract: The sensitivity of a nondispersive infrared gas analyzer increases with increasing pathlength, which increases the absorption of the infrared radiation by the gas whose concentration is to be determined. The present invention includes the addition of an obstructing element that further increases the average pathlength. In one embodiment the obstructing element consists of a highly reflective elongated cylinder located with its axis collinear with the axis of the tubular chamber. In another embodiment, the sample chamber includes a converging section, the smaller end of which is joined to an elongated tubular section of uniform cross section. The improvements are applicable to both pumped and diffusion-type sample chambers.

Abstract: A spectrophotometer for providing an image of a radiation scattering medium having one or more radiation attenuating constituents is disclosed herein. The spectrophotometer includes a light source for illuminating the scattering medium with electromagnetic radiation of at least one wavelength. In one embodiment a time-gated detector serves to detect, during a predefined detection interval, the electromagnetic radiation having traversed a distribution of path lengths during propagation through a region of the medium. A photon counting apparatus or the like measures the intensity of the detected portion of the electromagnetic radiation, wherein the measured intensity is a function of attenuation of the region within the medium. A display apparatus is operative to generate the image in accordance with the measured intensity.

Abstract: A system for measuring the physical characteristics of a hydrocarbon places a reference hydrocarbon cell in thermal contact with a sample cell containing an unknown hydrocarbon. A near infrared spectrum measurement is taken of both the cells. Measurement data from the sample cell is adjusted by the measurement data from the reference cell, and the adjusted measurement data is evaluated by a model to predict the characteristics of the sample. The model is built from a teaching set of hydrocarbons having known physical characteristics and the reference hydrocarbon. Each of the teaching set hydrocarbons is measured and then adjusted by a measurement of the same reference hydrocarbon, and the adjusted measurements are used to build the model.

Abstract: The present invention is a method to determine the oil content of a waxy isomerate by NIR radiation which is then used to control the separation of oil from the waxy isomerate.

Abstract: A spectrophotometric sensor assembly that may find particular use in a capnometer, a medical device for measuring the concentration of carbon dioxide in the exhaled breath of a patient, includes at least one microlamp. A microlamp is a very small source of electromagnetic radiation including a heated filament disposed over a substrate. The microlamp may be constructed using semiconductor fabrication techniques. The microlamp typically emits broad-band infrared radiation. Radiation from the microlamp usually passes through a filter, which preferentially transmits radiation of a preselected wavelength. The radiation then passes through a sample chamber and onto a detector. The concentration of a substance of interest within the chamber may be computed by determining the degree to which the radiation is absorbed in the chamber. In a preferred embodiment, an array of microlamps is sequentially triggered in a rapid manner.

Abstract: A system for measuring the permeability of membranes, particularly with reference to water vapor, utilizing a diffusion cell having a first water vapor chamber and a second gas flow chamber, the chambers being separated by the membrane to be tested. Gas flow through the gas flow chamber is conveyed to an infrared gas analyzer and to a gas flow sensor; the infrared analyzer provides an electrical signal representative of the water vapor content of the gas, and the gas flow sensor provides a signal representative of the rate of gas flow through the system; the analyzer signal is conveyed to an amplifier and the gas flow sensor signal is utilized to adjust the gain of the amplifier, the output of the amplifier thereby presenting a water vapor signal which has been adjusted to compensate for air flow through the system.

Abstract: A gas sample chamber that is particularly advantageous for use with a semiconductor laser has the form of an elongated hollow tube with a specularly reflective inside surface, a semiconductor laser located at one end of the tube and a detector located at the opposite end of the tube. In one embodiment, apertures in the wall of the tube permit a gas to enter and leave the sample chamber by free diffusion. In another embodiment the gas flows into the hollow tube from a pressurized source through a port or is drawn through the tube by a suction pump. In other embodiments, the tube is partitioned into two successive sections by means of a window located within the tube. The window is transparent to radiation of two different wavelengths that coincide with the absorption bands of two different gases. The semiconductor laser is tuned to these wavelengths successively so that two gas components can be detected and measured simultaneously.

Abstract: An apparatus for ultrasensitive detection of low concentrations of constituents using a broad band LED source is described. The apparatus provides enhanced resolution by synchronously detecting an imbalance between two analog signals due to absorption in a measurement cell at a wavelength of interest. Elements are provided to balance the signals in the absence of absorption to provide a reference point for concentration calculations. In accordance with several embodiments of the present invention, a time alternating signal for synchronous detection is achieved by combining signals from each of two alternating paths, only one of which travels through the measurement cell and which may have absorption. If there is absorption in the measurement cell, then the signal created by combining the alternating paths will exhibit residual modulation at the path alternation rate.

Abstract: An improved sample cell for use in a gas analyzer has a sample body with a measuring optical path extending traverse to the cell body. A sample gas inlet port is positioned at one end of the cell body, and a sample gas outlet port is positioned at the other end of the cell body. Porous plates can extend across the cell body, and appropriately-dimensioned apertures in the porous plates can ensure a consistent flow path of gas across the optical path without any stagnated flow patterns.

Abstract: A calibration method for gas concentration measurement with an NDIR technique based on optical absorption. Radiation is imposed onto the gas mixture under measurement contained in a measurement channel (3) isolated at least partially from its environment, the intensity of radiation transmitted through the gas is measured, the gas concentration is computed from the measured intensity, in order to calibrate the measurement apparatus the gas state variables are deviated in a controlled manner, whereby the level of transmitted radiation intensity is changed, and the intensity of the transmitted radiation is measured in at least two known points of the gas state variables, thus obtaining data for calibration of the measurement apparatus employed.

Abstract: Infrared radiation emitter units for gas analyzers and other applications. The emitter has a substrate with a film of electrically resistive, emissive material on one of its surfaces. The emitter is so mounted on an emitter unit base that it can freely expand as the emitter heats up. A lead frame commutator, employed to electrically connect the emitter to an external power source, also facilitates the assembly of the unit. A component with a plated, parabolic surface collimates and focuses into an appropriate beam the energy generated by the emitter.

Abstract: Method for determining oxygenate content and/or octane of hydrocarbon fuels suitable for automotive vehicles. Selecting nanometer frequencies in the range 1,300 to 1,350 reduces the temperature dependence of calibration equations that predict values representative of both oxygenate content and octane. This can be further improved by using only derivatives of selected temperature-dependent frequencies in addition to those in the 1,300 to 1,350 nanometer range. The selected frequencies preferably primarily correspond to C-H vibrational modes.

Abstract: A pneumatic infrared ray detector for use in a gas analyzer provided with a gas-slowly leaking mechanism capable of not only controlling a quantity of gas leaked in high accuracy but also increasing a range capable of controlling said quantity of gas leaked is provided. A body is provided with gas chambers and a detecting gas chamber and the respective gas chambers are communicated with said detecting gas chamber through gas passages. A ring-shaped leak-controlling sheet on the bottom surface of the detecting gas chamber is provided with a groove-like gas-leaking passage between the inner and outer circumferential edges thereof and a ring-shaped diaphragm and a vibrating diaphragm are built up on said leak-controlling sheet to be fixedly pressurized by means of a cover plate through a pressurizing member and a plate spring.

Abstract: The present invention is a method for improving the estimation of physical properties of a material, based on the infrared spectrum of the material, by concatenating additional data obtained from other measurement techniques to the infrared spectrum to fill the voids in the spectral data resulting from a lack of sensitivity by infrared spectrometers to trace compounds in the material. The augmented spectral data then is used to produce a calibration model for estimating the physical properties of the material.

Abstract: A pneumatic detector, non-dispersive infrared analyzer employing detector cell chambers in optical series. The invention having an auxiliary chamber communicating with the front chamber to increase the rear chamber's signal so as to balance the signals from the front and rear chambers. The use of xenon as a diluent gas in the detector chambers in combination with a mass flow detector to improve the sensitivity. The use of an improved synchronous detection method employing a voltage-to-frequency circuit to convert the detector signal to a synchronous high resolution digital signal. The use of an improved source electrically pulsed having low thermal mass and a large radiating area.

Abstract: A system for non-intrusive drunk driver screening comprising a wavelength modulated laser, harmonic detector, and signal analyzer apparatus for quantitative absorption spectroscopy detection of low level concentrations of alcohol molecules in a contained gaseous volume within the operator compartment of vehicles.

Abstract: Certain selected wavelengths in the near infrared spectra permit analysis of weight percent, volume percent, or even mole percent of each component, e.g. PIANO (paraffin, isoparaffin, aromatic, napthenes, and olefins), octane (preferably research, motor or pump), and percent of various hydrocarbons, e.g. alpha olefins. Analysis can be nearly continuous analysis on-line or at-line, as well as batch analysis, e.g. in a quality control laboratory. Preferably the NIR data is converted to a second derivative of the spectra and multiple linear regression performed to model the individual PIANO concentrations, and to predict physical properties of fuel blending components, e.g. research octane of reformate, etc.

Abstract: Certain selected wavelengths in the near infrared spectra permit analysis of weight percent, volume percent, or even mole percent of each component, e.g. PIANO (paraffin, isoparaffin, aromatic, napthenes, and olefins), octane (preferably research, motor or pump), and percent of various hydrocarbons, e.g. alpha olefins. Analysis can be nearly continuous analysis on-line or at-line, as well as batch analysis, e.g. in a quality control laboratory. Preferably the NIR data is converted to a second derivative of the spectra and multiple linear regression performed to model the individual PIANO concentrations, and to predict physical properties of fuel blending components, e.g. research octane of reformate, etc.

Abstract: An infrared attenuation measuring system, for the quantitative determination of the concentration of one or more components in an aqueous fat-containing sample, such as milk, by an infrared attenuation technique. The system comprising a set of waveband-related parameters containing information enabling the system to calculate the concentrations substantially independent of the degree of homogenization of the fat-containing sample, and/or to determine the degree of homogenization of the sample. The parameter set contains parameters which are related to wavebands containing a high degree of information about the homogenization degree of the sample. This may be wavebands containing little information about the chemical components of the sample, and/or wavebands containing a substantial amount of information about the chemical components of the sample. The system is calibrated with aqueous fat-containing samples with different degrees of homogenization.

Abstract: The improved sample chamber includes an elongated hollow tube closed at one end and having specularly-reflective inwardly facing surfaces. A source of radiation and a detector of radiation are mounted side by side in the open end of the hollow tube, both facing the closed end. A plurality of filtering apertures are formed in the tube, and each aperture is covered by a sheet of a semipermeable membrane that serves to prevent airborne particles larger than a predetermined size from entering the chamber while not interfering with the free diffusion of the gas to be measured into and out of the chamber. The use of an elongated hollow tube that is closed at one end results in no loss in the efficiency with which the radiation is conducted from the source to the detector while decreasing the external length of the chamber by 50 percent.

Abstract: An instrument for determining the concentration of a particular gas that might be present in a sample has no moving parts and is extremely compact and inexpensive. A novel waveguiding structure serves both as an optical element and as the sample chamber. As an optical element, the waveguiding structure collects radiation from a blackbody source located at the entrance end of the waveguiding structure and conducts the radiation through the waveguiding structure, concentrating it on two infrared detectors mounted at the opposite end of the waveguiding structure. As a sample chamber, the waveguiding structure causes the radiation to undergo multiple reflections that result in the average path length being substantially greater than the physical length of the waveguiding structure. Each of the detectors has its own optical filter, and baffling assures that each detector responds only to radiation which has passed through its filter.

Abstract: To measure water vapor and carbon dioxide, a gas analyzer includes a light source, a reference flow cell, a sample flow cell, a detector and a source of gas. The light source, flow cells and detector are arranged so that the detector detects light transmitted from said light source through the flow cells. The flow cells have folded paths for the light. A reference signal is subtracted from a sample signal to obtain an independant variable. Carbon dioxide and air mixed with carbon dioxide are supplied as required. The carbon dioxide is supplied from a container through capillary tubes. Heat is applied to the tubes to control the flow rate. A signal representing gross concentration of the carbon dioxide as a dependant variable is obtained from said independent variable from an empirically determined polynomial.

Abstract: A fire fighting trainer for use in training fire fighters is provided. The fire fighting trainer includes a structure having a plurality of chambers having concrete or grating floors. Each chamber contains one or a series of real or simulated items, which are chosen from a group of items, such as furniture and fixtures and equipment. The trainer also includes a smoke generating system having a smoke generator having a smoke line with an outlet for each chamber. The trainer also includes a propane gas flame generating system having at least one propane gas pressure controller and a gas line with a burner control and one or more single element or multi-element burners for each chamber. The trainer has a main control panel for regulating the flame generating system and the smoke generating system and for controlling the fire, or fires, and smoke in each chamber.

Abstract: To measure water vapor and carbon dioxide, a gas analyzer includes a light source, a reference flow cell, a sample flow cell, and a detector. The light source, flow cells and detector are arranged so that the detector detects light transmitted from said light source through said reference flow cell and through said sample flow cell and generates a reference signal representing the light transmitted through a reference gas in said reference flow cell and a sample signal representing the light transmitted through a sample gas in said sample flow cell. The reference signal is subtracted from the sample signal to obtain an independant variable. A signal representing gross concentration of the carbon dioxide as a dependant variable is obtained from said independent variable from a stored empirically determined third power polynomial. The polynomial includes terms having at least first, second and third powers of said independant variable.

Abstract: Methods for quantifying the oil and water fractions of a fluid stream. A first method broadly includes making optical density (OD) measurements of the fluid stream by detecting photons of a first predetermined energy where the oil and water absorption characteristics are substantially identical (e.g., 1710 nm wavelength), and determining the oil and water fractions f.sub.o and f.sub.w according to OD.perspectiveto.f.sub.w .alpha..sub.w l+f.sub.o .alpha..sub.o l where .alpha..sub.w and .alpha..sub.o are related to the absorption coefficients of the oil and water at the predetermined energy, l is the path width of the fluid stream, and f.sub.w +f.sub.o =1. A second method which eliminates scattering effects utilizes the photons at the first predetermined energy and further utilizes photons of a second predetermined energy which is sufficiently close to the first predetermined energy such that the oil fraction is a linear function of the OD over the energy range.

Abstract: A device for gas analysis, which determines the content of two or more gases in a gas flow. The device includes at least one source for emission of two or more ray paths of radiation of a detectable wavelength, a cuvette device having an inlet and an outlet for uninterrupted gas flow, and a detector device for conversion of the radiation into an electrical signal. The source(s), cuvettes, and detectors are arranged such that ray paths emitted from the source pass through cuvettes containing gas and to detectors to permit analysis of two or more gases in a gas flow. In a preferred embodiment, the cuvette device includes a block having cuvettes positioned in each of the ray paths, which cuvettes are interconnected to form an unbroken conduit for gas flow from inlet to outlet.

Abstract: A new non-invasive detection method for glucose and other constituents of interest in a sample has been developed. The apparatus and methods of the invention provide an analog of color perception of human vision, preferably in the near infrared region, replacing spectrophotometers and narrow band sources used in other noninvasive near infrared detection methods. A plurality of detector units are used, each covering a broad and overlapping region of the detected spectrum, paralleling color perception and colorimetry. In some circumstances, a neural net is used for analysis, allowing the system to learn. A novel method for background discrimination is also described.

Abstract: A rapid near-infrared instrument for measuring constituents of nonhomogeneous samples is disclosed which alleviates the need for taking successive measurements of the sample, and repositioning the sample for each successive measurement, by providing a novel illumination system including a light pipe which transmits near-infrared energy to the sample at a plurality of substantially separate and independent location. This arrangement permits a plurality of subsample measurements to be taken simultaneously which enables accurate constituent measurements to be made quickly and easily.

Abstract: A method of calibrating polarimeter to work at an unknown wavelength comprising calibrating the polarimeter at a standard wavelength, using the calibrated polarimeter to measure a sample, measuring the same sample at the unknown wavelength and setting the polarimeter to give the same measurement at the said unknown wavelength as at the known wavelength. The method is particularly applicable to be calibration of a saccharimeter to work at an unknown wavelength in the near infra-red for the measurement of dark sugar samples. The invention is also a polarimeter or saccharimeter for carrying out the method.

Abstract: An apparatus that conducts in situ analyses of fluids in real time is disclosed. The apparatus comprises bifurcated optic fibers, a pulsed light source, a light detector, a water-tight pressure case that houses the pulsed light source and the light detector, and a flow-through cell that receives one end of each bifurcated optic fiber. The flow-through cell may comprise a plurality of attached tube sections that define a volume which acts as a passageway for conducting fluids. One or more sections of the flow-through cell may be adapted to introduce a reagent into fluid flowing through the cell. Sections of the cell may contain potassium periodate and N,N-diethylaniline that are released into a fluid flowing through the passageway, enabling the spectrophotometer to analyze manganese (II) concentrations by monitoring the decrease in fluorescence accompanying the oxidation of DEA to 2 DEA'. The fluid may also be analyzed by measuring reflectance, absorption, turbidity, and fluorescence.

Abstract: An arrangement for making gas spectroscopic measurements includes a laser diode driven by a modulated control current, a monitor diode, a detector unit for receiving a measurement signal of the transmitted radiation and a lock-in amplifier. The method utilizing the above arrangement is improved in that the offset component in the output signal of the lock-in amplifier is eliminated. This is achieved in that the radiation power of the laser diode is controlled to a pregiven modulation profile with the monitor diode functioning as an actual-value transducer.

Abstract: An anesthetic agent analyzer having six or more independent analytical channels, where each channel comprises a first thermopile which receives incident infrared radiation and a second thermopile behind the first thermopile which is blocked from the incident infrared radiation and thus serves as a reference for detecting ambient temperature variations. The first and second thermopiles are connected in a "parallel opposed" fashion so that the effects of ambient temperature variations automatically cancel and the detectors may be readily configured in a detector package. The anesthetic agent analyzer of the invention is designed for use with a wideband infrared radiation source so that anesthetic agents having characteristic absorption bands in the far infrared wavelength range (6-15 microns) may be more readily detected and discriminated.

Abstract: An off-axis cavity absorption cell (10) includes astigmatic mirrors (22, 28). The cell design is based on a prototype design that yields a closed beam path having a desired geometry, but the mirrors are fabricated so that the ratios of their radii of curvature are actually larger than those calculated for the prototype. To achieve the desired closed beam path, the mirror spacing is adjusted from that of the prototype design, and the planes of their axes of greatest curvature are oriented out of the alignment that characterizes the prototype design. If the mirrors' manufacturing process yields errors in the curvature-radius ratios within certain prescribed limits, a cell of this design can be adjusted to achieve the closed beam path by simply changing the mirror separation and the "twist angle" between their respective planes of maximum curvature radius.

Abstract: A furnace with two hot zones holds multiple analysis tubes. Oxidized gases flow from outlets of the tubes to individual gas cells. The cells are sequentially aligned with an infrared detector, which senses the composition and quantities of the gas components. Each elongated cell is tapered inward toward the center from cell windows at the ends. Volume is reduced from a conventional cell, while permitting maximum interaction of gas with the light beam. Reduced volume and angulation of the cell inlets provide rapid purgings of the cell, providing shorter cycles between detections. For coal and other high molecular weight samples, from 50% to 100% oxygen is introduced to the tubes. Cells are suspended from adjustable holders on a frame which is spaced from a table. The table is moved by a linear motor and a fixed platen. Sides of the table are shielded to prevent electromagnetic and magnetic motor interference with detected results.

Abstract: A method and apparatus for detecting the presence of a predetermined hydrocarbon vapour of a predetermined concentration in a monitored area by: exposing gas in or from the monitored area to radiation from a Xenon flashlamp which includes ultraviolet radiation of a predetermined ultraviolet spectral range and infrared radiation of a predetermined infrared spectral range; detecting the radiation after having passed through the gas; and comparing the detected radiation with a reference of predetermined attenuation characteristics of the hydrocarbon vapour and concentration in the respective ultraviolet and infrared spectral range.

Abstract: Methods and apparatus for constructing optically stabilized, shutterless infrared capnographs are disclosed. The capnographs of the present invention provide the absolute concentration of the constituents of the respiratory airstream of a patient, without the thermal drift problems normally associated with thermopile detectors, thereby providing a device with a high degree of accuracy. The present invention eliminates the need for a mechanical shutter to modulate the incident infrared beam and the need for a modulated source, thereby increasing the reliability and response time of the devices disclosed. Capnographs which are substantially unaffected by changes in the ambient temperature at which they operate are provided by connecting pairs of optically filtered thermopiles in series and processing the resulting differential pair. In addition, techniques are provided for selecting overlapping optical filters for use with thermopiles with a minimum level of cross-talk.