Abstract: A diode laser spectrometer includes a sample chamber for holding a sample gas, e.g., human breath, having first and second isotopic species in an unknown concentration ratio and a reference chamber for holding a reference gas having the first and second isotopic species in a known concentration ratio. Laser light is directed through both chambers at wavelengths corresponding to absorption wavelength of the isotopic species, and the light is detected and sample and reference signals generated. The signals are processed by a computer to determine the concentration ratio of the first isotopic species to the second isotopic species in the sample gas. The diode laser is cooled by a thermoelectric cooler or a cryocooler operating as a reverse Sterling engine.

Abstract: Apparatus and method of monitoring fluid presence, wherein electomagnetic radiation sources (1, 2) provide respective reference and sample beams (12, 22), the wavelength of the radiation preferably being matched with that of the absorption spectrum of a fluid to be monitored. A first reference cell (13), containing a reference sample of the fluid to be monitored, has the reference beam (12) passed through it, whilst a second, sample cell (33) containing any working sample of the fluid to be monitored, has both the reference and sample beams (12, 22) passed through it. Subsequently, the reference and sample beams are detected independently of each other to provide respective signals representative thereof, which signals are then compared to determine the presence, and preferably also the concentration, of any sample fluid in the second cell.

Abstract: The object in a non-dispersive gas sensor is to minimize the use of moving parts, as those reduce the service life of a sensor. A preferred solution is such that it includes one infrared source (1), one short sample chamber (2) and one or generally more infrared detectors (9) operating over a certain wavelength band. If the number of detectors is more than one, it is important that the light arriving in all detectors has traveled through the sample chamber (2) as identically as possible.

Abstract: Apparatus and methods for monitoring characteristic absorption of a substance in a mixture include applying radiation pulses with a wavelength characteristic of the substance to be measured and a wavelength uncharacteristic of the substance to a measuring path and to a reference path without the substance mixture. The difference of signals generated between the measuring path and the reference path are conditioned to provide a measurement value.

Abstract: A measurement chamber for measuring the quantity and composition of liquids, fabricated of a uniform semi-transparent material for illumination using infrared light. The chamber construction alleviates the problem of bypass light via the side walls of the chamber, and the construction is simple and suitable for mass production.

Abstract: A gas analyzer capable of simultaneously detecting two or more components in a single-cell mode and a gas-analyzing mechanism suitable for simultaneously detecting two or more components in a cross-flow modulation single-cell mode are provided. A gas analyzer unit includes two measuring cells, light sources provided on one end side of each of the measuring cells, gas filter cells with interferential gaseous components hindering a detection of components to be measured enclosed provided on the other end side of each of the measuring cells, beam splitters included in two gas filter cells, first- and fourth and second- and third detectors provided on the side of transmitting position and the side of reflecting position, respectively, of each of the beam splitters and a sampling device connected with a rotary valve.

Abstract: RF modulation spectroscopy of a near-infrared tunable laser diode source is used to determine the oxygen concentration in a sample medium. A reference cell containing a known concentration of oxygen is used to calibrate the apparatus as well as to lock the laser on an oxygen absorption line. The temperature of the reference cell is monitored from which the pressure in the reference cell can be determined. Both the temperature and the pressure in the sample cell are monitored, either directly using independent transducers or indirectly using spectroscopic techniques. The oxygen content of the sample is determined, correcting for both temperature and pressure effects.

Abstract: A diode laser spectrometer includes a sample chamber for holding a sample gas, e.g., human breath, having first and second isotopic species in an unknown concentration ratio and a reference chamber for holding a reference gas having the first and second isotopic species in a known concentration ratio. Laser light is directed through both chambers at wavelengths corresponding to absorption wavelength of the isotopic species, and the light is detected and sample and reference signals generated. The signals are processed by a computer to determine the concentration ratio of the first isotopic species to the second isotopic species in the sample gas. The diode laser is cooled by a thermoelectric cooler or a cryocooler operating as a reverse Sterling engine.

Abstract: Optical analysing equipment includes a light source, a light receiver and an optical arrangement for producing a measuring beam and a calibrating beam from the light of the light source. A calibrating channel and a measuring channel extend form the light source to the light receiver. The light source and the light receiver can be arranged on opposite sides of the duct. In this case, the calibrating channel and the measuring channel include two tubes extending in parallel across the duct between the light source and the light receiver. The light source and the light receiver can alternatively be arranged on the same side of the duct. In this case, the measuring channel extends partially into the duct. The calibrating channel may then extend into the duct or be positioned entirely outside the duck. By light control means, the light receiver receives either the measuring beam or the calibrating beam.

Abstract: The photometer of the present invention includes an optical system in which an emission beam generated by pulsed ultra violet radiation from a source is split into a sample beam and a reference interference beam by spectrally selective mirrors arranged in series. These mirrors reflect a beam having a wavelength range corresponding to an absorption wavelength of the gas to be detected onto one solid state detector and to pass a beam to a second spectrally selective mirror where a beam having second range of wave lengths corresponding to an interfering gas is reflected onto a second solid state detector. This second beam serves to measure the interfering gas and also as an imperfect reference channel. In a preferred embodiment the radiation from the source is split prior to entering the sample cell.

Abstract: An arrangement for detecting elevator car position relative to a floor landing includes an optical potentiometer associated with both the elevator car and the interior of an elevator hoistway. One portion of the potentiometer is attached to the elevator car, while the other portion of the potentiometer is fixed within the hoistway. Car position is ascertained by illuminating portions of a fluorescent fiber optical cable and then reading electrical signals outputted by photodetectors at either end of the cable. The difference between the electrical signals corresponds to the distance of the elevator car from the landing.

Abstract: A portable refrigeration gas analyzer employs infrared spectroscopy to detect adulterant refrigerant gases in existing R12 refrigeration systems. The analyzer can detect contaminants such as R134a, R22, and butane in concentration as low as 1% by volume. A rugged opto-acoustical infrared narrow band sensor is suitable for field use in the repair of refrigeration systems.

Abstract: A method and an apparatus for the selective determination of an isotope portion of a measuring gas by means of non-dispersive spectroscopy. The method includes sensitizing in a first ray path to the isotope component and sensitizing in a second ray path to the isotope-pure measuring gas, and electronically amplifying the measurement results. In order to improve the selectively and the sensitivity while maintaining a simple construction, an additional optical filtering is carried out in the first ray path by a filter filled essentially with isotope-pure measuring gas and the electronic measuring value of the second ray path is entered by influencing the amplification factor and an offset in the electronic amplification of the first ray path.

Abstract: Methods and apparatus for detecting biological activity within a sample are disclosed. The present invention provides a combination of a first and a second infrared light source arranged on the side of a sample vial, and a first and a second narrow-band infrared detector similarly arranged on the side of the vial approximately opposite the sources. The disclosed arrangement cancels the sources of error while measuring the carbon dioxide content of the headspace gas above the sample. In operation, the present invention sequentially measures the photocurrents generated at each detector with no source turned on, with the first source turned on, and with the second source turned on and the first source turned off. The CO.sub.2 absorption coefficient of the vial headspace gas is then calculated based on the photocurrents measured. This present invention allows compensation for source aging, detector aging, and vial wall thickness changes.

Abstract: A measuring apparatus based on the NDIR process. Pulsed infrared light traverses in two parallel optical beams (3, 4) initially a cell (6) filled with .sup.13 CO.sub.2 and a cell (7) filled with .sup.12 CO.sub.2 and then, in parallel, two cells (8, 9) which are filled with the gas sample to be analyzed. Cells (8, 9) together with a capacitor microphone (15) serving as the pressure converting means form an optopneumatic receiver (17). By regulating the pressure in cell (6) the minimum of the pressure conversion signal is investigated and related to a correspondingly obtained reference value. The simply constructed apparatus permits a .sup.13 CO.sub.2 breathing test to be performed inexpensively.

Abstract: An infrared gas analyzer, of compact and inexpensive design, has improved detection sensitivity. The infrared gas analyzer includes an infrared radiation source, a measuring cell, a reference cell, and a detector. The detector includes two detector cells in which the same species of gas, as the gas to be analyzed, is enclosed. A gas flow channel connects the detector cells to each other. Two thermal sensors are disposed in the gas flow channel, each of which further includes pairs of thermo-elements. The thermo-elements are arranged in such close proximity to each other, as to originate a thermal coupling between the pairing elements, and the thermo-element pairs are separated by a distance across which thermal coupling between the thermo-element pairs becomes insignificant. The detector detects, by the thermal sensors, a gas flow indicative of infrared absorption intensity difference between the measuring and reference cells.

Abstract: A flame sensor comprises a cell (10) containing an infra-red absorptive fluid such as carbon dioxide gas. Heating caused by absorption of the infra-red radiation is detected by measuring a resulting temperature or pressure change.

Abstract: An improved apparatus and method for measuring the concentration of carbon dioxide in respiratory gases. The apparatus is a non-dispersive gas analyzer attached in series with the respiratory airway which is universally compatible with any host system. The analyzer includes a housing which supports a sample cell containing the respiratory gases, and which contains an infrared radiation source encased in shock absorbing material, means for directing the radiation into a collimated beam path through the sample cell, means for splitting the beam path and directing it towards a pair of infrared detectors for measuring the amount of absorption of carbon dioxide in the sample cell. The analyzer is further improved by the use of two heating servos, one for regulating the temperature of the sample cell windows in order to inhibit condensation build-up and one for regulating the ambient temperature surrounding the detectors so as to ensure more accurate measurements.

Abstract: A spectrometer comprises a tunable interferometer for producing a monochromatic continuous image at an image plane and including two mirrors having substantially parallel surfaces and an adjustable spacing therebetween, a radiation detector located at the image plane for recording the image, a filter arrangement for allowing at least one predetermined range of wavelengths to pass to the detector, and a lens arrangement for collecting radiation and limiting radiation incident on the interferometer to an angle which is substantially perpendicular to the substantially parallel surfaces of the two mirrors.

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: 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 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: An infrared sensor comprising a sensor substrate formed of a semiconducting material and at least one set of infrared sensing portions formed one each on the opposite surfaces of said sensor substrate, wherein said infrared sensing portions are superposed one each on bride portions formed on cavities formed one each on the opposite surfaces of said sensor substrate.

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: Disclosed is a method of fabricating a two-color radiation detector, and two-color photodetectors fabricated by the method. A structure is grown upon a substrate (10) to provide, in sequence, a LPE grown LWIR n-type layer (12), a MWIR p+ type common contact layer (14), and a MWIR n-type layer (16). Following growth of the MWIR n-type layer, a layer of passivation (18) is applied, and the substrate is removed to so as to enable further processing of the structure into an array (1) of two-color photodetectors. The three layer structure is bonded, prior to further processing, to a supporting substrate (22) with an adhesive bond made to the passivation layer. The supporting substrate is comprised of IR transparent material such as Group IIB-VIA semiconductor material, Group IIIA-VA semiconductor material, Group IVA semiconductor material, sapphire, and combinations thereof.

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: 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: A tunable laser trace gas analyzer determines the concentration of a target gas in a sample by comparison to a reference gas having a known concentration of the target gas. The trace gas analyzer includes a wavenumber-tunable laser and a gas receiving assembly through which the laser beam is transmitted. The gas receiving assembly comprises a sample gas chamber and a reference gas chamber. Radiation intensity sensors are positioned at remote ends of the sample gas chamber and the reference gas chamber to detect the intensity of the laser transmissions through the sample and reference gases. A beam splitter is positioned within the gas receiving assembly to direct one laser beam portion to one of the radiation intensity sensors and another laser beam portion to the other radiation intensity sensor. The concentration of the target gas in the sample is determined by repetitively modulating the laser drive current to cyclicly vary the laser emission wavenumber about an absorption line of the target gas.

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: Two gas-filled chambers (K1, K2) arranged one behind the other in the beam path, with frontal areas (F) transparent to the beam, are interconnected by a first line (L12) which contains a first pressure or flow rate sensor (SF1). A buffer space (P) is connected to one of the two chambers (K1) via a second line (L11) in which is arranged a second pressure or flow rate sensor (SF2). The output signals from both flow rate sensors (SF1, SF2) are taken via amplifiers (V1, V2) to a differentiator. The degree of amplification of at least one amplifier (V2) is tunable for equalizing. The field of application of the invention is in gas analyzers operating on the infrared absorption system.

Abstract: RF modulation spectroscopy of a near infrared laser diode source is used to determine the amount of a target substance in a breath sample. In this type of modulation the laser output is modulated to produce sidebands displaced from the laser carrier by the modulation frequency. The modulated beam is passed through a gas sample which differentially absorbs the sidebands, the result of which is the conversion of some of the laser frequency modulation into amplitude modulation which is subsequently detected using a broadband photodetector. In certain tests, the target substance is a particular isotope, whose concentration is measured as an isotope ratio. In order to measure the presence of first and second isotopic species, provision is made to provide laser illumination at characteristic wavelengths for absorption lines for the first and second isotopic species of the gas.

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: A high resolution infrared densitometer system is described which comprises an intense thermal light source, an optical system for projecting first and second images of the light source along respective parallel first sample and second reference optical axes, adjustable optical attenuators for selectively balancing the light intensity of the images projected along the sample and reference axes at selected optical density, a spectrometer for filtering background radiation from the projected images except for a selected wavelength, and a detector for measuring intensities of the filtered projected images. A method for making optical density measurements is described.

Abstract: An optical method for monitoring the products of combustion, particularly for the detection of upset conditions in the incineration of hazardous waste, is disclosed. On-line detection of upsets is extremely important to avoid sending untreated waste out the stack plume and to avoid the formation of hazardous products of incomplete combustion, such as dioxins. Small hydrocarbons are the strongest candidates for in situ monitoring of combustion efficiency. The combustion is monitored via infrared absorption using tunable diode lasers (TDLs).

Abstract: The dual path ultraviolet hygrometer makes use of two narrow spectrum light beams of different wavelengths, both of which are transmitted along two geometrically similar paths to measure and compensate for the presence of contaminants and to more precisely measure the water vapor content in the air samples. A first one of these optical wavelengths is highly absorbed by water vapor while the second optical wavelength is only slightly absorbed by water vapor. Both of these generated narrow band light beams are split so that two pairs of light beams are produced. Beams of both wavelengths are transmitted along the first optical path, which traverses the air sampling chamber. By measuring the differential absorption between the two light beams along this first optical path, the water vapor content of the air sample within the air sampling chamber is precisely measured by correcting for contaminant absorption.

Abstract: An optical transmittance apparatus has a pair of reference channels of glass rods and a pair of sample channels containing sample fluid. A beam splitter and mirror pass a first portion of an incident beam through an ingoing reference channel, and a second portion through an ingoing sample channel. The first portion is reflected back through an outgoing reference channel, and the second portion back through an outgoing sample channel. The beam splitter and mirror directs the outgoing beams into a common outlet path. A partial disk selectively passes either portion. For positioning the disk, poles of a magnet mounted on the disk axle face windings made about an axis perpendicular to the axle, the windings being on the opposite side of a barrier plate from the poles. Current of one polarity through the windings effects one orientation of the disk, and reversed olarity reorients it perpendicularly.

Abstract: A method of and device for calibrating infrared radiation transducers. A concentration factor representing the ratio of a data signal to a reference signal for a known concentration of a designated gas in a sample containing that gas is generated. The concentration factor is stored and used during subsequent calibration procedures. The calibration device has a zero cell and a span cell with windows for transmitting infrared radiation and radiation reflecting or absorbing material in the span cell. The span cell therefore provides a known and consistent level of radiation absorption.

Abstract: An apparatus and method measures the concentration of a gas. The apparatus comprises a radiation source (70) for emitting radiation onto the gas (79) to be measured, whereby the radiation source (70) is comprised of an anode (4) and a cathode (9), and as an emitting fill gas the same as the gas (79) to be measured; and a radiation detector (74) with which the radiation transmitted through the gas (79) to be measured can be detected. The cathode (9) functions as an electron emitter, and between the anode (4) and the cathode is connected such a low operating voltage that does not cause ionization or essential dissociation of the emitting gas. The design provides an approximate temperature tracking of the radiation source with the ambient temperature.

Abstract: A method for spectroscopically measuring a concentration of component gases in a gas mixture, wherein at least one component gas A has an absorption line spectrum and wherein the concentration of the gas A in the gas mixture exceeds the concentration of other component gases of the gas mixture to such an extent that measurement of the concentration of the other component gases would normally be interfered with by the gas A.

Abstract: A detector unit which is capable of outputting electrical signals proportional in magnitude to the intensity of that energy in a beam thereof which lies in two different wavelength bands. A beam splitter directs energy in those bands from the entire compass of the beam to a data detector and a reference detector, and bandpass filters and optical traps in front of those detectors ensure that only energy in the selected bands and from the beam reach them. The detectors are mounted in precisely aligned relationship with each other and the beam splitter on, and are electrically isolated from, a monolithic, conductive, isothermal support which allows them to be maintained at the same, selected temperature by a system including data and reference detector heaters and a temperature responsive controller.

Abstract: A transducer for nondispersive infrared gas analysis has heaters for the data and reference detectors to maintain the detectors at a selected temperature. A heater is also provided to heat the casing of an airway adapter associated with the transducer to a temperature high enough to keep condensation from forming. The detector unit is surrounded and electrostatically shielded by a boxlike component with barndoor extensions which are closed to shield the installed detector unit at that end of the shield through which the detector unit is installed. The detector unit, electrostatic shield, and a circuit board which carries power supply and preamplifier circuits are installed in the transducer housing which has separate end closures sealed thereto with a through fastener and internal guides for locating the shielded detector unit in the housing.

Abstract: A process and device for measuring the isotope ratio, specifically of stable isotopes, of chemical substances in a gas to be examined, the process including alternately charging a sample cell with a reference gas and a measuring gas containing the gas to be examined; adding a metrologically neutral gas to the gas to be examined; varying the mixing ratio of this measuring gas by changing the share of neutral gas being added; and calculation of the isotope ratio V.sub.p of the substance according to the equation: ##EQU1## The device includes a White cell having mirrors on each end of the longitudinal length of the cell, a pair of first beam openings located on a longitudinal end, a pair of second beam openings in spaced parallelism on the longitudinal sides of the White cell and a gas inlet and gas outlet located near each mirror.

Abstract: A noise suppression system is described for use with a laser measurement system in which a beam sampler divides the laser beam into a signal beam and a sample beam. The signal beam is passed through an optical system before being received at the detector while the sample beam is received directly at the detector. The beam sampler is selected such that the received sample beam has a slightly greater steady-state intensity than the received signal beam. The detector circuitry includes two linear wideband photodetectors which produce respective signal and sample currents of opposite polarity. The sample photocurrent is subdivided into two component currents, one of which has substantially the same direct current (DC) value as the signal photocurrent. This component is combined with the signal photocurrent to cancel undesirable noise components in the original laser beam.

Abstract: Optical gas analyzers are disclosed for analyzing gas samples, including a source of radiation, a gas sample cell through which the radiation passes, a mirror for dividing that radiation into a number of secondary radiation paths for each of the gases in the gas sample which is to be analyzed, with the mirror being arranged so that after a single reflection from the mirror each of the secondary radiation paths is directed to an optical filter which passes a preselected wavelength characteristic of the particular gas in question, and then to a detector for measuring that wavelength characteristic. These optical gas analyzers are preferably used in connection with gas samples which include anesthetic gases, along with CO.sub.2 and N.sub.2 O.

Abstract: A sensor and method for measuring the concentration of alcohol in an alcohol-hydrocarbon mixture for use with flexible fuel vehicles. The sensor and method are characterized by a pair of detectors or sensing elements which detect absorbance of two different wavelength bands of energy transmitted through the fuel. The first wavelength band is absorbed by the alcohol and substantially unabsorbed by the hydrocarbons and other non-alcohols in the fuel mixture. The second or reference wavelength band is selected where the absorbance of alcohols and hydrocarbons is essentially the same and preferably essentially zero. The output of the two detectors or sensing elements is ratioed to provide a signal representative of the alcohol content of the fuel mixture. In a preferred embodiment, the sensing elements are included in a differential thermopile.

Abstract: It has been determined that the symmetric stretching frequency of water at concentrations of 10 ppm and more in liquid hydrocarbons is effectively independent of the nature of the hydrocarbon. On this basis one can rapidly, accurately, and precisely measure such water concentrations by comparing the transmittance of a narrow band of infrared frequencies within the symmetric stretching band of a wet sample with the transmittance at a frequency in the 3770-4000 cm.sup.-1 range, performing a second comparison with a dried sample, and forming the ratio of the two comparative measurements as a measure of dissolved water content.

Abstract: A method and apparatus for non-invasively testing analytical substances in turbid matrices i.e. body fluids and tissues. In this method a sample is irradiated with a beam of electromagnetic energy at two alternating wavelenths, .lambda..sub.1 and .lambda..sub.2, at which the absorption by the background is the same but at one of which the radiation is absorbed by the analyte and at the other it is not. The apparatus comprises means which enable to control the input energy at .lambda..sub.1 and .lambda..sub.2 so that at the output from the sample the electric signals issuing after detection cancel in the absence of the analyte in the sample. When analyte is present cancellation no longer occurs and a signal proportional to the analyte concentration in the sample is produced. The apparatus is also designed for shifting the response back to zero when a calibrating known concentration of analyte is used as standard, thus providing a controllable zeroing base line.

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.

Abstract: The invention is directed to a sensor arrangement for optically measuring the components of a gas. The sensor arrangement includes a housing containing a transmitter, a receiver device, a heatable holder for a measuring cuvette and optical devices for establishing the beam path. The sensor arrangement is improved by limiting the heating of the cuvette walls to those areas which lie in the beam path without the pass-through area of the optical devices being narrowed by the heating device. Also, the cuvette walls are heated in the manner described above without electrical contacts being disposed on the cuvette or on the sensor. The heatable cuvette holder includes one window disposed in the beam path which is transmissive for the measuring radiation. When the cuvette is seated in the cuvette holder, this window lies in virtual contact engagement with the cuvette and has a surface facing away from the cuvette.