Abstract: A method and a circuit for processing the signals of an earth-horizon sen of a circularly orbiting earth satellite. The earth-horizon sensor operates in the infrared range and includes, in the focal plane of an input lens, a chopper disk which is periodically reciprocated with a determined chopper frequency (f) and has a diameter corresponding to the image of the earth, as well as a detector (1) receiving the periodically interrupted light radiation of oppositely located earth rims. The output signal of the detector (1) is demodulated synchronously with the chopper frequency (f) in order to derive an off-course signal. In order to suppress the influence of the earth anomaly, the amplified output signal of the detector (1) is additionally synchronously demodulated with the doubled chopper frequency (2f), according to the invention, in order to produce a symmetry signal.

Abstract: A method and apparatus for measuring the concentration of a substance capable of absorbing infrared, visible or ultraviolet radiation energy, the substance being in a mixture. The method and apparatus involve passing a beam of radiant energy having predetermined spectral response characteristics through the mixture, modulating the beam at a predetermined frequency .omega.

Abstract: A gas cell array absorbs infrared energy radiated by a viewed scene. A la interferometer has its resultant intensity changed by the cell's changing length. This is monitored by a vidicon tube that feeds the signal to a digitizer and onto a video display. The incident infrared radiation is chopped into quantized amounts of energy and memory units receive the digitized output of the vidicon tube. Subtractors receive vidicon tube signals simultaneously with quiescent reference levels data. The subtractors form a difference signal by subtracting the quiescent reference level signal from the immediate signal being passed to control threshold detectors. An extended dynamic range of 1,000:1 is accomplished for the preferred embodiment.

Abstract: An infrared ray detector comprises an infrared ray detecting member (25), a pair of opposing members (32, 33) each having a plurality of infrared ray transmitting portions (34, 35) and infrared ray non-transmitting portions (36, 37), a pair of vibrators (38, 39) and a driving signal supplying circuit (59, 60). The pair of opposing members (32, 33) are disposed in the area of incidence of infrared rays to the infrared ray detecting member (25), and are displaced periodically by the pair of vibrators (38, 39). The pair of vibrators (38, 39) are driven by a driving signal from the driving signal supplying circuit (59, 60), the amplitude of the driving signal being selected to be smaller than that of a driving signal used in a case where there are periodically repeated a state in which both of the infrared ray transmitting portions (34, 35) of the pair of opposing members (32, 33) are completely opened and a state in which those are completely blocked, subject to no change in an ambient temperature.

Abstract: An infrared ray detecting apparatus comprises an infrared ray detecting element (5), bimorph elements (8a and 8b), a transistors (53, 54), a DC-DC converter (55), and a volume (56). A square wave signal is applied to a base of the transistor (53) from a microprocessor (40) included in a microwave oven and a signal having a constant level is applied to a base of the transistor (54). The DC-DC converter (55) is continuously driven in response to an emitter output from the transistor (54) so that a constant voltage -E.sub.0 V which is extremely stable is supplied. A voltage -E.sub.s V which is obtained by regulating properly the constant voltage -E.sub.0 V by means of the volume (56), is applied to central electrodes of the bimorphs (8a and 8b), while a square wave signal varying between 0 V and -E.sub.0 V in response to an on/off state of the transistor (53), is applied to a surface electrodes of the bimorphs (8a and 8b).

Abstract: A focused optical input signal is applied to an optically absorbent wall portion of a supply nozzle 40 in a fluidic device to cause boundary layer separation of flow therein. The boundary layer separation turns the flow to achieve a desired output from the device.

Abstract: An unfocused optical input signal is applied to an optically absorbent wall portion of an interaction region 30 in a fluidic device to effect flow impedance modulation thereat. The flow impedance modulation adjusts the velocity profile of the flow to achieve a desired output from the device.

Abstract: A gas analyzer has a light source having a window, an open-ended, hollow cylinder aligned with the light source and through which the light from the light source passes, and a detector at the other end of the cell and having a window for receiving the light which has passed through the hollow cylinder. A chopper is provided in the hollow cylinder and is rotatable around an axis perpendicular to the optical path through the hollow cylinder for interrupting the light passing along the optical path. The hollow cylinder has a gas inlet therein at a portion where the optical path for the cell is not screened thereby. The ends of the hollow cylinder are adjacent the light source window and the detector window which serve as cell windows, respectively, at least one of these windows being spaced from the end of the hollow cylinder to define a gap therebetween constituting a gas outlet.

Abstract: In an infrared detector, a shutter is employed in an elastic wave element of a feedback type of oscillator containing the elastic element so that the elastic element receives infrared light intermittently. The period during which the number of peaks of the oscillation output waveform from the oscillator exceeds a predetermined value is set to be the opening or closing period of the shutter, the number of clock pulses from a clock signal generator is counted during the shutter opening or closing period, and the difference between the counted values is obtained, thereby detecting the energy of the infrared light. This detector features not only an extremely high sensitivity, but a high detection accuracy, as well as the production of a digital output.

Abstract: A spectroscopic technique in which the sample under investigation is probed with a generally monochromatic beam of light which has been modulated at two distinct modulation frequencies. The double modulation produces a plurality of sidebands, and the two modulation frequencies are related to one another such that a selection of sidebands falls into two groups of closely spaced component sidebands. A first group is disposed in frequency at the spectral feature of interest and serves to probe the spectral feature. The other group is disposed in frequency remote from the feature and serves as a reference group. Within each group the component sidebands are offset from one another by a characteristic offset frequency, which can be considerably less than the width of the spectral feature under investigation.

Abstract: In a method of distance measuring and an optical distance measuring apparatus, a pulse-modulated infrared light beam is irradiated to an object to produce a reflected light beam, which is then received by a resonance circuit, and intensity of output of the resonance circuit is measured, wherein the modulation of frequency is sweepingly varied within a predetermined narrow frequency range; thereby, even when the circuit constants of the resonance circuit varies due to temperature change and so on, the distance measurement result is not affected, and stable measurement of a long distance is possible.

Abstract: In a ratio-type double-beam infrared spectrophotometer, an output signal of the photodetector is frequency discriminated to derive therefrom a component having a fundamental frequency f corresponding to at least one of the sample and reference beam intensities and another component having a frequency 2f corresponding to at least the other beam intensity, and these frequency components are computed to determine the ratio of the sample beam intensity to the reference beam intensity. According to the invention, the component of fundamental frequency f is synchronously rectified into a rectified signal which is further differentiated into a differential value, the differential value is subtracted from the rectified signal to give a signal which is compensated for rapid changes of spectral absorption due to the presence of H.sub.2 O and CO.sub.2 in the beam paths during wavelength scanning and is used as the f-component signal.

Abstract: An apparatus for reading out an image by scanning comprises a stimulating ray source, a device for scanning a stimulable phosphor sheet carrying an image stored therein by stimulating rays forwardly and backwardly in a main scanning direction, a device for scanning the stimulable phosphor sheet by the stimulating rays in a sub-scanning direction normal to the main scanning direction, and a read-out device for detecting light emitted by the stimulable phosphor sheet when it is exposed to stimulating rays. A converging lens is positioned to converge the stimulating rays, and a light shielding member is positioned at the converging point to intercept the stimulating rays during the backward scanning period. Or, an acousto-optic modulator is positioned between the stimulating ray source and the converging lens to diffract the stimulating rays and generate diffracted light components other than a zero-order diffracted light component during the backward scanning period.

Abstract: A radiation beam, having passed through the mixture containing the component whose spectral composition contains at least one characteristic spectral line of the component, is caused to pass alternately along two channels one of which comprises a definite amount of the gaseous component and the other of which serves as reference. The second channel over which the radiation beam travels is limited to a diaphragm having a radiation transmission substantially equal to that of the first channel in the absence of said component in the mixture. The output beam from the two channels is directed towards a detector for detecting the variation of intensity of the beam through a filter for selecting said characteristic radiation.

Abstract: A double-beam spectrophotometer for spectral analysis of a sample in the infrared region is provided in which to eliminate errors in measurement of the absorbance of the sample caused by undesired thermal radiation from the sample itself, first and second sectors are used for division and recombination of beam paths and coordinated such that a detector which receives a beam along the combined beam path produces output signals consisting of components having a frequency f associated with the cycle of operation of the sectors and components having a frequency 2f, those components having frequencies f and 2f are independently derived out of the detector output signals, and the ratio of the components is computed, thereby obtaining the ratio of intensity of sample beam to reference beam independent of the undesired thermal radiation.

Abstract: Apparatus is disclosed to accurately measure and analyze multiple component interfering gases which coexist in the stack gas effluent generated from a combustion process which utilizes a non-dispersive, narrowband infrared absorption technique. The apparatus includes a probe in the stack with an optical measurement cavity (34) through which the stack gases are passed. A transceiver (14) mounted to the probe includes an optical portion operatively associated with the measurement cavity including a chopped light source (54), (60), (62) for projecting beams of light into the measurement cavity and a detector (86) for detecting the attenuation of the gases to provide a measure of the extent of absorption of each gas of interest. A control unit, preferably remote from the transceiver, preferably a programmed digital computer, and preferably via a J-box (18) converts the electric outputs to a corresponding % modulation and in turn corrects for temperature, pressure and interference between gases.

Abstract: A portable infrared spectrophotometer for nondestructive testing of coatings, plastics, rubber and other organic construction materials. A single source of infrared light is formed into two beams. One beam is directed to the surface of a sample where it is reflected off the surface of the sample at least four times. The other beam follows a similar path but bounces off a neutral surface. The two beams are combined and focused onto a detector. The output of the detector is proportional to the energy absorbed by the surface of the test sample. A pen recorder is used to provide a graphic display of the spectrum generated.

Abstract: A photofluidic interface that transduces optical control signals into fluid ontrol pressures is provided in which an AC modulated light source is utilized to transmit control signals to a photo acoustic cell that absorbs the light energy and converts it to heat energy thus creating pressure pulses within the cell. The output signal of the photo acoustic cell is then fluidically amplified, fluidically rectified and again fluidically amplified to create an output signal that drives an actuator.

Abstract: An infrared ray detector comprising an infrared ray detecting body, a pair of opposing portions, a bimorph vibrator connected to the pair of opposing portions for intermitting infrared rays incident upon the detector, and a housing containing these elements, the housing being provided with an opening for incidence of infrared rays. The pair of opposing portions comprise infrared ray transmitting portions and infrared ray non-transmitting portions. The infrared ray transmitting portions in one of opposing portions is periodically overlapped by the bimorph vibrator with the infrared ray transmitting portions or infrared ray non-transmitting portions in the other opposing portion, so that incident infrared rays are intermitted.

Abstract: A correlation spectrometer permanently incorporates a reference cell (12) and an electro-optical phase modulator (EOPM) (50) in the light path between a sample cell (30) and a detector (20). The effect of the EOPM is such that its frequency modulates all of the monochromatic component of the incoherent radiation passing through it. The EOPM is adjusted so that when it is ON all of the energy in the monochromatic components is thrown into sidebands (55) differing from the original frequencies by integral multiples of the modulation frequency, with the total amount of energy absorbed from the original radiation remaining constant. When there is no coincidence between the constituents in the two cells, the detector's output is the same when the EOPM is ON and when it is OFF. However, when there is coincidence the detector's output changes when the EOPM is switched between its two states. The change in the detector's output is related to the quantity of the constituents in the sample cell.

Abstract: A portable length probe having a length measuring wheel with light transmission holes at equally spaced angular intervals thereon, which wheel is rotatably mounted in an integral one piece nose body having a photo-responsive element and a light-emitting element disposed in aligned facing relation in a common bore formed in the nose body transverse to the wheel. The photo-responsive element is an infrared sensitive photo-transistor and the light emitting element is an infrared light emitting diode (LED), and both are encased in cylindrical opaque cases which fit in generally complementary sliding relation within the bore, the cases each having an optically open end facing one another. Increased accuracy is provided by employing frequency doubler circuitry in conjunction with the wheel, in which the wheel light transmission holes are substantially uniform in angular width and are spaced apart a distance substantially equal to such hole angular width.

Abstract: The microwave oven includes a heat chamber, an infrared detector for detecting infrared rays irradiated from an object to be heated in the heating chamber, a chopper for alternately interrupting the path of infrared rays to the detector, an oscillator for producing a reference signal used for driving the chopper, and a circuit for regulating the output of the detector and the phase of the reference signal. The infrared detector does not require any phase adjustment to accommodate frequency shifts due to fluctuations in the power frequency.

Abstract: The indiction of temperature discontinuities in a scene can be used to indicate the boundaries of objects, for example the level of the contents of a storage silo. The thermal radiation from the object scene is imaged upon a pair of adjacent pyroelectric radiation detectors 9, 10. The scene radiation is chopped and the difference in detector outputs displayed to the observer while the field of view of the detectors, aligned with a visual aiming sight, is traversed across the object. The location and sign of a temperature discontinuity in the visual scene enables the observer to measure the silo contents.

Abstract: A nondispersive infrared gas analyzer of the type wherein gas-filled chambers are arranged in the path of modulated infrared radiation. A measurement pickup is provided for producing a signal responsive to the response of a gas contained in the chamber to the infrared radiation. The infrared radiation is produced by a source of infrared radiation which is powered by a pulsed energy supply, the pulsed energy supply being responsive to control signals so as to provide pulses which have a duty cycle which is less than 1, and preferably between 0.1 and 0.5. The duration of the pulses is controlled in response to the maximum value of a measuring signal of an output of a measuring pickup. In other embodiments, the duration of the pulses may be determined empirically, by calculation, or by means of peak detector. This arrangement provides almost 100% modulation while considerably reducing power consumption and without loss of sensitivity.

Abstract: By the use of one or more beams of chopped, variable-frequency, monochromatic light to illuminate the sample chamber of at least one gas-filled cell including such sample chamber and a reference chamber joined to the sample chamber by a tunnel-like opening or orifice which permits fluid communication between the chambers and incorporating a thermal-flowmeter-type sensor element in the path of flow of the fluid between the chambers of each such cell, the compositional characteristics of one or more samples in each sample chamber can be determined accurately.

Abstract: A modified thermal viewer and method of operating same for detecting and tially analyzing a cloud for the presence of certain chemical compounds, whereby the cloud is viewed through two or more band-pass filters independently and consecutively with each filter responsive to a different band of spectral radiation characteristic of the particular chemical agent of concern.

Abstract: A heat-cooking apparatus such as an electronic oven of the type having an oven cavity, a heat source, an infrared detecting equipment adapted to detect the rate of radiation of the infrared rays from the surface of the material under cooking and a controller for controlling the heat source in accordance with the output from the infrared detecting equipment. The infrared detecting equipment includes a reflective plate and a shield cylinder which in combination ensure highly efficient and accurate detection of infrared rays over a long period of time.

Abstract: An arrangement for determining a medium by means of a temperature sensor which is kept at a given excess temperature, in which the power to maintain the given excess temperature is determined, which includes a source of measuring radiation, a source of auxiliary radiation and the temperature sensor being exposed to a ray path of the measuring radiation and the auxiliary radiation, and means for generating a signal representative of a property of the medium, such as its absorptive or reflective capacity, its polarization properties, as well as correlative properties derivable therefrom.

Abstract: Sand containing bitumen and like materials containing organic matter is analyzed quantitatively for its hydrocarbon content by use of a remote infrared sensor. In a preferred embodiment the bitumen is on a conveyor to further processing and if found unacceptable for processing by the method of the invention, the sand is automatically diverted. The invention also embodies the apparatus used for the analysis.

Abstract: Method and apparatus for high-sensitivity (.alpha..ltorsim.10.sup.-6 cm.sup.-1) optoacoustic (OA) spectroscopy of substantially transparent bulk condensed matter. Part of the sample to be investigated is irradiated by pulses of radiation, typically from a pulsed dye laser. The small amount of energy absorbed by the sample causes thermal expansion of the irradiated region, resulting in cylindrical stress waves being radiated from that region. These stress waves can be observed with appropriate detection means at a location remote from the source. The method is applicable to essentially transparent liquids, and solids, and to absorptive solids suspended in liquids, and the like. Possible choices of probe radiation are not only the conventional ones of visible, near UV, and near infrared electromagnetic radiation, but also, for instance, .gamma.-rays, x-rays, vacuum UV, and far infrared.

Abstract: A method and apparatus for detecting optical radiation by optically monitoring temperature changes in a microvolume caused by absorption of optical radiation to be detected. More specifically, a thermal lens-forming material is provided which has first and second opposite, substantially parallel surfaces. A reflective coating is formed on the first surface, and a radiation-absorbing coating is formed on the reflective coating. Chopped, incoming optical radiation to be detected is directed to irradiate a small portion of the radiation-absorbing coating. Heat generated in this small area is conducted to the lens-forming material through the reflective coating, thereby raising the temperature of a small portion of the lens-forming material and causing a thermal lens to be formed therein. The thus-formed thermal lens is optically detected by irradiating the thermal lens by a collimated light beam.

Abstract: An opto-acoustic gas analyzer has a black body light source, a chopper in the path of the light emitted from the light source for intermittently intercepting the light from the light source, a positive interference filter in the path of the light for filtering out light other than the wavelengths of light absorbed by the gas being analyzed, and an opto-acoustic detector which receives the filtered light and through which the gas to be analyzed is passed. A pressure change detector provided is provided in the opto-acoustic detector for detecting pressure changes in the gas and producing an electric signal corresponding such changes.

Abstract: An apparatus for measuring components of liquid samples, such as milk samples, based on the ability of these components to absorb infrared radiation at certain frequencies. A single radiation beam is directed through a cuvette containing the sample, and the apparatus comprises a plurality of pairs of optical filters. Each of these pairs is associated with a respective one of the components to be measured and comprises a component filter for passing infrared radiation at a narrow frequency band at which the radiation absorbing ability of the said component is relatively high, and a reference filter for passing infrared radiation at a different narrow frequency band at which the radiation absorbing ability of the component is lower.

Abstract: A thermometer is provided for remotely measuring the temperature of a heat source. The device utilizes an infrared sensor for detecting the temperature of a remote object and an output of the sensor is processed and used to drive a meter or other display device. An improved resonant circuit is provided for modulating the radiant energy impinging on the sensor to produce a pulsed output from the sensor. The modulating circuit includes a piezoelectric reed which deflects under an applied frequency and is located in the optical path of the system. The reed serves as an active element in an improved phase-locked loop used to drive and stabilize the optical chopper.

Abstract: An optical system for a spectroscopic analyzer. The system has a light source, a detector and a sample cell connected in a line, and in the sample cell or between the sample cell and one of the other elements is a light chopper device. The light chopper has a rotating element in the form of a disc-shaped member or members which periodically block light from the light source and pass light during the times it is not blocked. The rotating element is driven by a motor on the outside of the structure.

Abstract: Pulsed light and readily measurable pulsed electrical energy are independently applied to a solid black, conductive sample in a gas-filled photoacoustic cell, each causing the black sample to heat. The heating of the black sample causes a pressure wave in the cell, which can be detected and measured. By adjusting the pulsed electrical energy, the pressure wave resulting from the pulsed electrical energy can be made to relate to the pressure wave resulting from the pulsed light in a predetermined manner. The pulsed light input intensity can then be measured in electrical units based on the measurable input of the electrical energy pulses. In this manner, the invention can be used as a radiometer. A second application for the present apparatus is in calibrating photoacoustic spectroscopy (PAS) cells. The PAS cell can be self-calibrated by discontinuing the light pulses and relating the pressure wave output to the electrical energy pulse input.

Abstract: A method and apparatus that significantly increases the sensitivity and flexibility of laser optoacoustic spectroscopy, with reduced size. With the method, it no longer is necessary to limit the use of laser optoacoustic spectroscopy to species whose absorption must match available laser radiation. Instead, "doping" with a relatively small amount of an optically absorbing gas yields optoacoustic signatures of nonabsorbing materials (gases, liquids, solids, and aerosols), thus significantly increasing the sensitivity and flexibility of optoacoustic spectroscopy. Several applications of this method are demonstated and/or suggested.

Abstract: An improved ferroelectric imaging system comprises a chopper, lens system, ferroelectric detector matrix, switching matrix, temperature controlled heat sink, drive and read out electronics, video processor and display. The chopper interrupts infrared energy emanating from a scene, and the lens system focuses the chopped infrared energy on the ferroelectric detector matrix which produces electrical signals representative of the infrared energy impinging thereon. The signals are read out by the drive and read out electronics whose action is synchronized with the chopper action, processed in the video processor and displayed by the display. The ferroelectric detector matrix comprises a plurality of detector capacitor elements whose top plates are formed by conductor stripes longitudinally disposed on a dielectric of ferroelectric material and whose lower plates are a plurality of metal pads formed on the dielectric.

Abstract: Process for the photo-optical measurement of the absorption behavior of solid, liquid and gaseous media. A measurement light beam from an optical radiation source is made intermittent by a rotating chopper comprising a rotatable metal wheel. The chopper frequency is maintained constant by regulation of the speed of the metal wheel by two alternating-current magnets inducing eddy currents to slow or speed up the wheel. The actual speed of the wheel is detected and compared with a reference speed and the magnitude of the excitation currents is adjusted on the basis of the rotatory speed difference to effect the regulation of the speed of the chopper.

Abstract: An apparatus for the photo-optical measurement of the absorption behavior of solid, liquid and gaseous media. A measurement light beam from an optical radiation source is made intermittent by a rotating chopper comprising a rotatable metal wheel. The chopper frequency is maintained constant by regulation of the speed of the metal wheel by two alternating-current magnets inducing eddy currents to slow or speed up the wheel. The actual speed of the wheel is detected and compared with a reference speed and the magnitude of the excitation currents is adjusted on the basis of the rotatory speed difference to effect the regulation of the speed of the chopper.

Abstract: A single reticle is provided having spectral and spatial filtering characteristics such that it may be employed in radiation responsive systems for both passive tracking and active tracking employing a laser target designator.

Abstract: A process and apparatus for the photo-optical measurement of the absorption behavior of solid, liquid and gaseous media. The analysis medium and a comparison medium are exposed to two light beams. The light beams are broken up by a chopper means into a periodical sequence of light pulses and the measured difference of the beam attenuations in the analysis medium and comparison medium is evaluated in a circuit which is adjustable with regard to the intensity of the radiation from the optical light source and the sensitivity of the light receiver. The light pulses are divided by defined variation of their intensity into two different pulse series of which one series comprises measuring light pulses and the other series comprises control pulses.

Abstract: A method for electrically reading a target such as a pyroelectric one, in a camera tube. It consists in the repetition of a sequence of three phases: reading by an electron beam scanning process, compensation by secondary electron emission and levelling of the potential of the target, the duration of each of the phases being substantially equal to the duration of an analysis line of the target. The last two phases are provided for lines preceding the line read respectively by numbers p and k of lines with p<k.

Abstract: Method and apparatus for compensating spurious radiation detector signal output variations during operation of an infrared (IR) analyzer.

Abstract: A gas analyzer is provided which is particularly suited for making transcutaneous measurement of the CO.sub.2 concentration in the blood.In accordance with one embodiment of the invention, sample gases from the body are circulated in a cavity of the device. A rotating wheel in the cavity includes two reference cells and a sample cell which are sequentially rotated into the optical path between a source and a detector. Three signals are thereby provided which may be combined to give an output indication of the CO.sub.2 concentration in the body fluids. In a preferred embodiment, the sample cell is an "inverted cell" being in open communication with the sample gas circulating in the device so that the gas in the sample cell is a portion of the circulating gas which also surrounds the two reference cells. An output indication is thereby obtained which is insensitive to contaminants in the sample.

Abstract: A gas analyzer is disclosed which responds to the resonant absorption or emission spectrum of a specific gas by producing an acoustic resonance in a chamber containing a sample of that gas, and which measures the amount of that emission or absorption by measuring the stength of that acoustic resonance, e.g., the maximum periodic pressure, velocity or density achieved. In the preferred embodiment, a light beam is modulated periodically at the acoustical resonance frequency of a closed chamber which contains an optically dense sample of the gas of interest. The light beam is introduced into the chamber through a window transparent to the radiation in the spectral band of interest and located at a position in the chamber which can support a pressure maximum during acoustical resonance of the gas within the chamber. Periodic heating of the absorbing gas by the periodically modulated light beam incident on the gas then causes a cyclic expansion, movement, and pressure within the gas.

Abstract: A system for eliminating background signals in chopped infrared measuring systems employs operational amplifier principles for subtracting a reference signal of proper amplitude, phase and frequency from the background-plus-signal radiation. The output is converted to a dc voltage level directly related to incident flux.

Abstract: An infrared gas analyzer is provided with a first path for reference radiation and a second path for measuring radiation. A source emits infrared radiation into the first and second paths. A detector arrangement is positioned at the ends of the paths for sensing the intensity of reference and measuring radiation passing through the paths. A radiation-travel-control arrangement alternately blocks one and then the other of the two paths and during the blocking of each path causes radiation directed towards the blocked path to be deflected into the unblocked path so that such radiation is not wasted.

Abstract: A gas analyzer is provided which is particularly suited for making transcutaneous measurement of the CO.sub.2 concentration in the blood.In accordance with one embodiment of the invention, sample gases from the body are circulated in a cavity of the device. A rotating wheel in the cavity includes two reference cells and a sample cell which are sequentially rotated into the optical path between a source and a detector. Three signals are thereby provided which may be combined to give an output indication of the CO.sub.2 concentration in the body fluids. In a preferred embodiment, the sample cell is an "inverted cell" being in open communication with the sample gas circulating in the device so that the gas in the sample cell is a portion of the circulating gas which also surrounds the two reference cells. An output indication is thereby obtained which is insensitive to contaminants in the sample.

Abstract: A two infrared beam gas analyzer, with sample and reference paths and radiation chopper has two absorption cells as detectors wherein the pressures are compared in a first diaphragm capacitor and the sum with parameter modification by operation of pneumatic inpedances is formed in a second diaphragm capacitor. The ratio of the two capacitor outputs constitutes the output of the system. A compact unitary construction is described in detail including the detector chambers and one capacitor in a body serving as mounting element for the second capacitor with a frit like element interposed as pneumatic inpedances and rotational adjustment of that second capacitor as a whole results in parameter adjustment.