Abstract: An analyzer to detect a specific gas in the atmosphere by infrared absorption, having a porous tube surrounding an enclosed column of air, the porous tube having an average pore size to permit gas to diffuse through it quickly, and having within the tube an infrared source, an infrared detector and an optical filter that passes those portions of the infrared spectrum most strongly absorbed by the gas, the analyzer having a time base generator to pulse the infrared source and electronic means to measure the maximum and minimum signals from the detector and a meter to indicate the difference between the maximum and minimum as a measure of the amount of the gas in the column of air.

Abstract: Pulse modulated infrared energy is directed through a sample cell containing a gas mixture. The gas mixture may include a selected one of a plurality of gases. Each gas exhibits a characteristic absorption in the infrared wavelengths. A detector responsive to infrared energy at a preselected wavelength develops an AC signal having an amplitude proportional to the infrared energy passing through the sample cell at the preselected wavelength and having a frequency corresponding to the preselected pulse modulation frequency. The preselected wavelength is common to the absorption characteristic of each of said gases. The AC signal is processed to develop a DC signal having an amplitude determined from the AC signal. The DC signal is applied to an amplifier having a variable gain feedback which provides a plurality of gain steps. Each gain step is associated with a different one of the gases a single surrogate gas may be used to calibrate each gain step.

Abstract: An infrared gas analyzer is described wherein infrared energy is directed through a sample cell from a source at one end thereof. A detector at the opposite end of the sample tube monitors infrared energy of at least one pre-selected wavelength in order to produce a signal representative of the infrared energy passing through the sample cell. The analyzer is of modular construction including a disposable sample cell, an infrared source housing, a detector housing and printed circuit boards mounting signal processing components for the analyzer. A mounting base is adapted for receiving the sample tube, housings and printed circuit boards in operating alignment and interconnection with each other, detents positively securing the components in place.

Abstract: A method and apparatus are described for determining the partial pressure of carbon dioxide in the arterial blood of a patient. The method and apparatus are particularly useful where the patient is under anesthesia. Carbon dioxide concentration is measured at the end tidal of the patient's exhaled breath. Nitrous oxide concentration is also measured so that the measured values of the carbon dioxide concentration may be corrected in accordance with the measured value of the nitrous oxide concentration. Particular wavelengths of detection are described, together with other apparatus parameters to provide a high level of accuracy.

Abstract: A gas analyzer of the non-dispersive infrared type is described. An infrared beam passing through a sample cell containing a gas mixture to be analyzed is detected. The resulting electrical signals are processed to produce an output indicating the concentration of the constituents of the gas mixture in the sample cell. The gas analyzer includes provision for temperature stabilizing both a rotary filter wheel and the detector, and for compensating the output of the signal processor for variation in the absorption characteristics of gas with temperature. The emissivity characteristic of the infrared energy source substantially compensates for wavelength dependence of the detector response. The motor drive for the rotary filter wheel is servo-controlled in accordance with synchronizing pulses developed directly from the detector output.

Abstract: A gas analyzer and gas analyzing method are described of the non-dispersive infrared type wherein infrared energy is passed through a sample cell containing an unknown mixture of gas. The infrared energy passing through the cell is received by a detector and an electrical signal is produced representative thereof. A rotary filter wheel positions at least one filter in the path of the infrared energy, resulting in a pulsating detector output. The electrical signal is processed to produce an output indicating the concentration of the constituents of the gas mixture in the sample cell. Synchronization with the processed electrical signal is obtained by deriving synchronizing pulses directly from the electrical signal produced by the detector.

Abstract: An improved gas analyzer for measuring the presence of one or more gaseous compounds in a gas sample. The gas analyzer has an infrared source stabilized against temperature variations by a radiation loading scheme in combination with a selected source environmental temperature sensitivity to provide a stable source temperature without a conventional temperature controller. A rotating interference filter assembly is disposed in the optical path. This assembly alternately totally blocks radiation, passes radiation in a wave length band which will not be absorbed by a random gas sample, and sequentially passes radiation in one or more additional bands which will be absorbed by one or more gases in the sample cell. The sample cell features a unique enclosed cell with infrared transparent windows which are substantially free of impingement of contaminants of the gas sample thereon. A unique detector provides protection against deterioration from moisture while allowing easy and inexpensive assembly.

Abstract: A method and apparatus are described for detecting a selected gas in an unknown gas sample. The power output of a radiant energy source is modulated at a first frequency and passed through the sample, the density of the sample being varied at a second frequency. The radiant energy passing through the sample is detected by and converted to an electrical signal which is then processed in order to produce an output signal representative of the selected gas. Density of the sample is preferably modulated or varied periodically by means of a pulsating pump which also supplies the unknown gas.

Abstract: An improved gas analyzer for measuring the presence of one or more gaseous compounds in a gas sample. The gas analyzer has an infrared source stablized against temperature variations by a radiation loading scheme in combination with a selected source environmental temperature sensitivity to provide a stable source temperature without a conventional temperature controller. A rotating interference filter assembly is disposed in the optical path. This assembly alternately totally blocks radiation, passes radiation in a wave length band which will not be absorbed by a random gas sample, and sequentially passes radiation in one or more additional bands which will be absorbed by one or more gases in the sample cell. The sample cell features a unique enclosed cell with infrared transparent windows which are substantially free of impingement of contaminants of the gas sample thereon. A unique detector provides protection against deterioration from moisture while allowing easy and inexpensive assembly.

Abstract: An improved gas analyzer for measuring the presence of one or more gaseous compounds in a gas sample. The gas analyzer has an infrared source stabilized against temperature variations by a radiation loading scheme in combination with a selected source environmental temperature sensitivity to provide a stable source temperature without a conventional temperature controller. A rotating interference filter assembly is disposed in the optical path. This assembly alternately totally blocks radiation, passes radiation in a wave length band which will not be absorbed by a random gas sample, and sequentially passes radiation in one or more additional bands which will be absorbed by one or more gases in the sample cell. The sample cell features a unique enclosed cell with infrared transparent windows which are substantially free of impingement of contaminants of the gas sample thereon. A unique detector provides protection against deterioration from moisture while allowing easy and inexpensive assembly.