Abstract: A gas analyzer is described comprising a sample cell for containing a gas mixture to be analyzed, a source for producing and directing infrared energy through the sample cell, a rotary filter wheel having at least one filter thereon for passing infrared energy limited to a wavelength band within the characteristic absorption band of a predetermined gas and having a dark level region substantially opaque to infrared energy, a drive for supporting and rotating the filter wheel to successively interpose the filter and the dark level region between the source and the sample cell in the path of the infrared energy directed by the source, a detector for detecting infrared energy passing through the sample cell and producing an electrical signal representative thereof, and a signal processor connected to the detector for producing an output indicating the concentration of the predetermined gas in the sample cell by comparing the electrical signals produced by the detector with the filter positioned in the infrared e

Abstract: Automatic zeroing apparatus zeroes an infrared gas analyzer automatically upon the occurrence of preselected conditions to indicate zero in the absence of absorption of infrared radiation by a gas mixture being analyzed. The gas analyzer has a sample cell for containing a gas mixture to be analyzed. Infrared radiation directed through the sample cell is detected at a preselected wavelength to produce a detection signal. A signal processor outputs a signal systematically related to the difference between the detection signal and a reference signal. For zeroing the sample cell is filled with gas substantially nonabsorbent of infrared radiation at the respective characteristic wavelength. A comparator produces an error signal when the output signal differs from zero. A gain control automatically controls the signal level of the detection signal to reduce the output signal substantially to zero with the nonabsorbent gas filling the sample cell.

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: An infrared gas analyzer is described wherein infrared energy is directed from a suitable source through a sample cell, the infrared energy being interrupted at a predetermined frequency. Infrared energy of a preselected wavelength causes a detector for each monitored gas to produce a signal proportional to the infrared energy passing through the sample cell and having a frequency corresponding to the predetermined frequency. Each preselected wavelength corresponds to the characteristic absorption wavelength of a preselected gas. A signal processor for the analyzer includes a preamplifier adapted to compensate for temperature variations in the detector while an output amplifier is adapted to compensate for temperature variations in the sample cell in order to provide a more accurate output signal.

Abstract: A non-dispersive infrared gas analyzer is described. Infrared energy is directed through a sample cell, and is interrupted at a predetermined frequency. The infrared energy at at least one preselected wavelength is detected to produce an AC signal having an amplitude proportional to the infrared energy passing through said sample cell and having a frequency corresponding to the predetermined frequency. The preselected wavelength corresponds to the characteristic absorption wavelength of a preselected gas. This AC signal is processed to produce a DC signal having an amplitude proportional to the concentration of the preselected gas in the mixture being analyzed. The signal processor includes an output amplifier, a voltage biasing network including a summing junction connected to the input of the amplifier, and a first variable control manually adjustable to bring the current at the summing junction to zero in the presence of a non-absorbing gas in the sample cell.