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Digital anesthetic agent analyzer

  • US 4,692,621 A
  • Filed: 10/11/1985
  • Issued: 09/08/1987
  • Est. Priority Date: 10/11/1985
  • Status: Expired due to Term
First Claim
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1. A gas analyzer comprising, a sample cell for containing a gas mixture to be analyzed, source means for producing and directing infrared energy through said 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, drive means for supporting and rotating said filter wheel to successively interpose said filter and said dark level region between said source means and said sample cell in the path of the infrared energy directed by said source means, detector means for detecting infrared energy passing through said sample cell and producing an electrical signal representative thereof, signal processing means connected to said detector means for producing an output indicating the concentration of the predetermined gas in the sample cell by comparing the electrical signals produced by said detector means with said filter positioned in the infrared energy path and with said dark level regions positioned in the infrared energy path, said filter wheel including a second filter for passing first and second infrared wavelength bands, one of which is within a region of infrared absorption by water vapor and the other of which is not, both of said first and second wavelength bands of said second filter being outside the characteristic wavelength absorption regions of other gases present in the sample cell, the amplitude of transparency of said second filter at each of said first and second infrared wavelength bands being selected to track the variation in absorption of infrared energy at the wavelength of said first filter due to the presence of water vapor in said sample cell.

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