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Infrared gas analyzer with automatic zero adjustment

  • US 4,687,934 A
  • Filed: 01/10/1986
  • Issued: 08/18/1987
  • Est. Priority Date: 01/10/1986
  • Status: Expired due to Term
First Claim
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1. Automatic zeroing apparatus for zeroing 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 having a sample cell for containing a gas mixture to be analyzed, source means for directing infrared radiation through the sample cell over a range of wavelengths, direction means responsive to infrared radiation at at least one respective preselected wavelength to produce at least one repective detection signal systematically related to the infrared radiation at the respective preselected wavelength passing through the sample cell from the source means which respective wavelength corresponds to the absorption wavelength characteristic of a respective predetermined gas, and signal processing means responsive to said at least one direction signal for indicating the relative concentration of the respective predetermined gas in the mixture being analyzed, said signal processing means including reference means for producing a reference signal, and output means responsive to said at least one detection signal and said reference signal for outputting an output signal systematically related to the difference between said at least one detection signal and said reference signal, said automatic zeroing apparatus comprising:

  • means for filling the sample cell with gas substantially nonabsorbent of infrared radiation at the respective characteristic wavelength,comparator means responsive to said output signal for producing an error signal when said output signal differs from zero, andgain control means responsive to said error signal for automatically controlling the signal level of said at least one detection signal to reduce said output signal substantially to zero with said substantially nonabsorbent gas filling the sample cell.

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