Patent ID: 6509567
Filing Date: 2003-01-21
Classification: G01M,G01N

Abstract:
Portable apparatus for detecting gas by selective absorption of electromagnetic radiation to detect the presence of a particular gas in a gas mixture, the apparatus comprising:a) first emitter means for emitting a measurement infrared electromagnetic radiation beam in a wavelength band containing a wavelength at which the gas to be detected presents an absorption characteristic; b) second emitter means for emitting a reference infrared electromagnetic radiation beam, said first and second emitter means being activated in alternation; c) a measurement cell containing the gas mixture to be analyzed, which measurement cell has an inlet section and an outlet section and receives at least a fraction of the measurement beam through its inlet section; d) a filter cell containing a sample of the gas to be detected and having an inlet section and an outlet section, through which sections at least a fraction of the reference beam passes in succession; e) first detector means for detecting electromagnetic radiation beams; f) second detector means for detecting electromagnetic radiation beams; g) a beam splitter disposed in such a manner as to split firstly the measurement beam and secondly the reference beam so as to transmit a first fraction of each of the measurement and reference beams to said first detector means, and a second fraction of each of the measurement and reference beams to the second detector means; and h) processing and acquisition means for synchronously acquiring and processing the four signals US1, US2, UR1, UR2 delivered by the first and second detector means in succession when the first and second emitter means are respectively activated in order to determine the absolute concentration of the gas to be detected on the basis of the ratio R=(US1Ã—UR2)/(US2Ã—UR1) between said four signals where US1 and US2 respectively represent the signals delivered by the first and second detector means when the first emitter means is activated, and where UR1 and UR2 respectively represent the signals delivered by the first and second detector means when the second emitter means is activated.