Patent ID: 6067840
Filing Date: 2000-05-30
Classification: G01N

Abstract:
A method for indicating the concentration of a selected gas to be monitored comprising the steps of:forming a gas chamber, placing an infrared radiation detector having an electrical output signal within the chamber, placing a first infrared radiation source in the chamber at a first distance from the detector, placing a second infrared radiation source in the chamber at a second distance from the detector, the first distance being greater than the second distance, placing a selected narrow band optical filter between infrared radiation sources and the detector, allowing the introduction of a selected atmosphere into the gas chamber, alternately energizing the first and second infrared radiation sources and comparing the detector electrical output signal related to the radiation of the first and second infrared sources to determine the differential absorption of the selected wavelength as an indication of the concentration of a selected gas to be monitored in the atmosphere introduced into the gas chamber.