Patent ID: 6969857
Filing Date: 2005-11-29
Classification: G01J,G01N,Y02A

Abstract:
1. A sensor for detecting an infrared absorbing subject gas in a gas mixture, comprising: a sensor chamber being generally in the shape of a hollow tube; an infrared radiation source at a first end of the sensor chamber, operable to generate a beam of infrared radiation along the length of the chamber; a first filter operable to receive a portion of the beam of infrared radiation and passing a wavelength of radiation known to be attenuated by transmission through the subject gas; a second filter operable to receive a second portion of the beam of infrared radiation and passing a wavelength of radiation known to be not significantly attenuated by transmission through the subject gas; wherein the filters are arranged immediately adjacent each other to form a cross-sectional closed-shaped geometry having an inner filter and an outer filter; a chopper operable to selectively and in succession block and pass radiation from the first filter and the second filter, the chopper comprising a stationary array of light modulating elements that are controllable in two sections to alternately block and pass the radiation; wherein the sections of the array have the same geometry as the inner and outer filter; and an infrared detector for detecting radiation passed through the chopper.