Abstract

One of the widest used methods among the non-dispersive IR (NDIR) low-concentration gas sensors is the gas correlation filter. The optical principle uses a gas ampoule, filled with a known concentration of the gas to be measured, which is introduced in the IR light path by means of a rotating wheel. This gives a reference channel. The wheel also contains an identical gas ampoule filled with a non-absorbing gas (N₂) to give a signal channel. Simultaneously the light describes a long path through the gas cell containing the gas to be measured. Both channels impinge consecutively on the detector through a narrow band-pass filter.

© 1995 Optical Society of America