Abstract: A digital IR gas analyzer comprises a sample cell having a conical shaped interior wall and a filter wheel provided with HC, CO and CO2 interference filters. The filter wheel and IR detector are temperature stabilized. The HC, CO and CO2 gas samples are normalized to a precision reference voltage. The normalized samples are digitized and processed, i.e., for linearization, cross-talk correction and zero drift temperature compensation, by a digital processor. The processed samples are then converted to analog to drive HC, CO and CO2 meters. HC, CO and CO2 gas channels are zeroed simultaneously and calibrated automatically in response to control panel switches.