Patent ID: 7751051

Claim:
A method for automatically compensating for the presence of one or more background interferents in a spectroscopic measurement of a material through analysis of the spectroscopic measurement signal produced by a detector in response to detecting light transmitted through a sample chamber, said method being carried out using optical path gas filter correlation measurements wherein light from a broadband source is modulated using an absorbing gas filter containing a measure gas and a non-absorbing filter containing a reference gas, wherein the light is transmitted to said sample chamber, the method comprising the steps of: (a) manipulating artificially induced negative cross interferences in the measurement signal by varying differential gain applied to the signal and taking measurements using two or more baseline references at different non-zero gain levels; and (b) determining an auto-correction function from the manipulated measurement signal by determining a degree of mismatch between signals resulting from step (a) during calibration, wherein a change in said mismatch in subsequent measurements is an indication of background interferent concentration.