Method for Measuring the Concentration of a Gas Component in a Measurement Gas

A method for measuring the concentration of a gas component in a measurement gas using a gas analyzer, the method comprising:

• varying the wavelength of the light of a wavelength-tunable light source within periodically consecutive scan intervals for wavelength-dependent scanning of a gas component absorption line of interest;
• modulating the wavelength of the light of the wavelength-tunable light source with a frequency;
• guiding the modulated light through the measurement gas onto a detector;
• demodulating a measurement signal generated by the detector in the event of a harmonic of the frequency;
• and
• producing a measurement result by fitting a desired curve to the profile of the demodulated measurement signal,
• wherein a function orthogonal to the desired curve is provided, and an orthogonal component of the measurement result is produced by fitting the orthogonal function to the profile of the demodulated measurement signal,
• wherein, given a known concentration of the gas component to be measured, an interfering parameter is varied and it is determined in the process an error, which comprises an inphase component (Nin), in the form of the difference between the obtained measurement result and a desired measurement result, and the orthogonal component,
• wherein a relationship between the inphase component of the error and its orthogonal component is further determined, and
• wherein, in the case of the measurement of an unknown concentration of the gas component, the measurement result obtained in the process is corrected with an inphase component which is determined, with the aid of the relationship determined in the measurement calibration, from the likewise obtained orthogonal component.