Patent ID: 9140644
Filing Date: 2015-09-22
Classification: G01N

Abstract:
1. A method for detecting a concentration of a target gas, the method comprising: emitting wavelength modulated light by a laser light source, wherein an emitted wavelength range covers at least one absorption line of the target gas; detecting with a light detector a detector signal of light at various pressures of the gas mixture after the light has passed the target gas; and with an electronic control unit performing the steps of: demodulating the detector signal at a fundamental or harmonic frequency of wavelength modulation and extracting a concentration equivalent signal comprising a peak-valley or peak height; determining a point of lowest pressure dependency of the concentration equivalent signal in function of a wavelength modulation amplitude; and adjusting a working point of wavelength modulation amplitude to the determined point of lowest pressure dependency for a selected pressure range for the following gas concentration measurements, wherein a measuring frequency nf of the modulation frequency f is used, n being a positive integer.