Patent ID: 8891085

Claim:
A gas analyzer, comprising: a sample cell for allowing a sample gas to flow therethrough; a laser irradiation section for irradiating the sample cell with laser light with a specific light frequency which is absorbed by a component to be measured in the sample gas; a light source driving section for applying a drive current for generating the laser light to the laser irradiation section; a modulation section for modulating the drive current applied from the light source driving section to the laser irradiation section with a modulation frequency of a first frequency fa; a light receiving section for receiving the laser light having passed through the inside of the sample cell; a first signal processing section for detecting a harmonic signal intensity Signal(ν) by a harmonic synchronous detection method by synchronously detecting a light detection signal of the light receiving section at a frequency being an integral multiple of the modulation frequency; a second signal processing section for detecting a light intensity signal I(v) at the specific light frequency by capturing a light detection signal of the light receiving section not through the first signal processing section, and by cutting off a frequency component not smaller than the first frequency fa by means of a frequency filter; and an operation section for capturing the harmonic signal intensity Signal (ν) detected in the first signal processing section and the light intensity signal I(v) detected in the second signal processing section, to calculate a molecular number density c of the component to be measured in the sample gas, wherein the operation section includes a first operation means for calculating the molecular number density c of the component to be measured in the sample gas from the harmonic signal intensity Signal(ν) and a reference light intensity signal I 0 (ν), the reference light intensity signal being I 0 (ν) when the laser light is not absorbed by the component to be measured at the specific light frequency, and a second operation means for calculating the molecular number density c of the component to be measured in the sample gas from the light intensity signal I(v) and the reference light intensity signal I 0 (ν) by direct absorption spectrometry.