| 摘要 |
The invention relates to a method and a gas analyser for measuring the concentration of a gas component in a measurement gas. In order to measure the concentration of a gas component in a measurement gas (1), a wavelength-tunable laser diode (3) is actuated with a current (i), and the light (4) generated by said laser diode (3) is passed through the measurement gas (1) to a detector (5). The current (i) is varied in periodically-consecutive sampling intervals so as to sample a gas component absorption line of interest, according to the wavelength. The current (i) can also be sinusoidally modulated with a low frequency and low amplitude in the context of wavelength modulation spectroscopy. A measurement signal (14) generated by the detector (5) is evaluated in order to obtain a measurement result (16). To improve the measurement signal-to-noise ratio and thus achieve a considerably lower limit of detection with the same measuring path, the current (i) is modulated with at least one high (HF) frequency in the GHz range such that no wavelength modulation takes place. The amplitude of the HF modulation is selected at a maximum intensity using the linear dynamic range of the laser diode (3). The measurement signal (14) is demodulated before its evaluation, at the point of the at least one high frequency. |
