| 摘要 |
The invention relates to an absorption spectrometer which measures the concentration of a gas component in a measured gas and in the process operates according to a wavelength modulation spectroscopy method. The wavelength of the light of a wavelength-tunable light source is periodically varied over a gas component absorption line of interest according to a specified time function (11) and simultaneously sinusoidally modulated with a high frequency f and a low amplitude. The measurement signal of a detector, which detects the intensity of the light after passing through the measured gas, is demodulated in a phase-sensitive manner at the frequency f and/or one of the harmonics nf of the frequency and subsequently further analyzed. In order to carry out the demodulation of the measurement signal in a phase-synchronous manner relative to the modulation of the generated light, the modulation is started in each period or in each n-th period with the frequency f in a time interval (19) before the beginning of the time function (11) and is carried out with a higher amplitude than during the time function (11). The means provided for the phase-sensitive demodulation are synchronized during the time interval (19) using the frequency f contained in the measurement signal (20). Thus, a cable for transmitting synchronization signals is no longer necessary. |
