| 摘要 |
An optical spectrometer (10) for measuring low concentrations of gas constituent, such as SO2, provides automatic tracking of an absorption band of the constituent. A stepper motor (26) rotates an optical frequency modulator (24) in the spectrometer through a preset range to vary the frequency of the light passing through a gas sample (12) about an adjustable center frequency. The ouput of the spectrometer, which varies in amplitude with the change in frequency of the light due to the absorption characteristic of the gas, is filtered by a digital filter (64) and stored as a set of digital values in memory (44) of a digital processor (40). The maximum peak value of a set of peak values corresponding to different selected center frequencies is used to control the stepper motor to control the angle and hence the center frequency of the optical modulator to track the absorption peak of the constituent gas. |
