| 摘要 |
The application relates to a method for measuring the photoacoustic signal in a photoacoustic cell (4) with several light sources (5,6,7,8) that emit light at different wavelengths. The method comprises the following steps: Select a scanning frequency with which the signals are digitized; determine a modulation frequency for each light source (5, 6, 7, 8) by dividing the scanning frequency by an integer division value that is different for each light source (5, 6, 7, 8); simultaneous excitation with the light sources (5, 6, 7, 8), which respectively emit light at a different wavelength with the determined modulation frequency, wherein the produced sound pressure is measured by means of a sound pressure sensor (3), and the sound signal thus obtained is digitized; determine the absorption value to be assigned to the respective light source by evaluating a sequence of digitized measured values, the number of which corresponds to the product of a selected multiplication value and the division value, by means of a calculation method that filters out the measured value components that occur periodically with the period of the modulation frequency.
|
