| 摘要 |
A gas analyzer is disclosed which responds to the resonant absorption or emission spectrum of a specific gas by producing an acoustic resonance in a chamber containing a sample of that gas, and which measures the amount of that emission or absorption by measuring the stength of that acoustic resonance, e.g., the maximum periodic pressure, velocity or density achieved. In the preferred embodiment, a light beam is modulated periodically at the acoustical resonance frequency of a closed chamber which contains an optically dense sample of the gas of interest. The light beam is introduced into the chamber through a window transparent to the radiation in the spectral band of interest and located at a position in the chamber which can support a pressure maximum during acoustical resonance of the gas within the chamber. Periodic heating of the absorbing gas by the periodically modulated light beam incident on the gas then causes a cyclic expansion, movement, and pressure within the gas. The amplitude of the excursions increases until an amplitude is reached where the increased losses involving the amplified motions, compressions and thermal cycles are just sufficient to account the cyclic radiation energy received through the window. A differential pressure transducer is located within the acoustically resonant chamber and coupled thereto by pipes, ports or by immersion so that one of its ports is exposed to large pressure excursions of the acoustically resonant gas while the other port is exposed to significantly smaller or zero pressure excursions or to large excursions of opposing phase. Improved performance is obtained by designing the sensitive element of the pressure transducer so that it is mechanically resonant at a frquency identical to the acoustical resonance frequency of the gas containing chamber. A transducing system is inclined for converting the pressure variations of the resonant gas into electronic readout signals.
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