Patent ID: 8109128
Filing Date: 2012-02-07
Classification: G01N

Abstract:
1. A photo acoustic trace gas detector for detecting a concentration of a trace gas in a gas mixture, the photo acoustic trace gas detector comprising: a light source for producing a light beam; a light modulator for modulating the light beam into a series of light pulses at a chopping frequency for generating sound waves in the gas mixture, an amplitude of the sound waves being a measure of the concentration; an optical cavity for containing the gas mixture and for amplification of a light intensity of the light pulses; a transducer for converting the sound waves into electrical signals; and a feedback loop for regulating a ratio of a length of the optical cavity and a wavelength of the light beam for the amplification of the light intensity of the light pulses in the optical cavity, the feedback loop comprising: wherein the chopping frequency is higher than the modulation frequency.