Gas sensor for determining the concentration of at least one gas in a gas mixture and method for determining the concentration of at least one gas in a gas mixture with a gas sensor

A gas sensor for determining a concentration of at least one gas in a gas mixture, the gas sensor comprising:

• at least one light source, which is operable to be intensity modulatable;
• a measuring section, into which the gas mixture to be investigated is enabled to flow;
• a substantially gas-sealed detection cell including an optical window, wherein the detection cell forms an acoustic resonator, and a reference gas mixture containing at least one reference gas is filled into the detection cell;
• a detection unit, which is configured to register pressure and/or density fluctuations in the detection cell;
• and
• an electronic data processing/evaluation unit, which is configured to determine the concentration of the at least one gas in the measuring section, based on the registered pressure and/or density fluctuations in the detection cell,
• wherein the gas sensor is configured such that light emitted from the at least one light source is radiated into the measuring section, wherein at least a portion of the radiated light passes through the measuring section and then through the optical window into the detection cell, and
• wherein an intensity of the emitted light is modulated with a modulation frequency which differs from a resonant frequency of a mode of an acoustic resonance of the detection cell by less than 0.5 times the half-width of the mode.