| 摘要 |
A sensor for the measurement of carbon dioxide concentration within an air flow being input to a measuring cell (1) connected to at least one electroacoustic element (2, 3) for transmitting and receiving airborne acoustic waves within the measuring cell (1). The output signal of the sensor corresponds to the propagation velocity of these waves and an indirect measure of carbon dioxide concentration, with an automatic offset correction functionality for compensation of undesired offset variations of the signal, caused by temperature or humidity variations. Preferably, an accumulating function for minimizing the influence of the offset variations is included, which for humidity variations may consist of a material with high porosity and surface density of polar molecular groups. Temperature control of the inner sheath (4) is effected by a temperature sensor (11), a resistive heating element (12) in good thermal contact with the inner sheath (4), and a control circuit (13).
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