| 摘要 |
<p>In an improved non-dispersive infrared (NDIR) gas sensor for differentiating gases in a gas mixture, a radiation source, for example having two LEDs (1,2), emits radiation having first (3) and second (4) emitted bands overlapping in frequency. A modulator (5) is configured to modulate the emitted radiation so as to provide each of the first and second emitted bands with a discrete modulation signal. After the radiation passes through a gas sample chamber (6) , a radiation detector, for example a photodiode (7) , receives the radiation. Demodulated (8) detection signals for each of the first and second emitted bands are used to differentiate gases in the gas mixture, by subtraction. The emitted bands may have different power from different LED areas or duty cycles. Epitaxially grown or coated filters (10,11) on the LEDs trim the bandwidth of the emitted bands .</p> |
