High-sensitivity ethylene gas sensor based on NDIR and dual-channel lock-in amplifier

Abstract

Ethylene(C2H4) is a gas hormone released when plants mature, and can be used as a fruit ripe catalyst or preservative at appropriate concentrations. Usually, the gas concentration detection in this application requires its sensitivity of several ppm or even sub-ppm level. In order to meet this application requirement, a highly sensitive non-dispersive-infrared (NDIR) ethylene gas sensor was developed based on components including an electrically modulated MEMS infrared light source and a dual-wavelength thermal infrared detector, combined with a high-efficiency gas cell with reflected light path structure as well as a lock-in amplifier circuit. The simulated light power collection efficiency for gas cell has reached 92 % and the signal-to-noise ratio of the infrared detection circuit has attained 52 dB. Experimentally, after using a dual temperature compensation method, the relative error of the sensor in the concentration range of 1 ∼ 100 ppm would not exceed 10 %, the detection stability was around 1 ppm, and the detection limit was close to 1 ppm, which was potentially applied to the fields such as fruit maturity detection.