Research on the Seed Respiration CO2 Detection System Based on TDLAS Technology

Abstract

The traditional detection method of CO2 concentration in seed respiration has defects such as low detection accuracy, low detection efficiency, and inability to monitor in real time. In order to solve these problems, we report a seed respiration CO2 detection system based on wavelength modulation spectroscopy (WMS) techniques in tunable diode laser absorption spectroscopy (TDLAS). This system uses a 2004 nm distributed feedback (DFB) laser as the light source, and a double-layer seed respiration device (about 1.5 L) is designed based on Herriott cell with an effective optical path of about 21 meters. Then, the second harmonic (2f) signal is extracted by the wavelength modulation method for CO2 concentration inversion. When the ambient temperature and pressure changes greatly, the corrected 2f signal is used for CO2 concentration inversion to improve the accuracy. A series of verification and comparison experiments have proved that the seed respiration CO2 detection system has the advantages of strong stability, high sampling frequency, and high detection accuracy. Finally, we used the developed system to measure the respiration intensity and respiration rate of 1 g corn seeds. The respiration intensity curves and respiration rate change details show that the seed respiration CO2 detection system is more suitable for a small amount of seeds than nondispersive infrared (NDIR) CO2 sensor and gas chromatography in real-time monitoring of the breathing process.

High-Sensitivity Differential Helmholtz Photoacoustic System Combined with the Herriott Multipass Cell and Its Application in Seed Respiration

“…20,21 The TDLAS-based CO 2 sensor for seed respiration exhibits high sensitivity and high resolution. 22 However, TDLAS systems that pursue higher sensitivity require a longer optical path and therefore a larger volume or a more complex optical path design.…”

“…However, the sensitivity of NDIR CO 2 sensors is limited by the applied thermopile or pyroelectric detectors, generally 20–50 ppm, and improving the sensitivity must be at the cost of system size or the application of additional optics . Moreover, commercial NDIR CO 2 sensors require regular calibration and additional temperature drift calibration algorithms. , The TDLAS-based CO 2 sensor for seed respiration exhibits high sensitivity and high resolution . However, TDLAS systems that pursue higher sensitivity require a longer optical path and therefore a larger volume or a more complex optical path design.…”