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利用一个波长为3.291μm的室温连续、带间级联激光器和一个有效光程长为54.6 m的多通池,研究了用于中红外甲烷检测的压强测量及补偿技术。通过对测得的甲烷直接吸收光谱信号进行洛伦兹吸收线型拟合,测量了吸收池内气体压强并补偿了压强变化对甲烷浓度的影响。利用浓度为2.1×10~(-6)的甲烷气体样品,在1.33×10~4～10.64×10~4Pa的范围内进行了压强标定;对压强为9.31×10~4Pa、浓度为2.1×10~(-6)甲烷气体样品的压强测量结果进行阿仑方差分析,结果表明,当积分时间为2.2s时,压强的测量精度约为219.5Pa。在1.33×10~4、3.99×10~4和6.65×10~4Pa三种不同压强条件下,对浓度分别为1.0×10~(-6)、1.2×10~(-6)、1.4×10~(-6)、1.6×10~(-6)、2.1×10~(-6)甲烷气体样品的浓度和压强做了15组测量,验证了所给出的压强测量和补偿技术的可行性。
The pressure measurement and compensation technique for mid-infrared methane detection was studied using a continuous room temperature, band-gap cascade laser with a wavelength of 3.291 μm and a multipass cell with an effective optical path length of 54.6 m. Lorentz absorption linear fitting was performed on the measured direct absorption spectra of methane to measure the pressure of gas in the absorption cell and compensate for the effect of pressure on methane concentration. Pressure calibration was carried out in the range of 1.33 × 10 ~ 4 ~ 10.64 × 10 ~ 4 Pa with a methane gas sample with a concentration of 2.1 × 10 ~ (-6). The pressure was measured at a pressure of 9.31 × 10 ~ 4 Pa and a concentration of 2.1 × 10 The results show that the pressure measurement accuracy is about 219.5Pa when the integration time is 2.2s. Under the conditions of 1.33 × 10 ~ 4, 3.99 × 10 ~ 4, and 6.65 × 10 ~ 4Pa, the optimal concentration was 1.0 × 10 -6, 1.2 × 10 -6, 1.4 × 10 15 sets of measurements were made for the concentration and pressure of ~ (-6), 1.6 × 10 -6, and 2.1 × 10 -6 methane gas samples to verify the feasibility of the given pressure measurement and compensation techniques .