单组分双分析通道红外气体检测方法研究

基于单分析通道非分散红外(non-dispersive infrared, NDIR)气体分析技术, 提出一种单组分双分析通道气体检测方法. 根据SO₂的红外吸收特征, 采用逐线积分气体吸收模型和方法, 选择洛伦兹展宽线型并考虑温度和气压对积分线强、线型的影响, 确定了两个分析通道的滤波参数.使用7.32 μm和4 μm波段分别反演小于等于 280 ppm与大于280 ppm的SO₂浓度;使用最小二乘法, 以三阶多项式为拟合模型, 获得了两个分析通道的定标曲线.对系统的测量线性度、检测限和测量准确度进行了分析. 两个分析通道的联合可以实现约几ppm至10000 ppm的宽动态范围的SO₂测量, 且系统测量线性度大于0.99, 测量误差小于5%.既克服了NDIR气体分析技术检测灵敏度和宽动态测量范围不能同时兼顾的缺陷, 良好的系统测量线性度还为多组分气体分析的干扰修正提供了非常必要的前提条件.

Measurement of a gas using none dispersive infrared technique with two analysis channels

In this paper,we propose a method of measuring a gas by using non-dispersive infrared（NDIR） technique with two analysis channels.The filter parameters of the two analysis channels are calculated by line-by-line integral of the selected absorption spectrum of SO2.The influences of temperature and air pressure on strengths and Lorentzian shape functions are considered accurately in the calculation.The absorption wavelengths at 7.32μm and 4.0μm are chosen to detect the SO₂ whose concentrations are≤280 ppm and > 280 ppm,respectively.The calibration curves of the two analysis channels are obtained by least-squares fitting two 3-order polynomials.The linearity,the sensitivity and the accuracy of the analysis system are analyzed.SO₂ concentration with a large range from～5 ppm to 10000 ppm can be retrieved with the measurement linearity > 0.99 and measurement error < 5%.The reasonable tradeoff is made to optimize both sensitivity and measurement range jointly.A fair balance between measurement sensitivity and large span range is obtained.Furthermore,sufficiently good measurement linearity makes cross-interference correction possible in the NDIR multi-gas analyzer.