利用1.58μm半导体激光器测量CO气体浓度的理论研究

Study on a hybrid method about measuring the concentration of carbon monoxide gas based on 1. 58 pm diode laser

为了高精度、快速和实时测量冶炼炉中的CO气体浓度,采用1.58μm波长的分布反馈激光器和扫频技术来测量CO的吸收峰值处的谐波,理论分析了1次谐波和2次谐波最大值的混合计算来表示气体浓度的结果和实验验证,取得了扫描频率、调制度与谐波相对强度的数据。结果表明,这种混合计算方法有效克服了激光器的老化、离散性和调制度波动对测量结果的影响,测量的相对误差在小信号调制时呈现线性规律增加;在大信号调制时,呈指数规律增加,而随着电流频率转移因子增大而相对误差增大。利用吸收谱线在特殊频点的1次谐波和2次谐波强度的混合计算方法,能够高效、快捷、实时和高精度测量CO气体浓度。

In order to measure the concentration of carbon monoxide gas in a smelting furnace in real time and with high precision, an 1.58μm distributed feedback（DFB） laser was used to measure the absorption harmonics of different concentrations by means of laser frequency scanning. The hybrid algebra calculation of the maximum values of its first harmonic and second harmonics can effectively overcome the influence of laser aging, disperse and modulatinn change in the laser system on the measurement results. It is shown that the relative measurement error increases with the modulation linearly in the small-signal modulation and exponentially in the large-signal modu]ation. With the increase of transfer factor of laser driver current and laser frequency, the relative error will increase.The conclusion show that the CO gas concentration can be calculated efficiently, fast, in real-time and with high-precisinn by means of the hybrid calculation method of absorption lines at special frequencies of the first harmonic and second harmonic intensity.