摘要
首先介绍了波长调制光谱检测技术的原理,并分析了甲烷在1654 nm波长处的一次谐波频谱特性。然后分析了低通滤波器对波长调制光谱中一次谐波的影响,并给出了低通滤波器截止频率的选择范围。最后设计了模拟锁相放大器,其采用的二阶低通有源滤波器在滤波性能上比传统的RC低通滤波器有较大的提升。实验结果表明,经过优化的锁相放大器能够满足光声信号一次谐波检测的快速、高精度要求。
First, the principle of the spectroscopy based on wavelength modulation is presented and the spectral characteristics of the first harmonic of methane at the wavelength of 1654 nm are analyzed. Then, the influence of a low-pass filter on the first harmonic in wavelength modulation is analyzed and the cutoff frequency range selectable for the low-pass filter is given. Finally, an analog lock-in amplifier is designed. The filtering performance of the second-order low-pass active filter used in the analog lock-in amplifier is greatly improved in comparison with that of the traditional RC low-pass filter. The experimental result shows that the optimized lock-in amplifier can meet the requirements of fast and high precision first-harmonic detection of photoacoustic signals.
出处
《红外》
CAS
2011年第11期14-18,32,共6页
Infrared
基金
西南科技大学与四川省煤炭产业集团重大合作项目(07zh0164)
四川省教育厅重大培育项目(07zz039)
四川省安监局项目(07zd0103)
关键词
光声光谱
波长调制
锁相放大器
低通滤波器
photoacoustic spectroscopy
wavelength modulation
lock-in amplifier
low pass filter
