Modified balanced ratio metric detection system used for high sensitive vapor detection

Wei, Wei; Chang, Jun; Sun, Bo; Zhang, Sa-Sa; Zhu, Cunguang; Wang, Qiang; Lv, Guangping; Li, Zhi; Wang, Zongliang; Zhou, Shenjie

doi:10.1016/j.ijleo.2015.07.041

Cited by 4 publications

(2 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Once the radiation of the diode laser overlaps with a rotation/vibration transition of gas, absorption will generate and this results in light intensity attenuation. The transmitted intensity I out (t) at simultaneous time t associated with gas transition in a gas cell is given by the Beer-Lambert law [ 4 , 5 , 6 ]:

where I in is incident intensity, α[ν( t )] (cm −1 ) is the absorption coefficient at instantaneous frequency ν( t ), L (cm) is the optical path length, and C is the concentration of target gas (ppm; i.e., target gas density ratio in the mixed gas) in the gas cell. The approximation of Equation (1) is valid for small absorbance, i.e., α[ν( t )]CL << 1.…”

Section: Analytical Treatment For Waveforms Recoverymentioning

confidence: 99%

“…Tunable diode laser spectroscopy (TDLS) has become the primary technology for most kinds of gas detection, particularly for trace gas concentration detection [ 1 , 2 , 3 , 4 , 5 ]. Earlier, it was mainly the fundamental rotation-vibration absorption lines that applied TDLS to deal with the mid-infrared (MIR) [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modulation Index Adjustment for Recovery of Pure Wavelength Modulation Spectroscopy Second Harmonic Signal Waveforms

Wei

Chang

Wang

et al. 2017

Sensors

Self Cite

View full text Add to dashboard Cite

A new technique of modulation index adjustment for pure wavelength modulation spectroscopy second harmonic signal waveforms recovery is presented. As the modulation index is a key parameter in determining the exact form of the signals generated by the technique of wavelength modulation spectroscopy, the method of modulation index adjustment is applied to recover the second harmonic signal with wavelength modulation spectroscopy. By comparing the measured profile with the theoretical profile by calculation, the relationship between the modulation index and average quantities of the scanning wavelength can be obtained. Furthermore, when the relationship is applied in the experimental setup by point-by-point modulation index modification for gas detection, the results show good agreement with the theoretical profile and signal waveform distortion (such as the amplitude modulation effect caused by diode laser) can be suppressed. Besides, the method of modulation index adjustment can be used in many other aspects which involve profile improvement. In practical applications, when the amplitude modulation effect can be neglected and the stability of the detection system is limited by the sampling rate of analog-to-digital, modulation index adjustment can be used to improve detection into softer inflection points and solve the insufficient sampling problem. As a result, measurement stability is improved by 40%.

show abstract