Application of Lock-in Amplifier in TDLAS Technology

senkyi

Application of Lock-in Amplifier in TDLAS Technology [Copy link]

Tunable diode laser absorption spectroscopy (TDLAS) is a detection technology that can measure gas component concentration, temperature field and even velocity field in industrial applications. TDLAS is based on the Beer-Lambert law. When the laser passes through the gas molecule medium, as long as the wavelength of the laser is equal to the energy level transition of any molecule, part of the light will be absorbed. The relationship between the outgoing light intensity and the incident light intensity is as follows:

Where is the absorption coefficient per unit length of the medium; is the effective absorption length; is the number of molecules per unit volume (i.e., concentration); is the absorption cross section of the molecule, which is a Gaussian function of the wavelength. After frequency modulation, and when, the above formula is written as:

It can be seen from the above formula that the absorption of laser by molecules shows high-order absorption components. In the signal detection path, the phase-locked amplification technology is used to realize the second harmonic detection of the modulated signal, and the first, second or third order derivative of the Gaussian function is obtained by phase detection at the 1f, 2f or 3f frequency. In
this laser phase-locked system, the most critical part is to use the phase-locked amplifier to realize the two-way detection of the measured gas and the reference gas at the same time, and even to realize the three-way detection of the measured gas, the reference gas and the laser background. In this regard, the multi-way harmonic measurement function of our digital phase-locked amplifier OE1022 can successfully solve this problem.

For details, please see the link, reproduced from: https://zhuanlan.zhihu.com/p/3427248

zxcvbnm751120

This is the information I need for study. Thank you for sharing. The content is real, detailed and very good.