Microcontrolled Lock-In Amplifier for Spectroscopy Applications

This article describes the development of a dedicated microcontrolled digital lock-in amplifier based on an STM32 microcontroller chip. The prototype was used in experiments of wavelength modulation spectroscopy, directed to the detection of acetylene in a multiple-pass spectrometric cell having 78 cm of optical path length. Paired experiments were done with a commercial DSP7265 lock-in amplifier. A strong correlation between measurements was observed in general for varying concentration of acetylene, with a minimum correlation of 95% observed for the lowest acetylene concentration detected at 13 ppm.