Methane Detection at Low Concentration Based on 2f Harmonic Signal

Abstract

This paper presents the methane detection at low concentration based on 2f harmonic signal to achieve highly sensitive monitoring. Since methane is the characteristic gas in power transformer oil once a thermal fault at low temperature (<300°C). Based on wavelength modulation and tunable diode laser absorption spectroscopy(TDLAS) technique, the specific mathematical modeling of infrared gas absorption process, the input signal and the second harmonic signal after the methane gas through the absorption is calculated. Especially, the phase-sensitive detector lock-in amplifier is adopted to improve the sensitivity. Finally, the performance of the proposed methane detection schedule is simulated at the low hydrogen concentration. The results prove that the proposed optical detection has a high sensitivity of 0.052V at every 1 μL/L.