Quartz crystal tuning fork enhanced spectroscopy with self-calibration algorithms

Abstract

In this paper, a gas sensing technique based on quartz crystal tuning fork (QCTF) enhanced spectroscopy was reported with self-calibration algorithms by combing two key factors of resonant frequency and quality factor. To demonstrate this proposed gas sensing technique, methane (CH₄) was selected as the target gas, a gas sensor system based on near-infrared distributed feedback (DFB) diode laser near 1653 nm was developed by combining wavelength modulation spectroscopy (WMS) with second harmonic (2 f) signal detection technique. A hybrid single-frequency modulation algorithm was developed for real-time tracking the QCTF resonance profile, and a quality factor-based calibration algorithm model was developed for calibrating the 2 f signal amplitude on pressure of the QCTF detector working environment. Comparing to traditional scanning modulation frequency method (typical 30 s), the proposed self-calibration algorithms can realize resonant frequency calibration with 1 s response time, and a measurement error less than 1 % can be achieved within a large dynamic pressure change of 320 mbar, which shows a time resolution improvement of 30 times and a good adaptability to the field application.